breathing life into old chips

From: Tony Duell <ard_at_p850ug1.demon.co.uk>
Date: Sun Apr 6 13:06:18 2003

> > hi,
> >
> >> (the chip in question is a ST9293J9B1/AEL for the record,
> > What is this TV model & brand?
>
> It's a Ferguson T7073SJD, using an ICC9 chassis. One website containing a

FWIW, Thomson-built ICCn chassis are _notorious_ for dry joints!

> faults database listed the failure of that chip giving the exact symptoms that
> I see (no sound when the set warms up and the remote operation goes
> unresponsive).

Those databases are not that useful IMHO. What that entry means is that
somebody had a set with those symptoms, and that replacing the
microcontroller cured it. It doesn't mean there was any logical reason
why the microcontroller was the problem (maybe soldering in the new one
cured a dry joint). It doesn't even mean that this is the most common
cause of the fault.

>
> I've pulled the main board and will re-solder all the joints in that area just
> to check; there's only one electrolytic as part of the circuitry surrounding
> that chip but I'll replace it with a known-good just in case. Tony's point

You need the schematic (it should be available -- maybe even in the local
library -- look for the TV Servicing books). You want to check the reset
line, which may well be routed across the PCB from somewhere else.

> about the crystal was interesting - I didn't think those things ever failed.
> I'll see if I've got a spare to try anyway.
>
> The set's awful inside - very cheaply made with little thought to cable runs,

Well, all I can say is that in my experience Thomson sets are some of the
better made ones out there. They're not good, but you should try some of
the others!

-tony
Received on Sun Apr 06 2003 - 13:06:18 BST