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I will dig in. Im not going to give up on this. Maybe step away from it from time to time so I dont get too frustrated, but obviously, this is learning for me.
As an aside, and I dont know the rules on this here, in your opinion do you think your tutorial would enlighten me enough that I would be capable of diagnosing this without testing each component out of the board and without a schematic? I know you dont know me or my ability, just a general question in the presumption that I can understand everything in the tutorial.
Again, I appreciate your time and patience with me on this. I know I could have bought five more of these fully functional by now with the amount of time spent, but thats not the point of doing this, right?
As an aside, and I dont know the rules on this here, in your opinion do you think your tutorial would enlighten me enough that I would be capable of diagnosing this without testing each component out of the board and without a schematic? I know you dont know me or my ability, just a general question in the presumption that I can understand everything in the tutorial.
Again, I appreciate your time and patience with me on this. I know I could have bought five more of these fully functional by now with the amount of time spent, but thats not the point of doing this, right?
catching back up. Found that with all the working on this and flipping the boards over that a wire had become detached between the PS board and the audio board. I admit I was a bit frustrated that I felt I was going backwards, so I stepped away and did some caps on another amp. After that fixed the other amp, I felt renewed in my confidence and went back to this. We are back to pos rail not working. Everything else is the same as it was prior to me losing PS supply. In the diagram that I made, only pulling Q2 (for lack of better labeling) seems to get rid of the issue. Q2 collector is on the ground for both rails. So, I am not testing each component and eliminating them systematically until I can track down the one that is the issue.
I have a question though about zener diodes. Reading up on them, it seems they arent as easily tested as regular diodes and there are some zeners on this circuit. Is there a good way to test with them in the circuit?
I have a question though about zener diodes. Reading up on them, it seems they arent as easily tested as regular diodes and there are some zeners on this circuit. Is there a good way to test with them in the circuit?
ground for both rails = secondary ground.
It's possible that the problem is being caused by a component that's being switched on by another component.
Installing the lamp in the line between the boards for the positive rail will allow the amp to remain on. A competing heating up (allowed by using the limiter) may help.
You test zeners like other diodes. You don't generally test for breakdown voltage. That will show up in the circuit when the amp is powered up.
It's possible that the problem is being caused by a component that's being switched on by another component.
Installing the lamp in the line between the boards for the positive rail will allow the amp to remain on. A competing heating up (allowed by using the limiter) may help.
You test zeners like other diodes. You don't generally test for breakdown voltage. That will show up in the circuit when the amp is powered up.
"So, I am not testing each component and eliminating them systematically until I can track down the one that is the issue."
should have read: "So, I am *now* testing each component and eliminating them systematically until I can track down the one that is the issue."
The negative rail is unaffected by any of this. It remains constant as expected.
I can certainly put the light bulb in series between the audio board and the PS board, if that is what you mean.
So, zeners removed from circuit and just use ohms to test is acceptable? I read a bunch of stuff about adding batteries and things for testing them and wasnt sure.
should have read: "So, I am *now* testing each component and eliminating them systematically until I can track down the one that is the issue."
The negative rail is unaffected by any of this. It remains constant as expected.
I can certainly put the light bulb in series between the audio board and the PS board, if that is what you mean.
So, zeners removed from circuit and just use ohms to test is acceptable? I read a bunch of stuff about adding batteries and things for testing them and wasnt sure.
I test diodes on both diode-check and resistance. If they test OK, they're likely fine.
I posted on another thread:
This method of checking breakdown voltage was regularly useful for diodes/Zeners and other components. I had a variac that I drove into a bridge rectifier and capacitor to get to about 200v DC for testing.
You can use batteries but that would be useful only for lower voltages.
With either method above, you'd either use series resistors or some other limiter to protect the zener.
As was previously stated, you really don't need anything to check the breakdown voltage except the circuit that it's in. If it checks OK with a meter but the installed breakdown voltage is wrong, replace it.
I posted on another thread:
This method of checking breakdown voltage was regularly useful for diodes/Zeners and other components. I had a variac that I drove into a bridge rectifier and capacitor to get to about 200v DC for testing.
You can use batteries but that would be useful only for lower voltages.
With either method above, you'd either use series resistors or some other limiter to protect the zener.
As was previously stated, you really don't need anything to check the breakdown voltage except the circuit that it's in. If it checks OK with a meter but the installed breakdown voltage is wrong, replace it.
I made another mistake in my post. q2 (fictional transistor regarding the deviant schematic we have been using, but relevant to my simple one) has its EMITTER, not collector to ground for both rails. The PCB is printed this way. Im sorry for the mistake.
Ok and duly noted on the testing method for the zeners. I presume these dont normally have any physical signs of failure unlike the regular diodes that blow holes in themselves?
Ok and duly noted on the testing method for the zeners. I presume these dont normally have any physical signs of failure unlike the regular diodes that blow holes in themselves?
manually tested a lot of things on the audio board, everything i tested seems ok. I dont have a capacitor tester, so, not sure how to go about that.
I put the light bulb in series between the pos rail wire that goes to the audio board from PS rectifier and the moment it is connected, voltage drops to 2vac. Disconnect it quickly, and it return back to 33v. Hold it for 5 seconds and it does not recover for a while. Even after power cycling. Maybe 45 seconds for it to recover. even with the power off.
I put the light bulb in series between the pos rail wire that goes to the audio board from PS rectifier and the moment it is connected, voltage drops to 2vac. Disconnect it quickly, and it return back to 33v. Hold it for 5 seconds and it does not recover for a while. Even after power cycling. Maybe 45 seconds for it to recover. even with the power off.
continuously monitoring. Essentially, connected scopemeter, left pos rail disconnected, waited for it to power up, observed 33v square wave, touched wires together, observed voltage loss, immediately released and observed recovery.
scopemeter connected throughout the entire test. 2vac, as measured at the same test point of the pos rail. scopemeter connected to the same point at all times. This is pos side of probe to pos rail, and neg side of probe to the shared neg between the two rails where we have been focusing.
squarewave disappeared when voltage dropped out.
scopemeter connected throughout the entire test. 2vac, as measured at the same test point of the pos rail. scopemeter connected to the same point at all times. This is pos side of probe to pos rail, and neg side of probe to the shared neg between the two rails where we have been focusing.
squarewave disappeared when voltage dropped out.
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