25" Amplifone Brightness Problem

Well I dove into the 25" Amp tonight and installed the new Wintron HV
unit. I also installed a Zanen cap kit on the HV and deflection boards.
Tested all resistors to within 10% in circuit on the HV board. Did NOT
test any of the transistors but since I had them I replace the 2 voltage
regulators and BU406D. I have a beige board but it is the small version
that is like the blue updated version. There were 4001s and 50 ohm
resistors on the board (although only 1 was 5w the other was 10w). I
did test the old BU406D that I took out and it tested fine. I have a feeling
the HV unit (red) may have been functional. But the insulated voltage
reg was completly missing and one resistor had a leg lifted as though
someone had been testing something. I mentioned before that the tube
had a 1/8" or so phos burn in the center. Now I may know why.

I turned on the game (we did check +/- 24 at the regs before putting the
BU406D back in and every thing was in range. -24 was more like -32)
and we got a picture. But it was way too bright. You could see all the
traces being drawn and it was almost all white with a bright spot in the
middle but the picture being drawn on almost the whole screen. Possibly
the width was wider than the tube and the vertical height was shorter than
the tube. I tried adjusting the brightness (screen) on the focus assembly
but we didn't think it was helping at all. We later verified that it did
help
some but it is at it's lowest seeing now. Focus may or may not have helped
we just couldn't tell. The PCB was tested in a friends UR 5 months ago.
It worked fine (although he thinks it was too wide on his WG monitor too).
If it is on for a while you start to get more color and can see multiple
colors.
We did not touch R17 since it was sort of glued with red fingernail polish
or something so it wouldn't turn. We figured we would set the HV. I
used the voltage prob and only got 15.5k I turned R7 and got the pot to
it's limit and only got up to around 17.5k. Anode poped off a couple times
on me but I think I have it on good now. Also we tried to put the game
PCB in test mode to maybe get a pattern to adjust width but it seems to
go into test and say "No Errors" and then after 1/2 sec to 1 sec it would
go black on the screen (except for the white dot in the middle). In game
mode the game seemed to work fine.

I just don't like seeing that bright dot in the middle. In reality the
damage was
already done. But still it bothers me. Seems like a Z deflection problem
maybe? If there are any hints you could give me on what to look for that
would be great. I also have no FAQs on the deflection boards. Are there
any? I should also mention that I did NOT replace the 0-ohm jumper
since it was labled differently on my board from the FAQ (and it was white
and not brown). I also did not test the 555 timer since I don't have a
scope.

If the statment that 99% of the time when the red HV goes it takes the
BU406D with it is true (from the FAQ). Then is it also true that if the
BU406D tests fine when removed then 99% the HV unit is still good?
I don't want to run the red in there for obvious reasons. But I might not
toss it if it's good. Guess I need a ringer.

Thanks for reading this. I know it's long but wanted all the information
available for anyone that might have an idea what my problem is.

Thank you in advance for any help.

Greg

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Received on Wed Mar 6 19:11:52 2002