DBX 118 PSU

[Walrus]

Do you now have +12 on C4 positive and -12v on C4 negative with respect to OA2 Pin 1?

 

[Studiogearlover]

Do you now have +12 on C4 positive and -12v on C4 negative with respect to OA2 Pin 1?

Yes, I do have that .

 

[Walrus]

Yes, I do have that .

Excellent!
The hard part now is checking whether anything has been damaged by the overvoltage.... 

 

[Studiogearlover]

yes...!

I went through again on the ceramics and electrolytic s...

1. Ceramics so far ( I know that I am not suppose to draw conclusion with components in circuit, but sometimes could you give you some indication is anything is failing)

C3 suppose to be 100pf. I am measuring 12pf

C18 spot on

C12 according to schema 33pf but I am getting there 70pf.

I have replaced the C13 and C11 tantalums. The C11 gave me leaky readings in circuit before replacing to a new one. Now C11 reads no fault on my tester while in circuit, So that part I guess was already damaged at some point.

I am also suspecting that OA5 is out. Not sure if I could check this with a DMM ..

btw I have removed the RMS and the VCA boards there were not in yesterday too when I did the testing for safety purposes.

Happy Easter dudes!

 

[scott2000]

Yeah in circuit tests should be verified if showing wrong......usually it's just circuit throwing off readings but still....
ceramics are usually pretty tough......
I was also curious about C5 and 9.......the non-polars.......

Any electros or tants are usually weak links outside of any damage that could/may have been caused......... That's crazy if you were over voltaging everything as I understand..... who knows......maybe you got out ok.....

You can always check to make sure all the opamps are getting their power......

and you can Run a signal through the circuit and see where it gets funky.....

You should be pretty close I'd imagine....

Happy Easter!

 

[Studiogearlover]

Yeah in circuit tests should be verified if showing wrong......usually it's just circuit throwing off readings but still....
ceramics are usually pretty tough......
I was also curious about C5 and 9.......the non-polars.......

Any electros or tants are usually weak links outside of any damage that could/may have been caused......... That's crazy if you were over voltaging everything as I understand..... who knows......maybe you got out ok.....

You can always check to make sure all the opamps are getting their power......

and you can Run a signal through the circuit and see where it gets funky.....

You should be pretty close I'd imagine....

Happy Easter!

Thanks Dude...

C5 and 9 no polars a OK...they are 100V rated. ...I am really suspecting the OA5...maybe that has gone...

Do you know any now days replacement for that?

I can get hold of a

AD OP27GPZ

or

National LM308N

They are all within specs but not sure they would operate fully as it should...

 

[scott2000]

is that an LM301??

Hmmmm....Last time I checked ....about a year ago....lol....Mouser had a bunch.....now I guess they don't.....

Pretty sure I have some if you need......Just pm me......


I haven't looked at the modern replacement options so maybe someone else could jump in....


why are you suspecting it is bad???

 

[Studiogearlover]

Thanks!

Appreciate it..will check Mouser or Farnell out !

Yes, the LM301AN...thats is the only thing I am suspecting at this moment or the switch shorted...I don't know what else could be wrong to be honest with you...altough, i have not checked the resistors through...

 

[scott2000]

I've had luck tracing a signal to see what's happening in parts of circuits...... Opamps are pretty tough from my experience but they do go bad/get damaged...... especially when accidentally reversed...lol

If they're in sockets you may want to pull and re-seat them.....

I've had a bad socket before (small crack) that ran me around one time so anthing's game.....


Good luck!

 

[Studiogearlover]

I've had luck tracing a signal to see what's happening in parts of circuits...... Opamps are pretty tough from my experience but they do go bad/get damaged...... especially when accidentally reversed...lol

If they're in sockets you may want to pull and re-seat them.....

I've had a bad socket before (small crack) that ran me around one time so anthing's game.....


Good luck!

Hey

Thank you !!

I have visually checked the sockets and tested each pin for continuity also the pcb too, all the soldering wiring are pristine and nothing is out of ordinary or burning.

I went further and I have checked the voltages withot the RMS and VS board in also without any IC in , just the socket pins.

All the +12 and -12 are at present.

OA3 reads the following : ( and again those ceramic disc caps at C8 and C17 hmmmm)...


Pin4  -12 VDC
Pin 8  +12 VDC

The rest of pins are 0 mV, in fact all of the pins are starting around 120mV on my DMM and slowly decreasing down to in about 1 minute or so...

It seems that pin2, 3 and 6, 7 are all connected to those ceramic disc caps....15pf..so small value that I can not check this.

---------

The OA4 has different values and readings on each pin's so the OA5. So there are voltages there on each pin...

...something is going on at OA3.....?? 

 

[scott2000]

It seems that pin2, 3 and 6, 7 are all connected to those ceramic disc caps....15pf..so small value that I can not check this.

---------

The OA4 has different values and readings on each pin's so the OA5. So there are voltages there on each pin...

...something is going on at OA3.....?? 

I'm kinda lost /getting lost on what it is you are trying to say entirely ..... I really thing that plugging in some numbers over the schematic would really speed things up for anyone trying to help.......

OA 4 and 5 have either different pin outs or functions most likely and would result in different readings.....from 3??

Some areas of the circuit may not /should not have a dc reading.....etc...

If you send a signal/tone through, you may be able to tell where it goes awry???  Don't forget that would be an AC voltage...........

 

[Studiogearlover]

I'm kinda lost /getting lost on what it is you are trying to say entirely ..... I really thing that plugging in some numbers over the schematic would really speed things up for anyone trying to help.......

OA 4 and 5 have either different pin outs or functions most likely and would result in different readings.....from 3??

Some areas of the circuit may not /should not have a dc reading.....etc...

If you send a signal/tone through, you may be able to tell where it goes awry???  Don't forget that would be an AC voltage...........

I agree... i will stop for now and  thank you so far for the suggestions.

i think until I have brand new set of ICs and OP amps which I will know 100% sure is working ( I had only used ones so far) not not much I could or we could conclude of...

Thanks again...and will focus on getting a fully working  TL82s and LA301s... and then carry on afterwards..

8)