Hey people,
someone gave me this amplifier, which has been lying around in a garden-shed for the recent 5 years. It's about 30 years old and, if one is into integrated stereo amps, it's a nice amp to keep ( look at the specs, it's massive, powerful and even stable at 2 Ohms).
First repair was an electrolytic which was responsible for the speaker-output relais, which didnt pull. That was a known issue with this amp and I had a fitting electrolytic (ELNA 3,3µF/100V instead of ELNA 3,3µF/50V) in my spare-parts box,
Now it plays music, but only in "direct"-mode. The tone controls aren't working. I think I could repair it, with some more internet-recherche and some trial & error. Cannot be so difficult.
But, what could I do with this machine? I'm into activ speakers, so I've got no use for such a dinosaur. First I thought about selling it, but this thing has 20kg. Sending it as a parcel will be difficult, not to say impossible.
Another thought is, taking it apart and using it as a subwoofer amplifier. It could run i.e. two 10", or bridged one bigger sub, as it is 2Ohm stable. But, somehow, it would be sad, to take apart such a fine old amp.
What would you do?
best regards
J.
someone gave me this amplifier, which has been lying around in a garden-shed for the recent 5 years. It's about 30 years old and, if one is into integrated stereo amps, it's a nice amp to keep ( look at the specs, it's massive, powerful and even stable at 2 Ohms).
First repair was an electrolytic which was responsible for the speaker-output relais, which didnt pull. That was a known issue with this amp and I had a fitting electrolytic (ELNA 3,3µF/100V instead of ELNA 3,3µF/50V) in my spare-parts box,
Now it plays music, but only in "direct"-mode. The tone controls aren't working. I think I could repair it, with some more internet-recherche and some trial & error. Cannot be so difficult.
But, what could I do with this machine? I'm into activ speakers, so I've got no use for such a dinosaur. First I thought about selling it, but this thing has 20kg. Sending it as a parcel will be difficult, not to say impossible.
Another thought is, taking it apart and using it as a subwoofer amplifier. It could run i.e. two 10", or bridged one bigger sub, as it is 2Ohm stable. But, somehow, it would be sad, to take apart such a fine old amp.
What would you do?
best regards
J.
Attachments
Depends on it's physical condition really. If it's been exposed to damp and humidity for a long time, then it may have a lot of corrosion and might not be worth fixing. But if the condition is generally good with a few problems that can easily be solved, why not fix it? Saves it going into a landfill, even if you pass it onto someone who could use it.
This thing is a real beauty. When I saw the 2 transformators I first thought of a dual mono configuration. But no, it's 1 for the positive, and one for the negative rail. It has no corrosion or any other "time-related" damages except of dust, and I cleaned it from top to bottom with Q-tips.
Problem is the PSU-PCB which is located "down under",and has no airflow around it. Electrolytics are dying. I measured one 100µF with 130µF, and all other 100µFs with 90µFs or less. I exchanged as much as I could, but I went out of Capacitors.
Problem is the PSU-PCB which is located "down under",and has no airflow around it. Electrolytics are dying. I measured one 100µF with 130µF, and all other 100µFs with 90µFs or less. I exchanged as much as I could, but I went out of Capacitors.
Attachments
Service manual available free here.
https://www.audioservicemanuals.com...er-a-757/2456178-pioneer-a-757-service-manual
https://www.audioservicemanuals.com...er-a-757/2456178-pioneer-a-757-service-manual
check out tear down images in this thread
https://www.diyaudio.com/community/...a757-and-a-757-mk-ii-what-differences.335635/
and in German language under
https://www.hifi-workshop.com/?p=802
most complicated tear down procedure in integrated amplifiers, that I have seen until now,
OTOH this is essential for a properly carried out repair unfortunately.
Did the authorized Pioneer service centers have exact instructions for this at those days (service manual don't mentioned any advice concerning exactly steps for this very complicated tear down procedure) ?
It doesn't matter whether the area of the phono RIAA part needs service,, the power supply resp. voltage regulator board, the speaker protect relays or the controls of the pre-amplifier unit - everything is only accessible with great difficulty, i.e. with exorbitant effort.
Due to the thermal stress in many places, the reliability and longevity of certain components was not high.
https://www.diyaudio.com/community/...a757-and-a-757-mk-ii-what-differences.335635/
and in German language under
https://www.hifi-workshop.com/?p=802
most complicated tear down procedure in integrated amplifiers, that I have seen until now,
OTOH this is essential for a properly carried out repair unfortunately.
Did the authorized Pioneer service centers have exact instructions for this at those days (service manual don't mentioned any advice concerning exactly steps for this very complicated tear down procedure) ?
It doesn't matter whether the area of the phono RIAA part needs service,, the power supply resp. voltage regulator board, the speaker protect relays or the controls of the pre-amplifier unit - everything is only accessible with great difficulty, i.e. with exorbitant effort.
Due to the thermal stress in many places, the reliability and longevity of certain components was not high.
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