If the opamps are in sockets, remove them all and test again for supply shorts. if no shorts, start installing them one by one testing for shorts again.
been a while since I looked at that design, but standard troubleshooting procedures, isolate, method of elimination, etc
yes pics are always good for review.
been a while since I looked at that design, but standard troubleshooting procedures, isolate, method of elimination, etc
yes pics are always good for review.
I'll take some pics, I'm quite at loss as to what to do to fix it.
I took all op amps out and I'm getting -17 +17.
As soon as I put an op amp on A1L socket I get 8,85v and 6,93 V on A1R.
I took all op amps out and I'm getting -17 +17.
As soon as I put an op amp on A1L socket I get 8,85v and 6,93 V on A1R.
So you tried more than one opamp I assume?
And you got them from where?
I would have to look at the schematic? to see what it is doing in that position, in the mean time go over the comps in that area looking for something installed wrong value, backwards, etc, visual
And you got them from where?
I would have to look at the schematic? to see what it is doing in that position, in the mean time go over the comps in that area looking for something installed wrong value, backwards, etc, visual
You're making progress on troubleshooting it. Is that the only op amp that causes the voltage drop?
Does the comp references Carl uses match the design in Linear audio, which I have btw? so I'll look at it.
I see A1(LM4562) as the buffer from the balanced XLR/RCA jack?
That's it on p145 of LA vol5
pull A2 and try installing A1 and see if it does the same
I see A1(LM4562) as the buffer from the balanced XLR/RCA jack?
That's it on p145 of LA vol5
pull A2 and try installing A1 and see if it does the same
Last edited:
They do match. A1 is an input buffer driving the balance op amp. Nothing there that can be reversed really, just non-polar caps and resistors.
I tried 4 different op amps on three different sockets, I got all of them from Mouser, I wonder if I could've fried them someway
I might have some brand new op amps somewhere I gotta check in my stash.
I might have some brand new op amps somewhere I gotta check in my stash.
Do all the op amps behave the same? Does it matter what socket you plug them into? Have you double checked the supply connections to see if they are reversed?
Opamps are very sensitive to setting then the other way around in the socket. I have fried one like that and the rails were dropping voltage the same way you mentioned. The idea is to put them one after another until you find the damaged one
If I could add a couple things that are obvious but easy to forget ...
#1) Be sure to shut off the power to the main board before adding and removing parts.
#2) Be careful not to bend (or touch if you can avoid it) the op amp's connector pins while handling them.
#1) Be sure to shut off the power to the main board before adding and removing parts.
#2) Be careful not to bend (or touch if you can avoid it) the op amp's connector pins while handling them.
I first want to thank all of you who are helping me to find a way to repair this.
Then I tried several op amps with the same results.
I then tried with a single op amp to measure every socket here are the results:
A1R: 16,8. A1L 8,8.
A2R: 6,8 A2L 6
A3R 6,80 A3L 6,57
A4R 6,73 A4L 6,88
A5R 7,31 A5L 6,88
A6 6,8
A7R 6,8 A7L 6,79
A8R 6,9 A8L 6,95
With some op amps I only getting 8 v on A1R instead of 16,8 with the reference one
Then I tried several op amps with the same results.
I then tried with a single op amp to measure every socket here are the results:
A1R: 16,8. A1L 8,8.
A2R: 6,8 A2L 6
A3R 6,80 A3L 6,57
A4R 6,73 A4L 6,88
A5R 7,31 A5L 6,88
A6 6,8
A7R 6,8 A7L 6,79
A8R 6,9 A8L 6,95
With some op amps I only getting 8 v on A1R instead of 16,8 with the reference one
Last edited:
You need to be a lot clearer on what you are measuring. Where are you taking those voltage measurements from?
I'm taking them between 0V and V+ at the power input of the main board pcb.
I tried the same "reference op amp" on the A1L again and its back to 8v when I could get 16v on the previous test
I tried the same "reference op amp" on the A1L again and its back to 8v when I could get 16v on the previous test
It sounds like you have gotten the power supply reversed to the op amps at some point and have blown them and now they are shorted.
Your next step should be to verify the voltage between pin 4 and pin 8 on the op amp sockets with no op amps installed. With the negative lead in pin 4 and positive in pin 8 you should have around 34-36V present and the meter should be showing a positive measurement.
Your next step should be to verify the voltage between pin 4 and pin 8 on the op amp sockets with no op amps installed. With the negative lead in pin 4 and positive in pin 8 you should have around 34-36V present and the meter should be showing a positive measurement.
This is starting to make sense. it sounds like you have an open power trace on the board. Any op amp that gets plugged into either of those two sockets would be damaged and shorted.
With the power off measure the resistance between pin 8 on A2L and A3L, then do the same between pin 4 on A2L and A3L. That should tell you which trace is open.
With the power off measure the resistance between pin 8 on A2L and A3L, then do the same between pin 4 on A2L and A3L. That should tell you which trace is open.
Flip the board over and measure resistance between pin 4 of A2L and the capacitor beside it to see if they are connected. If not there is a break in that trace. If they are connected there is a break in the trace between the cap and A3L.
Once you figure out which trace is broken have a close look at it and see if you can see where it is. If there's a burn somewhere something shorted and overloaded it. If you see a tiny scratch or crack it was likely a manufacturing defect. Sometimes the trace is eroded away during etching too leaving a round hole though it, the solder mask does a great job of hiding it. Either can be repaired, but it would be wise to throw out any op amp that may have been plugged into those sockets.
Once you figure out which trace is broken have a close look at it and see if you can see where it is. If there's a burn somewhere something shorted and overloaded it. If you see a tiny scratch or crack it was likely a manufacturing defect. Sometimes the trace is eroded away during etching too leaving a round hole though it, the solder mask does a great job of hiding it. Either can be repaired, but it would be wise to throw out any op amp that may have been plugged into those sockets.