Admiral 14R12 Restoration

[Kevin Kuehn]

How does your 210 volt supply read at the fuse(M2)?

[edit] Don't forget to make sure your dag coating is grounded good, as I don't see any other HV filter cap going to ground.

[old_coot88]

Have you subbed the 6BQ6 yet? You van sub it with a 6DQ6 in a pinch. The 6W4 can be subbed with 6AX4 or 6AU4.

You failed to list voltage on pin 8 (cathode) of the 6BQ6. But on the schematic you indicate 5.6V. Are you still getting 5.6V there? If not, the tube is not conducting (or if it's too high, the tube is conducting too much).

Also try this - with the plate connector disconnected from the HV rectifier, use an insulated screwdriver and see if you can draw an 'air arc' from the connector. If the fly is putting out, you'll get an arc of a quarter inch or more. But don't short it to ground.

[Crist Rigott]

Originally Posted by old_coot88

Have you subbed the 6BQ6 yet? You van sub it with a 6DQ6 in a pinch. The 6W4 can be subbed with 6AX4 or 6AU4.

You failed to list voltage on pin 8 (cathode) of the 6BQ6. But on the schematic you indicate 5.6V. Are you still getting 5.6V there? If not, the tube is not conducting (or if it's too high, the tube is conducting too much).

Also try this - with the plate connector disconnected from the HV rectifier, use an insulated screwdriver and see if you can draw an 'air arc' from the connector. If the fly is putting out, you'll get an arc of a quarter inch or more. But don't short it to ground.

We'll start with this one first.
I added the voltage on pin 8. Listed voltage is 5.6v and I measured 6.3v.

Will do that arcing test next.

I have subbed the 6BQ6GT and the 1B3GT. Not much change in the HV. Actually what is installed is a 6DQ6GT. When I had good HV, I subbed a NIB 6QB6GT and the HV was lower, so I put the 6DQ6 back in.

I also subbed the 6W4 with no help.

[Crist Rigott]

Originally Posted by Kevin Kuehn

How does your 210 volt supply read at the fuse(M2)?

[edit] Don't forget to make sure your dag coating is grounded good, as I don't see any other HV filter cap going to ground.

I got 190v at the fuse. Earlier I cleaned the dag grounding wire mount and just ohmed it out and it shows zero ohms from the wire and from the dag.

[Crist Rigott]

I just tried the HV rectifier cap connector and I got a very healthy purplish 1/4 to 3/8 long arc.

So it looks like my problem might be with the 1B3GT or its connector. There are 2 resistors under the connector.

Could the door knob cap be bad?

[Eric H]

Originally Posted by Crist Rigott

Could the door knob cap be bad?

There's a slight possibility it could be bad and dragging the HV down, just disconnect it to test, the CRT has a Dag coating and performs the same function so it shouldn't be essential.

[Crist Rigott]

Originally Posted by Eric H

There's a slight possibility it could be bad and dragging the HV down, just disconnect it to test, the CRT has a Dag coating and performs the same function so it shouldn't be essential.

Eric,
I just tried what you suggested and disconnected the lug from the bottom where the white/red wires are connected. When I powered up the set, all I got was some arcing sound from the base of the HV rectifier. I moved things around but each time I got the arcing sound so I put it back together. Still only about 3Kv.

BTW, I used my multimeter to measure the door knob cap. It measured out to 630pf but is listed as a 500pf cap.

[Crist Rigott]

Everybody I do appreciate your help with this stubborn problem. I'm sure we'll get it fixed. I just wanted to say thanks for your help.

[old_coot88]

Originally Posted by Crist Rigott

...I moved things around but each time I got the arcing sound....

If you darken the room, it may be possible to see where the arc is.

[Kevin Kuehn]

Have you changed or tested the 1M resistor that's mounted under the 1B3 socket? Those often go very high in value/intermittent, or open. It's the 1M shown in series with the HV lead on the Sams schematic.

The boost voltage is derived by combining the 210 volt supply with the voltage of the lower flyback winding during horizontal retrace. It's a free source of energy during retrace, and so provides a boost to the 210 voltage supply that gets filtered and used for some circuits that work better with the higher voltage.

[Crist Rigott]

Originally Posted by old_coot88

If you darken the room, it may be possible to see where the arc is.

Just might do that if I have it apart again.