Admiral 14R12 Restoration

[Electronic M]

Another thing to consider is that if it is a flat faced CRT it could have poor edge focus by design...Early rectangular and large screen tubes had flat faces which was quickly moved away from by makers...You see as the beam is swept the physical distance the electrons travel increases as you move away from center. Curved screens were designed to keep electron travel fairy constant at all points of the screen during scanning....Some makers tried to apply sweep derived AC to the focus on flat faced tubes to reduce that effect, but on sets that lacked that you kinda have to live with what you have (which usually involved setting focus for a compromise between edges and center).

[Crist Rigott]

Originally Posted by Kevin Kuehn

You mentioned it was out of focus earlier in the thread. It could simply be the combination of a tired electron gun and it being over driven to achieve what seems like normal brightness and contrast. The further the beam deviates from center the harder it is to maintain focus. You may be able to tweak the ion trap and get the outer edges a little better, at the expense of less focus in the center.


I kind of miss the plated chassis. I thought it looked really nice after you cleaned it up, not that it looks bad now, I guess I just prefer the plated look.

Kevin,
I'll play with the ION trap a bit to see if it improves.

The plated chassis had a lot corrosion, not rust, but corrosion. I tried to rub it off but then that area was "polished" and still had the discoloration from the corrosion on it. I think at one time somebody spilled something down into it or most likely sprayed something into it.

[Crist Rigott]

Originally Posted by Kevin Kuehn

You also might want to double check that the dag contact spring is making good ground contact through the painted chassis.

Good idea! I'll clean that area up to make sure I have good contact.

[Crist Rigott]

Originally Posted by bandersen

Yes, the position of the focus coil could effect it. Also your ion trap magnet looks to be too far back on the neck. Usually they are an inch or more away from the base rather than right up against it.

Bob,

I'll try and re-position the focus coil. I'm guessing the it should be centered on the neck of the CRT when the adjuster is also centered?

When I got the TV the ION magnet was positioned all the way back. I'll move it forward to see what happens. though I did move it around when I first powered it up.

[Crist Rigott]

Originally Posted by Electronic M

Another thing to consider is that if it is a flat faced CRT it could have poor edge focus by design...Early rectangular and large screen tubes had flat faces which was quickly moved away from by makers...You see as the beam is swept the physical distance the electrons travel increases as you move away from center. Curved screens were designed to keep electron travel fairy constant at all points of the screen during scanning....Some makers tried to apply sweep derived AC to the focus on flat faced tubes to reduce that effect, but on sets that lacked that you kinda have to live with what you have (which usually involved setting focus for a compromise between edges and center).

Thanks Tom for that info. Maybe there might be a better compromise.

[Crist Rigott]

Guys, thanks for your comments. I'll try what was suggested. Your help is appreciated.

Well, I just lost HV and now no raster. I'm getting about 600 volts at the 2nd anode connection. I was messing around with the H freq. adjustment and then looked up and a dark picture tube! I tried to "undo" the adjustment but that didn't help. There was no popping sound or anything.

[Electronic M]

Originally Posted by Crist Rigott

Guys, thanks for your comments. I'll try what was suggested. Your help is appreciated.

Well, I just lost HV and now no raster. I'm getting about 600 volts at the 2nd anode connection. I was messing around with the H freq. adjustment and then looked up and a dark picture tube! I tried to "undo" the adjustment but that didn't help. There was no popping sound or anything.

If you have a scope check the osc. waveforms and frequency against sam's. A guick check to see if your osc is working close to right is to check the grid voltage at the H out tube.

[Electronic M]

Originally Posted by Crist Rigott

The plated chassis had a lot corrosion, not rust, but corrosion. I tried to rub it off but then that area was "polished" and still had the discoloration from the corrosion on it. I think at one time somebody spilled something down into it or most likely sprayed something into it.

If that 'corrosion' was green/white-ish green(sometimes yellowy) and fairly even then it is not corrosion, but rather Cadmium plating. It is natural for cad plating to turn green-ish with age, and it does not hurt anything when in that state. Best not to polish cadmium...It is rather toxic. I always leave the metal on cad plated chassis alone.

[Crist Rigott]

Originally Posted by Electronic M

If that 'corrosion' was green/white-ish green(sometimes yellowy) and fairly even then it is not corrosion, but rather Cadmium plating. It is natural for cad plating to turn green-ish with age, and it does not hurt anything when in that state. Best not to polish cadmium...It is rather toxic. I always leave the metal on cad plated chassis alone.

Tom,
This chassis didn't seem to have the CAD plating on it. The corrosion consisted of many, many small dots. It wasn't an even coating. Some areas even left some small pits in the metal.

[WISCOJIM]

I really like the appearance of your painted chassis, but I was always afraid that paint may interfere with good chassis ground connections. And most (radio) restorations with a painted chassis looked bad because it left all the other visible pieces looking old/cruddy. I wonder what will happen with those tubes so close to the high voltage cage. One looks like it has got only 1/8" clearance. Are they going to cook, burn, or blister your paint job? And the possible smell...

.

[Crist Rigott]

I've done some troubleshooting.

I did a voltage check on the 3 tubes V15 a 6SN7GT Horizontal AFC and Osc., the 6BQ6GT Horizontal Output, and the 6W4GT Damper tube. Here are my findings. 2nd values are my readings:

6SN7GT
1 -2.8v -25v I thinks SAMS made a mistake here. Riders shows -40v.
2 100v 105v
3 -22v -16v
4 -60v -59v
5 235v 190v

6BQ6GT
4 140v 128v
5 -8.6v -8.6v
6 220v 190v
8 5.6v 6.3v

6W4GT
3 320v 250v
4 320v 250v
5 220v 190v
6 310v 255v

The voltages don't look too bad. Most are a little low.

I did hook up my scope to the grid (pin 5) on the 6BQ6GT tube and here is what I got:



I then checked point "C" on L19 per Sams on adjusting the Horizontal Sweep Circuits. This is what I got after I adjusted "B3" on L19.



I don't know what the frequency was but the time dial was set 10us.



Here is a picture of the schematic showing the area:



I also ohmed out the fly-back and it checked out pretty reasonable.

EDIT! I remembered that I can hook up my frequency counter to my O'scope and I then adjusted the Horizontal Frequency "B2" to get 15,734 cps.
Another EDIT! I added the voltage on the 6BQ6GT Pin 8.

[Crist Rigott]

Is there any way to test what's going on with the flyback? Like seeing the voltage from the 6BQ6GT plate cap? Like measuring the voltage there? Everything I've checked so far checked good. I'm getting about 3Kv right now and have a faint raster. So I am getting some HV, just not enough. I don't have a flyback checker. How can I check the door knob cap? I'm trying to find out why my HV is so low.

Thanks for your help.

[Kevin Kuehn]

Your horizontal drive signal basically looks good, but your boost voltage is 70 volts low originating at pin 3 of the damper, which is why some of your other voltages are low. What is your scopes volts per division setting when you measured the signal at the grid of the horizontal output? Have you by chance tried another damper and HV rectifier?

[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.