21ax gassy or bad 3a3?

[SwizzyMan]

Just got my CTC-5 home from tvdude1. I had an image on the 21axp22 for about a minute before I turned the set off. Came back about 5 or 10 minutes later and noticed I couldnt get a picture anymore but I had HV. I looked at the gap between the G2 element of the electron gun and the other element and saw a faint blue glow. But then I noticed the 3a3 HV rectifier had a ring of brighter blue around the whole envolope. This all starts when the HV starts up. The 3a3 tests OK on my 600A and the 21ax tests perfect on all guns. The cutoff test on all guns performs nicely and is not jumpy and I can get it to hold in the cutoff set line. Could this be a HV issue or something wrong with the 3a3 or could my 21ax be gassy all of the sudden?

[Eric H]

More likely the 3A3 went bad, it shouldn't glow blue. It might check okay because your tester isn't putting 20kv on it.

A small amount of blue glow between the elements of a tube can be normal, if the whole neck glowed purple than I'd worry.

[SwizzyMan]

swapped the 3a3. The new 3a3 glows still and the blue glow between G2 is still there. Anyone else know what might be happening?

[DaveWM]

if it has HV and the CRT test good, then it HAS to be a bias issue or focus voltage. check both.
oh and a pic would help, blue glow sounds harmless, purple is bad, but better to let us see pic is worth a thousand words.

[Username1]

In your opinion do the heaters look like they are normally lit on the picture tube ?
Also, you should take a HV reading and see if it's normal..... +18K for a 5....
Did you do an actual HV reading with a meter.....?

.

[miniman82]

Check/replace your focus rectifier, no focus voltage will make a CRT not show a picture all else being the same. If it's not that, at least make sure focus voltage is making it to the CRT socket. Could also be the last video tube in the chain, if it died a sudden death any number of maladies could be haunting it.

[SwizzyMan]

Will do later this morning, accidentally pulled a socket pin out of the socket assembly while removing the CRT socket so will have to fix that first. I highly doubt the CRT is gassy if it can survive over 1300 miles of bumpy highways it can survive sitting in the 76 degree house I live in. Anyone have a general idea of how durable the 21axp22 is in terms of taking off the socket and putting it back on plus the bumpy ride home? Also happy New Year to all you folks here!

[tvdude1]

Have you recapped the set and also 2 of the main filters were leaking really bad. It was all original.

[Username1]

I think that tube only has a 1200 mile bumpy road rating.....



.

[jr_tech]

Did you check the 12BY7 second video amp?

jr

[Electronic M]

Sounds like it needs a recap....When an un-recaped set of that age starts loosing function it's time to change caps. You should verify all the B+ voltages.

In addition to the focus voltage G2 is important. If G2 is low from a bad B+ boost supply the screen won't light.

[ohohyodafarted]

Originally Posted by SwizzyMan

Will do later this morning, accidentally pulled a socket pin out of the socket assembly while removing the CRT socket so will have to fix that first. I highly doubt the CRT is gassy if it can survive over 1300 miles of bumpy highways it can survive sitting in the 76 degree house I live in. Anyone have a general idea of how durable the 21axp22 is in terms of taking off the socket and putting it back on plus the bumpy ride home? Also happy New Year to all you folks here!

OK lets use correct terminology. The end of the picture tube has a bakelite "base" with pins. The wires from the chassis has a "socket" that has "terminals" inside of it.

Are you saying you pulled a "PIN" out of the Bakelite "base" on the 21AX or did you pull a "terminal" out of the "socket" that hase wires connected to the chassis.

First, I do not think your 21AX went bad, but that is always a possibility. If your tube is gassy you would probably get the dreaded purple neck glow when you power the chassis up. 10 years ago I purchased a CTC5 Wingate from California. The seller told me it was operational a year prior to when I purchased it. It was shipped to me in Wisconsin and when it arrived the crt was gassy. I am not sure if it was the transportation or temperature changes that made it go gassy but it sprang a leak at the weld line. The usual place that a 21AX leaks is on the heli-arc weld where the front of the tube is joined to the rear funnel. It is very rare for a leak to form where the glass components are fused to the metal parts of the tube. It is even more rare for a leak to happen where the lead wires come through the stem under the Bakelite base.

Normally if a crt is gassy, the filaments will be very dim with 6.3 volts applied. And if you increase the voltage while under test on a tube tester the filaments will usually burn out.

Follow up on suggestions the other posters gave to see if you have focus and ultor voltages. Then see if you have video signals and correct bias voltages at the pins on the crt.

[old_coot88]

Originally Posted by ohohyodafarted

...Normally if a crt is gassy, the filaments will be very dim with 6.3 volts applied. And if you increase the voltage while under test on a tube tester the filaments will usually burn out.

If the tube has gone completely to air, another symptom is quickly apparent:
the cathode end of the neck gets really really hot, immediately. Like too hot to touch. And the heaters may not light visibly, because of being
immersed in a heat-conducting fluid (air). And the heaters pull 'waay too much current since they can't come up to full temperature.
If you put a tester on it, the transformer in the tester may be unable to supply that much current.

[SwizzyMan]

Sorry about the confusion. I pulled a terminal out of the socket that plugs in to the CRT base. Will do a chassis and replace the filters and work from there. But it is confusing that 10 minutes after I last had a raster I wasn't able to get one again. Now when I try and power up the set without the CRT plugged into the socket once the hv comes up about 2 seconds later I hear a pop from the cage I immediately turned the set off. I think this set just needs a full recap with some resistor replacement. I wanted to turn it on just to get a baseline.

[tvdude1]

I sold this set it had very good raster and with a vcr had all 3 good colors but lousy sync. It was fine the night before he picked it up. He is trying to run this old timer with bad filters and waxed caps. I had disconnected a can and jumped it to just make it light up.