Hi,
all of a sudden my beloved intergrated amplifier stopped working. When I turned it off and on again. I hear relays clicking, the VU meter illumination shortly flashes, then the relays click again, and the Standby LED flashes continuously.
Unfortunately I am not able to upload the service manual here that I found at several WWW sources, because with almost 12 MB it is too large.
According to the instructions given from page 26 on in that manual, I entered the self-diagnostic mode. The Standby LED flashes three times, followed by a short break, then it continuously flashes twice, followed by a short break etc.
This isn't a flashing pattern exactly described in the List of protection information. But if I neglect the first three flashes, the following ones (flash flash break, flash flash break etc.) might correspond with the pattern in the second line and hint to PS (power supply) protection.
The amplifier is of high complexity and the schematics are hard to read, at least for me. I even don't understand how the power output section works, but due to the four floating PSU rails I assume something like a Circlotron. So it might be well beyond my capabilities. Maybe there's another owner of such a beautiful and well sounding unit who has encountered the same or similar issue and fixed it successfully? Any hint will be much appreciated.
Best regards!
all of a sudden my beloved intergrated amplifier stopped working. When I turned it off and on again. I hear relays clicking, the VU meter illumination shortly flashes, then the relays click again, and the Standby LED flashes continuously.
Unfortunately I am not able to upload the service manual here that I found at several WWW sources, because with almost 12 MB it is too large.
According to the instructions given from page 26 on in that manual, I entered the self-diagnostic mode. The Standby LED flashes three times, followed by a short break, then it continuously flashes twice, followed by a short break etc.
This isn't a flashing pattern exactly described in the List of protection information. But if I neglect the first three flashes, the following ones (flash flash break, flash flash break etc.) might correspond with the pattern in the second line and hint to PS (power supply) protection.
The amplifier is of high complexity and the schematics are hard to read, at least for me. I even don't understand how the power output section works, but due to the four floating PSU rails I assume something like a Circlotron. So it might be well beyond my capabilities. Maybe there's another owner of such a beautiful and well sounding unit who has encountered the same or similar issue and fixed it successfully? Any hint will be much appreciated.
Best regards!
Hi Kay,
From your comments, I was expecting to find poor legibility in the manual, but now I see that it's just difficult to follow the topology of the amp. 😵
I found a crisp manual: https://www.manualslib.com/download/1074972/Yamaha-A-S3000.html
Can you spot anything obviously amiss in the power supplies? We can try to decipher amps as we go. No guarantees...
From your comments, I was expecting to find poor legibility in the manual, but now I see that it's just difficult to follow the topology of the amp. 😵
I found a crisp manual: https://www.manualslib.com/download/1074972/Yamaha-A-S3000.html
Can you spot anything obviously amiss in the power supplies? We can try to decipher amps as we go. No guarantees...
Thank you very much! I already found the manual you were pointing at. Elektrotanya from Hungary offers the same file. And yes, it is crisp and good to read, but very hard to understand.
If my assumption on the failure code applies (see page 26), there's a PSU issue. The microprocessor IC502 on Function Board 1 (page 67) watches the complete PSU, with the exception of the four floating power amplifier rails, by a port called PRV, at it's pin 85. The normal voltage should be 0.8 to 1.6 V. I measured 0.6 V. The PRV bus can also be found at the Main (3) and the Function (2) boards (pages 68, 69), among which the small signal PSU parts are distributed.
Yesterday I dismantled the unit to get access to all these boards. Surprisingly, all (!!) voltages are well within specs. But note the voltage drops given in red across the pass transistors Q57 through Q68, which differ between the positive and the negative branches, despite the symmetric design. In my unit the values are identical between the related + and - transistors, which I would have expected. Both 3V3 zener references D59, D60 also measure ok.
I deliberately raised the PRV voltage to 1 V by a 560 k resistor from the positive terminal of C12 on Function (1), but with no effect. The amp keeps staying in the protected mode.
All this leads me to the assumption that either the protection circuitry itself is the culprit, or my code deciphering is wrong and the issue is elsewhere in the unit.
Best regards!
If my assumption on the failure code applies (see page 26), there's a PSU issue. The microprocessor IC502 on Function Board 1 (page 67) watches the complete PSU, with the exception of the four floating power amplifier rails, by a port called PRV, at it's pin 85. The normal voltage should be 0.8 to 1.6 V. I measured 0.6 V. The PRV bus can also be found at the Main (3) and the Function (2) boards (pages 68, 69), among which the small signal PSU parts are distributed.
Yesterday I dismantled the unit to get access to all these boards. Surprisingly, all (!!) voltages are well within specs. But note the voltage drops given in red across the pass transistors Q57 through Q68, which differ between the positive and the negative branches, despite the symmetric design. In my unit the values are identical between the related + and - transistors, which I would have expected. Both 3V3 zener references D59, D60 also measure ok.
