THORN 9000 CHASSIS

When the set is switched on from cold, only channel “1”
can be obtained. If any of the other touch pads are tried, the
respective neon fails to light and after releasing the pad the
set reverts to channel “1”. After some twenty minutes, you
can change channel by keeping your finger on the appropriate touch pad: the picture is o.k., whereas before just
a raster would be obtained. The fault clears completely after
an hour. I’ve tried about half a can of freezer on the i.c., but
as this doesn’t restore the fault condition I’ve not changed
the i.e. On rare occasions we’ve found the channel “1” neon
(LP5O1) or switch transistor (VT505) to be responsible for
this trouble, but usually it’s the chip that is faulty. Be careful
with the replacement WIT6018 until you’ve got it connected
into circuit – it’s a CMOS device.