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Carver PM 1.5 Power Factor

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Topic: Carver PM 1.5 Power Factor
Posted By: ceharden
Subject: Carver PM 1.5 Power Factor
Date Posted: 26 January 2009 at 12:09am
Just had an interesting experience on the bench.  Been working on a pair of old Carver PM1.5's for a long standing forum member.  The one on the bench at the moment had been attacked by someone rather ham-fisted with a soldering iron and started working once the solder bridges and unnecessary wire links had been removed.  Have had to replace the low voltage supplies smoothing caps as they'd gone dry and stopped actually storing charge.  That was a highly entertaining job for starters because of their location and the fact that whoever built them had used a whole roll of solder on the board!  I could go on for ages about how strange a design they are: Lighting dimmer for PSU regulation, no less than three sets of supply rails, 10 output devices per channel but only two connected to the output!

Anyway, I started running the amp up into a 4R load as a kind of final check before screwing the case on and deeming it finished but after only a few seconds of running at full power (slightly clipping) the amp cut out.  Very quietly, no bangs or anything.  Turned out the mains fuse had blown (6.3A slow blow).  So I replaced it with the one from the other amp, same value.  Started the testing again and it blew the fuse again.  Now at this point I've run out of 6.3A 35mm fuses so it's now got a 20A one temporarily but have downrated the plug fuse to 5A for testing and I decide perhaps measuring the input current would be a good idea.

Very quickly the reason for the fuse blowing was obvious, the amp has an appalling power factor.  At low powers it's about 0.3, rising to 0.5 at high power.  To give you an idea, with the amp delivering 300WRMS from one channel into a 4Ohm load, it's drawing over 5A or 1300VA from the mains!!!  Just before it took out the 5A fuse in the plug I clocked it at over 3000VA and this is still only with one channel running!  Maximum output power is about 800WRMS/4R for short bursts (100 ms or so)





Replies:
Posted By: Wrighty
Date Posted: 26 January 2009 at 12:58am
I had one of these on the bench a while ago, which a customer said wasn't working. I took the lid off to have a look inside before I did anything and I thought the general design and construction was very strange indeed.

For starters, there was what resembled a model aircraft motor and propellor for a fan, which varied in speed according to the input and made a noise varying from quite annoying, all the way up to screaming for its life!

I ran the usual tests and came to the conclusion that there was nothing wrong with it, apart from the power LED for one channel not working. The level meter PCB was glued to the inside of the front panel, so I decided to leave it be!

I didn't actually do a flat out sine wave test, as I didn't want to stress an amp which was working but I had no service information for, knowing from the start that it was an unconvential design...


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ALL YOUR BASS ARE BELONG TO US.


Posted By: ceharden
Date Posted: 26 January 2009 at 1:25am
Luckily I was supplied with the service manual for these.  Without it the job would have been very difficult.

The amp has +/- 35V, 75V and 125V rails, all for an amp rated at something like 500W/4R.  8 output devices per side do rail switching/tracking and two actually drive the output.

The fan scared the sh1t out of me the first time the thermal switch cut in to take it to full speed.  I found myself grabbing for the power switch thinking the whole thing was going to blow up!  You probably didn't get to experience it at full whack.

The power supply is controlled by a triac in series with the mains transformer and the conduction angle is varied according to demand from the output stages.  The fan speed control is actually just a useful side effect!

Anyway, I've left that for now, got to work out where my hot glue gun is to mount the new caps in whatever space I can find!  Now on the bench is a Studiomaster 900E in which all the smoothing caps have failed at the positive terminal (as in corroded, you desolder the negative terminal and the cap comes off the board leaving the positive one still attached to the PCB!).



Posted By: Wrighty
Date Posted: 26 January 2009 at 1:41am
Yeah, I was dreading there being a fault on this one, as a quick search for some service info just revealed a load of dead ends...

I thought the fan speed switch on the front was an interesting inclusion for a pro audio amp until I fired it up and decided it was definitely necessary unless the amp is off stage somewhere! The fan speed seemed to be modulated by the input, so you could probably get a pretty good idea of the tune even when driving into a dummy load!

Apparently this is/was all amazing and innovative technology...

The Studiomaster sounds like fun - good luck finding some new caps that fit. If it's anything like most other amps, they'll be a funny size and I doubt the current incarnation of Studiomaster will have much to offer in the way of spares.


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ALL YOUR BASS ARE BELONG TO US.


Posted By: ceharden
Date Posted: 26 January 2009 at 1:54am
New caps weren't so much of a problem, RS had some of the right shape.  Did a 2000E last week with different value caps but the same problem, they must have bought a whole load of cheap sh1t caps.

However this one is still behaving strangely by turning the audio output on and off at 100Hz.  It was doing it much worse before I changed the main smoothing caps but hasn't cured it.  I don't have any service info for these and don't really want to pay for them....




Posted By: Wrighty
Date Posted: 26 January 2009 at 2:01am
When you say it's turning the audio output on and off at 100Hz, do you mean it's turning it off 100 times a second or it's turning it on and off randomly when you put 100Hz through it?

I'll be seeing a colleague of mine tomorrow who used to deal with Studiomaster a lot, back in the day and supplied a few of that series of amps over the years, so it's possible he's got some service info on them. I'll let you know how I get on...

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ALL YOUR BASS ARE BELONG TO US.


Posted By: ceharden
Date Posted: 26 January 2009 at 2:12am
If you could find out if he's got a schematic that would be fantastic please.

It's turning the audio on at 100Hz.  It's something like I get 8ms of on, then 2ms of off.

