My original problem was a defective Q3 IC TA 7136P1. I have replaced it twice and it shorts out. I have checked every component related to this IC and compared to the Q4 circuitry. With the IC out of the circuit the other channel works fine and all the voltages are normal. I am using TA 7136P for replacements. Is there something different about the P1 IC. According to pioneer it should be a good replacement.
this is my first post so I hope I am doing it correctly.
this is my first post so I hope I am doing it correctly.
Pioneer SA-6800 - Manual - Stereo Integrated Amplifier - HiFi Engine
Check the voltages at Q19 Q20; also (carefully!!) at Q1 pins 4 and 7. The stock +/-20V are already quite high for that opamp; if the transistors failed their supply voltage may be MUCH higher. Or if a resistor has burned, it may be Zero, confounding easy diagnosis.
https://cdn.datasheetspdf.com/pdf-down/T/A/7/TA7136AP_Toshiba.pdf
Check the voltages at Q19 Q20; also (carefully!!) at Q1 pins 4 and 7. The stock +/-20V are already quite high for that opamp; if the transistors failed their supply voltage may be MUCH higher. Or if a resistor has burned, it may be Zero, confounding easy diagnosis.
https://cdn.datasheetspdf.com/pdf-down/T/A/7/TA7136AP_Toshiba.pdf
it's odd that it would short out. That chip has about 3ma of pullup current, much more sink current. voltages should be around 20 - 22v positive and negative. P1 chip may reverse the (+) and (-) signal input pins ensuring it won't work.
This chip is also used in SX-780. I replaced it with 2 6922 triodes, much better.
This chip is also used in SX-780. I replaced it with 2 6922 triodes, much better.
The P1 version may be rated at a higher voltage, seeing that the regular TA7136P is only 40 V max and that's how high the supplies are in this amp. (Not uncommon back in the day, e.g. JRC made some +/-22 V rated 4558s which normally are rated +/-18 V max.) Tough. Do verify supply voltages in case there is a shorted regulator pass transistor. The new chips may also be fake.
There has been some discussion on how to replace these ICs in the past. They are early audio opamps with a single-ended output stage. Most manufacturers seem to run them hotter than suggested in the datasheet (the resistor between pins 7 and 5 sets reference current), presumably in an effort to improve distortion performance and voltage noise.
I suppose it would be possible to make an adapter board for one of these, maybe using an NE5534. The pins you are interested in are 2 (+in), 3 (-in), 6 (out), 7 (V+) and 4 (V-). People have, in fact, done so before:
TA7136AP replacement adapter - HOW TO USE - fmtuners
ta7136 substitution - ua726 (TL071 is not too great a match, but NE5534 could be accomodated in a similar manner - make sure you accommodate Cc between pins 5 and 8 depending on gain required, and I would also suggest including maybe 100 nF of rail decoupling between V+ and V- since these chips are fussier about that)
Vintage Audio Upgrades BA312 TA7136 - SparkoS Labs Inc.
I like the idea of using a 5534 (maybe even a 5534A). It is rated +/-22 V max, and with its low input impedance distortion and low current noise (even better in the A series part) would be a good match for the circuit with its somewhat high impedances. At the input levels encountered here its Achilles heel of common-mode distortion won't be relevant either, and circuit gain is so high at 20 dB that external compensation (Cc) may not even be required at all (though the layout won't be great with an adapter and all, so it may still be a good idea to have like 10 pF there). Supply current is likely to be in the same ballpark or even lower than the TA7136 (keep in mind that these are run boosted beyond datasheet levels, current may be doubled for all I can tell, so ~6 mA).
Getting the most out of an opamp like the 5534 will not be possible in this circuit, it would be a major revamp at the very least due to the tone control being involved (read: pots). Probably not worth it. It would be an attractive candidate for the phono preamp though (they are basically made for this - this was the latest and greatest audio opamp design in 1978, and it shows).
There has been some discussion on how to replace these ICs in the past. They are early audio opamps with a single-ended output stage. Most manufacturers seem to run them hotter than suggested in the datasheet (the resistor between pins 7 and 5 sets reference current), presumably in an effort to improve distortion performance and voltage noise.
I suppose it would be possible to make an adapter board for one of these, maybe using an NE5534. The pins you are interested in are 2 (+in), 3 (-in), 6 (out), 7 (V+) and 4 (V-). People have, in fact, done so before:
TA7136AP replacement adapter - HOW TO USE - fmtuners
ta7136 substitution - ua726 (TL071 is not too great a match, but NE5534 could be accomodated in a similar manner - make sure you accommodate Cc between pins 5 and 8 depending on gain required, and I would also suggest including maybe 100 nF of rail decoupling between V+ and V- since these chips are fussier about that)
Vintage Audio Upgrades BA312 TA7136 - SparkoS Labs Inc.
I like the idea of using a 5534 (maybe even a 5534A). It is rated +/-22 V max, and with its low input impedance distortion and low current noise (even better in the A series part) would be a good match for the circuit with its somewhat high impedances. At the input levels encountered here its Achilles heel of common-mode distortion won't be relevant either, and circuit gain is so high at 20 dB that external compensation (Cc) may not even be required at all (though the layout won't be great with an adapter and all, so it may still be a good idea to have like 10 pF there). Supply current is likely to be in the same ballpark or even lower than the TA7136 (keep in mind that these are run boosted beyond datasheet levels, current may be doubled for all I can tell, so ~6 mA).
Getting the most out of an opamp like the 5534 will not be possible in this circuit, it would be a major revamp at the very least due to the tone control being involved (read: pots). Probably not worth it. It would be an attractive candidate for the phono preamp though (they are basically made for this - this was the latest and greatest audio opamp design in 1978, and it shows).
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Sa6800
The TA7136P does have reversed inputs compared to the TA7136P1. The
TA 7136AP has the same inputs as the P1. I just installed them yesterday and the unit works fine. Now all I have left is the noisy power switch. I saw where someone was able to clean it up. Thanks for everybody's input.
Marty
The TA7136P does have reversed inputs compared to the TA7136P1. The
TA 7136AP has the same inputs as the P1. I just installed them yesterday and the unit works fine. Now all I have left is the noisy power switch. I saw where someone was able to clean it up. Thanks for everybody's input.
Marty
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