Anyone know of any "typical" failures on a Sony Trinitron KV-27S10
(manufactured 9/94) that would make it dead as a door stop? I had bought
the set for my parents, and had worked without a hitch for years. Just
recently they were watching it and the picture just disappeared. I recently
picked up the set from them (bought them a new one) and have done a cursory
external review of it. It's dead!

When plugged into the wall, sometimes can see a tiny arc at the plug when
put in the socket. No humming, no noise, no lights, nothing. Tried the
power button. Tried the remote. Again nothing.

Any suggestions as to what might be wrong or what to check? I am pretty
handy with electronic stuff, but mostly in the digital domain.

Thanks!

Don

There are a lot of possibilities and causes for the set to be dead.

You will need to do some basic troubleshooting and voltage measurements
for specific help. A good place to start could be the user switches,
check for 5V dc to see if the standby power supply is running, then you
can scope the system control ic to see if it is running.

Make sure you are fully aware of the safety required when working in
the tv set with it plugged in. I strongly recommend you have the tv
plugged into an isolation tranformer as it increases the safety margin
for both you and your test equipment.

If you do not know the difference between the tv sets hot and cold
grounds, do not attempt to do anything inside the tv until you find out
and the related implications of both.

Here is the FAQ where you can start: http://www.repairfaq.org/

Typical failu 2SC4927 shorted horizontal output, bad
connections @ the horizontal drive transformer, shorted
Q601, & 602 2SC4834 PWM switching regulators, open
.1 ohm fusible resistor R607, VDR 601 bad 1-807-288-11,
& "possibly" bad VDR 602, & 603, but these are usually ok.

Use Sony SP-Kit, & VDR 601. # 1-807-288-11, Sky.

I keep seeing this recommendation for changing the VDRs. While there may be
some value in changing them due to damage in the metal oxide from repeated
conduction events, when the HOT fails and takes out the power supply, the
VDRs are not likely to be a problem. VDRs are protection or dumping
devices. If they check open with a DMM they are not likely to be a problem
in the PS. They can be tested for clamping voltage, though if they are
failing, they fail by leaking rather than not clamping at near the rated
voltage. A handy way to test them is with the h-pulse drive on a sencore
tester and a scope.

It is more important to use the correct parts, ie higher rank 2sc4834 and to
verify the duty cycle of these. I use P rank versions, that we get very
inexpensively from ACME Enterprises in Orlando and match them. Virtually
all units that fail this way are fixed completely with just the HOT,
Q601,Q602, R607, and resoldering the components in the base circuit.

When the PS fails on its own or due to surge damage, it is important to
check all of the components in the primary, particularly the poly caps. Of
course, the VDRs are suspect in these cases. When the PS fails due to
loading such as a shorted HOT it is rare to see problems other than the
parts listd above.

Also, the 2SC4927 can be replaced with several other transistors that will
run cooler and may be more reliable. We have had success with the 2SD1881
but others will work as well.

Leonard

"Skype_man" wrote in message
.. .
Typical failu 2SC4927 shorted horizontal output, bad
connections @ the horizontal drive transformer, shorted
Q601, & 602 2SC4834 PWM switching regulators, open
.1 ohm fusible resistor R607, VDR 601 bad 1-807-288-11,
& "possibly" bad VDR 602, & 603, but these are usually ok.

Use Sony SP-Kit, & VDR 601. # 1-807-288-11, Sky.

"When the PS fails on its own or due to surge damage, it is important to
check all of the components in the primary, particularly the poly caps. "

.... check for blown fuse(s) in the power supply section,due to voltage surge
or lightning strike. This event is quite probable and is simple to detect
and repair. .... If not familiar with safety procedures, always unplug the
power cord first.

Dave




"Leonard Caillouet" wrote in message
...
I keep seeing this recommendation for changing the VDRs. While there may
be some value in changing them due to damage in the metal oxide from
repeated conduction events, when the HOT fails and takes out the power
supply, the VDRs are not likely to be a problem. VDRs are protection or
dumping devices. If they check open with a DMM they are not likely to be a
problem in the PS. They can be tested for clamping voltage, though if they
are failing, they fail by leaking rather than not clamping at near the
rated voltage. A handy way to test them is with the h-pulse drive on a
sencore tester and a scope.

It is more important to use the correct parts, ie higher rank 2sc4834 and
to verify the duty cycle of these. I use P rank versions, that we get
very inexpensively from ACME Enterprises in Orlando and match them.
Virtually all units that fail this way are fixed completely with just the
HOT, Q601,Q602, R607, and resoldering the components in the base circuit.

When the PS fails on its own or due to surge damage, it is important to
check all of the components in the primary, particularly the poly caps.
Of course, the VDRs are suspect in these cases. When the PS fails due to
loading such as a shorted HOT it is rare to see problems other than the
parts listd above.

Also, the 2SC4927 can be replaced with several other transistors that will
run cooler and may be more reliable. We have had success with the 2SD1881
but others will work as well.

Leonard

"Skype_man" wrote in message
.. .
Typical failu 2SC4927 shorted horizontal output, bad
connections @ the horizontal drive transformer, shorted
Q601, & 602 2SC4834 PWM switching regulators, open
.1 ohm fusible resistor R607, VDR 601 bad 1-807-288-11,
& "possibly" bad VDR 602, & 603, but these are usually ok.

Use Sony SP-Kit, & VDR 601. # 1-807-288-11, Sky.