1953 Admiral C2226Z Restoration

[cluelessgame]

I'm in the process of restoring a 21" 1953 Admiral super cascode model C2226Z (chassis 22A3AZ). I bought it in a local antique store from the original owner for $10.00. and to say it was a train wreck would be an under statement, and, unbeknownst to me, not a good project for beginners. I've re-capped the entire set, and replaced all of the bad tubes, and i'm still getting a dim picture with little contrast. I checked the HV and i'm about 3kv under what's called for, and I don't have a picture tube tester. I'm not sure if the picture tube is original to the set as I found stuffed inside the cabinet the warranty claim card, which has been filled out. The date on the card reads 5/31/55, but the date stamp on the chassis reads Oct 20 1953. This tube is a G.E. 21ZP4B. Also, I'm getting weird, jumbled, extraneous rasters on the top of the picture. Also, on the subject of rasters, they seem to like to double up instead of being evenly spaced, fiddling with the vertical sync helps, they wont stay apart for long. What areas do you all think the problem(s) lie? I've attached photos of what I'm dealing with:
1: pre-restoration power up (I didn't know anything then)
2: screenshot of present working condition: note the dim, low contrast picture with scrambled rasters on top; retrace lines are visible due to brightness cranked all the way up (I've also discovered that turning brightness all the way down dims the picture only slightly, but not blacking out the screen)
3-6: warranty card, enjoy!

[Electronic M]

The screen looks bright enough to me.... As for the lousy contrast: have you tried adjusting the AGC control(usually located on the back of most sets)? If AGC has a positive effect then center the contrast control and adjust contrast to be good at that point and then rotate the contrast to check if it will go higher without overloading synch if so then your good. If not then back the AGC down until the the synch is stable.

[cwmoser]

Originally Posted by Electronic M

The screen looks bright enough to me.... As for the lousy contrast: have you tried adjusting the AGC control(usually located on the back of most sets)? If AGC has a positive effect then center the contrast control and adjust contrast to be good at that point and then rotate the contrast to check if it will go higher without overloading synch if so then your good. If not then back the AGC down until the the synch is stable.

I'd like to try this with my Zenith porthole - but I don't fully
follow. Can you describe it more simply so I can understand?

Thanks

Carl

[cluelessgame]

Originally Posted by Electronic M

The screen looks bright enough to me.... As for the lousy contrast: have you tried adjusting the AGC control(usually located on the back of most sets)? If AGC has a positive effect then center the contrast control and adjust contrast to be good at that point and then rotate the contrast to check if it will go higher without overloading synch if so then your good. If not then back the AGC down until the the synch is stable.

my camera made it look much brighter than it actually was. All the lights were off, and I even had to put a blanket over the blinds on my window to get it dark enough for me to see it.

As for the AGC control, there is not one labeled as such anywhere on the set, there is however a Noise Gate and DX Range Finder control, both of which I have tried with no success.

[cluelessgame]

Okay, so I finally got around to purchasing a CRT tester off of Epay, a Sencore CR31A "Super Mack" tester. It came today and I was about to hook it up to the CRT when I realized that this tester didn't come with the type 1 socket

does anyone happen to know the pinout for that socket so I can at the least attempt to hook it up with paperclips and jumper wires?

There's always something wrong with everything I do

[Rich12]

I didn't have a chance to go through the attachment but I did some surfing online see if this helps.

[MIPS]

You mentioned replacing tubes and caps but I'm assuming you also went through and checked the resistors as well, right?

[Electronic M]

Originally Posted by cwmoser

I'd like to try this with my Zenith porthole - but I don't fully follow. Can you describe it more simply so I can understand?

Thanks

Carl

AGC is short for Automatic Gain Control and is the TV equivalent of the AVC circuit found in AM radios. It samples the demodulated TV signal in one of several ways and based on the signal level increases or decreases gain in the tuner and IF stages to keep the signal strength at the detector relatively constant. Some early sets (such as the RCA 630TS) lack AGC and use the 'contrast' knob as an RF gain control instead of a final video amp gain control (as later AGC based sets do). The AGC adjustment pot sets the video detector output level that the circuit maintains under normal-ish reception conditions. With AGC at minimum you should not get any video or sound, and with it at max the screen will show a contrast inverted/blacked out picture that will not sync.

The normal procedure for adjusting AGC is to turn it up until the set begins to loose sync and or contrast becomes excessive or inverted, then back the control off of that setting just a tad so that sync can be achieved and a good contrast control adjustment range is achieved. If contrast and sync overloads when contrast is at max after AGC has been set, then back the AGC control down a bit more til sync stabilizes.

