Level42
New member
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.
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.