Wells 4600 B+ floating / not stable

[JohnnySilverFace]

Hi guys, having a issue with a K4713 (13" 4600)
B+ is slowly moving a volt up and down (.5 each way) it takes about 4 seconds to cycle up then 4 seconds down.
Has anyone else ever run into this issue?

Monitor has all new caps, all reflowed
B+ pot has been replaced
HOT and B+ transistors replaced.

Thinking issue may be with the Horiz/Vert board, could a transistor cause this or is it more likely a trace/solder joint that I have missed in circuit?
Thoughts?
Thanks much!
John

 

[mecha]

I think it may have been a Randy Fromm instruction from many years ago, but B+ will change depending if the screen is bright (goes down) or dark (goes up)

people place such an extreme focus on B+ voltage, when it's just a negligible difference that doesn't matter. (the G07 crowd that genuinely believe there's that much of a difference between 117 and 120V)

only if it's very high or low and you get waves or barely see anything (when the filter cap actually is bad) will it be an issue.

does the picture look fine right now?

 

[CharlieG]

What is on the screen while this is happening?

 

[JohnnySilverFace]

Game Plays Great (Defender cocktail) and monitor looks really good.
Original issue that started this was the monitor would go into HV shutdown on startup until warmed up a bit , like 5 power cycles.
After Pot replacement I was able to dial down the DC a couple volts and now it starts up but has the weird floating issue. Set to about 124.5 V now.

*Not sure what normal shutdown voltage should be but as a side note if I go to 128V it goes into shutdown.

If a float of 1V is considered OK , the game is totally playable and looks good.

 

[CharlieG]

You're testing the B+ with the game running in attract mode? Not with a static image from a TPG or something? B+ will generally fluctuate as the monitor is drawing an image.

 

[JohnnySilverFace]

Just fired it up and pulled up the onboard convergence/ test grid screen and the voltage swing was same. It's about 1.3 volts total swing and its very slow and steady up and down, does not jump in large numbers etc.

 

[mecha]

Game Plays Great (Defender cocktail) and monitor looks really good.
Original issue that started this was the monitor would go into HV shutdown on startup until warmed up a bit , like 5 power cycles.
After Pot replacement I was able to dial down the DC a couple volts and now it starts up but has the weird floating issue. Set to about 124.5 V now.

*Not sure what normal shutdown voltage should be but as a side note if I go to 128V it goes into shutdown.

If a float of 1V is considered OK , the game is totally playable and looks good.

I think your mission was a success then