Fisher RS-2010 service help needed!

Ok, here is the scoop, my friend at work had been telling me he had a big Fisher that he wanted to get fixed, so I offered to take a look at it. He brought it in today and it turns out its one of the better ones, RS-2010 (and take my advice here, stick to the RS-10XX series, way better built). Hate to let this thing go to waste, its in pretty decent shape.

Well whats wrong is the receiver is locked in protection. I isolated and tested the preamp board so all is OK there, problem is definately in the output stage. I am pretty sure the STKs are toast, I pulled them amp board, to get to its bottom side see if anything looked amiss, looks like the thermal grease was a little dried up and they probably burned up, was driving 4 ohm speakers when it locked up. I know a few of you have worked on this model before, what I need to know is what exactly are the voltage readings that are supposed to be coming and going to the STKs. I don't have a service manual and its pretty much guesswork. Voltage off the tranny to the amp section is good, so I am guessing that the outputs are toast. If anyone can provide me with the pin voltages for the STKs it would be great. If one or both are toast then I will get some new ones on the way and have this thing up and running asap. If anyone has a service manual and could scan me the info or whatever is most convenient that would be great. I have some free time this week to work on this stuff, so of course I would like to get this thing all wrapped up. As quickly as possible if I can.

Any help greatly appreciated and many thanks in advance, I am sure my friend would much appreciate to have this thing running again.

No manual but what is the stk #. Is it 0100 or something? The 2007 is a 0080.

STK-0080 is what they are, two of them

The 100 watt integrated amp uses the same 80 watt chip!?!

Datasheet. http://www.datadart.com/al/sanyo/Stk00.pdf

Thats what they are. Certainly dropped a lot of quality out by this stage in the game, flashier looks than the 10XX series but build quality takes a major shakedown. This unit dates to May 1980, and with the 80s so goes the quality. Gone are the insane discrete 2SB600 2SD555 outputs (two pairs per channel) in the only 125wpc RS-1060 (all 57lbs of it). Gone, all those fancy rubber shrink boots, gone, all the extra metal shielding. About the only thing that did not take a hit would be the power supply itself, still relatively large (huge torroidal tranny, bit 15000uf caps). In reality the RS-1058 is probably better built. I mean its just so flimsy, no more super thick stamped steel, seems a lot thinner here and perhaps all that weight of the tranny (this thing still weighs close to 40lbs) makes it worse. Sad as that may be its still way way heavier than any modern day stuff. I mean I can get the parts cheap enough if thats what it is, and its probably worth fixing for the price I can get them. A rough idea of what sort of voltages I should be looking for should give me enough of a clue, if they are toast I will just slap a new set in and hope for the best (hate playing these guessing games, service manuals are much easier!).

STK0080 - ECG1322


AF PO, 80 W (ECG1322), Vcc = +/- 46 V typical. 10 pin SIP-M.

Pin 1: Input +
Pin 2: Vss -
Pin 3: Output
Pin 4: NC
Pin 5: NC
Pin 6: NC
Pin 7: NC
Pin 8: Output
Pin 9: Vss +
Pin 10: Input -

yrly. I pulled my RS-2010 out and put it on my bench and made some voltage measurements for you. Pins 2 & 9 should read your main rail voltage. Pin 2 = minus 60 volts, pin 9 = plus 60 volts. To measure dc offset, connect your + vom probe to the junction of the white ceramic rectangular emitter resistors. Most STK modules should measure 10 to 30 millivolts dc offset. If the dc offset voltage at the junction of the emitter resistors is high the STK output modules are shorted or leaky. The pins of the module are a little tricky to get a vom probe on so I would use, if you have them, the little hook type clips available at Rat Shack to hook on to the module pins. I have repaired many of these Fisher receivers with the STK power modules and 9 times out of 10 if one or both channels is dead, it is always the module that is bad. The main thing is to check the dc offset. The STK-0080 module is available at MCM electronics or if you don't object to NTE a NTE-1322 will work. By the way I did a full power test on RS-2010 and it measured 128 watts per channel at 8 ohms. Not bad for a STK that is rated at 80 watts.

Bill from Indy

Thanks guys for the info, I will test it out tonight and let you know what I find, should not be too hard, I left it where I had things last night when I was taking some measurements to make sure the tranny was still OK so I should be able to do it in a snap. I have a site bookmarked that sells the modules for something in the range of $11, minimum order $25 but I am sure I can find something else I need. Keep your fingers crossed for me that thats all thats wrong here, my friend seemed pretty excited when I told him I can possibly get it running again.

Ok, here is the update. Closer inspection under some brighter light revealed one of the traces had bubbled away from the board... I went ahead and tested anyway and yep the outputs were toasted. I asked my friend what exactly had happened to it and well it turns out the outputs had been shorted by accident at full volume. Still nothing looked amiss aside form the one trace, and as I said, testing revealed the outputs were indeed shot, so I ordered the parts anyway...

Package arrived today, brand new pair of STK-0080s. I spent a good half an hour taking the other two chips out, then soldered the new ones in. I jumpered around the bad trace with a wire, got everything where it looked like it should be, double checked some stuff, put her all back together and then came the moment of truth...

Plugged it in and powered it up for normal operation, of course this is where your heart skips a beat, having just spend $30 on a pair of outputs hoping you didnt do something stupid, or overlook anything... First relay clicks (it had before, this one is for the front panel lights so this was no surprise), and then... second relay clicks. Success!!! Sounds great! Tested some stuff, all seems to check out, so its going back to its owner tomorrow, I am sure he will be happy.

And I just wanted to say thanks for getting me the info to get this job done, not always easy without a service manual. You guys are great!

Good job yrly :thmbsp: and in these models no bias or dc offset to adjust. The only other issue with this series is the indicator lamps tend to burn out. Other than that they are pretty trouble free.

Bill from Indy