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 Post subject: Re: Tech-Master NIB TV Kit #5516
PostPosted: Dec Wed 28, 2016 4:49 am 
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Location: Waxahachie Texas
Tom,
I have to agree. Channel Master knows what it is doing. Seeing that this tube is aluminized, they went with a straight gun and eliminated the ION trap.

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 Post subject: Re: Tech-Master NIB TV Kit #5516
PostPosted: Dec Wed 28, 2016 5:03 am 
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OK everybody. I got my HV probe today and assembled it and hooked it up to my KG-625 VTVM. After a few minutes warm up time for both the TV and VTVM, I zeroed the VTVM and measured the HV at the door knob connection of the HV lead going to the CRT. 12Kv. I then measured at the CRT, 12Kv again. So I'm getting 12 KV at the CRT with the "stock" assembly.

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 Post subject: Re: Tech-Master NIB TV Kit #5516
PostPosted: Dec Wed 28, 2016 5:26 am 
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OK, I got a NOS Westinghouse 25DN6 and tried that instead of the 25CD6. I now have 14Kv! 2Kv by just using an alternate tube! This measurement was with the brightness turned all the down. At normal viewing levels I have 13.5Kv.


Still very unfocused.

Tom, I varied the voltage (0-300V) on the focus anode with no joy.

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 Post subject: Re: Tech-Master NIB TV Kit #5516
PostPosted: Dec Wed 28, 2016 6:10 am 
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Location: Waxahachie Texas
I boosted the B+ by 10 volts and picked up another 1Kv. With B+ from 124 volts to 134 volts I get another 1KV volts from 13.5Kv to 14.5Kv under normal viewing brightness.

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 Post subject: Re: Tech-Master NIB TV Kit #5516
PostPosted: Dec Wed 28, 2016 11:34 pm 
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Try making a duplicate boosted B+ pick off as I mentioned a few posts back. With less current flowing through the resistor and therefore less voltage drop you should get more voltage for the screen grid. And It is possible that there are two problems causing a unfocused picture. You could have some problem with the video being fed to the CRT along with a focus problem. So when adjusting the voltage on the focus electrode look only for the scan lines to become sharp. If you can get that then the focus is good and we can look elsewhere for a video problem.

By the way, how did you boost the B+?

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 Post subject: Re: Tech-Master NIB TV Kit #5516
PostPosted: Dec Thu 29, 2016 12:24 am 
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Tom Schulz wrote:
Try making a duplicate boosted B+ pick off as I mentioned a few posts back. With less current flowing through the resistor and therefore less voltage drop you should get more voltage for the screen grid. And It is possible that there are two problems causing a unfocused picture. You could have some problem with the video being fed to the CRT along with a focus problem. So when adjusting the voltage on the focus electrode look only for the scan lines to become sharp. If you can get that then the focus is good and we can look elsewhere for a video problem.

By the way, how did you boost the B+?

I boosted B+ by turning up the Variac while having a resistor in the filament string.

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 Post subject: Re: Tech-Master NIB TV Kit #5516
PostPosted: Dec Thu 29, 2016 12:27 am 
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I found the focus problem...most likely.

I pulled the base off the bulb and the focus wire was broken. Middle picture.

Unfortunately, I broke a filament wire in the process. Last picture.


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 Post subject: Re: Tech-Master NIB TV Kit #5516
PostPosted: Dec Thu 29, 2016 2:10 am 
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I managed to tack on some wires with alligator clips on one end. Then I tested the CRT.

Viola! I didn't take any time to do any adjusting of the picture.


Attachments:
100_5640a.JPG
100_5640a.JPG [ 98.94 KiB | Viewed 1367 times ]

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 Post subject: Re: Tech-Master NIB TV Kit #5516
PostPosted: Dec Thu 29, 2016 2:12 am 
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Tom, while the CRT was playing, I tried moving the pot on the focus line to vary from 0 to +300 volts. It didn't do anything.

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 Post subject: Re: Tech-Master NIB TV Kit #5516
PostPosted: Dec Thu 29, 2016 2:25 am 
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Crist Rigotti wrote:
Tom, while the CRT was playing, I tried moving the pot on the focus line to vary from 0 to +300 volts. It didn't do anything.

Ha. So the voltage does not matter, just so long as it is not floating. I would expect some effect on varying the voltage, at least a little bit. Perhaps when looking at the scan lines with a magnifier.

I hope you can attach some leads to those stubs that will stay connected.

