Quote:
Originally Posted by paulsherwin
I suspect you will find multiple transistor failures. DC coupled transistor amps like these are notorious for cascading component failure when something goes bang, and are difficult to fix. If you want to repair it I would identify cheap alternatives for the transistors and change *all* of them - it sounds drastic, but needn't cost a lot.
Alternatively, if originality isn't important then you could replace one or both power amps with cheap IC modules. These are available for a pound or two from Chinese eBay sellers.
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Thanks for your reply.
Multiple transistor failure was what I was worried about. I am happy playing around and trying to get it sorted, replacing the power amps is a good last resort though. I'll see how frustrated I get with it!
On replacing the transistors, do you have any tips on finding the modern equivalents? The first number below is the service manual part id, the second is the part number on the transistor. I have had a go at finding a replacement for each.
AF Amp: AF20, ME4102 - 2N5088 modern alternative?
AF Amp: AF22, ME0412 - 2N5087?
Driver: AF21, ME0404-2 - 2N2907A?
Driver: AF23, ME6002 - 2N2907A?
Output: OP8B, BRC 5296 - 2N5296?
Output: OP8A, BRC 6109 - 2N6109?
Two transistors (shown to the left of TR29 on the schematic) aren't listed in the service manual as transistors, but are labelled W11/W13 on the PCB and D11/13 in the services manual, with part number C1129 printed on them. I'm assuming that these are 2SC1129 transistors.
This website suggests that the BF959 are replacements for the C1129, but they seem to be fairly different in spec. I can always try to find 2SC1129 or 28 too.
Finally - do you happen to know what this type of speaker connector is called? I have attached a pic.
Thanks again.