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Video Problems with my TRS-80 4p

nfeasey

New Member
Joined
Jan 11, 2010
Messages
3
Location
California
Hi,
I recently pulled my 4p out of the closet. Powering it up, I found the monitor was flickering like in the attached photo and this short video. Any thoughts on how I can fix it?
Thanks!
Nigel
 

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Welcome to the forum @nfeasey , though it appears that you’ve been with us for quite some time!

As far as the flickering CRT goes, I’d recap the power supply. My 4p had similar issues until I replaced its caps, several of which were visually leaking.

A number of places sell capacitor kits, including Console5, who I bought from:

- Alex
 
Welcome to the forum @nfeasey , though it appears that you’ve been with us for quite some time!

As far as the flickering CRT goes, I’d recap the power supply. My 4p had similar issues until I replaced its caps, several of which were visually leaking.

A number of places sell capacitor kits, including Console5, who I bought from:

- Alex
Alex,
Thanks for the welcome and the advice. I've ordered the kit.
I feared I might have to play with the video controller board.
-Nigel
 
Just extracted the power supply. The capacitors look pretty new and shiny, which got me thinking maybe it had been recapped when I bought it.tempImageQSL5GB.jpg Digging through my email, I saw no mention of it being recapped; however, I did solve why I joined this forum 10 years ago: I bought the 4p from someone who was selling it here in December 2009. You never know though, so I'll try to test the capacitors and see what's wrong.
 
That psu is notorious for cracked solder joints at the connection pins. take a look on the underside of the board with a magnifying glass.
 
My PSU looked identical, so those are Tandy original caps. I pulled all the electrolytic caps, and 1 had visible leakage around the legs, and the other smelled horrible when I desoldered it, due to electrolyte leakage. So, you won’t be able to tell if there is an issue, without removing the caps.

- Alex
 
I see Rifas! The one halfway down on the right side and the one by the fuse look ok at the moment, but the one by the heatsink looks like it's cracking. Probably not the issue, but I'd replace all the Rifas before they do their thing. And it looks like maybe capacitor goo from the bottom of C18, bottom right capacitor in the cluster in the middle of the heatsink
 
Rifas dont "cause issues" you can snip them out if you want. They clean up line noise going back into the mains. They are a scapegoat everyone feels the need to mention. I mean I replace them. You dont have to but I do. And I have had many, many blow while I was powering a machine... So what.. Nothing is harmed.. Just makes the room smell like burned blueberry waffles and scares you momentarily.
 
I would consider trying to adjust the trimmer cap near the front middle of the 4p as well. it was causing my display to flicker. And I never messed with the power supply.
But that was the problem with my 4p mat not apply to yours
 
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