Help with a cheapish amp

[symon]

Hello folks,

I have Goodmans integrated amp which I would like to give to my stepson as part of his first separates system. But, one channel isn't working. I've taken the cover off, looked in and realised I have no clue as to what I am looking at. I was hoping something obvious would be wrong. But, not so.

So, does this sound like a fixable problem. If so, how do I fix it?

Just for added info, I attached 2 speakers, one worked, one didn't. So, I swapped the speakers round, with the same result - one channel gave out nothing.

I'd really like to be able to fix this if it is feasible, so any help would be much appreciated.

Thanks
Peter

[Tolstoi]

Hi Peter,
first thing to do is to look for any blown switches as far as you can make out any inside. Once had that with a Rotel amp.

Cheers

Joerg

[symon]

Thanks for the reply. I had a look and couldn't see anything that looked damaged or not as it should be. To be honest, that was what I was expecting to see.

[Tom472]

Well if one channel works and the other doesn't, the power supply is probably ok. Does it have output transistors/MOSFETS or is it a monolithic IC... i.e. what's attached to the heatsink (big piece of finned aluminium or the metal case), one big black rectangle or 4 or so three legged devices? (not sure I've explained that very well but hopefully you get my meaning)

If it has multiple output transistors, one or two of them could be blown, or perhaps a resistor somewhere in the output stage (this would be visibly blackened). This is very common if the amp has been worked hard (particularly in hot environments).

Tom

[symon]

If I remember right, one big black rectangle. I can look at that again this evening. I don't remember seeing anything blackened. But I will look again.
I suspect, in the end, I will take a trip to Cash Converters and get another amp.

[DSJR]

Due to my advancing age, I thought by Goodmans you meant the 1960's Maxamp............. Oh dear.......;)

Try to find a vintage Rotel 820 series on ebay. The BX varients had been designed more for European tastes and sounded much clearer and more neutral than their gadget laden seventies predecessors - less audible crossover distortion as well....

The Creek 4040 is still cheap enough and later ones very reliable andthe NAD3020/a/b is a stunning old bargain. The biggest bargain of them all for me though (unless them pinko fishies have 'ad 'em all) is the A&R A60. Even early ones are good, tweakable and the only thing that killed it off was its retail price compared to the competition by Rotel and Creek at the time).

[Tom472]

Yeh could be one of those faults you chase around forever, so maybe not worth the time any effort as there's plenty of good cheap stuff out there. I'm glad to try and help further if you're up for the repair challenge though.
Cheers
Tom

[symon]

I think what I might do is use it as a training/learning thing for me. I know pretty much nothing about the insides of stuff. So, having a broken thing to look at and fiddle with seems a good place to start.

Having had a look at e-bay it looks like I can get a good enough starter amp for cheap - a Cambridge Audio amp will probably be the sort of thing I get.

[greenhomeelectronics]

first check the obvious - is the balance control set to the middle position??
If it's an older amp there is a good chance that each channel will be seperately fused, check all fuses for continuity.
Also give all the controls a really good work out, including the selector switch, you would be surprised how many amps get thrown away when all they need is a squirt of contact cleaner.
Best of luck,
Dave.