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Amcrons - Dilemma

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ceharden View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote ceharden Quote  Post ReplyReply Direct Link To This Post Posted: 22 November 2023 at 11:48pm
Can't offer any good advice I'm afraid, haven't worked on a Macrotech for a long time and always found them a bit of a tricky customer.  Mainly because the grounded bridge topology means that it's sometimes hard to know what to use as a reference because 'ground' moves in the opposite direction to the output.  When you're chasing offsets, it can be hard to know which side of the bridge the fault is on.

Have you got one good channel and one faulty one?  If so, have you tried swapping parts between the two to see if the fault follows rather than doing a blanket replacement?

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Post Options Post Options   Thanks (0) Thanks(0)   Quote ChrisWard Quote  Post ReplyReply Direct Link To This Post Posted: 23 November 2023 at 8:36am
Originally posted by shaun1264 shaun1264 wrote:

If you going for replace the drivers and outputs.  They have to be matched VBE and Hfe 
Yes thank you, do you know the range or tolerance they should be Matched

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Post Options Post Options   Thanks (0) Thanks(0)   Quote ChrisWard Quote  Post ReplyReply Direct Link To This Post Posted: 23 November 2023 at 8:40am
I think its the Output Board.....as I have checked and replaced obvious culprits on the main board...but when i pull the pre-drivers out I can validate 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote ChrisWard Quote  Post ReplyReply Direct Link To This Post Posted: 23 November 2023 at 8:48am
I have a good side, and I've been using that as a reference, I also have another 601 that has a bad channel, but I also have 3 others (601, 1201, 2401) so I don't mind having spares as some components seem to be going obsolete.

I pulled the Output Resistors off to allow the DC Fault protect to keep the power on for longer, before it was cycling on/off and it was hard to get any readings...it seems to be the high side that is causing the problem.

The 601's are used in the high to top range in a so they have only ever had >1khz loads at 16 ohms  for their entire life..
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Post Options Post Options   Thanks (0) Thanks(0)   Quote ChrisWard Quote  Post ReplyReply Direct Link To This Post Posted: 29 November 2023 at 7:58am
Hi Guys.....so good news last night I found the main issue, it was a broken PCB track in the Voltage Translator section on the Main board...I was checking every component after reading some guy had wasted hours on a shorted cap....

I had also replaced 4 x 1N4148, the track was right next to a solder pad so even zooming in with a camera you can only just see it....I found it by tracking the Ch1 feedback route to the Voltage Translator with a DVM

It's producing a good output on the scope now, I still have a bright IOC led that needs resolving....

Good news is that I'm pretty clear on the function of most of this amp now, having studied the schematic for so long, also learnt some ways to isolate and bypass's functions, which is going to help me with amp no 2 another 601



Edited by ChrisWard - 29 November 2023 at 8:16am
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Post Options Post Options   Thanks (0) Thanks(0)   Quote ChrisWard Quote  Post ReplyReply Direct Link To This Post Posted: 30 November 2023 at 7:22am
Sorted the IOC issue being on constantly....this was C501 on the display board small 0.47 cap in the comparator feedback loop, its strange as it measured fine but clearly defective
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Post Options Post Options   Thanks (0) Thanks(0)   Quote ChrisWard Quote  Post ReplyReply Direct Link To This Post Posted: 21 December 2023 at 2:01pm
My 2nd MA601 had an issue with the Power Relay board next to the fan the Mains connector had a dry joint and the relay looked a bit tired to fixed and replaced the item
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Post Options Post Options   Thanks (0) Thanks(0)   Quote EmPro Quote  Post ReplyReply Direct Link To This Post Posted: 25 December 2023 at 10:56pm
I have 12 Crown Macro/Micro Tech's starting with 600 and finishing with 2400,remember this,when you want to fix an amplifier (in this case MT's) first time you clean it,second time you check the expensive parts to be fine (mostly the output devices) and then you start to restore all the solderings from A to Z in both outputs boards (the driver board is double soldered so don't bother) after you restore all the soldering you move to connectors,check them,clean them,restore the solderings as well and apply glue betwin them and board (so the presure of the flex cable won't push anymore in the solderings) after that move to the +-15vcc supply for driver board,you have there two voltage regulators one for negative and one for positive also check and remake the solderings,after all this you power on the amp and check the suppy voltages and odep voltages as well according to heatsinks temperature,and only now you can start to troubleshot the fault,when you are sure that all the parts from the boards are in good contact.

Edited by EmPro - 25 December 2023 at 11:02pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote EmPro Quote  Post ReplyReply Direct Link To This Post Posted: 25 December 2023 at 11:07pm
I had faulty reservoir caps,blown odep led,open wide CMR resistor,open wide potts,and blown output (just one),but cold solderings??? thousands of them so far,so that is the nr1 reason why an amp like MT is falling,after fixing all the issues and restore all the solderings never had any sort of faults again :) people keep fail to understand that old amplifiers 10+ years old require a lot of attention to solderings...and MT's are 25+ years old...so.....not to mention the thermal compound that is turning into dust after those years and leaves the outputs floating on the heatsinks....

Edited by EmPro - 25 December 2023 at 11:13pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote EmPro Quote  Post ReplyReply Direct Link To This Post Posted: 25 December 2023 at 11:22pm
I found MacroTech's and MicroTech's the best amplifiers that Crown ever made,thanks to Gerald Stanley the designer of Ground Bridge topolgy,once you have fully and proper restored one of these amps will run 2R stereo mode all day and night with no signs of getting tired Clap or bridged in 4R,these tasks kills most of the amplifiers made nowdays...they don't stand a chance.
Btw,don't use any of these amplifiers for mid-high demands,you just loose your time and not performing,the best performance you get when are used to drive low's and mid-low's!


Edited by EmPro - 26 December 2023 at 12:36pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Wikl109 Quote  Post ReplyReply Direct Link To This Post Posted: 26 December 2023 at 12:29pm
Geralt?
Cheers, Chris.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote EmPro Quote  Post ReplyReply Direct Link To This Post Posted: 26 December 2023 at 12:37pm
Originally posted by Wikl109 Wikl109 wrote:

Geralt?

Yep,saw it now LOL fix it
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