When the supply rails were sagging massively between mains peaks I could see why it was doing it but now that fault is cured I'm wondering what's going on.

Apparently the amps have some protection circuitry called 'gated output stage' or something wierd.  That would explain what I'm seeing but not why.  The second channel isn't doing anything at the moment but that's probably something simple....



Posted By: Wrighty
Date Posted: 26 January 2009 at 2:23am
A few ideas off the top of my head which you may well have already thought of and checked:

Have you checked the low voltage supplies (if there are any) on the input stages? I'd expect to see a +/-12V or similar supply, with its own rectifier, smoothing caps and regulators.

DC protection circuit gone mental? If there's no relay, it could be something similar to the LAB.1000 which (from memory) has some circuit involving a triac for DC protection...

Blimey, just noticed the time - better go to bed!!


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ALL YOUR BASS ARE BELONG TO US.


Posted By: Elliot Thompson
Date Posted: 26 January 2009 at 2:39am




The Carver PM 1.5 is from the mid to late 80's. So, it is not surprising it pulls a lot of current.

Last year someone from PSW was searching for the Carver PT 2400 & 1800 manual. I sent it to him for he bought a few at a great price. The PT 2400 used two separate power cords and required 20 amps (240 volts) to operate @ 4 ohms stereo but was rated 2 ohms per channel. The amplifier only delivered 1200 watts per channel @ 4 ohms and, the THD was very low. So, what you are experiencing seems to co-inside with Carver Amplifiers.

Carver is a Home Audio company and dabbled in Pro Audio for a short period. While there amplifiers worked fine for Home Audio they failed constantly for Pro Audio. If I remember correctly the PM 1.5 was rated 375 watts per channel @ 8ohms. Seeing that the PM 1.5 is a Home Audio amplifier, the fuse rating reflex Home Audio use under an 8-ohm load.

Here is the Schematic

http://www.schematicsforfree.com/archive/file/_newly_uploaded/carver%20pm%201.5%20-input%20board.jpg - http://www.schematicsforfree.com/archive/file/_newly_uploaded/carver%20pm%201.5%20-input%20board.jpg

http://www.schematicsforfree.com/archive/file/_newly_uploaded/carver%20pm%201.5%20-power%20supply.jpg - http://www.schematicsforfree.com/archive/file/_newly_uploaded/carver%20pm%201.5%20-power%20supply.jpg

http://www.schematicsforfree.com/archive/file/_newly_uploaded/carver%20pm%201.5%20-display.jpg - http://www.schematicsforfree.com/archive/file/_newly_uploaded/carver%20pm%201.5%20-display.jpg

Best Regards,

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Elliot Thompson


Posted By: jbl_man
Date Posted: 26 January 2009 at 9:07am
Chris,while you have it on your test bench,would it be possible take a photo of the inside and show us?

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Be seeing you.


Posted By: Deadbeat
Date Posted: 26 January 2009 at 3:03pm
The 'P' denoted pro models.

Just repackaged home ones, you can find their HT equivalents.

Even the 't' is carried over, if one has a PM1.5t, you've got one a Carver Special (transfer function-ized amp) - that emulates one of the $$$$ hifi amps.

When Phoenix gold bought them over, they kept quite a few of the schems -> the PT2400 and quite a few of them (non class D/lightweight amps) were like the older ones, rebadged hifi/ht amps.

Sound very good (I kept a Carver M1.5t in my hifi for a very long time...brill piece of kit), but what elliot said...

/uneeded info


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Away on extended leave.


Posted By: Elliot Thompson
Date Posted: 26 January 2009 at 3:53pm
If I remember correctly, the PM 1.5 is 600 watts per channel @ 4 ohms and, 375 watts per channel like I mentioned previously @ 8 ohms.

Whatever you do, don't use it @ 2 ohms per channel.

Best Regards,

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Elliot Thompson


Posted By: Howie
Date Posted: 26 January 2009 at 4:24pm
I worked for a company that had a load of them in the early nineties.
I remember one failing at a gig that was running monitors. It emitted a pulsed beeping sound. Very strange.  
The ultimate conclusion was that the conversion to 240v from 120v on these amplifiers was poorly done and needed a complete redesign of the power supply.
After many repairs and modifications, they were eventually sold on.


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http://www.gigrighire.co.uk


Posted By: Peter Jan
Date Posted: 26 January 2009 at 5:23pm
Originally posted by Howie Howie wrote:

I worked for a company that had a load of them in the early nineties.
I remember one failing at a gig that was running monitors. It emitted a pulsed beeping sound. Very strange.  
The ultimate conclusion was that the conversion to 240v from 120v on these amplifiers was poorly done and needed a complete redesign of the power supply.
After many repairs and modifications, they were eventually sold on.


The conversion is or was nothing more than putting two primary transformer coils in series or parallel. So at 230-240 Volts you might think the problem should be less as the current needed was about half of that on 120 Volts all things being equal. But I remember from those days that even at 230 Volt those amps sucked the mains in a very peaky way, especially when the mains were not stable in voltage. I have seen many fuses blow in those days in all those PM1.5(t) and M1.0t amplifiers of that era. Even 10 A slow-blow was not enough at 230 Volt. Looking at the schematics you can see that a dimmerlike triac circuitery driving the transformer with nothing to damp the inrush current. A comparator circuit senses the voltage of the high supply rails. When the mains are sagging, the triac fires the transformer at (more) rapid pace to keep the supply up, snowballing into fuses blown and sometimes even to a blown thermofuse inside the transformer.  When the mains are good or you don't perform sine-wave testing under 4 Ohm load, there is no problem, but real world use is often not that ideal. Those Carvers were not bad amps, but the way the their power supply was done, was not worked out as it should have been for normal daily use on the road.


