1950 Admiral 16" Set; Recapped... No Picture!!

[Magnavox300]

Originally Posted by JohnCT

OC is right.

If you have a pulse at the fly and no HV, the rectifier tube is the next suspect.

What I would do if I didn't have a HV probe handy is to hold an insulated screwdriver at my fingertips and touch the cap of the HV rectifier tube. In a dark room, you should see the soft blue arcing between the tip of the screwdriver and the cap. Make sure the tool keeps at least two inches of plastic between your fingers and the metal shaft. If that CCFL tube lights, you should get a soft arc from the cap of the HV rectifier tube to the screwdriver.

If you see the arc, move to the anode connection on the picture tube and see if you have it there. If not, the HV rectifier tube or doorknob cap might be bad.

John

Thanks, did what you suggested and yes, I did get a soft good stead arc at the cap of the 1B3... nothing at the CRT anode.
I then tried a bunch of used 1B3 tubes I had laying around, but still nothing...
Then I turned down the brightness halfway, and got a picture!

I was testing all the time with the brightness up, which should have been fine, since it was all the way up when I first got a decent picture.

Problem is, picture is barely visible now, and blooms and goes dark if I turn up the brightness more than halfway...

[Magnavox300]

Also washes out and brightens a little when I turn up and down the contrast, it almost acts like a brightness knob.

[Yamamaya42]

$120 for a B&K Precision HV44A High Voltage Probe ??

that's over 4x what I got mine for years ago

[bandersen]

Sometimes there is a high valued resistor in series with the HV lead that can go bad. Have you measured the resistance from the base of the HV rectifier to the metal cone ?

Be sure to discharge it first. ALso make sure the HV lead is making good contact with the metal cone. I assume there's some sort of clip on the rim ?

[Electronic M]

Originally Posted by Yamamaya42

$120 for a B&K Precision HV44A High Voltage Probe ??

that's over 4x what I got mine for years ago

Glad I don't buy my probes on eBay... I've gotten 3-4 used Pomona HV meter/probes similar to my model 4000 from swapmeets over the last 10 years and none has cost me more than 1/10th of that.

[old_coot88]

Blooming with brightness turned up is due to HV failure as CRT beam current lugs down the HV supply. Have you verified visually that the 1B3 filament is glowing (as suggested previously)? If it's not glowing, it hasn't got enough emission to sustain the HV under load.

(EDIT) If it's not glowing, I would temporarily jumper that 2.7 ohm resistor and see if the filament glows.

[Yamamaya42]

Originally Posted by old_coot88

Blooming with brightness turned up is due to HV failure as CRT beam current lugs down the HV supply. Have you verified visually that the 1B3 filament is glowing (as suggested previously)? If it's not glowing, it hasn't got enough emission to sustain the HV under load.

(EDIT) If it's not glowing, I would temporarily jumper that 2.7 ohm resistor and see if the filament glows.

The X-rays you would be exposing yourself to wont be THAT dangerous!

It's not like you will grow a 3rd eye or a 2nd head or anything!

[bandersen]

I read back through this thread and saw that you did check the 470K in series with the HV lead. I've seen those resistors act weird. Possibly as a result of carbon tracks from years of HV around them. Wouldn't hurt to replace it or jump it. Ditto to jumping the 2.7 ohm on the 1B3. Something is limiting your HV current.

[Yamamaya42]

this looks a lot like your chassis
https://www.earlytelevision.org/pdf/...sams_100-1.pdf
or pretty close
and it seems there is 1 1m resistor in series with the HV output lead,

[bandersen]

I believe he has a somewhat newer 21D1 chassis: https://www.earlytelevision.org/pdf/..._rider_tv6.pdf

[Yamamaya42]

between the 2, it should get him in the ballpark for what he seems to have, if he can't find what it is for sure, I was not able to find ant that has that weird arrangement of the HV rect on top of the cap in the pic like he showed.. that is a bit weird

[Magnavox300]

Originally Posted by bandersen

I read back through this thread and saw that you did check the 470K in series with the HV lead. I've seen those resistors act weird. Possibly as a result of carbon tracks from years of HV around them. Wouldn't hurt to replace it or jump it. Ditto to jumping the 2.7 ohm on the 1B3. Something is limiting your HV current.

Thanks, I will change out that 470K just in case, I think it measured 450K; and i'll jump the 2.7 like Old Coot suggested and see what i get...
First I'll look to see if the 1B3 tube has a glow at all, forgot to do that...

[Magnavox300]

Checked, and no glow at all on the 1B3 tube...
In the morning I'll change out the 470K, then jumper the 2.7 ohm and see if it glows... thanks everyone!!

[bandersen]

Originally Posted by Yamamaya42

between the 2, it should get him in the ballpark for what he seems to have, if he can't find what it is for sure, I was not able to find ant that has that weird arrangement of the HV rect on top of the cap in the pic like he showed.. that is a bit weird

Look at the last page of the 21D1 service info. It's shown in the middle of the page.

[Yamamaya42]

Originally Posted by bandersen

Look at the last page of the 21D1 service info. It's shown in the middle of the page.

I see it now :p