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TOH Guest
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Posted: Mon Jan 14, 2008 10:33 pm Post subject: Toshiba Model 32A10 |
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Hi there,
I have a Toshiba model 32A10, chassis number TAC 0019 tv. The picture is fine but the on screen display of the channel number, volume, or menu item does not work.
I purchased the schematics and have determined that QA01 ic TMPA8700CPN-1A05 generates the on screen display. It is an 8 bit micro that does the OSD and also generates test patterns. Pins 28 & 29 of this ic connect to LB01 IF Coil TRF1196D. This oscillator generates the on screen display. It is not oscillating. I removed the ic and the coil and thoroughly cleaned the pcb to ensure no residue is interfering with the operation of this high impedance circuit.
Does anyone have any idea what frequency this oscillator is supposed to run at? Additionally, any electrical specs on the TRF1196D would be appreciated (dc resistance, resonant freq, etc.)
Any info would be appreciated.
Thanks in advance,
Bob |
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vtech
Joined: 08 May 2006 Posts: 1264 Location: USA
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Posted: Tue Jan 15, 2008 12:10 am Post subject: |
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You may want to refer to the datasheet for the TMP8700. That would be the best place to find most of your specs.
I am not sure of a reliable way in testing the LC coil as it can only have a shorted cap or possibly an open coil( doubt in this case) . Also, while not familiar with the particular set, you may not be able to measure/see the oscillation; meaning that it may only resonate when/if there is a signal present?---not necessarily all the time like w/a standard crystal.
While it sounds more like a problem within the IC itself, there are other parameters needed such as V & H pulses . For specific operation, may want to refer to pages 110(OSD block) & 161(some LC coil info) of the TMP8700 data sheet.
Good luck |
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TOH Guest
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Posted: Tue Jan 15, 2008 2:17 am Post subject: Data Sheet Source? |
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Thanks for the reply!
Could you please forward the source of the data sheet for the micro chip? The one I download from Toshiba was only 10 pages with chip pinouts, maximum operating sprcfications, and a block diagram.
Thanks,
Bob |
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vtech
Joined: 08 May 2006 Posts: 1264 Location: USA
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Posted: Tue Jan 15, 2008 4:19 am Post subject: |
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Ok Bob,
You must have gotten the smaller version
Here's all you ever want to know about TMPA8700---- all 162 pages
http://tinyurl.com/23tzjs |
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TOH Guest
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Posted: Tue Jan 29, 2008 5:35 am Post subject: Toshiba 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!
Thanks!
Bob
Final Update:
Thanks to VTECH, I have the real version of the data sheet
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.
Thanks a million VTECH!!!!!!
Bob |
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vtech
Joined: 08 May 2006 Posts: 1264 Location: USA
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Posted: Tue Jan 29, 2008 7:04 am Post subject: |
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.. glad to be of help Bob.... Is that not great to tshoot & find a problem?
Only proves that nothing beats spending a little time,getting familiar & applying the basics as you did.
Greatt Job! |
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