Sanyo CPP2930 TV, chassis A8-A29

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I'm working on an intermittent fault in a Sanyo CPP2930 TV, chassis
A8-A29. The customer describes a vertical collapse (horizontal line)
followed by a shutdown and restart. After this happens, the volume is
at minimum.

This article ...

 http://www.siliconchip.com.au/cms/A_30635/article.html

... talks about a service bulletin "dated 27-4-94 (no. 24) for the
CPP2930 and 2530 models, the fault being: 'The TV set switches off and
on (CPU resets momentarily) on VCR search mode'."

The author states that "It was then just a matter of purchasing a kit
of parts and fitting them on the SYNC and RESET PC board (VE2689)".

I have the details of this rework (3 resistors, 1 capacitor) but am
not certain that it will address the aforementioned problem. Is there
anything else to check? A tap test has turned up no dry joints or bad
connections.

- Franc Zabkar
--
Please remove one 'i' from my address when replying by email.

Re: Sanyo CPP2930 TV, chassis A8-A29


Vertical collapse? I would suspect vertical IC or surrounding circuitry. Try
resoldering the IC first and check caps around it.

As for service bulletin -- I beleive it was due to the sync pulses being
wrongly detected byth TV when VCR does FF or FREW. Should not happen on
normal channel viewing.

Rudolf


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Re: Sanyo CPP2930 TV, chassis A8-A29


On Wed, 7 Mar 2007 15:34:39 +1100, "Rudolf"

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That's the first place I checked. I tried tapping and freezing but was
unable to produce a collapse. I did observe an initial warm up problem
where the height was reduced to about 2/3, and I traced the fault to a
dry electro, but I'm not convinced that the total collapse is caused
by the same component.

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Hopefully it is that simple, but I hate to fix something before I
witness the fault.

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The SC article suggests that a particular VHS tape was able to
consistently reproduce the fault. I suppose this could have been due
to dropouts, but the author suggested that it may have been due to
some Macrovision incompatibility.

One thing which is confusing me is that the "Reset and Sync" board,
which is the subject of the bulletin, appears to have two v/sync
sources, a TDA2579B and an LA7210. I guess the first is for TV, the
latter for VCR. I don't have a circuit diagram, BTW.

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- Franc Zabkar
--
Please remove one 'i' from my address when replying by email.

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