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chumba
Joined: 01 Jul 2009 Posts: 66
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Posted: Mon Nov 09, 2009 7:27 pm Post subject: Toshiba CF30F40R TV tuner problems |
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Have a Toshiba model CF30F40R TV with tuner problems. Intermittently the picture gets white lightning bolt-like flashes on the screen with accompanying loud audio static.
Looks like this:
Link:
http://img193.imageshack.us/img193/292/200902200005.jpg
Component inputs work fine and coax connector looks mechanically solid. Problem follows on channel 3 or 4. TV will sometimes go 4 hours without this showing up and then all of a sudden starts acting up.
Have already tried resoldering the tuner pins & case/ground to the PCB and blew out the dust. |
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chumba
Joined: 01 Jul 2009 Posts: 66
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Posted: Thu Nov 12, 2009 11:28 am Post subject: |
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Does anyone know the test points on this tuner to check for tuner supply voltage and channel switching pulse? This tuner has an AGC adjust screw on it that I haven't touched yet. |
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Jesse Mack
Joined: 22 May 2008 Posts: 600 Location: The Last Frontier
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Posted: Thu Nov 12, 2009 1:17 pm Post subject: |
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I would strongly suggest that you remove the cable box first. Hook up your DVD or VCR using RF I/O from the VCR or DVD going directly to the TV, without the Cable box in the loop, and see if the problem still exists.
Since it does not do this using other inputs you must remove the source from the equation as being the problem.
Jesse |
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chumba
Joined: 01 Jul 2009 Posts: 66
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Posted: Thu Nov 12, 2009 4:08 pm Post subject: |
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I have tried connecting another satellite box using the RF connection and the problem still persists on the TV. |
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JTS1957
Joined: 21 Jan 2009 Posts: 2395 Location: Far, Far Away
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Posted: Fri Nov 13, 2009 1:23 am Post subject: |
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I think Jesse means you should try a totally unrelated source (DVR/VCR connected to the RF input of the TV). Unless you are SURE that those particular receivers work on another TV - in the SAME location using the SAME wiring.
For example: what if the LNA for the satellite receivers has a problem.  |
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chumba
Joined: 01 Jul 2009 Posts: 66
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Posted: Sat Nov 14, 2009 8:53 pm Post subject: |
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The TV shows the same problem using a VCR source also. It looks like the tuner freq. lock may drift while the flashing & noise is occurring - it seems to be slightly mis-tuning to the high side of Chan. 3's freq. |
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chumba
Joined: 01 Jul 2009 Posts: 66
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Posted: Sun Dec 13, 2009 8:11 pm Post subject: |
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The following DC voltages were measured on this tuner, part # EL923L2:
Pin1: 2 mV
2: +32.4 V
3: 2.9 to 4.1 V
4: 3.4 to 4.2 V
5: not connected
6: 4.7 V
7: 5.1 V
8: 6.7 V
9: 8.6 V
10: 3.0 V
11: -0.2 mV
12: 2.1 V
13: all over the place
14: - 2.0 mV and goes to -1.4 mV when CHAN+ button pressed
15: 5.0 V
Does this point to anything? I believe the 32 V is the correct supply voltage and it is there. Anything else to check? |
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JTS1957
Joined: 21 Jan 2009 Posts: 2395 Location: Far, Far Away
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Posted: Sun Dec 13, 2009 8:22 pm Post subject: |
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If you are POSITIVE it is the tuner that is causing the problem ... why mess around? $27.00
www.tiptoptuner.com/
To prove, I'd pull the tuner and input an I.F. signal from an Analyzer to the I.F. pin FOIL. |
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chumba
Joined: 01 Jul 2009 Posts: 66
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Posted: Tue Dec 15, 2009 3:51 pm Post subject: |
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Am not positive it is the tuner, that's what I'm trying to find out.
Don't have a signal generator...could I instead remove the TV's tuner and inject the RF output of a VCR? |
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JTS1957
Joined: 21 Jan 2009 Posts: 2395 Location: Far, Far Away
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Posted: Wed Dec 16, 2009 1:29 am Post subject: |
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NO you can't.
The IF output of the VCR's tuner - MAYBE. But then you'd have to make sure you isolate one of the units from the AC outlet so you don't blow fuses when grounds are shared.
R.F. = Radio Frequency I.F.= Intermediate Frequency |
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