Chinon 9000 Help also 7500 8500 Audio problem

lvtv <laviejaTV DeleteThis @gmail.com> wrote:
>Help Needed. Service repair manual for CHINON 900 also 8500 7500 i
>think were similar.
>I have no audio, scchematics or circuit diagram specialy for audio
>head, may help me.

I think you will discover that it is very hard to find manuals for ANY
of these projectors. For the most part they were designed to cheap and
disposable and so service documentation was not widely distributed.

For the most part, though, it is not difficult to fix any of these. It
becomes a matter of injecting signal into the head with a signal generator
and tracing it stage by stage down the line. Most of these are just
single capacitively-coupled gain stages with a small power amplifier stages.
So putting an oscilloscope on the base of each transistor tells you most
of what you need to know.

Most of the problems turn out to be bad electrolytic capacitors and the
rest of them turn out to be in the power amp. I tend to just shotgun out
all of the electrolytics before I touch them because if the capacitors are
not bad yet, they will probably go bad soon.

>We are a non prof org from southamerica, i apologise my English.

Your English is much better than my Spanish.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."