Posted By: anatech
Date Posted: 26 January 2009 at 11:38pm
Hi All,
I saw this thread and had to respond.  I was the Canadian Factory warranty for Carver.

I think there was more to the 230 V conversion than primary changes.  The gate firing circuit had some changes also I think.

The Carver Pro were different than Carver home.  Similar, but different.  The power line sagging under current draw is a problem with any device that self regulates it's internal voltages, as the Carver product does.  If you have poor AC supplies, that is your problem.  Even normal amps will be affected as the voltage drops.  The Carver amps do draw their current in short spikes along with the music demands.  That's also why the fans change speed with the music.  They have their own winding and rectification, it's an indication of how much current the amp is drawing.

The main reason for Carver amplifier failures?  Simple.  They had to be run full range or bass only.  Running them mids and or highs only would lock up the commutators to high B+ and the amp would go into thermal runaway.  That's as long as your AC supply was good.  These amplifiers are actually very efficient, but your pf measurement gets messed up with the way the amp draws current.

These amps work a bit differently than normal amps.  That "dimmer" power supply actually pre-regulates the energy into the amplifier.  It is carefully balanced so as not to create a net DC in the mag coil core (it's not a normal transformer at all!).  IF you were to short the triac and apply power, all your supply voltages would be many times what they should be.  The mag coil will draw very high current when presented with a sine wave all by itself.  That is normal for this part.

I hope that helps figure these out.  They are actually very reliable when properly used.  The care and feeding was in the owner's manual, but who reads those?

-Chris


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You did what?? !


Posted By: Deadbeat
Date Posted: 27 January 2009 at 10:45am
Great info!

Can you elaborate on the difference, I'm curious as this is the info I've always been given about them (and I owned a rack for a while...LOL)


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Away on extended leave.


Posted By: Peter Jan
Date Posted: 27 January 2009 at 1:56pm
Originally posted by anatech anatech wrote:

Hi All,
I saw this thread and had to respond.  I was the Canadian Factory warranty for Carver

That makes us collegues, I had the Belgian-Holland repair centre for many years.

Originally posted by anatech anatech wrote:


I think there was more to the 230 V conversion than primary changes.  The gate firing circuit had some changes also I think.

I can tell for a fact that there was nothing more to it. The European models were no diffferent than US models. For some time the amps came wired for US use and we did the simple rewiring of the primary windings as it was printed in the manual and inside the covers of the amplifiers. The amplifiers even had the US power connectors and we needed to change it for the our type of connector. Other countries might have been different, but that's how they came to our regions. Later on they came wired for our countries, but still all had the same printed in the manual and inside the covers and the transformers were also entirely the same as before.

Originally posted by anatech anatech wrote:


The Carver Pro were different than Carver home.  Similar, but different.  The power line sagging under current draw is a problem with any device that self regulates it's internal voltages, as the Carver product does.  If you have poor AC supplies, that is your problem.  Even normal amps will be affected as the voltage drops.  The Carver amps do draw their current in short spikes along with the music demands.  That's also why the fans change speed with the music.  They have their own winding and rectification, it's an indication of how much current the amp is drawing.

The main reason for Carver amplifier failures?  Simple.  They had to be run full range or bass only.  Running them mids and or highs only would lock up the commutators to high B+ and the amp would go into thermal runaway.  That's as long as your AC supply was good.  These amplifiers are actually very efficient, but your pf measurement gets messed up with the way the amp draws current.

I never said Carver amplifiers failed a lot, like in : "burned components", they didn't !  The majority of complaints came from users that had troubles with mains power and it was not always with too heavy loads and/or full range use.
Carvers had a more efficient power supply that worked well 'IF' the mains were good. But come on, let's be serious, how did you explain to a client it was his problem that the AC mains were at fault when other brand amps in the same rack didn't act up the way those Carvers did ? I did my share in defending Carver amps those days and explaining how to use them properly, but almost nobody is using them on the road anymore and in the second hand market, they don't even get you 100 Euro for one in pristine condition. That's just the reality of things.
Mind you, I have a bunch of Carvers still doing their job very well in fixed installations and I'm not one bit worried about them. Regular maintenance and an occasional fan or other small items needs replacing once in a while, but no more than any other decent brand.

Originally posted by anatech anatech wrote:


These amps work a bit differently than normal amps.  That "dimmer" power supply actually pre-regulates the energy into the amplifier.  It is carefully balanced so as not to create a net DC in the mag coil core (it's not a normal transformer at all!).  IF you were to short the triac and apply power, all your supply voltages would be many times what they should be.  The mag coil will draw very high current when presented with a sine wave all by itself.  That is normal for this part.

I'm sorry, it is a normal transformer. Ever fed such a transformer straight from a variac ? You would know if you ever tried it. You are right that an AC mains full sinewave would give a multiplication of the intended secondary voltage and draw an insane amount of current, it's just the way the transformer is made in terms of absolute values and ratios. It has less core because it doesn't need to be full-on all the time.
Mr. Carver did come up with some clever solutions to reduce weight and get slightly better efficiency through that dimmer-like steering of a transformer that was conceived to work that way. And multiple voltage secondary supply rails - maybe not the first to do it, but that's another discussion. But I totally disagree with all that fancy namegiving and marketing chit chat of something that has always relied on the working of magnetic field build up due to current flowing through windings round a metal core to begin with... an ordinary transformer. Maybe not used in a regular manner, but still a plain and simple transformer. If I (or whoever) were to put the nametag "Magnetic Field Technology" on any ordinary amplifier, it would still be valid to name it like that... know what I mean ?
Bob never really lied about things, it's just the way it was presented, that suggests some special high-tech stuff were it is simply not there. Why must I suddenly think Herr "doctor" Bose ??  Strange... Big smileLOL

Originally posted by anatech anatech wrote:


I hope that helps figure these out.  They are actually very reliable when properly used.  The care and feeding was in the owner's manual, but who reads those?

