Tech-Master NIB TV Kit #5516 - Page 12 - Videokarma.org TV - Video

Electronic M · #**166** 12-22-2016, 03:58 PM

Anything in 30% tolerance is fine/normal in most sets. You may have touched the wrong damper pin...One normally has meter killing HV on it.

old_coot88 · #**167** 12-22-2016, 05:37 PM

You'd think the kit maker woulda pasted on a hazard warning in big red letters "Do not attempt to measure plate of H.out tube or cathode of damper tube", since there's a very high level spike there.

Crist Rigott · #**168** 12-22-2016, 09:00 PM

I hear ya! My inexperience showed up on that one. The schematic shows to have 350 volts on pin 3 of V13 12AX4 the Damper tube.

Still a bit puzzled as to why that would happen and especially when the schematic says 350 volts.

Crist Rigott · #**169** 12-22-2016, 09:02 PM

I thought I'd try direct video injection. I injected the video signal directly into pin 2 of the 12BY7A amp. The picture got only slightly better, but still way out of focus.

bandersen · #**170** 12-22-2016, 09:14 PM

What voltage do you have on G2?

Crist Rigott · #**171** 12-22-2016, 09:16 PM

Quote:

Originally Posted by bandersen

What voltage do you have on G2?

Which tube? On the CRT G2 is pin 10 and that has 301 volts as I let the TV play right now.

Crist Rigott · #**172** 12-22-2016, 09:29 PM

Another thought just occurred to me. When I was doing the voltage checks, the tubes were installed. Could the 350 volt marking on the schematic meant with the tubes removed? Though I don't see how you can get some voltages without them being installed. Just thinking out loud.

old_coot88 · #**173** 12-22-2016, 10:22 PM

Quote:

Originally Posted by Crist Rigott

Another thought just occurred to me. When I was doing the voltage checks, the tubes were installed. Could the 350 volt marking on the schematic meant with the tubes removed? Though I don't see how you can get some voltages without them being installed. Just thinking out loud.

Well, if the 12AX4 were removed, you wouldn't have any voltage on pin 3 (cathode) because it would break the DC current pathway for B+ to the rest of the H.sweep circuit. (Besides, with the tube removed, the other tubes won't light because it's a series heater string.)

The 350V is the raw, unfiltered B Boost voltage, and you sure as heck don't want to measure it at the damper cathode (!). If the kit maker actually measured it there, they were using a beefy old analog meter with mechanical movement that smoothed out the high level spike. And they were highly negligent in not posting a hazard warning.

bandersen · #**174** 12-23-2016, 12:00 AM

Quote:

Originally Posted by Crist Rigott

...This is an aluminized tube so no ION Trap.

Just because it's aluminized doesn't mean it doesn't need an ion trap magnet. The data sheet says you need a single ion trap magnet. Don't see any exception mentioned for the "C" version. Also is it a rebuild ? If so, it might have a straight or bent gun.

Crist Rigott · #**175** 12-23-2016, 12:07 AM

Quote:

Originally Posted by bandersen

Just because it's aluminized doesn't mean it doesn't need an ion trap magnet. The data sheet says you need a single ion trap magnet. Don't see any exception mentioned for the "C" version. Also is it a rebuild ? If so, it might have a straight or bent gun.

Bob, yes it is a rebuild. It does have a straight gun and it has 2 labels warning not to use an ION trap.

bandersen · #**176** 12-23-2016, 12:14 AM

OK, they sure made that clear! I'm out of ideas except low HV.

Crist Rigott · #**177** 12-23-2016, 12:24 AM

Quote:

Originally Posted by bandersen

OK, they sure made that clear! I'm out of ideas except low HV.

Appreciate the help and your videos.

Crist Rigott · #**178** 12-23-2016, 08:17 AM

At the suggestion of someone, I wired in a 2 meg pot to take the focus electrode, pin 6 of the CRT, from ground to 300 volts. I did and that didn't help at all. I also checked to be sure I had continuity from the CRT harness to the CRT base when the connector was plugged to the CRT. That checked good.

Maybe a broken focus wire from the base to the bulb?

dieseljeep · #**179** 12-23-2016, 10:04 AM

Quote:

Originally Posted by Crist Rigott

At the suggestion of someone, I wired in a 2 meg pot to take the focus electrode, pin 6 of the CRT, from ground to 300 volts. I did and that didn't help at all. I also checked to be sure I had continuity from the CRT harness to the CRT base when the connector was plugged to the CRT. That checked good.

Maybe a broken focus wire from the base to the bulb?

I've seen the e'stat tubes focus well without anything connected to pin 6.
Being a newcomer to the hobby, you don't have access to any of the junk us collectors have, such as another, smaller CRT or maybe a magnetic focus unit.
I know, the gun structure is different on a e'stat focus tube but maybe a magnetic focalizer would help.
BTW, that's the focus look like on the 5AXP4 test tube.

Crist Rigott · #**180** 12-23-2016, 07:09 PM

Quote:

Originally Posted by dieseljeep

I've seen the e'stat tubes focus well without anything connected to pin 6.
Being a newcomer to the hobby, you don't have access to any of the junk us collectors have, such as another, smaller CRT or maybe a magnetic focus unit.
I know, the gun structure is different on a e'stat focus tube but maybe a magnetic focalizer would help.
BTW, that's the focus look like on the 5AXP4 test tube.

The focus on the 5AXP4 is much better.