*solved* K4600 cap kit and now black screen

tenjuna

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I had a K4600 that was working but needed a cap kit. Did that and reflowed all of the connectors and now I get no video. If I turn the black level all the way down I get a white screen with raster lines. If I turn the Screen knob on the neck board I get a red hazy screen but no gameplay.

I have replaced the black level pot twice, rechecked caps, fixed questionable traces, and I am at a loss as to what to try next. The only thing I am doing just to be sure is trying to buy a replacement video interface board, as it had a lot of lifted pads and traces (though I bodged them all and checked continuity).

Anyone have any ideas? I cannot think of anything else to try at this point.
 
Look at Randy Fromm Flowchart for K4600. In your case says to check transistors TR/Q201 TR/Q202 and diodes ZD201/ZD202 and pot VR201.

Flowchart attached here.
 
They only slot in one way, and I went through the flowchart already. I have a P313 video interface board, I am going to try and buy a P317 and see if that helps any.

Appreciate the replies.
 
They only slot in one way, and I went through the flowchart already. I have a P313 video interface board, I am going to try and buy a P317 and see if that helps any.

Appreciate the replies.

Cool, I couldn't remember how they were keyed.
 
Definitely let us know if a different board helps. My K4600 that has the same issue has a P317 board, I'm going to try replacing TR201, TR202, and ZD201. The transistors seemed okay with my multimeter but the diode was measuring a bit iffy compared to the other zeners I have on hand.
 
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I am actually doing the same with my P313. Even though they are testing fine, there really isn't much else in line that could be causing this so it's worth shotgunning a few bucks at it.
 
Definitely let us know if a different board helps. My K4600 that has the same issue has a P317 board, I'm going to try replacing TR201, TR202, and ZD201. The transistors seemed okay with my multimeter but the diode was measuring a bit iffy compared to the other zeners I have on hand.

FYI, I am replacing R422 on the neck board as well for good measure. As far as I can tell TR201, TR202, ZD202/202, VR201, R222 is pretty much the parts pathway so may as well replace them all at once. I also have a few boards coming plus an XY board just in case.
 
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Following up after doing some more experimentation this morning.

After reading a bunch of old posts with others having the same issues, the common theme seemed to be VR201 issues or cold solder joints. This morning I tried reflowing the connectors on the XY board again, but this time I removed the solder entirely and put fresh on.

I also turned down the black level pot to just above it's CCW most setting. Since going all of the way CCW would give a white screen and raster lines, my theory was maybe the new pot was turning it full black even at the halfway point. So I put it at "9:00" where full CCW is like "7:30".

One of those things has given me my picture back. Hopefully this helps someone that inevitably has a K4600 problem after recapping.
 
Following up after doing some more experimentation this morning.

After reading a bunch of old posts with others having the same issues, the common theme seemed to be VR201 issues or cold solder joints. This morning I tried reflowing the connectors on the XY board again, but this time I removed the solder entirely and put fresh on.

I also turned down the black level pot to just above it's CCW most setting. Since going all of the way CCW would give a white screen and raster lines, my theory was maybe the new pot was turning it full black even at the halfway point. So I put it at "9:00" where full CCW is like "7:30".

One of those things has given me my picture back. Hopefully this helps someone that inevitably has a K4600 problem after recapping.
Great that you got yours going again, guess I'll try reflowing mine again, remove all the solder completely this time.
 
Following up after doing some more experimentation this morning.

After reading a bunch of old posts with others having the same issues, the common theme seemed to be VR201 issues or cold solder joints. This morning I tried reflowing the connectors on the XY board again, but this time I removed the solder entirely and put fresh on.

I also turned down the black level pot to just above it's CCW most setting. Since going all of the way CCW would give a white screen and raster lines, my theory was maybe the new pot was turning it full black even at the halfway point. So I put it at "9:00" where full CCW is like "7:30".

One of those things has given me my picture back. Hopefully this helps someone that inevitably has a K4600 problem after recapping.

reflowing done incorrectly causes more problems then you can imagine and that is why you should follow our video instructions on reflowing correctly and so should everyone. the term i think confuses people as its NEVER adding solder but removing all and reinstalling all new solder. its especially bad because most don't even clean their pcbs so that even introduce all the outside contaminants into the solder that is caked on the pads when they melt the old solder.

Great that you got yours going again, guess I'll try reflowing mine again, remove all the solder completely this time.
make sure to watch the video too.
 

reflowing done incorrectly causes more problems then you can imagine and that is why you should follow our video instructions on reflowing correctly and so should everyone. the term i think confuses people as its NEVER adding solder but removing all and reinstalling all new solder. its especially bad because most don't even clean their pcbs so that even introduce all the outside contaminants into the solder that is caked on the pads when they melt the old solder.


make sure to watch the video too.
Actually it was that very reply you gave to someone years ago about a K4600 that made me remove the solder this time. So yeah thank for that and all the great parts!

Now that I know the videos are there I will check them out. Definitely not an expert over here, just a hobbyist trying to get his games running :)

Thanks!

Cain Cross
 
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