Greetings!
I'd be taking a soldering iron to re-heat several joints in and around the power supply connectors in hopes to reduce voltage drop across oxidized contacts...
Regards!
:+> Andy <+:
Thanks for that lesson there Andy. All this IC logic and stuff is really new to me. And I think you hit on a few things that is vital to the operation of these things. I had a friend many years ago that ran an Arcade service. What he did was buy and rent these to different locations around the county. I would stop in and his dad would be in the back room with a roll of solder and a iron. I ask what you doing, his reply was "I don't know, this is what they told me to do when these quit".
He knew nothing about electronics but did know he had to reflow solder joints.
Anyway this is why I quoted this part of your post.
As you can see in the pics below the PLL board is not bolted down. Just sits in a foam shell inside the internal RF shield. It has stiff wire connections that run to feed throughs that lead out of the box. Then there are chokes going to more feed throughs that lead out of the outer box.
While checking a few things I decided to lift the board from is resting place to peek under it. After that I placed it back in and fired it up.
The darn thing started working lol.
I am able to even reproduce the fault by wiggling the board a bit. So one of those stiff wires has a bad connection either at the board or the feed points.
First pic is how the board rest in the internal shield
Second shows these stiff wire connections
Third pic is the crystal oven in my newest 2040
Forth pic is the oven in the failed 2040
Next thing to do is re-solder both ends of the connection wires and a few spots on the board. Specially under that oven!.
This should put the unit back in operations.
Since there are no electrolytic on the PLL board I have to pull the audio board out and replace those caps in the power supply. Kind of strange to put the power regulation on the same board as the audio circuits eh?
Then finally reconstruct the oven enclosure. Not sure what type of foam they used here. But it has to be pretty tough not to melt. Well this one did but the other one has not. When you turn the power switch off the oven stays on.
To keep the temperature stable I have to find something to replace the melted and warped foam with.