I do agree that they were reliable amplifiers in terms of mechanics and electronics. It's just that most users, especially in road use, not even got them to work reliable enough in pretty favorable conditions either. And you can defend Carver amps as much as you want, like I did for a long time, that doesn't change the fact that the power supplies, whatever fancy name it was given, are not really roadworthy.... not in this world anyway.



Posted By: anatech
Date Posted: 27 January 2009 at 4:43pm
Hi Peter,
Actually, I did see some changes in the triac firing circuits in at least one manual.  I lost access to all my service information after I sold my company about 10 years ago.  However, I do clearly remember some other changes were made on at least one product.

As far as Bob Carver and his marketing, that truly dove me nuts.  It annoyed me to no end because it only confused the issues when trying to train an external shop or new technician.  We are very alike in that way.

"Carvers had a more efficient power supply that worked well 'IF' the mains were good. But come on, let's be serious, how did you explain to a client it was his problem that the AC mains were at fault when other brand amps in the same rack didn't act up the way those Carvers did ?"
Sorry, I don't know how the quote function works on this board, please bear with me.
We constantly had to deal with that issue, more so than you ever did.  Consider that these amps only draw 1/2 the current at your higher mains voltage.  Those clients of yours must have had abysmal mains connections!

The explanation would run along these lines.  First you explain that the Carver power supply regulates it's internal power supply voltages.  This guaranties consistent power output and distortion levels.  Of course, you know that, but do your customers?  Anyway, that means that if the mains voltage drops, the current must increase to compensate.  This is exactly like any computer switch mode power supply.  Most other branded amplifiers simply allow the internal voltages to drop.  This does have an effect on performance, they just don't notice this.  You know as well as I do that most operators assume everything is okay as long as okay sound comes out and smoke doesn't.  That is the extent of what operators will notice.

Now, if you have a professional sound company with poor mains distribution, doesn't that sound unprofessional to you?  That is another point I make, and I have been told that improving this weakness has also improved the performance of all the other products in use.  No surprise there.

At any rate, I've never had a problem explaining this to people.  I just get tired of doing it.  The harder thing to explain to people is how such a light thing that doesn't normally get hot can deliver all the power that the big, heavy hot things do.  American roadies would tend to use the light amp for mids and or tweeter duty.  Not something these amps will survive.  That just re-enforces the erroneous thinking.

"I did my share in defending Carver amps those days and explaining how to use them properly"
I'm just setting the record straight.  I am not devoted to Carver amps, but I do know them well, and I also understand how misunderstood their operation is, as evidenced by the start of this thread.  Am I wrong?

"but almost nobody is using them on the road anymore and in the second hand market, they don't even get you 100 Euro for one in pristine condition. That's just the reality of things."
Well, yeah.  No kidding!
Tell me, how much is a BGW worth?  I could pick many brands that we can say the same thing about.  So can you.  There was no proof of anything in that statement.

The one reason that Carver product had trouble with in the mobile field was the terrible quality of service that is acceptable in the industry.  The only worse workmanship I have seen is in the DJ market and modifiers of home audio.  We would receive an amplifier from a touring company that had failed yet again, other brands.  Upon opening the amp up, we were able to see the worst types of work ever done on amplifiers.  Solder splashes and globs running loose.  Mixed output transistors, some not even rated high enough.  The work was so bad that we were amazed these amps didn't explode on powerup.  Now, you take that lack of understanding and terrible workmanship and attempt to service a more complicated amplifier the same way and you will have instant destruction.

In short, touring companies need amplifiers that complete morons can fix.  We did have a couple competent touring companies that used real technicians that had long, happy relationships with Carver amplifiers.  This industry caters to the lowest common denominator, the least capable link in the chain.  Stay at or below that link and you'll be fine.  So a Carver amplifier did answer the needs of what the touring companies required on the road.  Light, reliable power amplifiers.  Unfortunately they were too complicated to keep in service for the average technical level in that industry.  You can't blame the amp for that, but you can the advertising guys or the salesmen in that industry.

Just my opinion and read of the situation.  Not once did I say this design was a good idea in all situations.

"Regular maintenance and an occasional fan or other small items needs replacing once in a while, but no more than any other decent brand."
That's about right.  What was really nice is that an output failure didn't normally cause much damage or take out a speaker.  The protection was excellent.

"I'm sorry, it is a normal transformer. Ever fed such a transformer straight from a variac ?"
Why, yes I have.  Every single time I troubleshoot one or power it up for the first time.  However, not once have I said these were not a transformer.  What I said was that they do not behave like a normal transformer.  I believe my actual quote is "it's not a normal transformer at all!"  How does that disagree with the point you have tried to make, except that you implied these are regular transformers that are somehow defective in design possibly?  Now, as a distributor, how many requests for replacement transformers from other technicians did you receive?  I know from experience that most technicians tried to order a power transformer believing that the original had failed.  That's why I singled this out.

Since when do normal transformers draw heavy current with a sinewave at 60% of full voltage?  They don't.  These are not normal power transformers, but they are a type of transformer.  The waveform that this transformer normally operates with is not a sinewave, that you can not deny.  My point here was that you can not treat this Mag Coil as if it was a normal transformer.  Can you deny that?  Now, the only reason I call this part a "mag coil" is because that is what it is called at Carver.

