Re: Amplifone monitor and Zannen cap kit

On Wed, 19 Nov 1997, Dan Rasmussen wrote:

> Hi,
>
> I have been working on my Amplifone monitor and have what really feels
> like a stupid question regarding a cap kit. (I did call Zannen about
> it and they couldn't quite answer the question so I'll ask here...). There
> are two 100uf, 50V caps on the deflection board (c19 & c20) which were
> included in the kit. The caps in the kit had an unfamiliar marking on
> them for polarity. Instead of a "-" sign on the striped side of the cap,
> it had "ce". I just assumed that was negative and installed it that way
> but now I am wondering (and I don't want to re-fry my boards). When I
> called Zannen, Aubrey just told me that the side with the short lead is
> the negative side, which is a nice thing to know but too late for me. Does
> anyone know if the side marked "ce" is the negative side?

        I have a Zanen Kit for the Amplifone at home, and I will check to
see which is the short lead when I go home later (if somebody doesn't give
you an answer before then)
 
> I asked Aubrey some other questions, these were his answers (note that
> they are paraphrased, not direct quotes):
>
> Q: Why replace the HV board's C1 and C2 (470uf, 50V) with 1000uf,
> 50V caps?
> A: Better performance, don't worry about it.

        These are just filter capacitors, so they should be OK. Are these
the ones that you are supposed to replace with low ESR caps or not? I
always forget if that's C1, C2 or C3, C4. As an aside, were low-ESR caps
the "standard issue" on the Amplifone? I replaced these (the ones
that are supposed to be low-ESR) with "regular" caps, and everything seems
fine.

> Other questions.... I'm still not sure if my HV board is good and would
> like to first test the monitor without it. Can I just run it with the
> HV board disconnected and listen to the deflection board to hear if its
> drawing vectors. I have had to put some work into the deflection board
> because R31, R30, R28, R35, .... were fried (espcially R30, it was
> completely toast, and burned a nice little hole in C13 and almost through
> the board). This happened when I was running the machine without the HV
> board attached and now I'm afraid of toasting the deflection board again.
> Any comments on this? How should I go about testing?

        Yeah, you can run it with the HV board unplugged and look at the
spot killer. Of course, since the video B+ gets fed back from the HV
board to the deflection board, you're not really testing it completely.

        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.
 
> Two traces have separated from solder side of the deflection board where
> R30 burned. I have worked around it for now but is there a way to re-attach
> these traces to the board?

        Krazy glue might work. Usually I just don't worry about it.
 
Joe
Received on Wed Nov 19 13:21:15 1997