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M.Joshi

Thank you to everyone who has replied so far with possible suggestions.

Rubbishrat - I am repairing this T.V for someone else so they would be using it with the built-in antenna.

I don't if this is any help but, the original problem with the television was power related (Blown fuse, 1N4007 bridge diode S/C and MJF18001 als S/C). I purchased a reliability kit for this common power supply problem for the chassis (CUC7303) which includes replacement parts for the diode bridge, a BUT11A instead of the MJF84001, some zener diodes, electrolytic capacitors and resistors.

Could one of the replacement parts indirectly be related to the diagonal lines problem?

Thanks.

Quote:

Originally Posted by Asimov

"M.Joshi" bravely wrote to "All" (20 Feb 05 18:08:50)
--- on the heady topic of "Very Strange Antenna Problem?"

M. From: M.Joshi
M. Xref: aeinews sci.electronics.repair:11029

M. I am trying to diagnose a problem with a 14" Grundig CUC7303
M. television. When using the built-in antenna, there are diagonal lines
M. across the screen for each channel. On certain channels it is not as
M. bad.

M. The strange thing is that, when an external antenna (Outdoors) is
M. connected, these diagonal lines appear to go away?

M. I assumed that this may be a problem with either the tuning or I.F
M. circuitry?

M.Joshi,

It is possible the TV's built-in antenna is picking up stray RF from
the TV's own microcontroller. I have a Sansui TV which was bad for
this. I had to isolate one particularly noisy output line and add
little series resistance to limit the risetime. It was a little tricky
because it was the line to turn on/off the psu. Too much resistance
and it wouldn't turn off and too little and the rfi increased a lot.

However, many compact fluorescent lamps generate a non-negligable
amount of RFI. If you have one of these near the TV try replacing it
with an ordinary filament type.

Good luck,

A*s*i*m*o*v

.... Digital circuits are made from analog parts.