That is the most complete, simple explanation of AGC I can give, let me know if it (and what part) don't make sense, and I'll try to clarify.

[tom.j.fla]

If you have not found the AGC control yet look for a control marked range, rf range or rf range finder and adjust as Tom C said. All the best, Tom

[cluelessgame]

I found the AGC (labeled "DX Range Finder") and it has no effect as far as brightness is concerned. I checked all the resistors in close proximity (circuit-wise) to the picture tube and all seem to be in spec, and all the voltages are reasonable

I managed to hook up the CRT tester via nails and jumper cables using the information Rich12 provided (thankyou) and although no shorts were present, it seems the picture tube is completely dead: no emission or gun balance (cutoff) whatsoever. I checked and double checked my connections and they all appeared to be correct. what seems weird is that there is NO needle response at all for emission (and a slight drift from extreme to extreme of the knob for cutoff), but a raster/picture IS visible - a VERY dim one, but one none the less.

Also, the tube doesn't appear to have seen very many hours. the gun hasn't turned blue/violet from heat the way shango066 points out in some of his videos, And one would reasonably expect the previous owner would have retired the set LONG before emissions got this bad on its own. (Although, I guess I should mention that I'm only 21, and I've never actually seen a TV running with a weak picture tube - and know that that's the problem; I have nothing to refer to)

I did try the rejuve1 function, but nothing happened. I'm hesitant to try rejuve2 until I know for sure I have access to a replacement tube, or find the correct adapter socket for the tester just on the off chance I didn't jumper it correctly (I at least know I hooked the filament leads correctly)

I also tested the tester on another known-to-be-good color crt from an old computer monitor and everything appears to work, so I have ruled out the tester itself being faulty. I chose to purchase this particular tester after watching this video: https://www.youtube.com/watch?v=pOXJLlho2eI
The original tube in that video had the EXACT SAME symptoms my crt is having and I was hoping mine had a removable G1 short as well.

I guess this means I'm now truly in the market for a new 21ZP4
maybe if nothing else I'll try and see if Kamakiri still has his and if he'd be willing to freight it to me....from NY to all the way to TN...

[DavGoodlin]

I have a 1955 GE with the same CRT (a Sylvania 21ZP4, so it was replaced) Mine is also low emission and would need replacement if I choose to restore the set.

While your picture looks as if the main problem is low emission, you may have a voltage issue at the CRT. The other issues like retrace lines can be dealt with later.

Do not forget that this CRT also has an Ion trap magnet that needs to be adjusted or you'll get a dim or no picture. See below from 1956 GE tube data handbook.

21ZP4-B.pdf

[Phil Nelson]

I would second the advice to try adjusting the ion trap magnet before doing anything else (especially before trying more rejuvenating procedures, which can kill an otherwise good tube if used indiscriminately).

The ion trap magnet is a thin circular assembly that fits around the neck of the picture tube between the yoke and the tube base. Its placement is critical -- if misadjusted, it can cause the picture to be very dim, or even completely dark.

The idea is to move the ion trap while watching the screen, and adjust it for maximum brightness. It can be slid forward and backward on the neck, as well as rotated around the neck.

In a normally working TV, you'll find an obvious "sweet spot" where the screen looks brightest, and many other positions where it's dim or completely dark.

Some ion trap magnets have a little arrow that should point toward the front of the TV, but many do not. If you have removed it during the course of restoration, it's possible that you reinstalled it backward. If trying the magnet in every possible position doesn't change your picture at all, it does no harm to flip it. Just mark one edge or take a photo to remind yourself how it was installed when you got the TV.

Phil Nelson
Phil's Old Radios
http://antiqueradio.org/index.html

[cluelessgame]

yes I'm well aware of the ion trap magnet and it is in the best possible sweet spot. I even tried flipping it to no improvement

[cluelessgame]

Ended up dropping $205 on a new one from Video Display Corp. (http://vdc.mybisi.com/product/21zp4) not sure if it's actually the correct tube but it has a 1 year warranty and I guess I can return it if it isn't...the product picture doesn't look anything like a 21ZP4 but I'm hoping that's just a generic stock photo. Was there ever an overlap of monochrome tube numbering?

I'm also not sure if it'll have the dag coating as it's not an "A" or "B" style. Is Aquadag something that's sold in brick-and-mortar stores or just online?

[DaveWM]

time to trouble shoot.
1st thing is to inject a composite video signal at the control grid of the video out. Looks like a reversed image on the CRT.

See if that works. FYI I had a set that did the exact same thing, (weak reversed pic) it was the result of a cap installed by the PO as part of a mass shot gun recap, where one lead was attached to the wrong terminal of a term strip.

https://www.youtube.com/watch?v=qkJ3yp0c2v4