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  #61  
Old 06-18-2016, 08:59 PM
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N2IXK N2IXK is offline
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Power applied.

Heaters start warming up, and....

It Lives!!!

First light: June 17, 2016.

After a couple minutes of snapping pictures and sniffing for smoke, I flipped on the built in dot generator and got pretty much what I expected. Could have been cover art for a 60's psychedelic band. Convergence just about as far out as it is possible to be in every direction. Horrible purity, and overall reddish cast with blurry retrace lines, but it makes an image! My visitors seemed puzzled why I was as happy as I was with what we saw. Had to explain the large amount of adjustment and tweaking that needs to be done to a set of this vintage to get everything just right. And that having a picture even this good means that 90% or more of the set is already working properly.

A quick purity setup, static convergence setup and greyscale adjustment produced a nice stable black and white image. A few tweaks of the 3.58 osc and burst phase got a reasonable color image, and tweaking the AGC got it fairly viewable in about 20 minutes.

Today I went through and finessed things in a bit better, and got things as good as the "non instrument" alignment procedure is going to, I think. I plan to follow the full alignment procedure detailed in the final volume of the manual set, and at least verifying that the IF and chroma circuits are lined up. Several coils and traps are left unadjusted when using the simplified procedures, and I think I can squeeze a bit better image out of this thing with a real instrument alignment. Both the color and tint controls have a very limited range of action, right around the center of travel. Color level particularly touchy to set to get reasonable skintones without over or saturation.

It's been a month and a half since I started this journey, and had a great time doing it! Will begin looking for a suitable NOS replacement tube and designing some kind of cabinet for this beast. Any leads or ideas gratefully accepted...
Attached Images
File Type: jpg First Light.jpg (75.9 KB, 67 views)
File Type: jpg first dots.jpg (114.1 KB, 68 views)
File Type: jpg First Crosshatch.jpg (112.1 KB, 58 views)
File Type: jpg First Video.jpg (76.6 KB, 88 views)
File Type: jpg Bars.jpg (67.9 KB, 82 views)

Last edited by N2IXK; 06-18-2016 at 10:00 PM.
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  #62  
Old 06-18-2016, 09:00 PM
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N2IXK N2IXK is offline
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Couple more pics...
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File Type: jpg Screenshot.jpg (82.6 KB, 88 views)
File Type: jpg Shop.jpg (96.7 KB, 81 views)
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  #63  
Old 06-18-2016, 09:41 PM
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That thing looks awesome! Almost like a brand new set
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  #64  
Old 06-25-2016, 07:56 PM
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Over the last week or so, I have managed to track down a potential source for a replacement tube, and should have it in the next few days. New tube is a 25VCZP22, which appears to be a tension banded successor to the bonded faceplate VAB/VAD types. Hoping it fits the mask on my set OK. Datasheet comparison looks promising.

Spent an hour or so setting up the UHF tuning presets. To use all 12 presets, I selected all the now defunct local UHF stations I can remember, and added a handful of others. 14 and 83 just to cover the entire band for testing purposes, 37 just in case I want to listen for aliens, and channel 62 to tune in the occasional Blonder/Tongue modulator broadcast of "UHF". Dialed all channels in using a VA62. All the channel number stickers were in great shape, and applied to the UHF channel display wheel.

Varactor UHF tuner works VERY nicely, good stable reception on all channels. Did any commercial sets have varactor UHF tuning in 1969?

Am pondering how best to add a composite AV input to this set. Video amplitude out of the detector measures about 2Vpp, but proper polarity. Applying a proper level video signal from the VA62 right into the video cable to the IF module gives a GREAT picture. I need to design a video amplifier with a gain of ~2, preferably to operate from the single ended 30V power supply available in the set. Shouldn't be too big a deal using a modern video opamp. Line level audio input will probably be done by just rewiring the provided "HiFi out" line level audio output jack to be a line level input to the top end of the volume pot.

The set has an unused position between 2 and 13 on the VHF tuning dial (where UHF would be on a non varactor setup) which displays "H" (for Heathkit I guess) on both UHF and VHF tuning dials. I am contemplating rigging up a switch/relay to automatically select the AV input in this tuner position, so as not to have to add a separate line/RF switch.

Dynamic convergence has drifted a tiny bit in the last week or so (maybe 8 hours run time). Nudged it back, but obviously going to be redone again at CRT swap.

Contemplating a cabinet design to be a winter project. Thinking wooden front and bottom, with transparent top, sides, and back.

Last edited by N2IXK; 06-25-2016 at 08:13 PM.
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  #65  
Old 07-01-2016, 02:34 PM
msimendi msimendi is offline
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I've wanted to ad a composite video input to my GR-900 also. I found a circuit from an Early Television Foundation presentation from some years back. I built it but it wasn't flat out to 4.5 MHz so I abandoned the idea.

