FINALLY fixed my Amplifone deflection PCB 100%

Level42

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I've rebuild my Amplifone deflection PCB "ages" ago...but I started having problems some months ago....

It would run 100% for about 20 minutes or so. But then the screen would start to blank for like a second and then come back. It would also sometimes show some horizontal "wiggle" in the lines, esp. on the trench level.

When I kept running it the blanking became more frequent and taking longer. When it happened the spot killer LED turned on. If I let the machine cool down, it would run fine again for 20 minutes and the same thing starting to happen again.

Note that I already had installed an extra 230VAC fan blowing up (installed under the HV board so that it blows over both the HV- and deflection boards).

So I did another run of about 20 minutes of play and when it started to go blank, I went to the back and starting pushing and tapping parts around the board. At one point I found that if I pushed the top most MPSU57 transistor (the small one on the heatsink) the spot killer would kick in constantly. Release and it went out again.
So I found the location. Examined the board and sure enough there was a light break in the soldering of one of the legs. It looked very much like this (this is actually from a resistor in the same top corner of the PCB):


I tried fixing it a couple of times, but never got it 100%. I found a LOT of bad solderings in this area. The reason is simple enough: since it's in a cockpit, this corner of the deflection PCB is probably the hottest spot in the cabinet.

In the end, I decided to make some bridges from the tracks to the transistor since the soldering eyelets had gone bad. This looked whacky, and also turned out to work whacky.

So, I bought some new transistors, the bigger sized version (highly recommended) and installed it. I scrapped away some of the covering of the tracks and soldered the (long) legs from the transistor to them.

And ever since, it's working GREAT ! Not a single blank anymore, even when pushing and tapping on and around it.

Anyway, the conclusion is:
1) if you have a cockpit (or have a deflection board that comes out of one) be sure to check all the solderings using a loupe, and trying to "wiggle" the parts while you look at the solderings...
2) USE A FAN...it is already a highly suggested addition, I'd say it's simply an absolute neccesity to keep your SW/Amplifone healthy.
 
I also think I have found what the problem of a "walling" WG 6100 may be: picture is not wide enough.

Since I worked on my board, the H pot had moved a bit and now the picture was well within the edges of the screen, so much that it started to "wall" or fold over on the sides.
It looks exactly like the problematic WG6100 I worked on before.

MAYBE the width simply can't be adjusted wide enough on the WG6100 when it's running a 25" tube...it would figure since it's been designed to run a 19" tube...

This will need a little more investigation....
 
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