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Pioneer A-80 Integrated

chicks said:
I was planning on replacing them with LEDs. What value series resistor did you use?
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I don't remember but I just used ohms law and whatever the voltage was that fed the previous lamps (6 or so volts?). I mounted them in the little red and green rubber thingies that the previous bulbs were in. I didn't glue them down but I did shrinkwrap the leads.
 
OK, thanks. I just finished replacing the LEDs with what I had in the parts box, Red and Green. The Green is a lot dimmer than the Red, so looks fine IMO as the power indicator. The Red commands attention, a good deal brighter than the other LEDs on the face, so works well for the protection indicator.

The schematic shows the lamps going to a common 12V supply through a 100 ohm resistor. Didn't want to deal with getting to the board, so just added another 220 ohm resistor in series with the common LED anodes, works great! Didn't use the boots, the LEDs are held in by tension. Heat shrinked the joints, plenty of extra lead length on the original lamps, made the mod pretty simple without needing to remove those #*^#*!&* vertical boards.

Next up - tracing the right channel issue. Oh, for an O'scope!
 
rotina said:
fine amp! mine has leds on pc board on the right side of it. have you noticed the (missing ?) bolts on the power transformer? very nice amp the phono section is just awesome
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Yep, there are four LEDs on the input board, no idea why they're there, haven't looked at that part of the (huge) schematic. It's printed split over two ledger-sized (11" X 17") sheets, and is still pretty hard to read.

There are two holes that appear to be for bolts on the top of the power tranny, but no marks in the varnish to indicate they were ever there. The lateral copper wrap and the metal band around the laminations appear to be doing the job just fine. There are bolts through the bottom two holes.
 
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Scuzzer said:
I've found a couple of them for dirt cheap on CL. The last one I bought was a steal. Seriously pennies on the dollar compared to ebay.
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Yeah, and just as soon as I get rid of about four turntables, six pairs of speakers, a receiver, amp and tuner or three, I just might have room on the bench for one. :sigh:
 
That's what basements are for. I hate selling stuff so I just keep stacking it on the shelves down there.
 
Did some basic troubleshooting on the right channel. Test probe to the input of the power amp on left channel: lots of hum through speakers. Test probe to input of power amp on right channel: nuttin'

Resistance from the output transistor emitter resistors through the protection relay to the right speaker terminal: zero ohms. Hooked speaker directly to the output board, bypassing the relay and speaker selector switches - nuttin'.

So, problem is on the power amp board. Will need to pull the entire massive heat sink with power boards and output boards intact through the bottom of the chassis in order to access the board while powered up for testing.

Was hoping for something simple, like an open coupling cap, but no - the power amps are entirely DC coupled. Not quite sure how the output voltage can be balanced in a DC coupled amp that isn't amplifying, but this one is way more complex than most, with all that "Dynamic Power" circuitry.

Ah well, needed to clean the heat sink anyway... First thing tomorrow.
 
OK, after having pulled the right output board and checking every marked voltage on the schematic, everything measures good. WTF?

After mulling it over for a bit, decided to get smarter. No 'Scope, but we do have that little self-powered Minimus 7. Hooked up the old iPod clone to the Aux1 input, put the Minimus 7's input first on the left power amp input point (faint music), then the feedback loop input point (loud music). Moved to the right channel, same thing. WTF? The right channel is working, just not getting to the speaker terminals. I checked the #*^*! relay's resistance yesterday (didn't I?), it was zero ohms. Started tapping on the relay, and bam!, music starts coming out of the right speaker!

Crap, now I have to pull another one of those tight vertical boards to fix or replace the relay... <groan>
 
Had to pull the entire back off to access the output board. This may be a nice piece of gear spec-wise, but it sure wasn't made for ease of maintenance! Cleaned the relay contacts, manually held it closed, zero resistance from the output transistors to the red speaker terminal on the right channel. Let's button 'er back up!

Plugged in the iPod clone, hooked up the right speaker, powered up - nuttin'. WTF? Checked the resistance from the output transistors to the Red speaker terminal while powered on - zero ohms. Double WTF? Did a signal test with the Minimus 7 - good signal at the output trannys AND at the Red speaker terminal! Triple WTF?

OK, if the signal path is good all the way through, but the speaker isn't being driven, it's either the speaker or the wire to it, right? But they check fine on the Left channel! Finally, just for grins, decide to measure the resistance from the Black speaker terminal back to the - side input terminal on the output board. Open circuit!!! It's just a stud and a huge trace on the circuit board!

Turns out there were bad solder joints on both Black speaker terminals to the output board, and the "B" side Black terminal on the Left channel. Reflowed all eight terminal joints, and finally, the sweet sounds of Diana Krall coming through on both channels!

A final bias tweak, and I'm calling this one done!
 
markthefixer said:
Welcome to my daily life.... :D
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Did this for eight years in the Navy (many years hence), thought it would be fun to get back into it for a while. It is - on '70's gear. This sucker is packed in tighter'n sardines.

Anyhow, think I'll stick this in the main system for a while, I do like the cosmetics, plenty o' power, and the possibility of trying out a MC cart one day. My little Sony XDR-F1HD tuner ought to work just fine with this.

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I got the little Bro the A-40 and it's a keeper headed to a shop system soon as I can get some stuff cleaned out to be able to set it up. Hopefully with a pair of HPM-60's
 
Chicks, if you would have just posted pics I might on my way to fixing mine. Just kidden, glad you got it runnin.
 
Jcricket said:
I have the A-70, the little brother to your amp. Mine is supposed to be something like 100wpc(IIRC). Yours must be approaching monsterhood for power. I'd like to hear your impressions when you get it running.
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Well, it's certainly not lacking for power. The volume control is set below 9:00, about as far as I can crank it before SWMBO starts complaining. :) I listened quite a bit over the weekend after replacing my Sansui 9090DB with it. It's definitely far less visually dominating than the 'sui - the big JVC deck is now the focal point of the system.

Can't say that I can really hear a difference between quality amps. The 'sui didn't sound distinctly different than the MAC-1700 it replaced, and the A-80 doesn't sound different to my ears than the 'sui. They all sound great to me. I know the A-80 has far less distortion than the other two, so maybe I would hear a difference in a direct A/B test.

I like the A-80 for its understated look, its great ergonomics (much better than the huge 9090DB), its huge power reserve (apparently with good efficiency), and its ability to handle MC cartridges, for future upgrades.

The satisfaction of salvaging a non-functioning GW "score" and making it a centerpiece of a great system is perhaps the best part, a feeling of accomplishment.

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I am very impressed with my A70, crystal clear yet silky smooth. My Klipsch is very efficient so I do not need the power (now playing at under 1W), base is solid and the whole thing is just tight.

Would imagine the same for its bigger brothers. I think these are the fathers of the later "Elite" series.....whatever that means
 
Have the an A-80 restored and in excellent shape and just picked up an A-90 also in excellent condition. Will do some comparison and post. Also currently using a SA-9800 in excellent shape.

Love the As but the SA-9800 is really smooth with a loads of features.
 
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