How about injecting it right after the diode and before the final IF stage? Haven't tried that yet as it is in a sealed can.
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  #66  
Old 07-01-2016, 03:20 PM
andy andy is offline
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...

Last edited by andy; 11-20-2021 at 03:10 PM.
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  #67  
Old 07-01-2016, 08:55 PM
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I have serious doubts about the safety of tubes that have undergone the standard cat removal procedure. The whole purpose of that resin was to effectively form a glass/resin/glass laminated panel, similar to automotive safety glass. Without the resin layer, it is just an unprotected CRT behind a second sheet of non-safety glass (the reinstalled faceplate). At least the older sets actually used a laminated glass safety panel in front of the unprotected CRT. The faceplates on laminated tubes are just tinted or frosted glass, which would only add to the shrapnel from an implosion if not bonded with the resin.

Obviously CRT rebuilders must have had a way to remove and rebond these faceplates properly when rebuilding tubes, as the resin would never have stood up to oven bakeout. Does anyone know how this was done? It isn't addressed in the excellent film made of HawkEye's rebuilding process over on the ETF site. I imagine that it takes some special setup (like vacuum impregnation) to ensure no trapped air bubbles in the resin. Clear 2 part urethane casting resin is available from several suppliers, and would probably be a good substitute for the PVA that was originally used, if a way was available to get a void-free fill.

The 25VCZP22 that I found locally turns out to have issues with the red gun, so probably won't be used. The ETF has a pair of NOS 25VABs available for $75 each, so if one of them is cat-free I will likely purchase one of those. They are in the process of checking them for me. The VCZ would have actually been a nicer tube, being a tension banded type with no cataract worries at all. Bummer about the red gun...

Last edited by N2IXK; 07-01-2016 at 09:06 PM.
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  #68  
Old 07-24-2016, 04:57 PM
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N2IXK N2IXK is offline
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The new tube arrived yesterday, and looks like a beauty. A Sylvania "AA" grade, all new "Chromatrix" tube. Completely cataract-free, and with a date code of "2013" which I am guessing is a code of some kind, not a 3 year old tube. Box looks a good deal older than that. Even got the warranty registration card (should send it in for a laugh!) Thanks to Steve at the ETF, and a friend of mine who was able to bring the tube from Ohio back to NJ for me, saving $$$ on shipping

Tube tests perfectly on the CR-31A, and will be installed after I return from a week's vacation.
Attached Images
File Type: jpg Carton.jpg (93.7 KB, 40 views)
File Type: jpg Label.jpg (62.7 KB, 46 views)
File Type: jpg Tube.jpg (54.8 KB, 44 views)
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  #69  
Old 07-24-2016, 06:18 PM
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Quote:
Originally Posted by N2IXK View Post
I have serious doubts about the safety of tubes that have undergone the standard cat removal procedure. The whole purpose of that resin was to effectively form a glass/resin/glass laminated panel, similar to automotive safety glass. Without the resin layer, it is just an unprotected CRT behind a second sheet of non-safety glass (the reinstalled faceplate). At least the older sets actually used a laminated glass safety panel in front of the unprotected CRT. The faceplates on laminated tubes are just tinted or frosted glass, which would only add to the shrapnel from an implosion if not bonded with the resin.

Obviously CRT rebuilders must have had a way to remove and rebond these faceplates properly when rebuilding tubes, as the resin would never have stood up to oven bakeout. Does anyone know how this was done? It isn't addressed in the excellent film made of HawkEye's rebuilding process over on the ETF site. I imagine that it takes some special setup (like vacuum impregnation) to ensure no trapped air bubbles in the resin. Clear 2 part urethane casting resin is available from several suppliers, and would probably be a good substitute for the PVA that was originally used, if a way was available to get a void-free fill.
In this post, I described a process that I have observed:

http://www.videokarma.org/showpost.p...11&postcount=2

jr
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  #70  
Old 07-24-2016, 08:42 PM
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N2IXK N2IXK is offline
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Interesting. Thanks for posting that. The PPG number you posted appears to be an automotive paint, not a bonding resin. I have used various products from Forsch Polymer Corp. over the years, and they have a few resin systems that seem like they would work well for this application, with low uncured viscosity and good transparency when cured.

May have to give it a try on a dud tube at some point to see if the cataract problem can be solved without compromising future safety.
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  #71  
Old 07-25-2016, 02:55 PM
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Quote:
Originally Posted by N2IXK View Post
Interesting. Thanks for posting that. The PPG number you posted appears to be an automotive paint, not a bonding resin.
I tried to dredge another number out of the old memory cells, but I keep comming back to PPG 5252. Dead cells? Two numbers associated with this task had a nice rhythm, like 5252 and 1418 for the UL crt implosion test document. Wonder if the 5252 number got recycled to another product after the process was retired.

The resin that was used was heated (85 C ?) in small batches and the mek-p catalyst was added and mixed in just before the pour was made. When cured, the resin had a rubbery consistency.

Good luck with your experiments,
jr
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