JVC DT-V1710cg won't degauss

[grossbard]

I measured constant 120VAC across the two hot side relay pins, so I assume it's working. I also measured 120VAC from relay pin 1 to posistor pin 2.

Is this a case of the voltage going through, but the degauss coil not receiving enough current? I can't think of what else it could be, but I'm no expert...

[zeno]

There are 2 major ways modern sets DGS.

1) a PTC resistor in series with the DGS coil. It is AFTER the
on/off switch or relay. Every cold start the set will DGS , the
PTC will heat & show an open.

2) DGS relay. Micro IC sends a brief pulse to the relay driver transistor.
A quick "click-click" is heard. Often they DGS on turn off, the opposite
of the usual.

Every PTC resistor I have seen bad has physically fallen apart. Watch
for cold joints especially on the DGS relay, very common !

73 Zeno
LFOD !

[grossbard]

I reflowed the coil connector, PTC pins, and relay pins. No dice.

The PTC is in a black box, so I can't tell if it's damaged or not. I suppose I could desolder it and see if there's anything shaking around inside....at no point did it ever feel warm to the touch, either.

When I press the degauss button, I do NOT hear a relay clicking, so is it likely the relay is bad? I already ordered a replacement PTC and finally found the correct relay after a bit of searching...maybe I should just shotgun in replacement parts for the entire circuit...

[zeno]

Nothing learned by shot gunning.

All voltages etc are typical
PTC should read apx 120 ohms cold
DGS coil is a near short.
Relay could be stuck or have an opened coil. ( tap it )
Usually there is a little diode across the coil that can short.

The drive transistor as follows
DGS OFF E= 0v B= less than .7 V C= 12 V
DGS ON E= 0V B= .7 V or more C= near 0 V
Remember the ON state only lasts a second.
Start at the base & look for the quick jump in voltage, work
your way down stream from there.

Good luck
Zeno
LFOD !