• The move to the new server is done. There are some software and database maintenance updates in process. This has us passing the hat around to help out. We appreciate any donations. Seriously, even a dollar helps. The payment page may be found here - https://www.audiokarma.org/support.html

SA-9800 Re-Work Begins

Brent/Mark,
Information here is great!! Just ordered all the parts discussed here for my SA9800 that I purchased in 1980 with the TX9800 which I just completed overhauling.

Thanks for all your help!!
Chris
 

Attachments

  • SA9800_Before1.jpg
    SA9800_Before1.jpg
    47.6 KB · Views: 137
  • TX9800_Done.jpg
    TX9800_Done.jpg
    51.3 KB · Views: 132
Got the DC Offset and the Bias on both L and R sides adjusted to 70mv. Now to clean her up inside a bit more and tidy up the wiring and the rebuild (Internally at least) will be complete. Then it is on to the faceplate and new solid oak case build.:banana:
 
Just thought I would post a few pictures of where the internal work sits as of today. I also went ahead and replaced the output transistors with On-Semi MJL3281 and MJL1302. As you can see in the photos, there was quite a bit of modification done to make this work. I was going to go with the "Phoenix" type connectors, but opted against it and went with direct soldering straight from the Amp boards. It turned out well.

Other than this mod, it went well and pretty smooth. The amp sounds really nice and smooth.

Also, to help out fellow AK'rs, I am going to post some of MY voltages below so if anyone might want to take a look at what I have as references for a working unit, they will be memorialized here in one single post. If 2 voltages are shown, the first voltage is the "expected" voltage and the one to the right of that is my actual voltage. Just keep in mind that these are not gospel, but to simply give a reference as I know there are quite a few people working on SA-9800 amps watching this thread, and hopefully in the future this might help others out as well. Also keep in mind that the voltage reading may have fluctuated a bit as the unit continued to warm up as the voltages were taken, hence a bit higher readings on the Power Amp Left board as compared to the Right side.

AWR-194 (Power Supply Assy)
pins 1&2: -52v regulated, -52v
pins 3&4: +52v regulated, +52v
pins 5&6: +32v regulated, +32v
pin 7: +18v regulated, +18v (provides power for display circuit)
pin 8: 0v, ground
pin 9: -50v, raw, unregulated
pins 10&11: -32v regulated, -32v
pin 12: +49v unregulated raw
pin 13: +69v unregulated raw
pin 14: 0v, ground
pin 15: -70v unregulated raw
pin 16: +6.7vac, this is an AC voltage
pin 17: +53.4vac, this is an AC voltage
pin 18: +53.7vac, this is an AC voltage

GWH-130 Power Amp (Right)
pin 3 +52v: +52v
pin 4 -52v: -52v
pin 7 -50 to -55v: -55v
pin 15 +50 to +55v: +55v
Voltages driving the transistors:
pin 8 -0.592v
pin 14 +0.601v
pin 11 0v: 0v
The emitter voltages:
pin 9: -34.0mv
pin 10: -34.8mv
pin 12: +33.1mv
pin 13: +32.4mv
Idle current measured between pins 18(+) and 20(-): +70.0mv (Thanks to the new single-turn Bourns pot)

GWH-129 Power Amp (Left)
pin 34 +52v: +52v
pin 33 -52v: -52v
pin 30 -50 to -55v: -55v
pin 22 +50 to +55v: +55v
Voltages driving the transistors:
pin 23 +0.592v
pin 29 -0.583v
pin 26 0v: 0v
The emitter voltages:
pin 24: +36.2mv
pin 25: +35.2mv
pin 27: -34.0mv
pin 28: -33.2mv
Idle current measured between pins 39(+) to pin 37(-): +70.0mv (Thanks to the new single-turn Bourns pot)

Rectifier board:
pin 16: +55v
pin 17: -55v
pin 13: -55v
pin 14 : +55v
 

Attachments

  • DSC00009.jpg
    DSC00009.jpg
    93.5 KB · Views: 206
  • DSC00008.jpg
    DSC00008.jpg
    77.6 KB · Views: 223
  • DSC00006.jpg
    DSC00006.jpg
    128.8 KB · Views: 198
  • DSC00001.jpg
    DSC00001.jpg
    124 KB · Views: 212
Last edited:
Brent,
Was there a specific reason you changed out the output transistors? What where the part numbers did you replaced them with?

Thanks
Chris
 
Last bit of work before calling it done inside. I went ahead and did the additional adjustments on the amp. They are the Output Power Indicator Calibration (Meters), the Preamplifier (MC Amplifier and EQ Amplifier) adjustments. The meters were really close to the 10w reading with a 1k
test tone at 8.9v at the speaker outputs. It's all tuned up as best I can possibly do. Although I will likely not use it with a Turntable, it is set if I do choose to. And I know the meters are reading accurately for the wattage output as well. All good.
 
Nice. I hate to sound dumb but what are the replacement caps you used for the 4 main caps. Perhaps you already posted it but i'm just not seeing it.
 
cmitchell03 said:
Brent,
Was there a specific reason you changed out the output transistors? What where the part numbers did you replaced them with?

Thanks
Chris
Click to expand...

See post #65 for info. I changed them due to believing (even though they tested good with the 6-way diode test out of circuit) that they might have potential unforeseen issues. Not sure if they did/do, but figured it would be best to replace them with newer well-respected transistors. Partly because I wanted to experiment a bit, and partly because I wanted to have some robust transistors for outputs in place.
 
Not sure I will get off so easy on the main caps for the next rework project, my M-25. But have time, as I have significant cosmetic work to do on this 9800 yet. Case and faceplate.
 
And the case rework begins... Got the wood (solid Maple) and made some cuts this morning. This case will be MUCH easier, upon further assessment, than either the SX-3900 or the SA-9100 cases I built. It's going to look nice when done. I hate the original wood/cases that Pioneer put on these fine machines. One word describes it... Cheap. No hurry because the faceplate is still being sanded/polished out and needs to go to etching yet at some point.
 

Attachments

  • DSC00007.jpg
    DSC00007.jpg
    61.9 KB · Views: 120
  • DSC00016.jpg
    DSC00016.jpg
    66.8 KB · Views: 120
  • DSC00017.jpg
    DSC00017.jpg
    68.2 KB · Views: 126
And a couple more photos of the sides and top all cut and sanded, ready for the next steps... drilling, spacer block installation, assembly and finishing. The second photo shows the routered inside portion of the top piece, which gives clearance for the faceplate upper bracket and screws.
 

Attachments

  • DSC00001.jpg
    DSC00001.jpg
    68.1 KB · Views: 112
  • DSC00002.jpg
    DSC00002.jpg
    61.8 KB · Views: 94
royf said:
very cool. Are you going to use the same grill piece??
Click to expand...

I am. But, it has a scratch on the back portion of it about 2" long and it is bugging me. Otherwise the grill looks clean. I might strip it and prime and re-paint it first. I did that on both the SX-3900 and SA-9100 and used that automotive enamel texture heat resistant paint (EDIT: Rustoleum Hammered spray paint - Black). Came out nice.

I usually don't half-ass things and likely will re-paint this one too, as the rest of it will look pretty top-shelf when done. I sure know the amp sings nicely. Played it all evening (about 6 hours) Saturday night pushed pretty well through a pair of JBLs and it sounded great.
 
Last edited:
You must log in or register to reply here.
Back
Top Bottom