Toshiba CN36Z71 shaky pix


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Toshiba CN36Z71 shaky pix

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vcrguy
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Nov 7, 2004, 1:10 AM

Post #1 of 2 (1876 views)
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Toshiba CN36Z71 shaky pix	Can't Post

Have a Toshiba Model CN36Z71 (Chassis TAC 9925, Mfr. Feb. 2000) 36" tv that came in with a blown
fuse F470 (2a/125V250V) for the main B+ line and a shorted HOT (Q404, D2553). After replacing
these components, set turns on with what seems to be a vertical problem. The picture is stable
for about ten seconds and then begins to shake vertically. The shaking ceases after about five
seconds and the picture becomes stable for another ten seconds when it begins to resume the process
all over again. This happens a few times until the pix disappears and a dark screen with very
faint red retrace lines appear.The main B+ line measures 124.2 volts when the pix is stable
and jumps to an erratic 129 volts when the pix shakes. The vertical supply from the flyback
(pin 6, diode D302) is 27.72 volts when the pix is stable and changes to 28.63 volts when the
pix shakes. This set uses the vertical IC TA8427K. Due to the initial problem, have ring test
the flyback which appears to be ok. I also checked caps in horizontal deflection circuitry
as well as electrolytics in vertical section. I must mention that original tube and box were
left at customer's residence and I am using an RCA CTC203 25" tube setup for testing. Any help
would be appreciated. Thanks ahead, Ron.

vcrguy
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Nov 12, 2004, 9:21 PM

Post #2 of 2 (1857 views)
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Re: [vcrguy] Toshiba CN36Z71 shaky pix [In reply to]	Can't Post

As I had mentioned, I used a 25" RCA CTC203 to test the chassis (instead
of carting around a 36" monster from the customer). Apparently, this was
the problem. I have used this jig to test 36" RCA's without any problems.
However, it does not work on the Toshiba chassis. Once I reconnected the
chassis to the customer's 36" tube/yoke, the tv worked like a charm. I
can now blame the vertical shakiness on the mis-matched yoke. Also, I
discovered that the 12 volt regulation section had problems .
The feed resistor developed ring cracks. The support caps around the
actual regulator were leaking. I wish Toshiba would have placed this
circuit where I would normally find it. I would have discovered the problem
earlier. So this is how the whole thing started. 12 volt regulator develops
problems and creates intermittent feed to jungle ic. Jungle ic, in turn,
develops intermittent horizontal drive to driver and in turn to horizontal
output. When output is underdriven, it shorts. Thank God flyback is ok.
Same situation on Sonys with ring cracks on driver transformers and
RCA CTC203 with ring cracks on L4401 coil which is base feed to horizontal
output. Thanks everyone for your help. Ron.

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