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  #31  
Old 12-29-2015, 04:32 PM
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Ooh, that looks pretty clean and original on the under side.
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  #32  
Old 12-31-2015, 02:28 AM
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Tom Albrecht did a nice description of his repair of an Inductuner shaft a while back that may help you.
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  #33  
Old 01-09-2016, 03:22 PM
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The GE monitor will be the next to get serviced.....It is perhaps the first GE device with a CRT I've opened up that I can honestly say looks very well built.

I'd guess this was a non-standard size rack-mount chassis given that the only way to remove the chassis is from the front, and that the 6 screws holding it were on the face panel.



The four jacks on the back seem to be V sync, H sync, and two bridged video terminals. I've found a switch on top of the chassis for selecting internal or external sync so it would seem it is designed to be capable of syncing to composite video....That will make feeding this set video much easier!



All the tubular caps are in nice easy places to get to, and of nice common values that my dwindling cap stock is still flush with. The variety of different cap types from Sprague Vitamin Q to those cheap yellow "Astron" caps often found in Heathkits of the era makes me wonder if it was repaired a lot or if GE just used whatever caps were cheap any given day of the week.... There was also a solder splash in it that would support it being serviced at some point.
It says 'GE closed circuit television' on the front so I'd guess it is an industrial, but not broadcast monitor...Still it is built well enough to be either.
This will be my first time restoring an industrial grade tube device.




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Last edited by Electronic M; 01-10-2016 at 02:52 AM.
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  #34  
Old 01-09-2016, 03:27 PM
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More pictures.



Only thing I've had to guess on so far is the missing HV rectifier tube (and the rating of the top fuse)....It is a 9-pin tube with a top cap...The only tube like that I know of is type 1X2, and it's pin-out seems to match the socket (also my 14" GE portable TVs use that tube that way) so I'm going to go with it for now.
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  #35  
Old 01-09-2016, 03:41 PM
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1AX2 is possible, but not likely.
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  #36  
Old 01-09-2016, 03:45 PM
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That GE monitor is very interesting. So is that a GE 12KP4 CRT?
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  #37  
Old 01-09-2016, 05:15 PM
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It certainly looks aluminumized.
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  #38  
Old 01-09-2016, 08:15 PM
Olorin67 Olorin67 is offline
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Will be cool to see it come back to life, after I had stored it for 25 years...I don't suppose there's much hope of finding a schematic for something like this?
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  #39  
Old 01-10-2016, 02:44 AM
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Quote:
Originally Posted by Olorin67 View Post
Will be cool to see it come back to life, after I had stored it for 25 years...I don't suppose there's much hope of finding a schematic for something like this?
Wow, this set has been stored longer than I've lived...
If it was broadcast gear or the right person hung on to the schematic, then it might still exist someplace...Finding it is the hard part...I'm accustomed to flying blind on some projects (as I'm doing here)...

It now basically lives. I was able to test and replace all bad caps (except for the lytics) in 1hour and 5 minutes. The Vitamin Q style caps were still good as new (as in previous encounters with those great caps) so I plan to leave them in. I proceeded to variac it up and was able to get a picture, but the sync and other things were not as stable as they should be.





I then removed the face and CRT to clean them and the chassis. I found the black mark in the center (that looked like ion burn) was just dirt, and that one of the lytics had got warm and peed it's self...I had time to test and replace (cause they were bad) all but the one insulated can (untested) and a small tubular lytic under the HV section (that tested good) which I may replace just for the heck of it. Tomorrow (well technically later today) those caps will be dealt with, the tubes will be tested and I'll put the CRT back in and give it a retest.



Quote:
Originally Posted by Kevin Kuehn View Post
That GE monitor is very interesting. So is that a GE 12KP4 CRT?
Yup! The set has it's (most likely) original GE 12KP4A, still going strong.

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  #40  
Old 01-10-2016, 09:08 AM
Olorin67 Olorin67 is offline
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Cool! I found that set around 1988, next to the trash chute in the basement of MSOE dorm RWJ. Wasn't sure what I wanted it for.. but couldn't' see it thrown out. Sent most of the years in my old room in my parents house, then in my storage locker. I wonder what MSOE used it for originally?, must have been an expensive piece of equipment back then.
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  #41  
Old 01-11-2016, 02:35 AM
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Quote:
Originally Posted by Olorin67 View Post
I wonder what MSOE used it for originally?, must have been an expensive piece of equipment back then.
There are a few possibilities: security camera duty (there were tons of security cameras there when I was getting my degree and they may have had use for one or two back then), 'Chicken stick' remote monitoring of dangerous equipment, TV repair course guinea pig (they use to offer degrees in radio and TV repair in the tube era), etc. Only way to know for sure would be to ask a staff member that was around when it was in service.

I've got it working good enough for my taste now. There is some new pincushioning of the horizontal that bugs me a bit, but I'll ignore that for now. It is easy to get drive lines if the width and drive controls are not balanced.



Most of the tubes have 57-22 and 188-4 I'm guessing that means 22nd week of 1957 and 188-4 is probably GE's EIA code. Given the CRT says 57-30 I'd guess this set was made in mid to late 1957. All but 3 tubes in it were original looking GEs tubes...two were Sylvania one was missing.
There is a part of me that finds it ironic that a monitor that has several desirable audio tubes in it (12AX7 12AU7 12AT7) has no audio section. What is weird is that it seems to use a 12AU7 as the vertical output...It strikes me as sending a kid to do a man's job...
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  #42  
Old 01-11-2016, 11:11 AM
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Plenty of sets used a 12AU7 video output, including the Raytheon/Belmont I've been working on. RC 19 lists it specifically for that application at 2.75 Watts plate dissipation. It's interesting how GE chose the 12KP4 in 1957. They must have felt is was a more robust tube than the others available, or possibly they were sitting on a big stock pile of them.
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  #43  
Old 01-11-2016, 02:24 PM
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Quote:
Originally Posted by Kevin Kuehn View Post
Plenty of sets used a 12AU7 video output, including the Raytheon/Belmont.
I don't know if they used it for video output (that would seem like a normal application to me), but they did use the 12AU7 for vertical output in my GE (and that strikes me as odd).
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  #44  
Old 01-11-2016, 03:27 PM
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I've also seen it used in Stromberg-Carlson sets as the vertical output, sections parallel connected. Sweeping a 19" tube no less! But yeah, video amplifier, sync separator, oscillator, you name it. 12AU7 isn't exactly equivalent to 6SN7 but is almost as ubiquitous in postwar sets.
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  #45  
Old 01-11-2016, 05:59 PM
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Quote:
Originally Posted by Electronic M View Post
I don't know if they used it for video output (that would seem like a normal application to me), but they did use the 12AU7 for vertical output in my GE (and that strikes me as odd).
I misspoke and said video output(which is what my Raytheon has). But in fact RCA's RC- 19 Receiving Tube Manual list's it's max ratings (each unit) as a vertical deflection amplifier.
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