Philips 27CE3590 TV set: Symptoms of aging

[Chris]

Hello!

I have an old Philips 27CE3590 set which has some (probably age
related) problems. Since you guys have been extremely helpful in the
past, I thought I might try to ask here to see if anyone has any tips
to share.

Problem 1:
About four years ago the HVPS broke down, which turned out to be a
fried fuse resistor. The symtomps then was no picture, but everything
else worked fine except for a loud pop from the speaker when the set
was put into standby. After replacing the resistor, the problems went
away.

However, after a few years, the loud popping came back. Sometimes,
there is also a second pop after the set has been in standby for an
hour or so. Rather annoying... Seems like there is some kind of
power-off discharge circuit that has stopped working properly?


Problem 2:
Probably a FAQ item, but I poked around a bit and didn't find anything
about it. The problem is a high frequency wiggling ("buzz") in the
picture. This has grown worse over the years, but has now reached a
point where it's becoming quite unacceptable. Looks like some kind of
problem with the horizontal sync. I've been told that the likely cause
is a worn-out capacitor, but what should I try to replace?


I'd be grateful for any hints!

Cheers
Chris

 

[Chris]

Problem 2:
Probably a FAQ item, but I poked around a bit and didn't find anything
about it. The problem is a high frequency wiggling ("buzz") in the
picture. This has grown worse over the years, but has now reached a
point where it's becoming quite unacceptable. Looks like some kind of
problem with the horizontal sync. I've been told that the likely cause
is a worn-out capacitor, but what should I try to replace?

Update:
After further searching I think I've found the solution to this
problem. I'm still stuck with Problem 1, though.

A few additions:
- The set has a CP110 chassis.
- The loud "shutdown" pop very clearly comes from the speaker, but
there are no other sound artefacts, like hum or noise.

 

[eddumokweer]

The cp110 chassis is in 2 different chassis available.

The difference is in the powersupply.

Some powersupply's have an extra pcb with a electrolityc capacitor mounted
on it. This electrolityc switches the power on and off if capacity or esr is
not good.

You can check the powersupply with a lamp 100W 230V over the 140Volt, and
the horizontal cable disconnected.

Greetings Peter

 

[Chris]

Thanks Peter!

I'm don't fully understand how this relates to my "popping" problem
though.
The set comes on and goes off as it should (except for the popping
noise).

I spent some time with the schematics, and found some interesting
things.
It appears that the set would not exactly be Energy Star compliant as
the standby signal from the controller seems to select between the 9V
and 32V winding as the LVPS sense voltage, i.e. the LVPS still
provides power to all outputs in standby mode, but at 1/3 the normal
voltage.

The inverse of the standby signal is routed from the LVPS to the audio
amplifier where it feeds a transistor that, AFAICT, is supposed to
pull the output stage feedback loop to ground whenever the standby
signal is active. In addition, the TDA8190 data sheet says that is
has an internal flyback killer on the output to prevent popping caused
by flyback voltage from the speaker.

I was thinking that perhaps this muting transistor or the internal
flyback killer was broken, but this doesn't really explain why there's
a second pop long after the set has been put into standby.

 

[eddumokweer]

Check this page for many cp110 problems
http://www.avrepair.info/faults/PS011650.HTM

Greetings Peter