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Ah yes, thanks. I planned on getting the SM. I will look there.

I bought an Akai GX-635D yesterday. These were in a bag with a disassembled reel hub. Any idea what they are? I'm doubting they're even for this unit but I want to make sure before I move on with the project.

It seems like you're serious...IPA, while being short for a delicious beer, is also short for Isopropyl Alcohol. You do not want to drink the latter.

That was it! It's working now. Thanks for all the help! There are a couple other issues. I have popping with each press of the volume and balance buttons. It gets louder as the volume goes up. Also, the low filter can't be turned off.

That has to be it. I changed out CR12, 13, 15 & 16, same result. But, the parts list I'm going by, Ser. No 2001 & Up, calls for 1N5255B 28V ZNR 5% for CR12 & CR13. The schematic I'm using looks like it uses the Ser. No. 2000 parts list which calls for 1N5241B Zener which is an 11V 1W zener...

That's a good thought but they're 28V. I have a couple extras so I will change them again as soon as I have time.

They're the same according to the silk screen. Maybe it's wrong and I could try reversing 12 & 13. Update: never mind, orientation is correct.

I replaced Q11 and that corrected its voltage and that to C55. So now, my only issue is the lack of voltage on the cathode and anode sides of CR13 and CR12, respectively. I have ~29.0V on the anode and cathode sides of CR13 and CR12, respectively, but less than a volt where I should have 16.8...

I replaced the outputs and voltage regulators and pulled R73 to check, and it measures 10kohm. I'm still getting only ~10V on the negative side. Am I relegated to checking the relays? If so, how should I go about doing that?

I got the parts list from the service manual on hifi engine, the schematic there is unreadable. There are two parts lists in the service manual, one labeled 2000, the other labeled 2001 & up. My unit is a combination of the two but 98% of the parts on mine match up with the 2001 & up list...

R72 & R73 are 10kohm

R72 gives me 10Kohm in circuit. Does that indicate R73 is toast?

R73 (10Kohm), in circuit, starts at about 11.5 Kohm and goes up to a little over 12 Kohm. C53 on mine is 2200 pFf. C34 and C134, C21 and C121 are 470uF. I have extras I can install. Before I disassemble to gain access to the foil side of the board to confirm R73, among other things, is there...

I'm getting 33.9V at the collector of Q8, 28.4V at the emitter

Thanks for that schematic. The collector of q9 measures only -10V. The other three transistors in question are ok. Would this cause no output? How do I check the relays? Would low voltage to a relay prevent it from switching properly?

I picked up an SAE P101 Preamp at a thrift shop. It was in horrible shape as it had gotten wet at some point in its life - leads were rusted, caps were shrunken looking. Long story short, I replaced every capacitor and some resistors, diodes and transistors that were destroyed or rusty. Unit...

Yes, should have mentioned that - the popping from the volume knob is gone. Also, no clicking from the filter switches, sort of. I got a very light click on the first movement up and/or down of the filter switches but then no clicks for any subsequent movements. After letting it sit for a...

Today I went in and changed R41, R42, C15 & C16 on the control board. And while I was in there I changed the tantalums (C13 - C20) on the Switch board. She's all buttoned back up and making sweet music again. I intended on getting good pictures of the Switch board since I didn't the...

There's a few threads here on AK too. here's one.

One thing I noticed is that when adjusting volume there is a very light pop at each gradation or step of the knob. any ideas? Another thing, I realized that the crappy rebuild kit I bought didn't include replacements for the tantalums on the switch board. Anything I should keep an ear out for...

Reassembly, rechecking voltages, offset and bias, was all that was left. Once that trimmer (VR1 on 070) was replaced and everything was dialed in, I was done. Yesterday evening I put her all back together and experienced audio nirvana. I love this amp and I'm so glad I got up the courage to...

The next two boards are where things get hairy. Disassembly makes it look like the amp puked its guts... I started with the Control Amp board (AWG-031) which wasn't bad. After gently moving everything forward I had good access. The last board I did was the Switch Circuit board...

On to the Protection Circuit. This one was not fun as it required soldering and desoldering in a tight space. But, all went well.

Next was the smaller Power Supply board (AWR-0770). Easy Peasy...

My next board was the Power Amp board (AWH-037). No issues here. Before and after pics... I was nice to have easy access to this board. I propped the chassis on a 2x4 and used clamps to support the board for easy access to the foil side.