Let talk: TN50X81 (chassis TAC9960), convergence stuff

[Jason D.]

Hi all, I have a set in for "shut down" with LED flashing. Quickly
traced to the "protect" pulling up on shutdown. Tried convergence
power disconnected and tv fired up. Bingo. Unsoldered both
STK392-110 IC so I can make sure the convgerence generator module
(stand up long retangular metal box) is outputting six correct signals
to STK392 ICs. Aha several were badly distorted or almost gone,
except two out of four were good. Opened it up showed several ICs and
pulled down two datasheets on both ICs. Other than that, one big
square SMD Toshiba IC.

Will finish isolating to specific IC failures tomorrow hopefully.

Six PCM56P (D/A converters)
Three MC33079D (Quad opamps)

Which IC is most likely to fail? MC33079D or PCM56P?

This is remarkable that I did this without schematic.

Cheers, Wizard

 

[[email protected]]

IC? Most convergence module failures I have seen were due to the
surface mount capacitors. If it has then, ESR all of them before
replacing any ics.

 

[Jason D.]

IC? Most convergence module failures I have seen were due to the
surface mount capacitors. If it has then, ESR all of them before
replacing any ics.

HMMM! I would have, except this module does not use electolytic SMD
capacitors like samsung does. Three filter caps (through holes and
it's not the type to leak) for voltage planes bypasses, Rest are SMD
ceramic capacitors.

Cheers, Wizard

 

[tvmirage]

Hi Jason!

Well, im new to this forum....hopefully I can help!!...your proble
is probably the eeProm IC in the Digital Convergence, QH174. I las
have a service Note from Toshiba

Model:TN50X8

Fault
Set in ShutDown Mod

Bulletin

1) Unplug the red, green and blue convergence yokes from th
convergence output board

2) If the set then fires up, replace the QH174 Eeprom and set up th
convergence

3) Resolder the convergence output board and clean P726B plug an
socket using a fibre glass brush. This will remove any tarnish tha
can cause the convergence to change

Im not sure how safe it is for the CRT's to unplug the yokes, I burn
a tube in the past cause of that but form what oyu mentioned...th
eeProm is faulty. Replace and align Convergence...good luck!!

 

[[email protected]]

They are only saying to unplug the convergence yokes, not the
scan/deflection yokes. Make sure you know which ones are the issue.