K4900 wave

Star City

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I recently picked up a Congo Bongo cabinet that was converted to a heavy barrel. It was playing blind. The fuse was blown. I jumped the fuse and it came on and looked pretty good actually. I know…dangerous, and not smart. I did it anyway and nothing happened. l won't do it again. I've learned a lot so far. Anyway, was working but had a wave rolling from right to left ( I believe this would be top to bottom when considering the way it's mounted?) I shut it down and ordered a cap kit, cleaned the chassis as good as I could and did the cap kit (including the filter). I would say the cap kit made it look better overall but the wave remains. After lots of googling and chatting with Grok, these are things I have done

Cleaned edge connector.

Tested all grounds..all checked out good. Even added a few extras here and there…no change

Tested voltages on the power supply ( it looks to have been installed somewhat recently) all voltages were within range and stable.

The sync wire was ran to the -V and jumpered to -H, I tried removing the jumper and also just running the wire to only -H. No change

Tested B+ voltage at leg farthest away from tube on R503. A steady 154vdc

Where do I go from here? Voltage regulator? When I did the cap kit I reflowed the jumpers and a few other areas I felt looked suspect, and tried my best to check for any more problem areas but I admittedly don't know what the heck I'm doing here. I had one extra capacitor that had a location I cannot find. I wanna say c373. And the instructions had two different capacitors shown for c702. One had an higher voltage so I used that one. I don't know if that was right. Appreciate any direction.
 
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I recently picked up a Congo Bongo cabinet that was converted to a heavy barrel. It was playing blind. The fuse was blown. I jumped the fuse and it came on and looked pretty good actually. I know…dangerous, and not smart. I did it anyway and nothing happened. l won't do it again. I've learned a lot so far. Anyway, was working but had a wave rolling from right to left ( I believe this would be top to bottom when considering the way it's mounted?) I shut it down and ordered a cap kit, cleaned the chassis as good as I could and did the cap kit (including the filter). I would say the cap kit made it look better overall but the wave remains. After lots of googling and chatting with Grok, these are things I have done

Cleaned edge connector.

Tested all grounds..all checked out good. Even added a few extras here and there…no change

Tested voltages on the power supply ( it looks to have been installed somewhat recently) all voltages were within range and stable.

The sync wire was ran to the -V and jumpered to -H, I tried removing the jumper and also just running the wire to only -H. No change

Tested B+ voltage at leg farthest away from tube on R503. A steady 154vdc

Where do I go from here? Voltage regulator? When I did the cap kit I reflowed the jumpers and a few other areas I felt looked suspect, and tried my best to check for any more problem areas but I admittedly don't know what the heck I'm doing here. I had one extra capacitor that had a location I cannot find. I wanna say c373. And the instructions had two different capacitors shown for c702. One had an higher voltage so I used that one. I don't know if that was right. Appreciate any direction.
that would suggest your voltage regulator is bad, yes

there's 2 versions of the K4900. the cap kit covers both. if you had a 47 uf 160V cap at C313 using the 100 uf 250V replacement was right. the K4906 model is the old one.

the C373 is a capacitor that goes across D306 (the - side aligned with the banded cathode side of the diode). I don't think this exists on the K4906.

I've never replaced a voltage regulator on a K4900, I don't even know what the part number is. I would suggest you get one of the blue TO-3 mica insulators, that way you just clean up the old thermal paste and throw away the clear plastic insulator and use the mica in its place. they don't require thermal paste. @paul400 might be able to help more.
 
The voltage regulator appears to just bolt on with two bolts/screws. It's an str381. The c702 was the capacitor that was listed twice. Both same uf, one just had higher voltage. I used that one. There is no c373 location on the board and there was no additional capacitor I could find. There was an another that was on top of a resistor and it did not appear to be labeled correctly on the board. I replaced it with one that was the appropriate values.
 
So I took another look this morning and the one that goes on top of the d306 was the c366, but the "c366" marking is in a different spot nowhere near the capacitor.

Edit: Here is a picture. I guess I shouldn't say "nowhere near" but it's definitely not in the right spot.
 

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Voltage regulator was the fix. Too bad this cabinet is roached. It was a good one to do some learning on.
 
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