One of the small rectifiers at the end of the 9 mosfets is reading low (less than 10 Ohms, moving around) tab to sink. That's just holding the tab down on the tape with the probe. Center tab also, less than 1 ohm
No, but both its tab and center lead read short to the mounting ring where the board mounts to the sink. The other transistors, including the corresponding rectifier on the other side, do not.
That's one of the rectifiers that produces the power supply drive voltage. That should not have any contact to the secondary (causing the RCA shields to read 1.8 ohms to the sink).
Did you tighten all of the transistors down tightly to see if any were shorting when tight?
Did you tighten all of the transistors down tightly to see if any were shorting when tight?
Just laying the board into the sink causes the tab to sink reading to go short. Slowly lift it out and it goes open ... for the one rectifier.
Just that one rectifier. Not the same one on the other side, or any others. Its tab and second terminal is shorted to the metal mount points on the board that touch the sink when you seat it. They are ground, there are four of them on the power supply side where the board screws to the sink. In other words, its tab a second terminals are shorted to ground.
If the tab is connected to the grounding pad, that's OK.
Is the din connector shorting to the heatsink?
Are you still reading 1.8 ohms shield to ground?
Is the din connector shorting to the heatsink?
Are you still reading 1.8 ohms shield to ground?
Sorry if I'm confusing the issue. The tab and second terminal of the rectifier next to the 9 mosfets on one side of the power supply are shorted to ground. The other is not. Bad device?
OK. Well that's the only one reading short from tab to ground and if I follow I guess that is OK.
You can't ignore the short that you had between the shields and ground.
What's wrong with the channel that's not working correctly?
Do you have access to a scope?
What is the DC voltage on the 3rd leg of the muting transistors?
What's wrong with the channel that's not working correctly?
Do you have access to a scope?
What is the DC voltage on the 3rd leg of the muting transistors?
It now reads the same seated or not. Before, it would read short. I ground back an overly large solder joint that was near or in contact with the sink when the board is seated.
No
This has been corrected. Still noise.
I get a steady tone, about the frequency of an elevator tone, in both channels. It is louder in one than the other. It does not respond to gain adjustment. It is present whether or not there is signal drive. Otherwise the amp seems normal.
No. But I could buy one.
I can check.
-15 is OK.
If you're going to do this type of work, you need a scope but I don't want you to buy a piece of junk.
Do both channels produce clean audio other than the noise?
If you're going to do this type of work, you need a scope but I don't want you to buy a piece of junk.
Do both channels produce clean audio other than the noise?