Picture collapses (daily now) to horizontal band about 1 or 1.5 inches wide. Accidentally discovered that a good thump on side of set restores picture completely to normal (till next Time). Now its taking more & more thumps to restore so time obviously for repair. Please what to do, is this a specialists job?

Thanks
Peter O

Peter O, June 2005

Frame output faults are just about the No.1 most common fault in all TV's. Actually, my own TV is a Mitsubishi which I believe uses a similar circuit to yours.

Basically, the frame output IC dissipates a fair amount of energy as heat (it's on a heat-sink). Several capacitors are fitted in that circuit to control the characteristics of the amp.

Components, especially capacitors tend to change value as they age and due to heat. If the capacitors don't operate as intended the IC will run even less efficiently and dissipate even more power. It's vicious circle & the end result is crystallized connections & breakdown of the soldered joints.

When you thwack your TV, you make or break the poor connection(s). Although you still have your aged capacitors to replace to get the frame amp. to run correctly again.

Capacitors are fairly cheap. I would normally replace the frame IC along with the poor capacitors (as it will have suffered somewhat) and resolder the bad connections for a reliable repair.

Cobweb, June 2005

Thanks for the advice.
As a matter of interest can you explain how thumping the set sides fixes faulty soldered joints or failing capacitors, which I fully accept will almost certainly prove the essence of the problem.
Also I am interested to know why Mitsubishis should be prone to types of fault which at first glace would appear to be a characteristic of all TV circuits.
Peter O

Peter O, June 2005

Quite common in Mitsubishi's. The frame output circuit will need resoldering and several electrolytic capacitors will no doubt need replacing as they tend to dry out and go low in capacitance. It's a repair only a qualified TV engineer should carry out, although parts-wise it should not necessarily be very expensive. In the UK I would probably charge about £55-£75 depending on how time consuming the job turned out. If it's in a sunny country near the sea and you pay my travel, I might even do it for free.

Cobweb, June 2005