Re: Amplifone

> Can a bad HV board fry an otherwise working deflection board?
> Can a bad deflection board fry an otherwise working HV board?

I can't say 100% for sure, but I'd say it's a likely Yes, both ways.
I have personally had a bad HV board blow up a good deflection
board while testing, though it was just the once, but enough
learning for me :-)

The HV board has the +/- 24V supplies in it, and they go to the
deflection board. I suspect a failure or spikes on the +/- 24V
rail caused by a fault on either board can cause damage to either
board. It's more likely to harm the deflection board though, by
causing latchup of the push-pull deflection transistors or drive
circuitry. The deflection board that blew on me when I had a faulty HV
unit connected had some deflection transistors fail as a
dead short (and blew the fuses on it).
It's not as likely the other way, but possible if a bad power supply
rail voltage, spikes or ripple cause the HV unit BU406D drive transistor to
lock on or change the duty cycle greatly, it may overheat or overvoltage
the transformer or drive transistor.
The only way to test properly would be to power up and test the boards
individually, especially test the HV unit without the deflection board
plugged in, which isn't too hard to do. You could put some load
resistors on the +/- 24V output of the HV unit to check the supply capacity and voltage,
and also check and adjust the HV level with a proper isolated HV probe,
and that may make it safer to plug the deflection board in once you know the +/- 24V
supplies and HV level are ok.

Do you have the Amplifone manual and schematics and other troubleshooting documents?

Marc

----- Original Message -----
From: "Bret Pehrson" <bret@classicade.com>
To: "Vector" <vectorlist@synthcom.com>
Sent: Monday, July 02, 2001 4:22 AM
Subject: VECTOR: Amplifone

> Can a bad HV board fry an otherwise working deflection board?
>
> Can a bad deflection board fry an otherwise working HV board?
>
> ---
> Bret Pehrson
> http://www.vaps.org/members/nv/bret@classicade.com.html
> mailto:bret@classicade.com
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>

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Received on Sun Jul 1 19:22:15 2001