Re: TECH: dead Amplifone

If you pull the BU406D out, you can power the HV board up and verify your regulators are working properly,
and that the waveform on the 555 output is correct (through the chain to the BU406D).

Other than that, there's not much you can do.

A HOT HOT (pun intended) is generally a good indication of a bad HVT.

The only other thing you might check is shorted secondaries, which on that board is limited to
video B+ and heater.

-Mark

btw, tom, your red hvt is bad (go figure) and actually has the same symptoms as Karl's.

----- Original Message -----
From: Karl Doe <kdoe@totalise.co.uk>
To: <vectorlist@synthcom.com>
Sent: Tuesday, November 12, 2002 8:08 AM
Subject: VECTOR: TECH: dead Amplifone

> Hi,
>
> After 9 years of loyal service I've lost my HV board :( The person playing
> the game said the image lost focus then the screen went blank- the infamous
> 'red is dead' problem?
>
> I don't have an HV ringer and don't know anyone in the UK that has so before
> I send $200 to WinTron I'm having a quick look at the circuit and would
> appreciate any help, this is what I've already tested:
>
> The BU406D runs hot after being powered up for a few seconds but tests ok
> using the method in the Amplifone FAQ- it shouldn't run that hot that
> quickly should it?....but I thought it would almost certainly be toast if
> the HVT went.
>
> I'm reading a junction drop of 1.64v on the 1500v rectifier CR3 (is this
> normal?)
>
> The zero ohm jumpers (on both PCBs) and R12 are ok
>
> The over voltage trip LED is NOT lit.
>
>
>
> Thanks in advance
>
> Karl.
>
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Received on Tue Nov 12 07:04:35 2002