What type of logic do you get on the standby input to the supply? I would
be looking farther back. The IC you are showing appears to be the driver
device for the switching supply.

The supply is probably listening to whatever is telling it to cycle when it
is supposed to be staying in standby. I would look at the circuit area that
responds to generate the standby command logic.

In many older monitors I have had defective caps in various areas cause
these types of faults. About 90% of the various faults are created by caps
going too high in ESR.

--

Jerry G.
======


"Michael Collard" wrote in message
news I have a Compaq s910 which works fully except for a clicking sound from it
when the monitor enters standby mode. What I know so far is that the
clicking is just the degauser relay (nothing arcing). The monitor can only
enter standby mode for a split second before powering up the transformer
and tube etc, then a split second later goes back to standby mode and
repeats the process forever.

There is a IC (3843B) on the board which is cauing the main transformer to
kick in, but don't know if its the problem or just a side effect. I have
measured voltages from around the place and firstly have to say that I
don't understand how the aforementioned IC can even function in that AC
enviroment.

I have got the schematics for everything. The important bits:

http://members.iinet.net.au/~quadfour/3842B-3843B.pdf - IC schematics
http://members.iinet.net.au/~quadfour/s1494-1.pdf - s910 PSU schematics
http://members.iinet.net.au/~quadfour/temp.jpg - shows some voltages
I've found.

The schematics of the 3843B mentioned voltages well below the ~140AC I am
seeing on its side of the transformer. Together with that I don't have a
solid grasp on this (enough to replace components).

Any ides on how to pinpoint the reason for the 3843B turning everything on
after a split second of the monitor being in standby mode?

Cheers
Michael