I think right now you have chosen to take issue with the idea that I am defending "Carver".  That I think is your main problem with my post.  I have attempted to state facts in order to help people properly troubleshoot and service these products.  Nothing more.  If you have a problem with the advertising Carver had, take it up with Bob Carver himself.  There is a Carver forum in the 'States where you can contact him, and a web site too.  I have never talked to the man, just dealt with the technology.

-Chris


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You did what?? !


Posted By: Peter Jan
Date Posted: 27 January 2009 at 8:15pm
Chris,

This is already going somewhat off topic ( nah... really ?? LOL)  but I dive in one more time and than I'll stop. It's not that I don't want to hear your opinions, experiences and knowledge, but it's going a bit too far maybe for others if we keep doing this Wink.

Originally posted by anatech anatech wrote:

Hi Peter,
Actually, I did see some changes in the triac firing circuits in at least one manual.  I lost access to all my service information after I sold my company about 10 years ago.  However, I do clearly remember some other changes were made on at least one product.

Hmm.. yes I also noticed a few changes over the years, for some amplifiers, but I'm not sure it had something to do regarding issues that might arise when operating at 110 or 230 Volts AC.

Originally posted by anatech anatech wrote:


As far as Bob Carver and his marketing, that truly dove me nuts.  It annoyed me to no end because it only confused the issues when trying to train an external shop or new technician.  We are very alike in that way.

"Carvers had a more efficient power supply that worked well 'IF' the mains were good. But come on, let's be serious, how did you explain to a client it was his problem that the AC mains were at fault when other brand amps in the same rack didn't act up the way those Carvers did ?"
Sorry, I don't know how the quote function works on this board, please bear with me.
We constantly had to deal with that issue, more so than you ever did.  Consider that these amps only draw 1/2 the current at your higher mains voltage.  Those clients of yours must have had abysmal mains connections!

No they didn't always have sagging mains or long cables or loose connections or something. But I wished many times it would have been the problem.

Originally posted by anatech anatech wrote:


The explanation would run along these lines.  First you explain that the Carver power supply regulates it's internal power supply voltages.  This guaranties consistent power output and distortion levels.  Of course, you know that, but do your customers?  Anyway, that means that if the mains voltage drops, the current must increase to compensate.  This is exactly like any computer switch mode power supply.  Most other branded amplifiers simply allow the internal voltages to drop.  This does have an effect on performance, they just don't notice this.  You know as well as I do that most operators assume everything is okay as long as okay sound comes out and smoke doesn't.  That is the extent of what operators will notice.

Now, if you have a professional sound company with poor mains distribution, doesn't that sound unprofessional to you?

I don't see why it would seem unpro to have a bad mains, as if you always have a choice. For starters, I doubt that every decent sound company in Canada has it's own bulletproof generator(s) as standard equipement and even if it was that way, that would not explain for the all problems you had to deal with. Here we have to run either from a generator supplied by a company that does nothing but supplying generators or run from fixed in house mains distribution and I think that's not different in your part of the world ?

Originally posted by anatech anatech wrote:


That is another point I make, and I have been told that improving this weakness has also improved the performance of all the other products in use.  No surprise there.

Yep, improving mains will likely make some other epuipment perform better, depending on how bad the mains are to begin with, that's reasonable to say. But it was very frustrating to see the voltage being very steady everywhere in the rig and still have blown fuses in the Carver amps. I could not blame every generator or fixed mains every time it happened. I said I have a fair amount of amps still running in fixed installs, café's, discotheques en such, those are the places to expect poor mains and typically the places where they are run hard.  I can't explain why they perform nicely in less favorable places and act up badly in situations that are safe to say being top notch.

Originally posted by anatech anatech wrote:


At any rate, I've never had a problem explaining this to people.  I just get tired of doing it.  The harder thing to explain to people is how such a light thing that doesn't normally get hot can deliver all the power that the big, heavy hot things do.  American roadies would tend to use the light amp for mids and or tweeter duty.  Not something these amps will survive.  That just re-enforces the erroneous thinking.

You are probably right about it, but I can't really say I saw Carver amps go bad from mid or high duty only or I can't say for sure that was the main reason some burned out. The amplifiers end stages very rarely went bad. Maybe that's why I never gave it much thought.

Originally posted by anatech anatech wrote:


"I did my share in defending Carver amps those days and explaining how to use them properly"
I'm just setting the record straight.  I am not devoted to Carver amps, but I do know them well, and I also understand how misunderstood their operation is, as evidenced by the start of this thread.  Am I wrong?

I should have put it like this : "defending" between marks. I'm not devoted to Carver amps either. And yes, you are right that the working is often, if not always misunderstood.

Originally posted by anatech anatech wrote:


"but almost nobody is using them on the road anymore and in the second hand market, they don't even get you 100 Euro for one in pristine condition. That's just the reality of things."
Well, yeah.  No kidding!
Tell me, how much is a BGW worth?  I could pick many brands that we can say the same thing about.  So can you.  There was no proof of anything in that statement.

An old BGW ( or QSC or Crest or... ) are worth a normal amount of cash over here and what's more important, they are still wanted as in "want to use them". Carver amps are not wanted, not even for free. I know I can or you can pick out many brand or types to make a point in whatever direction and a lot of wanting or not wanting an amp has probably more to do with hypes or brand availability back in the days. Maybe a tiny bit of proof here ? No ? Wink.  Just kidding, don't answer that or we will keep going on ... and on and ....

