Bad SMPS in tv has wrong voltages

[BFriedl]

I am troubleshooting a SMPS for a projection tv (Mits VS-6051R v10 chas)
and Even with dummy load, output voltages are all messed up. I have
already replaced the caps on primary side. Could it be the regulator IC?
or the Optoisolator?


--
BFriedl
A+ Certified Technician
AIM: UACybercat
** Bear Down Arizona! **
******* Go Cats! *******

 

[Jerry G.]

This can be anything along the feedback path. The main regulation is
controlled by changing the duty cycle of the drive. If something in the
feedback including resistor values, the opto-isolator, and etc, are
defective, this can cause the total voltages to be wrong. Usually, in the
design they target one voltage as the reference, the others are regulated
from that reference. There are a number of approaches to how they design
these types of supplies.

Also do an ESR test on all the electrolytic caps on the output side of the
supply. If there are some that are high ESR, this may allow some noise to
occur, and offset the regulation. I have seen this in switching supplies.

--

Greetings,

Jerry Greenberg GLG Technologies GLG
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"BFriedl" <junk-remove-@bfriedl.com> wrote in message
news:hXWxb.16123$o9.12682@fed1read07...
I am troubleshooting a SMPS for a projection tv (Mits VS-6051R v10 chas)
and Even with dummy load, output voltages are all messed up. I have
already replaced the caps on primary side. Could it be the regulator IC?
or the Optoisolator?


--
BFriedl
A+ Certified Technician
AIM: UACybercat
** Bear Down Arizona! **
******* Go Cats! *******