Amplifone help needed

Hi all,

This past weekend was a dark time for my Amplifones .. I need some
serious help. I'll explain the best that I can.

Last week, my WinTron unit arrived, so I decided to install it this
weekend. Originally, I had one completely working HV board with the red
transformer, and I had one non-working HV board. In the non-working
board, I replaced the BU406D just for grins, installed a cap kit, and
basically tested every component to make sure that it was going to work
when I installed a working HV transformer into it.

Because I knew that my working board was in good shape, I decided to
install the WinTron unit into it. I figured that if I install the
WinTron into board #2, and it has a problem, I might break the WinTron.

I installed the WinTron into board #1, and the working red HV
transformer into board #2.

Now here is where the problems began. I hooked #1 up, and the screen
was incredibly bright, and all the colors were washed out. Everything
was white. The neck of the crt was glowing much brighter than it ever
had normally, and then the monitor display changed and only displayed
RED. I assumed that the brightness was just turned up too high, so I
turned it down. The brightness did decrease ever so slightly, but not
enough. Even in the lowest position, the screen was still blazing away
like you wouldn't believe.

I checked my HV, and it was at the appropriate 19.5KV. I figured that
perhaps my drive and bias pots needed serious adjustment with this new
transformer, so I exercised those pots and saw only miniscule effects on
screen.

Basically, what I can tell is that the heater is glowing entirely too
brightly, and I can't turn the brightness down enough. I verified that
all wires going to the focus block are good. I even measured the block
with my ohm-meter to make sure that none of the resistors opened up.
They all checked out good. I triple checked all my wiring of the HV
transformer before powering up. I can't figure out what possibly is the
problem. The only guess I have is that the WinTron unit is defective
and its outputting at least the wrong heater voltage ...

What I don't know is whether or not a brightly glowing heater would
cause this symptom or not. I even tried lowering the HV, and this had
no effect on the screen brightness. All it did was shrink the size of
the screen.

-------

Ok, so I had some bad luck with #1. I figured that I'd at least get #2
working. I hooked it up, and I got HV, (I could hear it!) but the
heater didn't even glow! ARGH! No picture, needless to say.

-------
Now that I had sucessfully destroyed two HV boards, I figured I'd
continue.

I decided to try to get back to a working state. I removed the WinTron,
and put the original HV transformer back into board #1. I even swapped
a different tube into the mix (known working) and another deflection
board with properly adjust gain and bias pots. When I turned this on, I
had an over bright screen, washed out colors, but a normal heater glow.

Fiddling with the screen brightness still was not enough to make the
screen dim enough.

The HV checked out at 19.5KV.

I can't figure out anything else on the monitor that I can possibly
adjust to make it look correct. This is driving me mad!

I noticed one really weird thing though. I noticed that if I raised
then lowered the screen brightness rapidly, that the display would look
absolutely NORMAL and perfect for about 1 second, then it would quickly
become too bright.

I turned it all off and let it stew. I'm really out of ideas for the
moment. I can't figure out why it is that any of these problems
happened as they did.

-------

Basically:

1)Why was the heater voltage too high with the Wintron? Can it be
adjusted?
2)If I could lower the heater voltage, would that make the screen less
bright?
3)If yes to #2, why was the screen too bright in my 3rd experiment even
though the heater glowed normally?
4)Since the HV was measured at the normal 19.5KV, what else can I adjust
on the HV board to make the (apparently) out of whack voltages, correct?
5)What do you suppose happened to my red HV unit when I put it into an
apparently defective HV board, and then transplanted it back? It still
generates HV, heater, etc, and I get a picture (my 3rd experiment).
6)Is it possible that the WinTron unit is defective, and that now I also
have a bad red HV unit to boot?

At least I am learning. :-) At least, that's what my wife tries to
remind me of. That's what I tell her when I have all these failed
experiments. :-) But this time, it's getting harder to remember that.

If you have some time, and some clues, I'd really enjoy hearing from
you. I'll provide more details if you have more questions.

Thanks!
Joel-
Received on Mon Nov 3 07:52:40 1997