I deliberately raised the PRV voltage to 1 V by a 560 k resistor from the positive terminal of C12 on Function (1), but with no effect. The amp keeps staying in the protected mode.
All this leads me to the assumption that either the protection circuitry itself is the culprit, or my code deciphering is wrong and the issue is elsewhere in the unit.
Best regards!
I think you've already done what I was going to suggest--- namely work through the checks detailed on pages 27 and 28. And I like your experiment on the PRV voltage.
I like to believe I'm reasonably good at reading schematics, but I'm lost in the maze. I can find the transistors you mention in the list on page 81, but can't find them in the schematics. Would point me to the right page?
Thanks!
I like to believe I'm reasonably good at reading schematics, but I'm lost in the maze. I can find the transistors you mention in the list on page 81, but can't find them in the schematics. Would point me to the right page?
Thanks!
My unconfirmed guess is that each channel is implemented with TWO amps tied in a bridged drive that floats (hence the multiple supplies) and the floating architecture allows one one speaker lead to be grounded. It's akin to a conventional stereo amp tied for bridged mono drive. But the floating configuration allows one speaker lead to be grounded. Then the whole affair is duplicated to form a second channel.
I think...
I think...
Hi Kay,
I have to retract my earlier theory. I wasn't even looking at the correct area of the amp. I eventually found the blurb linked below. It does indeed appear to be a Circlotron design. I'm very sorry for earlier my faulty guess.
https://usa.yamaha.com/products/audio_visual/hifi_components/a-s3000/features.html#product-tabs
I'm still interested in attempting repair if you are. It's very difficult to follow the Yamaha schematic, but it reminds me of the Sumo Nine amp from James Bongiorno, also a Circlotron design.
I love trouble-shooting!
Best,
Steve
I have to retract my earlier theory. I wasn't even looking at the correct area of the amp. I eventually found the blurb linked below. It does indeed appear to be a Circlotron design. I'm very sorry for earlier my faulty guess.
https://usa.yamaha.com/products/audio_visual/hifi_components/a-s3000/features.html#product-tabs
I'm still interested in attempting repair if you are. It's very difficult to follow the Yamaha schematic, but it reminds me of the Sumo Nine amp from James Bongiorno, also a Circlotron design.
I love trouble-shooting!
Best,
Steve
Yes, a Circlotron design, or a H bridge. Be that as it may, something very weird. And the fact that the output terminals (the symbols that look like horns...) are distributed all over the schematics drawing doesn't help to understand it either.
Best regards!
Best regards!
Yes, I also found the horn symbols confusing but eventually decided they were intended as aids to imply those leads eventually connect to speakers.
So what bias voltage to you observe on those two leads? They should be nearly equal and about +47V.
So what bias voltage to you observe on those two leads? They should be nearly equal and about +47V.
Back to your Yamaha link above, Steve. I do confirm that the A-S3000 really is a very good sounding amplifier, but I don't know if this mainly can be deduced from it's Circlotron'ish power stage design, as Yamaha emphasizes that much (»Floating and Balanced Power Amplifier«). There are umpzillions more conventional and not that complicated designs out there, and of course also here in our community, that don't leave anything to be desired in terms of tonal qualities.
Sorry, I don't follow your 47 V assumption, as the PSU rails aren't related to ground, and as if it were so, this potential would appear at the speaker terminals when the output relays are engaged. Although possibly not lethal, 47 Vdc is considered a safety risk, at least here in Europe. Although the unit itself has no PE connection, it gets it from other units connected to it.
I measured some lowish (< 10 mV) voltages at all four speaker leads, which is ok, I think.
Best regards!
Sorry, I don't follow your 47 V assumption, as the PSU rails aren't related to ground, and as if it were so, this potential would appear at the speaker terminals when the output relays are engaged. Although possibly not lethal, 47 Vdc is considered a safety risk, at least here in Europe. Although the unit itself has no PE connection, it gets it from other units connected to it.
I measured some lowish (< 10 mV) voltages at all four speaker leads, which is ok, I think.
Best regards!
Here you can study the "Floating and Balanced Power Amplifier" drawn in a more convenient way.
https://www.diyaudio.com/community/...-balanced-power-amplifier.290584/post-6993346
https://www.diyaudio.com/community/...-balanced-power-amplifier.290584/post-6993346
What an interesting thread, Jony! I'm quite amazed. Thank you very much for your hint!
Best regards!
Best regards!
Thank you for setting me straight about the floating supplies and the voltages at the speaker terminals.
I was inferring +47V as +47.08V is noted on the drain of Q113. It and the drain of Q119 are depicted as driving the "horns." Do I have this correct? Can you advise where the VM reference lead is taken for these measurements? I would think that voltage on the drain of Q119 would have to be very similar to ensure low voltage across the speaker. Is it possible that the +46.98V noted near Q119 is its drain voltage and is merely poorly placed in the drawing? I haven't been able to find the nominal voltage of the floating supplies--- they must be less than 63V given voltage rating of caps. Would you advise?
