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Pioneer SA-7800 recap with pics

leesonic

leesonic

Captured on security camera...
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Here are some pictures of the Pioneer SA-7800 I just recapped.

The phono stage wasn't working, so I replaced the six transistors as well. Wish I could find some suitable heatsinks for the TO126 transistors, I tried two different kinds from Radio Shack, too big. I even bought a length of 3/4" square U-shaped aluminum channel from a hardware store, but haven't tried it yet.

Phono board before.

SA7800recap01.jpg


Phono board after.

SA7800recap02.jpg



I guess "audio grade" KWs were probably overkill for the display board, but I had my Mouser search set to filter only KWs when I ordered these. The trimmers I replaced with Bourns single turn, and mounted them on the other side of the board as they weren't bottom adjust.

Display board before.

SA7800recap03.jpg


Display board after.

SA7800recap04.jpg



Tone control board used all bipolar caps, so I replaced these with Nichicon Muse ES.

Tone control board before.

SA7800recap05.jpg


Tone control board after.

SA7800recap06.jpg



Surprising lack of electrolytics on the power amp board, so much so I forgot to take a picture "after". UPDATE : Just added an after pic, showing the Bourns multi-turn trimmers.

Power amp board before.

SA7800recap07.jpg


Power amp board after.

SA7800recap08.jpg


Power supply caps were replaced with Nichicon KG Gold Tune. I had to drill the board for the slightly smaller lead spacing.

Power supply before.

SA7800recap09.jpg


Power supply after.

SA7800recap10.jpg


Lee.
 
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Very nice and I must commend you on your workmanship. It is much more professional and neater than the factory assembly. Original caps, whilst no doubt electrically mounted OK were just all over the place.

Good on 'ya Mate!
 
kvflyer said:
Very nice and I must commend you on your workmanship. It is much more professional and neater than the factory assembly. Original caps, whilst no doubt electrically mounted OK were just all over the place.
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Thanks for your compliments. I wonder that sometimes when I open up a piece of vintage equipment, why they didn't take a little more care in placing the components? Maybe they had a quota to meet? I'd sure like to go back in time to Japan and watch some of these things being made...

Lee.
 
leesonic said:
Thanks for your compliments. I wonder that sometimes when I open up a piece of vintage equipment, why they didn't take a little more care in placing the components? Maybe they had a quota to meet? I'd sure like to go back in time to Japan and watch some of these things being made...

Lee.
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That would be China these days.... It's amazing what little kids can do with a soldering iron...

That's some really nice work on a beautiful amp!
 
Hi Lee, beautiful recap job! I'm also planning on doing a recap for my SA7800 (since he quit giving sound last week).

In the power supply, isn't it a problem that you replaced the 8000uF caps with 8200uF caps? If not, how comes they work fine too? Or would you suggest the correct value is always the best option?

Thanks!
 
BEAUTIFUL! Those Pioneer amps are REAL lookers! NICE.......and great photos too.

What kind of main outputs are in that unit?
 
I've not been here for a couple of years and still this all intrigues and delights me. The front panel on yours looks lovely too, mine has a few ugly scratches on it :(

I currently own two SA-7800, my friend borrowed one and thats supposedly making horrible popping sounds whilst my personal one has been stored safely a good while.

I've had the parts for a while to do exactly what you have just done. I think I even bought a replacement protection relay too, if I remember rightly. In the coming weeks I'm gonna be getting it all out and starting again.

Cheers for the thread, reminded me how much fun it is to tinker with these things. Also, what did you use to get it so clean? Looks pristine inside.
 
A truly awesome job, well done! :yes:

I've just got my SA-7800 back to life and looking to re-cap too. :thmbsp: I use the same nichicon caps as you although what did you use for the orange LR (low resistance) caps?

Cheers
 
VintageMad89 said:
A truly awesome job, well done! :yes:

I've just got my SA-7800 back to life and looking to re-cap too. :thmbsp: I use the same nichicon caps as you although what did you use for the orange LR (low resistance) caps?

Cheers
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Nichicon UKL, (for Pioneer ceanl designation caps) NOT low resistance, low leakage/noise - they are the only ones out there with the necessary leakage specification. It DOES make a difference, I PROVED it years ago.
 
markthefixer said:
Nichicon UKL, (for Pioneer ceanl designation caps) NOT low resistance, low leakage/noise - they are the only ones out there with the necessary leakage specification. It DOES make a difference, I PROVED it years ago.
Click to expand...

What he said. You can see them in the pictures, they're the ones with the white stripe identifying the negative terminal, as opposed to the gold stripe. Surprisingly, there aren't as many low-leakage ones in this amp as, say, the Kenwood KA-7100s that I've worked on.

Lee.
 
Thanks both of you, I have a few amps/receivers with them and could never find a suitable replacement. Just wondered what the best thing to use was :D

Cheers
 
Bump

Sorry Lee, forgot to ask- what kind of variable resistors did you use to replace the bias control pots? (Values etc)

Cheers!
 
I have had an sa-7800 and a tx-7800 for a month or so now, haven't done anything except deoxy the switches, pots and connectors.

Haven't had a problem until today when I hooked up an old turntable and the volume pot had to be turned to Noon to hear a thin reedy sound.

I tested out another turntable and same result.

These are not mc cartridges or anything fancy (Technics sl-q2 with stanton cartridge and a Denon 80's model as far as I can tell basic MM carts)

So I have downloaded the service manual and although I can't print out that huge schematic--I have looked through the manual briefly but didn't see anything regarding testing out the phono section--did I miss something?

I did an exploratory this afternoon and got the phono board disconnected from the front chassis and with all the tight wires that are wirewrapped in several different directions keeping it pretty tightly in its current position and I couldn't get a good look at the component side.

It looks like there are several test points on the circuit boards but the only test voltages I see are for the bias at the testpoints down next to the heatsink.

What would your first step? Re-capping? I saw something about leaky caps in certain areas reducing the gain of the phono preamp. Don't want to mess up anything that's already working fine.

sorry for long winded run-on sentences

thanks

Daniel
 
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please start your own thread, this is called a thread hijacking.

Yes, the 7800 phono components are not easy to get to. But the measuring points are very accessible.
 
Leesonic, can you post a list of the parts you used to restore that beauty? I'll add a link for the SA-7800 to my post with the other Pioneer recap lists! :banana:
 
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