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Pioneer SA-9800 restoration and upgrade

Haven't touched this since November 2015. The work I do for other people, and other projects of my own always seem to put this on the back burner.

Lee.
 
Tried looking at this again last night. These amps are a real PITA to get apart, you have to take everything apart to get to stuff. I pulled the tone board and filter board looking for dry joints or incorrectly installed components. I spotted a couple of dry joints on the ribbon cable leading from the tone board to the filter board, and I have that good feeling you get when you take a break from a project and think you've found the problem. Put it all back together, it still has the same slight hum in the left channel that goes away somewhat when you switch the tone controls on. Dead silence from the speakers when I pulled the pre/power jumper, so the problem is in the preamp.
 
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Swapped over a tone control board and the display board from a parts SA-9800 I've had almost as long as this one. Success! It seems to be working now with no strange hums from the preamp. The question is, do I recap the replacement boards or leave them as-is? The new display board is a lot brighter than the other one, I was almost going to go down the road of using the additional regulator supply as posted in some other threads.

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You're having strange hum on the pre amp? Have you checked the regulated voltages to the pre amp section are correct?
 
Phew!

I almost thought I blew a channel just then. I was driving my metal coned Advent/Dayton Frankenspeakers with the 100w light peaking on the meters. It just turned out the tape monitor switch needs a little DeOxit.

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Uh oh!

I was playing this tonight, and I heard some crackling from downstairs. I thought it was the tape monitor or source switch that needed a little more DeOxit treatment, usually the right channel drops out. But when I came upstairs, it was the left channel. Turning the volume up a little bit to see if I could play through it, I could see the woofer almost going in and then not coming back out.

Time for a little more investigation methinks.
 
The same thing happened tonight, only this time I was ready. It appears to be thermal, it takes about 30 mins to an 1 hour (wasn't really timing it) until the problem manifests itself.

With the speakers on the A terminals and the scope on B, I could swap between looking at the waveform with no load, and with the speaker load.

30Hz test tone without the speakers connected.

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30Hz test tone with the speakers connected.

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60Hz test tone without the speakers connected.

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60Hz test tone with the speakers connected.

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1KHz test tone without the speakers connected.

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1KHz test tone with the speakers connected.

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Music with speakers connected. Notice how the left channel waveform looks weird.

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I tried swapping the speaker cables from one speaker to the other. I also tried swapping the scope cables, and also the connections at the amp. It's the left channel, and switching between normal and reverse doesn't change, so that sort of rules out the preamp.

Lee.
 
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I played it last night, and it seemed to sound fine again. Longer and louder, go figure.

Lee.
 
Hello guys, I was playing my pioneer SA-9800 and I heard when the relay click, and it just stop playing. I opened it up and check the fuses, and they're okay: I used a dim bulb tester and power it up.

The bulb on the tester didn't shine, so I know it's not shorting, the fluorescent display is shining but no output, which means the relay is closed. Does anyone have any idea what it might be? And how do I drain those big capacitors?

I’m looking for a schematic diagram to locate the problem, I can’t seem to find a clear one, any recommendation?

Thank you

Laurence.
 
Samsonk1d1 said:
Hello guys, I was playing my pioneer SA-9800 and I heard when the relay click, and it just stop playing. I opened it up and check the fuses, and they're okay: I used a dim bulb tester and power it up.

The bulb on the tester didn't shine, so I know it's not shorting, the fluorescent display is shining but no output, which means the relay is closed. Does anyone have any idea what it might be? And how do I drain those big capacitors?

I’m looking for a schematic diagram to locate the problem, I can’t seem to find a clear one, any recommendation?

Thank you

Laurence.
Click to expand...

You will get more feedback if you start your own thread on this. Some people consider this thread highjacking to post on other people's threads. Personally, I don't really care.
 
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