Onkyo-593 No power and now clicking sound

[madan1]

Check again d901 in diode mode for short (I do not remember by heart the internal schematics of the bridge rectifiers, so I test each pin to each other pins, then switch the probes and again).
You can use IPA to find the hot component(s) - drop IPA on the component and see how fast evaporates.
Thermal print labels also can be used - cover area with a label and see where it will get black.

This power rail doesn't have too many common points to ground - q502, d516, q501, q434+q436... all other possible paths include too many components that have to be shorted. So try injecting voltage again and check that components if they are getting hot.

[Sisko]

Check again d901 in diode mode for short (I do not remember by heart the internal schematics of the bridge rectifiers, so I test each pin to each other pins, then switch the probes and again).
You can use IPA to find the hot component(s) - drop IPA on the component and see how fast evaporates.
Thermal print labels also can be used - cover area with a label and see where it will get black.

This power rail doesn't have too many common points to ground - q502, d516, q501, q434+q436... all other possible paths include too many components that have to be shorted. So try injecting voltage again and check that components if they are getting hot.

Hi there.

Ok I checked d901 in diode mode and no shorts I even took the time to take it out and recheck it just to make sure and it's OK. So while the d901 was out I decided to do another
voltage injection just in case and again no hot spot any where.

Ok decided to recheck q901 if it was working and it is faulty will not give 12v output under a 14.5v on my bench power supply, I get 0vdc on the output. So will need to reorder one again. Again no more short on c902 when q901 isn't there.

THANKS!!!

[madan1]

If the short is gone, you can try powering up the unit (without q502 and q901). Preferably through a dim-bulb tester, but even without, looks like the smps ic has a working protection and a test should not do more harm.
A good result would be stable power rails (stable voltage on c905, c902 c901 c911 c912).. from the schematics and the smps documentation, looks like the smps IC supports low and high power modes, so not really sure what should be the voltage.

[Sisko]

If the short is gone, you can try powering up the unit (without q502 and q901). Preferably through a dim-bulb tester, but even without, looks like the smps ic has a working protection and a test should not do more harm.
A good result would be stable power rails (stable voltage on c905, c902 c901 c911 c912).. from the schematics and the smps documentation, looks like the smps IC supports low and high power modes, so not really sure what should be the voltage.

Hi there.

Ok plugged the power up and the dim-bulb lit very briefly and I heard a very faint click then a small buzz that doesn't stop, I checked c901 and it started at 32v but voltage getting high fast and not stopping at all , c902 no voltage at all.
I didn't check any other caps because of the buzzing noise and didn't want to burn anything else. I should get my part q901 tomorrow. What would be the normal voltage at c901 there isn't anything on the shem that says what voltage?

Thanks!!!!

Sisko

[madan1]

Ok plugged the power up and the dim-bulb lit very briefly

That's the smoothing caps on the primary getting charged.

and I heard a very faint click then a small buzz that doesn't stop,

Is the buzz coming from the transformer(s)?

I checked c901 and it started at 32v but voltage getting high fast and not stopping at all , c902 no voltage at all...What would be the normal voltage at c901 there isn't anything on the shem that says what voltage?

Did it exceed 40-45V?
Manual says, according to the model, it should be 30 or 40V (+/- few volts)
On c902 the voltage should be same but with opposite polarity.
If there is no voltage on c902 you have the following options:
there is short on that rail
d901 is bad
the transformer is bad

It would be interesting to know if the 12v rails are present (c921/c911 and c922/c912)

[Sisko]

That's the smoothing caps on the primary getting charged.



Is the buzz coming from the transformer(s)?




Did it exceed 40-45V?
Manual says, according to the model, it should be 30 or 40V (+/- few volts)
On c902 the voltage should be same but with opposite polarity.
If there is no voltage on c902 you have the following options:
there is short on that rail
d901 is bad
the transformer is bad

It would be interesting to know if the 12v rails are present (c921/c911 and c922/c912)

Hi there

Ok tested c911 and it has 12v, c912 0v, c921 9.10v and c922 0v. Ok rechecked c901 and it goes beyond 40v and not stopping. D901 was tested before I put it back and it was good.
I wanted to say that this amp has a protection mode circuit (in red on pic that I have provided) and wondered if it's why I don't get any voltage at c902? As I can see IRS2092 (q501) is part of this "protection"
circuit and I have 2 new ones IF ever I need to change this part. I got my q901 parts (got 2) today.

THANKS!!!

Sisko

[madan1]

Not having the -12V rails is no bueno. It is tapped into the transformer before D901.
At this point I can figure out only two reasons for not having the negative rails - dead short on one of the rails or the transformer winding for the negative rails is gone.
The protection circuit switches off the smps IC on the primary side by shorting VREF to DIS with opto Q955. Usually this is triggered by overvoltage, undervoltage, over-current and high temp.
One last try before focusing on the transformer - desolder d901, d912 and d911. This will disconnect the transformer windings from the main power rails.

