G'day everyone,

I have a problem with a Philips TV (Chassis FL 1.0), I think with the
tuner, the FQ816 ME/IF.

Have already replaced all the elco's and the input MOSFETS (BF998), but
that didn't cure the problem (noise only, no reception; scart works
fine). Have put in a new tuner (new, old one :-) also with new elco's,
but same problem as with original tuner....)

However, I noted that with careful prodding with the 'wet finger'(TM),
I could get perfect reception. This injected +12V on pin5 (not
connected in this chassis to anything else).

So, my guess is that somehow, the gain of the TV tuner is reduced, but
by injecting +12V (+5V also works, but more noise in picture) via a 22k
resistor, gain can be externally adjusted (this is used in SOME FL 1.0
chassis that have 'Cable MAC', whatever that is; mine doesn't have
anything connected to pin 5)

Questions:

- how is gain adjusted internally in this tuner? analog, via one of the
(internal) ICs in the tuner, or via I2C?
- anyone have a guess what may be the problem with these 2 tuners, or
could it be in the TV itsself? (it could be if gain was encoded via
I2C)

- does anyone have a schematic of this tuner (FQ816)? Philips doesn't
make them available (at least, I can't find them)

BTW, the FQ816 tuner accepts RF and puts out video (CVBS), audio and IF
(38.9MHz), so it's basically a 'tv in a tin can'

Hope any can help out,

Grtz,

Peter Dingemans
The Netherlands