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
peter snipped-for-privacy@hotmail.com