After that check for short on c912 c912 and again c901 and c902. Do not solder them back before fixing the short.
And while you are there - check c903 for short and r901 for correct value (6.8ohms)

[Sisko]

Not having the -12V rails is no bueno. It is tapped into the transformer before D901.
At this point I can figure out only two reasons for not having the negative rails - dead short on one of the rails or the transformer winding for the negative rails is gone.
The protection circuit switches off the smps IC on the primary side by shorting VREF to DIS with opto Q955. Usually this is triggered by overvoltage, undervoltage, over-current and high temp.
One last try before focusing on the transformer - desolder d901, d912 and d911. This will disconnect the transformer windings from the main power rails.

After that check for short on c912 c912 and again c901 and c902. Do not solder them back before fixing the short.
And while you are there - check c903 for short and r901 for correct value (6.8ohms)

Hi. I forgot to say that I have checked c904 and had around 38v and -38v.

[Sisko]

Not having the -12V rails is no bueno. It is tapped into the transformer before D901.
At this point I can figure out only two reasons for not having the negative rails - dead short on one of the rails or the transformer winding for the negative rails is gone.
The protection circuit switches off the smps IC on the primary side by shorting VREF to DIS with opto Q955. Usually this is triggered by overvoltage, undervoltage, over-current and high temp.
One last try before focusing on the transformer - desolder d901, d912 and d911. This will disconnect the transformer windings from the main power rails.

After that check for short on c912 c912 and again c901 and c902. Do not solder them back before fixing the short.
And while you are there - check c903 for short and r901 for correct value (6.8ohms)

Hi there

Ok checked R901 got 10.7 Ohms, c902 getting short on + and getting reading on -, c901 getting reading on + and short on -, c911 getting reading on + and getting short on -, c912 getting short on + and - (but - doesn't beep), c903 no short on either + or -.

THANKS!!!

Sisko

[Sisko]

Hi there

Ok rechecked the r901 out of circuit and I get 7.4 Ohms the other time it was still soldered on (yeah my bad).

[Sisko]

Not having the -12V rails is no bueno. It is tapped into the transformer before D901.
At this point I can figure out only two reasons for not having the negative rails - dead short on one of the rails or the transformer winding for the negative rails is gone.
The protection circuit switches off the smps IC on the primary side by shorting VREF to DIS with opto Q955. Usually this is triggered by overvoltage, undervoltage, over-current and high temp.
One last try before focusing on the transformer - desolder d901, d912 and d911. This will disconnect the transformer windings from the main power rails.

After that check for short on c912 c912 and again c901 and c902. Do not solder them back before fixing the short.
And while you are there - check c903 for short and r901 for correct value (6.8ohms)

Hi there

Ok I did answer this question a few message back and didn't get any reply as of yet, anything else to test/try? So waiting for your answer on what to do next.

THANKS!!!

Sisko

[R_J]

Why are you checking R901, you should be checking R912, if you have no -12vdc R912, L912 or D912 are likely open. Or the transformer winding between pins 8 and 9 may be open.
R901, C903 will not cause this fault, my guess would be open L912

[Sisko]

Why are you checking R901, you should be checking R912, if you have no -12vdc R912, L912 or D912 are likely open. Or the transformer winding between pins 8 and 9 may be open.
R901, C903 will not cause this fault, my guess would be open L912

Hi and thanks for your answer! Ok I was told by Madan1 to check r901 (check c903 for short and r901 for correct value (6.8ohms)) and that's what I did.

As I said to Madan1 I don't do electronic repair regulatory so I'm not used to do something as deep as this one here BUT I've always love fixing electronics since I was a kid but never had the time to really do the
deep stuff like this one, I just do this 1-2 times a year so it's a bithard for me to learn "how" to locate the problems. At first I thought this would be a fuse blown but it isn't so decided to dive in and try to fix this anyway
and give me a chance to "learn" as I go. So please I ask you to just understand my situation, I know this is easy for you as you can see all of this and understand what could be the problem but for me yeah it's a bit
hard BUT I'm determined to try to fix this but with some help and guidance and patience.

Ok Madan1 told me to remove d911 and d912 and before this I still have D901, Q901 and Q502 removed and If you have red my previous messages there was a short on C902 while Q901 was soldered there. Ok
what do you want me to do here to put back the D911 and D912 back and check voltage?

THANKS!!

Sisko

[R_J]

Ok tested c911 and it has 12v, c912 0v, c921 9.10v and c922 0v

I did not know that you had parts removed when you did this test, with D911 and D912 you would not get the + or - 12v. You seem to have more than one problem; I was just looking at the missing -12v on C912 that you posted.

[Sisko]

I did not know that you had parts removed when you did this test, with D911 and D912 you would not get the + or - 12v. You seem to have more than one problem; I was just looking at the missing -12v on C912 that you posted.

Hi and thanks for your reply! How can I attack this 2 problems? Can you help me a bit with this or give me any suggestions?

Thanks!!!

Sisko

[Sisko]

Hi all just wanted to say that I have decided to terminate this repair since it’s been hard to find the problem and like R_J said that there could be more than just 1 problem so with this said I’ve decided to stop trying to fix this amp. Still I want to say a BIG THANKS to Madan1 for his help in this and I’m sorry if I may have had problems understanding your test requests. Again THANKS!!!😊👍