K4600 help after cap kit!

Radford119

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I just recapped a WG K4600 series chassis and it worked great for about 10 minutes and all of a sudden started cutting in and out. A few seconds of this and now the monitor shows no picture and I have no neck glow. When the monitor was going out it made a noise like it is powering up and then powering down.

- Double checked all the caps and everything is correct as far as I can tell.
- The B+ is reading about 170v

Where do I go from here and is the B+ adjustable? Anyone have a flow chart for this monitor? Thanks for any help, I appreciate it.
 
According to the Randi Phromm flowchart, your B+ should be 127VDC (measured @ the blue lead of TR502). If it's 160V (or 170V...), it's too high, and you likely have horizontal deflection failure.

The aforementioned flowchart then suggests you swap in a working vert/horiz board. I'm guessing you don't have one... in that case, it says to measure the voltage on the metal case of TR601: 0V or 160V?
 
According to the Randi Phromm flowchart, your B+ should be 127VDC (measured @ the blue lead of TR502). If it's 160V (or 170V...), it's too high, and you likely have horizontal deflection failure.

The aforementioned flowchart then suggests you swap in a working vert/horiz board. I'm guessing you don't have one... in that case, it says to measure the voltage on the metal case of TR601: 0V or 160V?

Thanks for the response. I don't have another XY board to swap in. The measurement of the case of 601 is also 160v+.

Do I have a bad TR502?
 
Thanks for the response. I don't have another XY board to swap in. The measurement of the case of 601 is also 160v+.

Do I have a bad TR502?

It says: "Check TR351-354. Try replacing C356, C358 & C362. Bad solder joints are common on connectors (I concur with this)." ...then it says to call him for help if all else fails.
 
I will test them out. Does anyone know if it is common for this chassis to do that after being capped?
 
Thanks Ken, I will check them out tonight. What would cause the chassis to put out 170v on the B+? Would cold solder joints do that? Does this monitor have some auto shutdown on it? Am I doing damage by running it at 170v repeatedly while trying to troubleshoot?

Added: I noticed VR501 is locked down with some glue. Would it be possible to dial it back to 127v if I got it loose? Or is this probably not the cause of the 170v?
 
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According to the Randi Phromm flowchart

WU44t.jpg


;)

I find k4600's are a bugger to work on. At least if you have more than one you can swap around the plug-in boards to determine where the problem is. I'm not sure if cold solder joints would cause your problem, but I'd definitely touch up the solder on all the header pins anyways. I do that regardless whenever I work on these. And yes, it's common for any monitor to stop working after a cap kit. Look at all the ".. problem after cap kit" threads in this sub-forum. :)
 
What would cause the chassis to put out 170v on the B+? Would cold solder joints do that?

Added: I noticed VR501 is locked down with some glue. Would it be possible to dial it back to 127v if I got it loose? Or is this probably not the cause of the 170v?

170V is what you get on the B+ line with no load on it. It means that the HOT isn't "doing its thing" and pulling the B+ thru the flyback. If the HOT were bad, it'd likely be short, and you'd have a blown fuse instead. In your case, it would appear that what drives the HOT is the issue. What drives the HOT is the H/V board.

Yes, bad solder joints could do it. The signal for the horizontal deflection is generated on the H/V board, and the HOT is on the main PCB... they are connected at P302/J302. So a bad connection there could prevent the H/V boards signal from getting to the base of the HOT... I'm sure there are other places that could cause the issue also. Be wary of any place something plugs into the main PCB--inspect very carefully or just re-solder for good measure.

Don't try to adjust the B+ down. The issue isn't adjustment; it's a lack or horizontal deflection which isn't loading it.

Does anyone know if it is common for this chassis to do that after being capped?

A lot of problems seem to crop up after a cap kit. There could be a number of reasons for this:
1) mistakes get made in replacing the caps. Double and triple-check you work for mis-placed caps and reversed polarity.
2) damage can be done in the process. Check for leads having been bent and shorted, or stress at headers causing cracks.
3) some theorize that new caps put more operational stress on other components which were formerly marginally working.


:D
 
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Retouched pretty much all the solder joints on both daughter boards and the main board. Plugged it up and it came back to life! Thanks everyone for your help and the advice.
 
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