Originally posted by anatech anatech wrote:


The one reason that Carver product had trouble with in the mobile field was the terrible quality of service that is acceptable in the industry.  The only worse workmanship I have seen is in the DJ market and modifiers of home audio.  We would receive an amplifier from a touring company that had failed yet again, other brands.  Upon opening the amp up, we were able to see the worst types of work ever done on amplifiers.  Solder splashes and globs running loose.  Mixed output transistors, some not even rated high enough.  The work was so bad that we were amazed these amps didn't explode on powerup.  Now, you take that lack of understanding and terrible workmanship and attempt to service a more complicated amplifier the same way and you will have instant destruction.

I agree that poor workmanship would make for a good deal of problems, that's goes for every piece of epuipment. The more complicated something is, the more easy to ruin too. But it doesn't account for the problems Carver amps had out of the box.

Originally posted by anatech anatech wrote:


In short, touring companies need amplifiers that complete morons can fix.  We did have a couple competent touring companies that used real technicians that had long, happy relationships with Carver amplifiers.  This industry caters to the lowest common denominator, the least capable link in the chain.  Stay at or below that link and you'll be fine.  So a Carver amplifier did answer the needs of what the touring companies required on the road.  Light, reliable power amplifiers.  Unfortunately they were too complicated to keep in service for the average technical level in that industry.  You can't blame the amp for that, but you can the advertising guys or the salesmen in that industry.

Just my opinion and read of the situation.  Not once did I say this design was a good idea in all situations.

"Regular maintenance and an occasional fan or other small items needs replacing once in a while, but no more than any other decent brand."
That's about right.  What was really nice is that an output failure didn't normally cause much damage or take out a speaker.  The protection was excellent.

"I'm sorry, it is a normal transformer. Ever fed such a transformer straight from a variac ?"
Why, yes I have.  Every single time I troubleshoot one or power it up for the first time.

I meant really straight from a variac, not in the amplifier with the triac circuit.

Originally posted by anatech anatech wrote:


However, not once have I said these were not a transformer.  What I said was that they do not behave like a normal transformer.  I believe my actual quote is "it's not a normal transformer at all!"  How does that disagree with the point you have tried to make, except that you implied these are regular transformers that are somehow defective in design possibly?  Now, as a distributor, how many requests for replacement transformers from other technicians did you receive?  I know from experience that most technicians tried to order a power transformer believing that the original had failed.  That's why I singled this out.

I had to replace only one transformer. Many requests from other service centres, but only one was defective in all those years. I did not say or imply they were maybe defective in design, but they were not made to be full-on connected to 110 or 230 V AC.

Originally posted by anatech anatech wrote:


Since when do normal transformers draw heavy current with a sinewave at 60% of full voltage?  They don't.  These are not normal power transformers, but they are a type of transformer.  The waveform that this transformer normally operates with is not a sinewave, that you can not deny.  My point here was that you can not treat this Mag Coil as if it was a normal transformer.  Can you deny that?  Now, the only reason I call this part a "mag coil" is because that is what it is called at Carver.

I agree if you say you can't treat it as a normal transformer in that triac circuit with 110 or 230 AC. That's why i said if you had it straight on a variac, you would see it's just a regular transformer that does nothing wrong if you feed it with a lower voltage. I did just that and it has a normal primary to secondary ratio, doesn't hum strange or draws current in abnormal amounts. Probably the way it was made won't make for a very efficient transformer if used at normal 50 or 60 Hz full sinewave low voltages, but it was not made for that. It was made to perform in another environment and I think those transf... err .. okay, you convinced me.. let's call it Magnetic Coils from now on Big smile , did a good job.

Originally posted by anatech anatech wrote:


I think right now you have chosen to take issue with the idea that I am defending "Carver".  That I think is your main problem with my post.  I have attempted to state facts in order to help people properly troubleshoot and service these products.  Nothing more.  If you have a problem with the advertising Carver had, take it up with Bob Carver himself.  There is a Carver forum in the 'States where you can contact him, and a web site too.  I have never talked to the man, just dealt with the technology.

As a matter of fact I did take it up with Bob Carver in person at a fair in Germany, but he just stuck with the marketing lines as they were printed in various folders and advertising at the time. Well... what did I expect to hear anyway ? It was a bit naive from my side to think that he would go slightly off the record for an in depth conversation on a public fair.
For what it's worth, i have no issue with your postings even if you did try to defend Carver products. But I do get nerveous if someone says things that are not entirely technically correct or complete. And that's my bad, I tend to go to the bottom with it Embarrassed.
But no more... I'm done. Feel free to comment if you have the time for it and you feel like it.
All in good humour of course Wink

Cheers - Peter


Posted By: Dom
Date Posted: 27 January 2009 at 8:31pm

Could you elaborate to someone who's not an electronic engineer why running these on mids and highs is bad?

I've got a number of PM-1.5 amps and generally use them for mids and highs...  There's nothing in the manual to suggest that you shouldn't, in fact there's a section on using them to run bi amped systems, with one channel running compression drivers.  The only warning is along the lines of "be careful when running tweeters as this is a manly beast of an amp that can put out 600w of diaphragm melting power"....
 
Cheers
 
 


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"It sounded like a million fire engines chasing ten million ambulances through a war zone and it was played at a volume that made the empty chair beside me bleed."


Posted By: anatech
Date Posted: 28 January 2009 at 3:59am
Hi Peter,
Given that I'm a brand new member, from the other side of the pond yet, I can accept that you wouldn't know where I was coming from.  Nor I, you.  I think we mostly agree on these things.