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 Post subject: Re: Tech-Master NIB TV Kit #5516
PostPosted: Dec Thu 29, 2016 6:25 am 
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Well, the new wires are soldered on the CRT and sensor safe silicone has been added. Tomorrow I'll assemble the base to the bulb.

I used Dremel Cut-Off wheels by hand to start scratching the glass away. Then I switched to a #11 hobby blade and scraped the glass away. Then I used the hobby knife to scrape the wire clean and then tinned it.

I used some 30awg magnet wire and cleaned off the enamel. I then formed a very small coil of 2 turns. Yup, I'm using the coil method to attach the new wires to the stubs. A little flux and the wire was positioned on the stud and then soldered. A very nice shaped blob of solder told me I had it licked!

I then cleaned the joints with acetone to clean off the flux. A final rinse of alcohol and on went the sensor safe silicone.


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 Post subject: Re: Tech-Master NIB TV Kit #5516
PostPosted: Dec Thu 29, 2016 4:03 pm 
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I put the base back on before I went to bed last night. I used the same sensor safe silicone. I then soldered the wires to the pins. Cleaned up the pins and we are ready to go.

I hooked the CRT back up to the TV and success!


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 Post subject: Re: Tech-Master NIB TV Kit #5516
PostPosted: Dec Thu 29, 2016 5:09 pm 
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I added a 10 ohm 25W resistor to the filament string. The filament string is for 115vac and my wall outlets provide 124vac. I thought that the 124vac would be a bit too much for the filament string, hence the resistor. The filament string is now at 117vac using my wall outlet. I used such a big resistor because I had one on hand and also I like to way oversize these things.


Attachments:
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 Post subject: Re: Tech-Master NIB TV Kit #5516
PostPosted: Dec Thu 29, 2016 5:34 pm 
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Priceless!

Old NIB TV kits are priceless.


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 Post subject: Re: Tech-Master NIB TV Kit #5516
PostPosted: Dec Thu 29, 2016 6:01 pm 
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With the TV plugged into the wall (124vac) I'm getting 135v B+ and 13.2 to 14.6Kv depending on the brightness setting.

This is with a 10 ohm resistor in the filament string and a 15 ohm resistor in the power line going to the rectifier.

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 Post subject: Re: Tech-Master NIB TV Kit #5516
PostPosted: Dec Thu 29, 2016 9:26 pm 
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Great fix on those CRT pins! Apparently at some point in that tubes history the base had become loose and the wires were twisted and fatigued until one finally broke. It's not uncommon for one of us hobbyists to re-glue a loose base. Unfortunately a broken focus pin would never show up on a common CRT test.

Is it possible your scan is more compressed at the bottom compared to the top(in need of a vertical linearity adjustment)?


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 Post subject: Re: Tech-Master NIB TV Kit #5516
PostPosted: Dec Thu 29, 2016 11:23 pm 
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Location: Waxahachie Texas
Kevin Kuehn wrote:
Great fix on those CRT pins! Apparently at some point in that tubes history the base had become loose and the wires were twisted and fatigued until one finally broke. It's not uncommon for one of us hobbyists to re-glue a loose base. Unfortunately a broken focus pin would never show up on a common CRT test.

Is it possible your scan is more compressed at the bottom compared to the top(in need of a vertical linearity adjustment)?

Thanks Kevin.

I agree about the base being loose and a wire broke.

I'm sure the scan and a lot of other picture problems exist. All I did was tweak 1 coil to resolve the Horizontal and just twiddled the Vertical height and linearity, brightness, contrast, etc to get a picture.

Very soon I'll be doing a full alignment.

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 Post subject: Re: Tech-Master NIB TV Kit #5516
PostPosted: Dec Fri 30, 2016 3:20 am 
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Nice job on saving that tube! How odd that it had a broken wire, otoh I wonder about some of the NOS CRT's floating around, I've had a couple of them with flaws, makes me wonder if that was why they never sold.

I had a 7JP4 that had one of the deflection wires bent over under the cap, it would arc when powered up, got it fixed but it was a pain. I have a NOS 17" RCA Silverama, still in the box, with a speck of debris in the Phosphor, not a fatal flaw nowadays but back when it was sold it would have been a no-go to sell to a customer.


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 Post subject: Re: Tech-Master NIB TV Kit #5516
PostPosted: Dec Fri 30, 2016 3:22 am 
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Thanks Eric.

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 Post subject: Re: Tech-Master NIB TV Kit #5516
PostPosted: Dec Fri 30, 2016 5:45 am 
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Good job on fixing that CRT. Was the base loose when you got it or did it look like someone had re-glued it at some point?

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