4915 Medium Res recapped, now doesn't work

joeycuda

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I'm hoping someone can help me figure this out - Paperboy project. Monitor was working, but cracked solder joints on input connector pins.

As I would in a restoration, I pulled the chassis, cleaned it, and replaced all the electrolytic caps, except the huge filter cap. Reflowed the input connector pins. Now, I get nothing on the screen (black).

Neck has glow, screen control has no effect.

I pulled it back out, verified that none are backwards, no leads left on and shorting, no solder splashes, caps have correct value (some higher voltage) - based on manual.

What should I check next? Thanks in advance!

Joey
 
Hmm, are you 100% sure you have your video connector on correctly after pulling the monitor out and putting it back in? Sometimes it is possible to have the connector seated on the chassis and be off by a pin.. I'd also double check the connection on the boardset as well.
 
I did have this happen another time and it was the video connector off one pin. I checked that this time.

I'll reinstall tonight and check the B+ and get back. thanks..
 
I think I checked the B+ correctly..

The larger of the 2 resistors..the big one isn't mounted on the PCB, but off the top/edge/outside of the chassis, like the pic below

checking at the rear of resistor (towards back of game), I get 159.3vdc. Front edge of resistor, I get 122vdc. I wasn't sure which end was correct to check..

Wells%20Gardner%2025K4900.JPG
 
B+ is a little low (should be 130) but seems close enough that you should have some life.

Look for cold solder on the flyback. Is your anode cup seated in properly?

You say you have neck glow? Check R416 on the neckboard anyway. You may also check Q201 and Q202, although those would only cause a problem if you had raster...
 
Hmmmm...no raster, but do have heater glow...I'd go thru and check for cold solder joints. Touch up everything you can. Especially do the entire neckboard.
 
R416 either looks toasty on one end or rusty. The other 3 resistors, R410-412 look similar though, as if one end is rusty/brown and the coating is chipped off of the end.

Another thing that caught my eye, and I can't see how I did this, so must be factory correct (looks weird)-

Pin 5 of the neck socket ("5G1") is pulled up, as in the socket leg pulled up and not soldered thru the PCB. Socket leg is pulled up, with a white wire soldered to it, going off board.

I'm seeing very faint solder crack rings at the larger resistors thoughout, so I'll try touching up solder joints next.
 
I think I checked the B+ correctly..

The larger of the 2 resistors..the big one isn't mounted on the PCB, but off the top/edge/outside of the chassis, like the pic below

checking at the rear of resistor (towards back of game), I get 159.3vdc. Front edge of resistor, I get 122vdc. I wasn't sure which end was correct to check..

Wells%20Gardner%2025K4900.JPG

Double check... man, I can't remember the numbers... R313 IIRC. The resistor that's standing on end in the upper right of that picture. Make sure it has a GOOD connection to the "frame" holding it up. I've had several of them where it gets a cold solder joint there which effectively kills HV to the tube. Touch it up regardless... it can test good while out of the monitor, but be just a hair off when installed. The frame it's on is the actual connection for it to the chassis... the lead coming from the top of the resistor is soldered (poorly most of the time) to that "frame" around it.
 
Good tip, Scucci, thanks..just looked at that solder joint, and it looks ok, but I will touch it up. I think I see quite a few faint crack rings around resistors solder joints, at the solder pad on the PCB, but no major bad solder joints as I've seen before.

What bugs me is that it worked before, with a slightly squished picture.

This may be the 2nd time I've recapped a working monitor and it not worked 'better' afterwards! Thanks all.. I will work on it one night this week and post results.
 
Last ditch effort tonight. I desoldered and resoldered the larger resistors and some other joints on the neck board. It worked. Well..mostly..I can't seem to adjust the vertical size quite enough - only fills 80% of screen, but it's playable. It really seems like the pot is bad, as it has small zone of adjustment, then the adjustment just freaks out.

Thanks all for the advice. Now on to the rest of the Paperboy restoration-
 
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