Re: Please help with Amplifone monitor for Quantum

Hi Micheal!

Did you replace ALL the transistors and any discolourd resistors? I
assume that the caps you replaced were all 105degree ones.
Did you turn the HV pot all the way down, that is counterclockwise? The
red LED is the OverVoltage indicator, and it can be triggered by either
a problem in the HV regulation OR a problem with the wiring on the
Screen/Focus control.

If you have a variable power supply you might try powering the puppie up
gradually and scoping the 183V line to see what happens. That's what I
do with a problem unit...
The Game board should be disconnected for these tests, and short the
inputs to the monitor XY lines to ground. This will give NO deflection
to the output transistors, much like running an audio amp with a shorted
input there is no danger of damage (well almost no danger).
John :-#)#

MKDUD@aol.com wrote:
>
> Hello,
>
> Please help if you can. I've got an Amplifone monitor that I just can't
> seem to get going. I've installed a new WinTron HV transformer, and installed
> a
> Zannen kit. The game PCB is producing good x and y signals. I'm getting no
> spot
> killer, and I can hear deflection chatter coming from the yoke. (spot killer
> does light at power-up for an instant like it should.) I'm getting no HV, no
> heater glow. I've replaced the BU406D on the HV board, and also have replaced
> the 7824 and 7924. The "overvoltage" light comes on frequently from the HV
> board, but after tweaking the pots on the HV board, the most HV we could get
> was 8-10 KV, while hearing a wierd hiss from the anode. We did check both post
> on the HV board, they test good. The anode is pluged in to the tube, and is
> tight. While watching the meter (HV probe installed under the anode) the HV
> began to climb to a more "normal" range (approached 18kv), the anode just
> started to make a more "normal" power up sound, then we heard something pop
> that sounded like it came from the deflection board. Now there is no HV at
> all.
> What goes to pin #2 when installing the WinTron HV transformer? (This is
> the former pin #2 on the HV board that was used by the old HV transformer.)
> According to Gregg's faq, pin #2 has nothing connected to it. Also, I have an
> earlier Amplifone HV board that has 2 locations labled as "heater". I've got
> the grey wire (from the WinTron HV unit) attatched to the "htr" location to
> the
> left of the brightness knob. I've installed the new HV transformer just like
> the Faq says. What are some of the other components should check on the HV
> board & deflection board?
> When the older Amplifone HV units blow, what parts usually go out with it
> (Aside from the Bu406d?) Can the old HV unit also blow components on the
> deflection board when it goes?
> Can somebody please tell me where I should be measuring voltages on the
> deflection board (and HV board) so I can figure this out? Please help if you
> can, I'm really stuck on this.
>
> Thanks Very Much,
> Michael Kelley

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