1979 GTE Sylvania GT Matic CX9164W chassis E24-3

[pac.attack76]

I can't find a schematic and I have no idea where the damper is on this 😞

[Alex KL-1]

The diode damper probably will be the largest cased diode near the flyback, connected at least to some pin of it, sometimes in parallel with HO transistor, and other side (cathode) generally is ground on simple TV's (if is separate, like John said).
Of course, for some TV's, other or others diodes can be associated to primary winding, but is more common on newer TV's (like supply for RGB video output). So is good to check diodes nearby the flyback to be sure.
Another potential part suspect can be the pulse capacitor, the one that tune the flyback pulse, and is rated at least with 1600V (some nF), also near the flyback, and probably at same line with HO transistor. Polypropilene on newer TV''s, and perhaps something-with-oil on older TV's. Normally this fails open, but to be sure, is good to check.

[JohnCT]

Originally Posted by pac.attack76

I can't find a schematic and I have no idea where the damper is on this 😞

It might be right on the back side of the socket of the horiz output. It can either be a black barrel body or a grey round ball - either will have fairly thick leads.

Electrically, the cathode of the diode will be connected to the collector (metal case) of the horiz output and the anode connected to the emitter of the transistor (ground). If you look behind the socket, it should be there.

If it's not, trace the wire from the collector (screws are collector) to the main board to locate the diode.

Clip or unsolder one end, reinstall the horiz output, and see if the short to the case is gone. If it is, the diode is shorted but do NOT run the TV without the damper connected or you will immediately destroy your horiz output which right now is still good.

John

[pac.attack76]

Can't find anything in that mess. So much going on in there. I took a few shots hoping someone recognizes something. I see the back side of the output, screws and wires running down.

[Alex KL-1]

Yes, seems to be difficult; too many wires and so on. The solution is to follow each flyback wire, and see what ones ends at diodes, to measure them.
Not seem to have any diode in the HO transistor socket.
I sse some relatively fat diode near the socket with "24" number on it. Is impossible to know if is relative to flyback, without following the flyback wires.
Sometimes, in the hurry, I simply measure every diode near flyback at time I'm worked with TV's (is faster anyway).
The suspects are removed and measured externally to be sure.
I see one small diode in parallel with a small capacitor in one photo. These one seems to be improbable, but anyway, is good to check on the DMM diode scale.

Other thing, since manufacturers not want to use 2 times same funcion component, is good to measure on diode scale the HO transistor you removed from TV. Measure from collector to emmiter. In one side, basicaaly with negative (black) proble connected to collector (case), and negative to emmiter, the DMM will measure something between 0.5 and 0.8, and, for another side (reverse, with red onde connected to case), will measure OL. If measures this manner, the damper diode is internal/integrated to transistor case.

[JohnCT]

Originally Posted by pac.attack76

Can't find anything in that mess. So much going on in there. I took a few shots hoping someone recognizes something. I see the back side of the output, screws and wires running down.

There are three wires on the back of the horiz out socket. The wire that's attached to one of the screw posts is the collector. Follow that down to the board where it will be connected to the damper diode assuming the TV has an external one.

What is the part number of the horiz output?


John

[pac.attack76]

I can't find any numbers on that output. Maybe if we could figure out which one this chassis is designed to use.

[JohnCT]

Originally Posted by pac.attack76

I can't find any numbers on that output. Maybe if we could figure out which one this chassis is designed to use.

I scrapped all of my GTE/Philips schematics years ago along with most of my SAMS of those years.

If anyone has any SAMS still, it's in 1751 folder 2.

John

[damen]

Sams 1751-2 shows the damper diode as "SC448". It's on the circuit board between the yoke socket and the focus control area. It's between the horizontal linearity coil, L470, and a large cap labeled C448. Sorry, can't post pictures.