My amplifone monitor... update

Hello again,

Thanks to joelr@an.hp.com for letting me know about the ce being
the negative side of the caps. Anyway, I got the boards together and
plugged them in last night and had another light show. Again I fried
a bunch of resistors: R30, R35, and R34. This time I also blew out
F2. Looking back at what jwelser@ccwf.cc.utexas.ed had to say:

> The only things that can sink enough current to toast resistors on
> the defletion board are the deflection transistors, or maybe even the
> pre-drivers. I doubt an HV problem caused those to toast. If you have a
> short on the HV board, one of the two fuses located near the connector
> that goes to the HV board will usually blow (or both might blow...) A
> "normal" deflection board won't toast istelf as a result of this, and
> operating the deflection board with the HV board unplugged has the same
> effect as having those fuses blown.
>
I had hoped that the new transistors (Q16, Q17) had solved the problem.
After watching the sparks (plasma) fly, I figured Q14 and/or Q15 were
the problem. Sure enough, I pulled out Q14 and it was shorted all the
way around (I think Q15 had problems too). The transistors on the other
side of the board (Q4, Q5) seem to be OK. So, where can I find these
parts: MPS-U07 and MPS-U57? The Woodcock/Scheive material I have looked
at tells me that NTE188 and NTE189 are equivalent parts.

Thanks.

Dan R.
dras@sw.stratus.com
Received on Thu Nov 20 08:31:26 1997