Amplifier Repair help needed- Perreaux 6000b

[Quakeos]

Hi guys!

I have an old perreaux 6000b amplifier from somewhere around the 1990s and it needs a bit of love so I cleaned it as best I could without digging down too far.

The first issue = Channel A had distortion. Therefore, I took apart some of the amp and cleaned the pots. The pots run muuuch smoother,

However rookie error! I left one of the small circuit boards swinging in the breeze as I was rushing and got lazy and turned it on and that little pcb went BANG. no audio through any channels now.

The bang came from the small PCB touching the chassis. Thankfully no blown caps. SO I turned it around to find that some of the trace of copper has been blown right to shit.
So I tried to fix it with a bit of solder in place with the trace, taking care that it doesn't interact with any other traces. Now whenever I turn the amp on, it blows the main fuse.

Any idea here guys? I attached the photos below of the PCB and the solder joint. Cheers.

 

[petehall347]

can you post a pic of the other side of the board please ?

 

[Quakeos]

Thanks for the reply petehall347, here's the picture

 

[petehall347]

what number is that ic chip ? trying to figure out whats its for .
every component on that board needs testing for shorts .
do you have a schematic / service manual for the amp ?

 

[bberkom]

I’d also want to use some wire to bridge that burned trace between components and not just solder. Is that red box a relay of some kind? Maybe a protection board?

 

[petehall347]

ic might be a dual channel op amp .. can only guess without knowing what it really is .plenty of diodes to short and other semiconductors .

 

[petehall347]

did the main fuse blow the first it went bang ?

 

[Quakeos]

Cheers for the response guys... I'm currently at work and will take photos when I get back, I originally did use wires to bridge the blown out traces. The main fuse did not blow when it went bang. Perhaps its something isolated shorting it? I will try taking it apart again and seeing if there is anything funny going on. Visually on the board, it looks like nothing is gone?

Thanks guys really appreciate it

 

[petehall347]

trying to see what that board is for to see if any more damage likely . looks like it might be for bridged output switching . hard to say ...

 

[Quakeos]

This amp is a non bridgable two channel amplifier. The cables from this amp lead to the XLR inputs. There is another board on top where the pots are that has a very similar circuit with more bits and bobs for the pots and what not.
It may be an interesting design feature, and im just confused as to why it may be shorting but I think at this point the best solution will be taking it apart and seeing if there is anything funny.

 

[slimecity]

Service data for these things are very hard to come by BTW, even in New Zealand.

There are some experts on these amps but they are generally NZ-based. There are one or two that use this site....

 

[petehall347]

input board then ? i do suspect something shorted on that board whatever it does .

 

[Quakeos]

its so strange! whenever I re join the traces with wires acting like them, it pops the fuse every time! , remove the wire, and no fuse blown, along with no audio! could it be that the resistors (little tiny black ones) on that circuit board (thats where the blow was) could be shorted and causing this issue? cheers

 

[bberkom]

Those black components with silver bands are diodes, and yes it could be one of those that is bad. Anything on that board is suspect.

 

[century tek]

When it shorted and the traces blew, that's when it shorted a component instantly. Without pics and I'm just guessing here, but maybe look around the area where it went bang. It's 99 out of 100 that most likely a transistor or diode that got shorted and when you fixed the traces, it revealed itself.

 

[petehall347]

i cant find what that board does . i see a relay and unknown ic that might well help knowing its id number . having trouble seeing what cooked that trace . if it goes to a diode it should maybe be simple . if it goes to the relay it might be a different matter .. that board needs a good looking at first .

 

[Quakeos]

Where the traces blew, directly above it lies those 4 diodes. I will replace all four and hopefully have luck with it working again. Does it work so systematically that if these are fixed the amp could entirely work again? cheers

 

[century tek]

Those four diodes are probably in a bridge rectifier configuration and can be easily checked for shorts with a basic DVM or ohm meter but I wouldn't replace them just willy nilly unless you know for proof positive that one or more is bad.

Guessing usually leads to more pain and grief especially when you thought that the diodes might be the problem when in reality it could have been something else near or in the vicinity of the diodes. So you had better check them with a meter. If you don't know how, maybe post your city and see if another AK'er is close by to help you out.

 

[Quakeos]

Those four diodes are probably in a bridge rectifier configuration and can be easily checked for shorts with a basic DVM or ohm meter but I wouldn't replace them just willy nilly unless you know for proof positive that one or more is bad.

Guessing usually leads to more pain and grief especially when you thought that the diodes might be the problem when in reality it could have been something else near or in the vicinity of the diodes. So you had better check them with a meter. If you don't know how, maybe post your city and see if another AK'er is close by to help you out.

Thanks century tek. I just see the diodes as so likely being the cause of the problem as thats where it went kablamo.

 

[Quakeos]

Gents I replaced the diodes and it works!!! however still darn distortion through channel A.