Speakerplans.com Homepage
Forum Home Forum Home > General > Amp Forum
  New Posts New Posts RSS Feed - Carver PM1.5 developed a buzz
  FAQ FAQ  Forum Search   Events   Register Register  Login Login

Carver PM1.5 developed a buzz
 Post Reply Post Reply Page  12>
Author
Message
  Topic Search Topic Search  Topic Options Topic Options
slabraider View Drop Down
New Member
New Member


Joined: 12 January 2012
Location: Nottingham
Status: Offline
Points: 7 		Post Options Post Options   Thanks (0) Thanks(0)   Quote slabraider Quote  Post ReplyReply Direct Link To This Post Topic: Carver PM1.5 developed a buzz
    Posted: 23 February 2012 at 2:25am
Hi

I have just removed one of my 3 Carver pm1.5 from a rack where it has be used for powering a pair of highbass/lowmid drivers. I have set this amp up at home (after removing the fan) to power my in house system as it is no longer needed for my PA system.

Anyway, to get to the point. Now I have connected it to my full range speakers I notice it has developed a subtle but intolerable high frequency buzz. If it helps I have also notice the pitch and gain of the buzz alters when it switches to it's second power rail?

Does anyone have any suggestions what I should test first or have any advice where to start? I must admit these amps confuse me a bit, like nothing I have seen inside

Cheers
Back to Top
BUZguy View Drop Down
Registered User
Registered User


Joined: 17 November 2011
Location: South Wales
Status: Offline
Points: 323 		Post Options Post Options   Thanks (0) Thanks(0)   Quote BUZguy Quote  Post ReplyReply Direct Link To This Post Posted: 23 February 2012 at 8:31am
first thing I would check is the ground lift switch if it has one. there may be different earthing on your home system. Beware of removing fans. even if the amp is run at low volume there may be other parts of the circuit that require a steady flow of cool air.

Edited by BUZguy - 23 February 2012 at 8:33am
Back to Top
service dept Steve View Drop Down
Registered User
Registered User
Avatar

Joined: 30 January 2010
Location: S.W.London
Status: Offline
Points: 1452 		Post Options Post Options   Thanks (0) Thanks(0)   Quote service dept Steve Quote  Post ReplyReply Direct Link To This Post Posted: 23 February 2012 at 9:04am
Ah, Carver pm1.5. DO NOT BLOW IT UP OR IT WILL BE A BIN JOB
Is the noise mechanical (ie: does it come from the case) The smpsu on these amps work at a very low, AF, frequency and use a conventional, laminated transformer for the job. As the transformer rattles at 1khz it is mounted on a tray which is isolated from the box by rubber standoffs which perish allowing the tray to contact the housing.
If it comes from the speakers you may have an earth loop as mentioned earlier or the power supply capacitors may need to be changed or upgraded.
As mentioned before: do not blow this amp up as some parts are VERY obsolete indeed.
We are not "they", We are "the others" - http://www.servicedept.co.uk -
Back to Top
jbl_man View Drop Down
Moderator Group
Moderator Group
Avatar

Joined: 12 January 2005
Location: London.
Status: Offline
Points: 6685 		Post Options Post Options   Thanks (0) Thanks(0)   Quote jbl_man Quote  Post ReplyReply Direct Link To This Post Posted: 23 February 2012 at 9:11am
These are mid to late 80's Steve? So knocking on 25 years old now.
Be seeing you.
Back to Top
service dept Steve View Drop Down
Registered User
Registered User
Avatar

Joined: 30 January 2010
Location: S.W.London
Status: Offline
Points: 1452 		Post Options Post Options   Thanks (0) Thanks(0)   Quote service dept Steve Quote  Post ReplyReply Direct Link To This Post Posted: 23 February 2012 at 9:23am
Got to be that sort of age I would think, I have got one in "deep storage" - I managed to track down a supplier of "Transistors" for the power supply but they were fake and I have never since found a source since. One day I will redesign the supply to take a different device. Ed, who shares my unit, uses one every day to power his radio.
It was good tech, badly done. It was pretty much everything that was wrong with switched mode power supplies, pioneering stuff though.
We are not "they", We are "the others" - http://www.servicedept.co.uk -
Back to Top
Centauri View Drop Down
Registered User
Registered User
Avatar

Joined: 29 November 2004
Location: Australia
Status: Offline
Points: 1398 		Post Options Post Options   Thanks (0) Thanks(0)   Quote Centauri Quote  Post ReplyReply Direct Link To This Post Posted: 23 February 2012 at 9:41am
Originally posted by service dept Steve service dept Steve wrote:

I managed to track down a supplier of "Transistors" for the power supply but they were fake and I have never since found a source since.

I managed to get a couple of the MJ10023s through Farnell recently - think they came from their US outlet.

Originally posted by service dept Steve service dept Steve wrote:

It was pretty much everything that was wrong with switched mode power supplies, pioneering stuff though.