On Bob Carver, I hear he is approachable.  But in a show setting I doubt you are going to get anything but slogans.  You have no idea how much I hate the marketing lingo, probably as much as you do.

Hi Dom,
Sure thing.
These amplifiers (and some others) reduce the amount of heat generated by switching the supply voltage on the output transistors up, then back down as needed.  This also reduces other stresses on the actual transistor.  The most important being "secondary breakdown".  Just remember this allows the amplifer to be more reliable while also reducing the number of output transistors needed for the power class.

So, normally your outputs will be sitting at 35 VDC (or 42V - can not remember of the top).  When a musical peak comes along, that supply voltage may need to be on the order of 65 VDC (very approximate).  A still louder musical peak may require still higher supply voltage, that will be between 120 and 125 VDC depending on the setting the last technician adjusted it to.  Remember, a Carver amplifier regulates it's own supply voltages.  Once the supply voltage is increased, the output stage will start generating normal amounts of heat and the heat sink is not designed to dissipate all that heat energy.  Therefore it's a good thing that the supplies automatically drop back down to their idling conditions.

So, what's wrong with higher frequencies?  Well, the supply voltages are switched up and down by power transistors and some circuitry so that they "commutate" (means switching).  The lower voltage supplies are protected from these higher voltages by power diodes that only allow current out and not back in.  That's the mechanism, now for the point.  The commutation is timed to be "up" by some minimal time.  This time being held on is fine for bass frequencies, but higher frequencies can complete a ful cycle (going full positive, then negative and positive again).  The timing of this may continue to trigger the commutators up so that they never turn off.  The supply voltage no longer tracks the output waveform and is held on, or "locked up" as we would say.  Now the output section is running continuously at high voltages that it was not designed to.  The output stage is now throwing off as much heat as a "standard" amplifier, but the Carver has tiny heat sinks and not enough output transistors.  It basically cooks itself to death, or the output transistors may fail due to "second breakdown" issues.  Either way, this big, powerful amplifier dies while driving what appears to be an easy load.  You would also hear the amp "growling" inside, plus the fans would be runnign full tilt.  Those are sure signs of trouble.

The main problem is that most people don't believe these amplifiers really deliver the advertised power.  They do, they really, really do (as long as the AC supply can hold up). SO a Carver really ought to be driving bass bins, or full range speakers, where the bass frequencies allow the supply voltages to drop back to normal as they were designed to do.  If you were to see the output waveform, and the supply voltage on a dual trace oscilloscope, you would be able to see the supply voltage increasing just ahead of the music waveform, then back down again.  The supply voltage tracks the low frequency notes.  If you increase the frequency, at some point you will see that the supply voltage can not return to the lower voltage state and it always remains high.

I hope that helped a little bit Dom.  You can always "Google" the term "second breakdown".  In a nut shell, what this means is that a bipolar transistor can not deliver high current with high voltage across it.  Say a transistor is rated at 250 VDC and 16 amperes (like the Carver output transistors).  The heat dissipation rating on the part is 250 watts.  So, one would figure that any combination of voltage across the transistor, multiplied by the current would be safe unless the result exceeds 250 watts (votage X current = watts).  The problem is that hot spots develop in the transistor itself that greatly reduces the amount of dissipation (= heat energy in watts).  This is called "secod breakdown.  So, to give you an example, the Carver output transistors are good for approximately 1 ampere when there is 95 VDC across the transistor.  The part is MJ15024 and MJ15025 if you would like to look it up.  This information is read off a graph on the datasheet I'm going to try attaching.  Darn, I have to find instructions for this site.  Click http://www.onsemi.com/pub_link/Collateral/MJ15022-D.PDF - http://www.onsemi.com/pub_link/Collateral/MJ15022-D.PDF tosee this information.

-Chris


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You did what?? !


Posted By: Phil Ad
Date Posted: 23 November 2009 at 7:09pm
Hi Guys,

I have some Carver gear (C1 preamp, M1.5t power amp, TX11 tuner).  Got them when working the states some 25 years ago.  Carver kindly converted them for 240V operation and converted the tuner to work in the UK.  All for v little cost - Excellent service I should add!  While I don't use the tuner the amps get daily use and  have served me well.

Recently I have noticed a problem with sibilance that I strongly suspect originates from one of the amps.  (should know for sure this week end!) as I am getting a new AV receiver and will connect the rest of the kit to it and see if the problem goes away.  It has not suddenly started but I think has been creeping up on me for a while.  Since the rest of the kit is pretty new I suspect the amps.

Anyhow a couple of questions:
1) Does anyone know where I can get the amps serviced for a reasonable price.  They have not been worked on since leaving Carver in the US and other than a sometimes noisy volume control, and the above problem, work well.
2) I am not an engineer - could my problem with sibilance be down to something failing/wearing out in the amps.

I guess I should just retire them but I have a soft spot for them and think that, with care, they might outlast me!

Phil


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Phil


Posted By: Phil Ad
Date Posted: 23 November 2009 at 7:12pm
Hi Guys,

I have some Carver gear (C1 preamp, M1.5t power amp, TX11 tuner).  Got them when working the states some 25 years ago.  Carver kindly converted them for 240V operation and converted the tuner to work in the UK.  All for v little cost - Excellent service I should add!  While I don't use the tuner the amps get daily use and  have served me well.

Recently I have noticed a problem with sibilance that I strongly suspect originates from one of the amps.  (should know for sure this week end!) as I am getting a new AV receiver and will connect the rest of the kit to it and see if the problem goes away.  It has not suddenly started but I think has been creeping up on me for a while.  Since the rest of the kit is pretty new I suspect the amps.

