'47 magnavox - gutless high voltage....

[nasadowsk]

Originally Posted by Don Lindsly

More information would be helpful.

Ok, I'll keep answering Qs as needed - this is a work in progress.

I did find two out of tolerance resistors the other day that helped the slow start issue, and slightly boosted the P-P up (maybe 2 or 3 volts)

Is there any light on the screen at all?

Yes.

If so, is the picture full width?

Yes/no. If the brightness is a bit low, it'll go full wide.

Is the picture trapazoid or a rectangle?

Honestly, I haven't looked. The CRT's aimed at the wall now. I can spin the chasis around to look.

Is there any high voltage or damper cathode voltage at all if you remove the damper tube?

Didn't even think to check that

Have you replaced tubes including the 6BG6, damper tube and 1B3?

Changed all but the 6BG6, which I'm going to order a few next week (I need 2 or 3 anyway).

What is the 6BG6 screen voltage?

I'll measure and report this.

What is the 6BG6 control grid voltage?

Ditto.

Does the AC arc on the top of the 1B3 increase with the tube out?

AC arc? I'm not getting any arc or hiss at all

I'm pretty sure the 500pf HV doorknob is bad, since the set holds NO HV charge at all, so that's gonna be replaced, too. Vishay still makes 'em, Mouser sells 'em, but a bit pricey ($50-75 for one, depending on voltage)

60 volts p-p sounds a bit low, but I've never measured on a working set. I was always under the impression that the drive pulse beat the snot out of the output tube...

What's odd is the flyback seems to ohm out right. I don't want to point my finger there until I rulle out the easy stuff, though

[Don Lindsly]

1. The 6BG6 is a real possibility.
2. Test the "doorknob" by removing the CRT socket, run the TV for a couple of minutes, shut off and see if it retains a charge at the anode. You should test at the 1B3 bottom since disconnecting the anode will eliminate the capacitor formed by the CRT aquadag coating.
3. Check the resistors under the 1B3 if/when you replace the doorknob. There are usually two. One is a low value (2-5 ohms)filament dropping and the other is a high value (470K-2.2 meg) filter. They don't need to be exact; +/- 20-30% is OK for now.
5. Remove the doorknob and see if you get any more high voltage. If everything else is OK, the TV will work without it. (There may be some other minor symptoms.)
6. Do you have a chassis or model number?

[nasadowsk]

1. The 6BG6 is a real possibility.

Gonna be on order monday...

2. Test the "doorknob" by removing the CRT socket, run the TV for a couple of minutes, shut off and see if it retains a charge at the anode. You should test at the 1B3 bottom since disconnecting the anode will eliminate the capacitor formed by the CRT aquadag coating.

Oh, it's, well, dead as a doorknob. Holds no charge at all. Not anything like the Bendix I have where I swear the thing's haunted - ground it and it pops back from the dead a few minutes later.

3. Check the resistors under the 1B3 if/when you replace the doorknob. There are usually two. One is a low value (2-5 ohms)filament dropping and the other is a high value (470K-2.2 meg) filter. They don't need to be exact; +/- 20-30% is OK for now.

Hmmm, That's another place I'll have to check...

5. Remove the doorknob and see if you get any more high voltage. If everything else is OK, the TV will work without it. (There may be some other minor symptoms.)

The HV's pretty much the same, maybe an extra kv, if that much.

6. Do you have a chassis or model number?

Ahh yes, it's a Magnavox chassis CT238.