Especially the layout (or lack of..) - prick of a thing to work on....
Back to Top
service dept Steve View Drop Down
Registered User
Registered User
Avatar

Joined: 30 January 2010
Location: S.W.London
Status: Offline
Points: 1452 		Post Options Post Options   Thanks (0) Thanks(0)   Quote service dept Steve Quote  Post ReplyReply Direct Link To This Post Posted: 23 February 2012 at 9:50am
Oddly the amp section was fine, loads of room, nice logical layout, the power supply had obviously been the subject of many design changes as it was jammed in a little box in one end and had so many little bits of wire everywhere, looked like an Italian had been sick in it, then came the bits of card stuck here and there.
The very last source to dry up was Farnell, over here that was years ago though. Thanks for the tip though. There could be a stash somewhere I suppose but in the meantime I recommend to everyone not to damage these amps.
We are not "they", We are "the others" - http://www.servicedept.co.uk -
Back to Top
MessyM2k8 View Drop Down
Registered User
Registered User
Avatar

Joined: 29 October 2008
Location: Norwich
Status: Offline
Points: 387 		Post Options Post Options   Thanks (0) Thanks(0)   Quote MessyM2k8 Quote  Post ReplyReply Direct Link To This Post Posted: 23 February 2012 at 10:29am
http://uk.mouser.com/ProductDetail/NTE/MJ10023/?qs=yvBPN8423pUwH95S2Bu3qQ%3d%3d

349 in stock......
Back to Top
slabraider View Drop Down
New Member
New Member


Joined: 12 January 2012
Location: Nottingham
Status: Offline
Points: 7 		Post Options Post Options   Thanks (0) Thanks(0)   Quote slabraider Quote  Post ReplyReply Direct Link To This Post Posted: 23 February 2012 at 10:51am
Originally posted by BUZguy BUZguy wrote:

first thing I would check is the ground lift switch if it has one. there may be different earthing on your home system. Beware of removing fans. even if the amp is run at low volume there may be other parts of the circuit that require a steady flow of cool air.

It suggests to remove the fan in the original manual if it is to be used in a home installation so I have taken it out and monitoring the heat. 

Any tips on investigating a possible earth fault in one of these?

Thanks
Back to Top
service dept Steve View Drop Down
Registered User
Registered User
Avatar

Joined: 30 January 2010
Location: S.W.London
Status: Offline
Points: 1452 		Post Options Post Options   Thanks (0) Thanks(0)   Quote service dept Steve Quote  Post ReplyReply Direct Link To This Post Posted: 23 February 2012 at 10:53am
Originally posted by MessyM2k8 MessyM2k8 wrote:

http://uk.mouser.com/ProductDetail/NTE/MJ10023/?qs=yvBPN8423pUwH95S2Bu3qQ%3d%3d

349 in stock......


Unfortunately mj10023 isn't the correct part, it is a close-ish substitute, current is ok but is very close to max on voltage, it's the mj10025 that is the correct part. There should be some out there but there are so many fakes and at the end of the day you have a not very highly regarded amplifier for your trouble.
We are not "they", We are "the others" - http://www.servicedept.co.uk -
Back to Top
slabraider View Drop Down
New Member
New Member


Joined: 12 January 2012
Location: Nottingham
Status: Offline
Points: 7 		Post Options Post Options   Thanks (0) Thanks(0)   Quote slabraider Quote  Post ReplyReply Direct Link To This Post Posted: 23 February 2012 at 10:56am
Originally posted by Is the noise mechanical (ie: does it come from the case) <br> [/QUOTE Is the noise mechanical (ie: does it come from the case) 
[/QUOTE wrote:


Sorry I wasn't clear. The buzz is coming fr

Sorry I wasn't clear. The buzz is coming from the speakers the amp itself runs silently.

I have 3 of these and I do treat them with great care as they are sooo irreplaceable. I am always on the look out and poised to buy more but you don't see many now :-( 
Back to Top
slabraider View Drop Down
New Member
New Member


Joined: 12 January 2012
Location: Nottingham
Status: Offline
Points: 7 		Post Options Post Options   Thanks (0) Thanks(0)   Quote slabraider Quote  Post ReplyReply Direct Link To This Post Posted: 23 February 2012 at 11:01am
Originally posted by <br>Especially the layout (or lack of..) - prick of a thing to work on....<br>[/QUOTE
Especially the layout (or lack of..) - prick of a thing to work on....
[/QUOTE wrote:


Looks like they just tipped the ingredients for an amp in the b

Looks like they just tipped the ingredients for an amp in the box, shook it and closed the lid.
Back to Top
 Post Reply Post Reply Page  12>
  Share Topic   

Forum Jump Forum Permissions View Drop Down

Forum Software by Web Wiz Forums® version 10.11
Copyright ©2001-2012 Web Wiz Ltd.

This page was generated in 0.093 seconds.