I assume the amp is still in protection mode and that you're measuring before the speaker relays. Thanks for indulging me as I fumble through the schematics.
I was inferring +47V as +47.08V is noted on the drain of Q113. It and the drain of Q119 are depicted as driving the "horns." Do I have this correct? Can you advise where the VM reference lead is taken for these measurements? I would think that voltage on the drain of Q119 would have to be very similar to ensure low voltage across the speaker. Is it possible that the +46.98V noted near Q119 is its drain voltage and is merely poorly placed in the drawing? I haven't been able to find the nominal voltage of the floating supplies--- they must be less than 63V given voltage rating of caps. Would you advise?
I assume the amp is still in protection mode and that you're measuring before the speaker relays. Thanks for indulging me as I fumble through the schematics.
The power amp PSU rails are fed with 33 Vac by the mains transformer, bridge rectified and filtered by 22 mF capacitors each. So the DC voltage indeed is about 46 Vdc.
Yes, I measured at the leads coming from the PSU capacitors, before the speaker relays.
Indeed, the service manual power amp schematics (p. 69) is more than puzzling. According to it, and as you yet said, a potential of +47.08 Vdc should be expected at the power device's Q113 drain. Now compare it to the other half: There's +46.98 Vdc noted at Q119's source, which seems a lot more reasonable.. And why is there written »no_use« for both transistors? And why is the CCS around Q110 crossed out, while the same arrangement appears at the other side?
I really don't get it....
Best regards!
Yes, I measured at the leads coming from the PSU capacitors, before the speaker relays.
Indeed, the service manual power amp schematics (p. 69) is more than puzzling. According to it, and as you yet said, a potential of +47.08 Vdc should be expected at the power device's Q113 drain. Now compare it to the other half: There's +46.98 Vdc noted at Q119's source, which seems a lot more reasonable.. And why is there written »no_use« for both transistors? And why is the CCS around Q110 crossed out, while the same arrangement appears at the other side?
I really don't get it....
Best regards!
Oh, how silly must I have been to overlook this hint! Instead, I dismantled the unit from it's rear to get direct access to the different PSU sections on the FUNCTION 1 and 2 boards and found all voltages spot on.
Anyway, I'm still scratching my head why the amplifier keeped to be in protection mode after I increased the PRV voltage to more than 1 V. PRV is a bus than meanders all through the unit and monitors all small signal PSU sections (even the AC lines out of the main transformer), using a sophisticated network of voltage dividers. The microprocessor IC502 measures the PRV voltage and says the PSU is ok if it is between 0.8 and 1.6 Vdc.
Best regards!
Edit: I don't spot any test points at the FRONT PCB, neither in the schematics (p. 70) nor on the PCB layout drawings (p. 60)???
Anyway, I'm still scratching my head why the amplifier keeped to be in protection mode after I increased the PRV voltage to more than 1 V. PRV is a bus than meanders all through the unit and monitors all small signal PSU sections (even the AC lines out of the main transformer), using a sophisticated network of voltage dividers. The microprocessor IC502 measures the PRV voltage and says the PSU is ok if it is between 0.8 and 1.6 Vdc.
Best regards!
Edit: I don't spot any test points at the FRONT PCB, neither in the schematics (p. 70) nor on the PCB layout drawings (p. 60)???
Last edited:
Some test points, looking for symmetry rather than absolute values.
Maybe list other points you've tested, need to work through the TP's on page 27
Page 68 Function 2/2
W54 Coordinates M1
MC +18
MC -18
MM +20
MM -20
W53 H10
LINE1 +/-20
W52 M1
+/- 27
Page 67 Function 1/2
CB508 G2
+/- 12C
Maybe list other points you've tested, need to work through the TP's on page 27
Page 68 Function 2/2
W54 Coordinates M1
MC +18
MC -18
MM +20
MM -20
W53 H10
LINE1 +/-20
W52 M1
+/- 27
Page 67 Function 1/2
CB508 G2
+/- 12C
Thank you. All voltages, including yours', are spot on. I disassembled the unit partially just to get access to the Function 1 and 2 boards and measured directly at the PSU SS device pins. The Main 1 PCB is freely accessible.
This is one of the reasons to assume that the protection circuitry itself is faulty. The other one is that it can't be cheated by raising the PRV voltage to some value between 0.8 and 1.6 V.
Best regards!
This is one of the reasons to assume that the protection circuitry itself is faulty. The other one is that it can't be cheated by raising the PRV voltage to some value between 0.8 and 1.6 V.
Best regards!
I hope that you will not reach the same conclusions as me on several relatively recent Yamaha devices which are overdue on my shelves, namely that they are fully operational but require an OEM Yamaha flash/read, of course only available in an official Yamaha repair station.
I follow your (your with BSST and mbz) troubleshooting with great interest.
I follow your (your with BSST and mbz) troubleshooting with great interest.