Vertival amplifier in TV MITSUBISHI CT-25B2

[Bernard]

Hello all,

The verical amplifier IC in these TV is burnt beyond recognition. It
seems that it is a TDA 81xx ?
Is there a kind soul who could tell me the exact réfence, please
(maybe TDA 8178a)?

Thanks a lot!

 

[Nigel]

Hello all,

The verical amplifier IC in these TV is burnt beyond recognition. It
seems that it is a TDA 81xx ?
Is there a kind soul who could tell me the exact réfence, please
(maybe TDA 8178a)?

Thanks a lot!

This set uses the Euro 12 chassis and failure of the TDA8178S (IC451) is
usually caused by excessive HT.

In the PSU, replace C905, C906, C909 and C920. Check values of R961, R972 &
R960. Check D907 - it may be shorted. Use a variac after repairing the PSU -
the correct HT is 145v.

Check if 28v supply is present at pin 2 of IC451.Check R976, D952 and C956.
Check if C452 and D451 are open circuit. Check for field drive at pin 7 of
IC201 and field ramp at pin 6.
Scan coils can go o/c and connectors at their plug/socket should be checked
for dry joints, as should pins 6 & 7 of IC201.

 

[Nigel]

This page may also be of use to you

http://www.dede75007.com/page2.html

 

[Bernard]

Dear Nigel,

Thank you very much for your kind help and your time!!!
I'll examine this soon and post the results.