Re: Amplifone HV

Joseph J. Welser wrote:
>
> Fellow vector posse,
>
> I just swapped an Amplifone back into my Quantum, and have made the
> determination that my HV transformer is bad (surprise, surprise.)
>
> The only reason why I post this is because of all the mention of
> the BLACK HV transformers being indestructable, and this is the kind we're
> talking about here....
>
> I have good +-24V. I measured the following voltages (rounded) on the
> BU406D (which I tested, and it looks good) B: -24V, E: -24V, C: +24V
>
> Now, having a Vbe of ~0 surprised me at first, but it seems that the
> BU406D has an internal resistor between the Base and Emitter. The other thing
> that sounds off warning bells is the 48V Vce. The BU406D was cool to the
> touch, and with 48V across that CE junction, I figured it should be at least
> warm (if there was any current flowing through it.)
>
> I'm getting a B+ of like 22V or 23V (I'm sure it's 24V minus the diode
> drop of CR3)
>
> So whaddaya think? I've read Gregg's FAQ, and there isn't much about
> the Amplifone in there....
>
> Thanks,
>
> Joe
>
> BTW: If I didn't mention it explicitly, I'm not getting any high voltage. I
> don't hear a high-pitched tone, or a crackle, or anything from the HV unit.

I would check the base of the BU406D for a signal. The problem is
probably in the switching section, or with the coupling transformer.
I do not have the schematic here with me at the moment, but, check these
things to be sure.
Received on Mon Sep 1 06:51:10 1997