does anyone have real skills on a pioneer spec4?
I have one on the table that poses a problem for two weeks.
the two power circuits are working, have been overhauled and adjusted, the two channels of the protection circuit are working and have been fully updated, despite this, the amp of the left channel refuses to control its output relay (while the track works perfectly, that the relay is new and that if I plug the other amp on this way, the relay works normally), moreover, the problem side works continuously for 48h and has a perfectly stable offset and bias .
I specify that ALL the resistances, diodes, capacitors, transistors have been dismounted, tested with several devices, then soldered.
I must also add that from time to time, without a particular rule, the relay runs then cuts and it can be for 1 sec or 30 sec or 10 sec, cold, or hot.
I hope I have been clear enough in my explanations.
I have one on the table that poses a problem for two weeks.
the two power circuits are working, have been overhauled and adjusted, the two channels of the protection circuit are working and have been fully updated, despite this, the amp of the left channel refuses to control its output relay (while the track works perfectly, that the relay is new and that if I plug the other amp on this way, the relay works normally), moreover, the problem side works continuously for 48h and has a perfectly stable offset and bias .
I specify that ALL the resistances, diodes, capacitors, transistors have been dismounted, tested with several devices, then soldered.
I must also add that from time to time, without a particular rule, the relay runs then cuts and it can be for 1 sec or 30 sec or 10 sec, cold, or hot.
I hope I have been clear enough in my explanations.
Check the anodes of D3, D4, D5 in the protection circuit when the channel is in failure mode. The one with low voltage will tell you what problem the protection circuit is detecting. This protection scheme is used in MANY Pioneer amplifiers and receivers. I usually find that transistor Q12 is intermittent and detecting an overcurrent that just doesn't exist. C12 between the base and emitter could also be bad especially if it's one those light blue Sanyo capacitors. In fact ALL of the Sanyo capacitors need to go, definitely bad actors.
c12 was replaced by a mkt 0.22uf 100v and it was actually blue sanyo at the origin.
they read well but in doubt ...
Q12 has been tested with two transistor testers, it is ok.
I did not go to the oscilloscope (component test) but I think I will change it because anyway it will end up posing problem.
I will take the measurements on the anodes of D3,4 and 5 to try to understand.
it's rare that I block on a breakdown, thank you for the help.
they read well but in doubt ...
Q12 has been tested with two transistor testers, it is ok.
I did not go to the oscilloscope (component test) but I think I will change it because anyway it will end up posing problem.
I will take the measurements on the anodes of D3,4 and 5 to try to understand.
it's rare that I block on a breakdown, thank you for the help.
Those transistors will test OK on a tester but fail in actual use. IF you know the amplifiers are good pull that transistor to see if your problem goes away. D3 will have the low reading if Q12 is acting up.
I just ordered 4x 2sc2383 to replace the 2sc869 ,I should have them in the week.
As soon as I have them, I give it a try and I'll let you know.
As soon as I have them, I give it a try and I'll let you know.
Q12 on the amp board, 2SC869. 2SC869 is a known troublemaker, leaky even though they test OK. The leaky E-C current is what puts the channel into protect mode as the protection circuit doesn't know any better.
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llwhtt,i can tell you SIR !!!
I had 1 c1845 and I could not resist, I put it up and it's the biggest advance on this amp for two weeks!
the relay is not yet very stable but the amp works almost normally.
it must be said that it remains the c869 on the other amp.
I'll wait nicely for my 2383 and I'll tell you if it's stable after changing both.
Damage that you are on the other side of the Atlantic, I will have paid you a beer with great pleasure!
now i'm going to pass the c869 on the oscilloscope in component test to see its signature.
I had 1 c1845 and I could not resist, I put it up and it's the biggest advance on this amp for two weeks!
the relay is not yet very stable but the amp works almost normally.
it must be said that it remains the c869 on the other amp.
I'll wait nicely for my 2383 and I'll tell you if it's stable after changing both.
Damage that you are on the other side of the Atlantic, I will have paid you a beer with great pleasure!
now i'm going to pass the c869 on the oscilloscope in component test to see its signature.
i trying a second c1845 for test and it's good,the SPEC went back to normal life .
to return to c869, they read normal up to about 30Vdc, beyond, they are passing between collector and emitter.
to return to c869, they read normal up to about 30Vdc, beyond, they are passing between collector and emitter.
The trouble with some of these components testers is they only put a few milliamps through the device.
Quite often failure mode only occurs at high current or high voltage.
You are right Nigel! On the other hand, something works well in this case it is test the transistor cold and heat with the soldering iron and redo the test, the gain of the transistor falls to 1 point something.
by the way, I am not enthusiastic about this amp.
yes it works well
yes he is powerful
but there is no magic, just sound.
he came with his preamp that works very well, I also tried it live with a cd player output variable and voila, without more ...
I had a M22 a few years ago and it's really something else!
but it's not the same thing either.
I will be able to return it to his owner without any remorse
yes it works well
yes he is powerful
but there is no magic, just sound.
he came with his preamp that works very well, I also tried it live with a cd player output variable and voila, without more ...
I had a M22 a few years ago and it's really something else!
but it's not the same thing either.
I will be able to return it to his owner without any remorse
When I hear such statements I look at the designs to see possibly why you think so.
I do not know about amplifiers making magic nor how the M22 does it vs the Spec 4
I see that the two share almost the same topology, M22 is rated at 30W/channel/8-ohm but has lots of reserve capacity 30mFx4. 2 pairs of o/p bjts, 70W/10MHz, 2EF so it would suffer from beta droop, loading the VAS, (this maybe is your magic) average design for the era, excellent build quality
I see it has a separate regulator for each channel, much like AU-X1, but Sansui has a better regulator design.
One of the finest Pioneer designs I have looked at is the M-Z1.
I do not know about amplifiers making magic nor how the M22 does it vs the Spec 4
I see that the two share almost the same topology, M22 is rated at 30W/channel/8-ohm but has lots of reserve capacity 30mFx4. 2 pairs of o/p bjts, 70W/10MHz, 2EF so it would suffer from beta droop, loading the VAS, (this maybe is your magic) average design for the era, excellent build quality
I see it has a separate regulator for each channel, much like AU-X1, but Sansui has a better regulator design.
One of the finest Pioneer designs I have looked at is the M-Z1.
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