Anyhow a couple of questions:
1) Does anyone know where I can get the amps serviced for a reasonable price.  They have not been worked on since leaving Carver in the US and other than a sometimes noisy volume control, and the above problem, work well.
2) I am not an engineer - could my problem with sibilance be down to something failing/wearing out in the amps.

I guess I should just retire them but I have a soft spot for them and think that, with care, they might outlast me!

Phil

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Phil


Posted By: anatech
Date Posted: 23 November 2009 at 9:16pm
Hi Phil,
There is going to be some aging effects with your equipment, so the work involved to put things right will cost some money.  At the end of the service job, you should have reliable equipment that runs at least as good as it did new.  Understand that even the amplifier will represent some hours of work to be done. 

What does this all mean?  Well, it means that returning your equipment to original operating condition is going to cost you some money.  The voltage conversion jobs you are asking about aren't too bad for labour costs, so don't judge on this (as your previous service was aimed at this).  Your problems are really an indication of a restoration project, not a repair.  The term "reasonable" will mean something entirely different to your technician than what your understanding might be.

Is this a "Carver thing"? - no.  All equipment has very similar aging issues that affect all parts.  You will have some heat and high voltage related issues as well as your supply voltages are + / - 125 VDC, for a total of 250 VDC across the supply rails.  Understand that this is considerably more than what you normally see in a consumer amplifier.  You have an extremely powerful amplifier there.

Are these worth repair?  - ahh yes.  If you don't believe me, just price out some equipment today with similar power output.  That's if you can find anything well made at that power level.  My position is that your equipment is certainly worth a complete servicing.

Quote:
1) Does anyone know where I can get the amps serviced for a reasonable price.

That question may easily lead you to a very expensive experience.  It's the wrong question to ask.  You really should be asking for a good audio service person or shop, adding that you are looking for an ex Carver warranty service person.  These are very important points to consider.

A good audio technician is going to save you money, even if his hourly rates are higher than everyone else.  I've seen this time and time again.  Less expensive shops or technicians almost never finish a job with a properly serviced and adjusted item.  So, at the very best, you do not receive the quality and performance that your stereo is capable of.  Tell me again why you bought a good stereo?    I'm thinking that the performance and quality of the equipment was your concern.  So, why throw it away by using an iffy service guy??

Now, why an ex-warranty technician for Carver?  This is because Carver products often do not work the same was other, similar equipment does.  These differences demand that the technician be aware what the differences between your equipment and something else is.  It is entirely possible for an inexperienced person (on Carver equipment) to cause catastrophic and permanent damage.  Fun to watch, not fun if the equipment was yours.  (note the past tense)  The worst thing that can happen is that your equipment is returned running (notice I didn't say fixed or repaired).  Things are off, but it makes sound.  You run the equipment for some time, a year or more, as things slowly cook inside.  By the time it finally fails, the damage is extensive and possibly permanent.

All these things can be avoided by simply using a qualified audio technician who has extensive knowledge on this product line.  BTW, Lightstar and Sunfire amps are completely different.  A technician who only knows these (I doubt the Lightstar, very few people know those) hasn't a clue how the earlier products work.

Have you noticed I keep referring to an "audio technician"?
Most technicians who service televisions and VCRs have a completely different mindset than an audio technician does.  The difference is enough to prevent a proper job being done to any audio equipment.  Over 30 years of experience has shown this to be true time and time again.  Even car audio people look at things differently than home audio.  Close, but not close enough.  You need to find a good audio technician familiar with your equipment.

So, in Canada you could have come to me, or a few other people depending on where you were.  In the 'States, your options are limited as Carver had very few external warranty locations there.  I believe the old service people have a shop in the Washington area.  Bob Carver has contact with them as well, so I highly recommend you search them out.  I'm sorry that I don't have this information at hand, or I would have given it to you.

Best, Chris


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You did what?? !


Posted By: ceharden
Date Posted: 23 November 2009 at 9:38pm
While I will not claim to be a Carver expert, I have worked on the amplifiers before and have a reasonable understanding of the way they work.

However it might be that to return the amp fully it will require someone with more extensive test equipment than I have.

I am willing to take a look and I'll reply to your email when I have a few more minutes.  Currently battling with trying to stop one of my own designs oscillating at about 2MHz!




Posted By: Guy Johnson
Date Posted: 30 December 2009 at 7:10pm
I knew a studio where they ran six PM 1.5s powering two ATC 100s. Sounded fantastic. No problems diving HF or MF drivers. I own an old Carver that was on the highs on an abused PA, and that was fine. Surely, there will be enough pauses in the signals to allow the supplies to settle down? 

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I'm Pink, therefore I'm Spam.


Posted By: studio45
Date Posted: 30 December 2009 at 7:58pm
A small live music venue near me has a PM1.5 driving 4x JBL 1" comp drivers 5k-20k, and has been for about 20 years without incident. I think perhaps the low duty cycle of this frequency range with music signals allows time for the heat to dissipate. In operation, its level meter LEDs only move at all on a particularly loud "S" from the singer.

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Studio45 - Repairs & Building Commotion Soundsystem -Mobile PA


Posted By: anatech
Date Posted: 05 May 2019 at 7:02pm
Hi Studio45,
You are just really lucky then.  If you ever drive that amp hard you'll be overheating it, which you probably are right now.

The time constant on the commutators are set for bass or full range music.  They will tend to stay locked up being used for mid-high duty.  You're lucky, that's all.  One day the cumulative effects of higher operating temperature may bite you.  Failure rates double for every 10 °C rise in operating temperature.

-Chris



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