Toshiba 32" model 32A10

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I have a 32" Toshiba that displays a picture, but the on screen
display of the selected channel, volume, or menu item when menu is
selected does not appear. I have successfully followed the procedure
for initializing the registers in the QA02 processor but still no
display. Any ideas?

Bob

Re: Toshiba 32" model 32A10


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Update:

Found a block diagram of the Toshiba TMPA8700CPN micro proc (QA01 in
the schematic). It produces the On Screen Display found in the TV.
Pins 31 &32 have a 8MHz oscillator attached that is functioning. Pins
28 & 29 are connected to LB01, a TRF1196D IF Coil. I do not see this
oscillator functioning. Anyone out there know what the characteristic
of the TRF1196D coil are? (DC resistance?). Additionally, would anyone
know what frequency this oscillator is supposed to run at?

It would be my conclusion that either the TMPA8700CPN micro proc
(Toshiba part number 23000287) or the TRF1196D IF Coil (Toshiba part
number 23262280) would be the issue. I have removed both parts and
cleaned the circuit board to remove any residue that might cause this
high impedance circuit to malfunction.

If any of you out there are interested, I have the schematic diagrams,
etc. and could email them .

Any help would be appreciated!

Cheers from Canada!

Bob

Re: Toshiba 32" model 32A10


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Final Update:

TMPA8700CPN data sheet input output circuitry section revealed that
the oscillator is gated and that was why it was not observed to be
working. When a button is depressed, the osc. starts and runs for the
duration of the display. I observed a frequency of about 1KHz.
Assuming this was the dot clock for the display, the frequency should
be at least 8 dots/char X 32 char/scan line X 15,750 scan rate =
4,032,000Hz. The osc. must actually run faster because of the
requirement for margins on the left and right sides of the display as
well as retrace time.

I once again removed the TRD1196D coil.. Its DC resistance measured
about 860K. I decided to mechanically open up the part and see what
was inside. I found that the measured DC resistance was the result of
pollution inside the part and the coil itself was open. Using my fine
tip soldering iron and my magnifying lens, I managed to restore the
connections. DC resistance turns out to be less than 1 ohm.

The Oscillator now runs at 5.7Mhz and the display works fine. The osc.
is gated by the horizontal sync signal to avoid jitter.

Bob

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