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 Post subject: Re: Tech-Master NIB TV Kit #5516
PostPosted: Dec Fri 30, 2016 7:35 am 
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Location: Waxahachie Texas
Tom Schulz wrote:
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?


The base was loose when I got it. I don't think anybody tried to re-glue it. I didn't see any other glue except what I would consider OEM. The CRT had a single layer of filament packing tape around the base and bulb. It was old and "sticky" IIRC. So the base was loose sometime ago and somebody put some tape on it. Remember I was given the CRT and it was new rebuilt but without the box. My guess is that LarryW got it from one of the estate sales he went to a while ago. It was with a bunch of other CRT's in his warehouse.

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 Post subject: Re: Tech-Master NIB TV Kit #5516
PostPosted: Dec Sat 31, 2016 9:43 pm 
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Here is what I used instead of the cork they supplied with the kit.

It is a very close cell foam that I get at Hobby Lobby. This is about 1/16 thick. I used some spray contact cement to glue them in place.

I used the same stuff on the "inside" of the CRT strap so there isn't any metal to glass contact.

I also made a "stand-off" from 1/16 phenolic sheet to help manage the HV lead from getting too close the the chassis and the lead from the fly-back to the HV rectifier.


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 Post subject: Re: Tech-Master NIB TV Kit #5516
PostPosted: Dec Sat 31, 2016 9:51 pm 
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There was a post either in this thread or on the other forum, suggesting that I might need some more filtering. Well I clipped in another 220uf cap parallel with C43B. There was no change to the B+ supply but the picture seemed a bit more stable. Hmm..... so I added another 220uf to C43A and again the B+ stayed the same abd the picture remained stable.

So if I add these E-caps to each C43A and C43B it will bring each up to 440uf. Does anybody see anything wrong with doing that? Would a lesser uf work?

I'm including a picture of that section of the schematic.


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 Post subject: Re: Tech-Master NIB TV Kit #5516
PostPosted: Dec Sat 31, 2016 10:27 pm 
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Location: Waxahachie Texas
I've been doing some investigating the focus problem I had with the help of another person offline.

Basically I cannot duplicate the focusing problem I had before I repaired the broken wires on the CRT.

If it was a broken wire I should be able to duplicate it by disconnecting pin 6 from B-. When I do, the picture remains in focus! NOTE - On the schematic, the blue wire from pin 6 shows it goes to chassis ground. This is an error on the drawing. It really goes to B-.

I've tried disconnecting wires on pin 2 and pin 10 with the same results, It still stays in focus. I even went back to the kit supplied 25CD6 and still stayed in focus.

I'm at a loss as to what caused the focus problem. I do know that after I fixed the the broken wires and reattached the base, the CRT stays in focus.

I'm including a section of the schematic so you can see what I'm talking about and maybe offer some reasons or suggestions.


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 Post subject: Re: Tech-Master NIB TV Kit #5516
PostPosted: Jan Sun 01, 2017 1:09 am 
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Location: Waxahachie Texas
I added the extra 220uf e-caps, on each to C44A and C44B. The picture seems more stable now.

I spent a little time centering the picture and adjusting the height and Vert. Lin and here is the picture a scene from Veggietales.

Seems pretty good. The width is much too wide even though at very near the end of the adjustment. Any ideas as to what can be done to shrink it some like change a cap or such.


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 Post subject: Re: Tech-Master NIB TV Kit #5516
PostPosted: Jan Sun 01, 2017 2:36 am 
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Crist Rigotti wrote:
I've tried disconnecting wires on pin 2 and pin 10 with the same results, It still stays in focus.

Wow! Was there any change in the picture when you disconnected those wires?
I do have a set with an electrostatic focus CRT where the focus electrode is not connected. I was going to try different voltages but did not bother when I found that the focus was good without doing anything.

I will offer a guess. Perhaps there was some debris in the electron gun that fell out when you set the CRT on it's face to work on it.

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 Post subject: Re: Tech-Master NIB TV Kit #5516
PostPosted: Jan Sun 01, 2017 6:37 am 
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Location: Waxahachie Texas
Tom Schulz wrote:
Crist Rigotti wrote:
I've tried disconnecting wires on pin 2 and pin 10 with the same results, It still stays in focus.

Wow! Was there any change in the picture when you disconnected those wires?
I do have a set with an electrostatic focus CRT where the focus electrode is not connected. I was going to try different voltages but did not bother when I found that the focus was good without doing anything.

I will offer a guess. Perhaps there was some debris in the electron gun that fell out when you set the CRT on it's face to work on it.

Tom,
Here is what I found:
Disconnected pin 6 (Focus) = No change at all.
Disconnected pin 2 (G1) = Stays in focus but retrace lines show up.
Disconnected pin 10 (G2) = Picture stays in focus but slowly gets dark in 30 seconds.

As far as having the CRT on its face, I've been tipping it up on its face many times during troubleshooting.

I'm really at a loss as to what was causing the out of focus picture before the "fix".

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 Post subject: Re: Tech-Master NIB TV Kit #5516
PostPosted: Jan Sun 01, 2017 6:41 am 
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I tried to increase the resistance of R63 (pin 8 25DN6) to see if I can reduce the width. I increased it to 6.8K and finally saw the width go down. But my HV went from 13.5Kv to 10Kv. Not good. I'm including a picture of the Horizontal section to what I'm talking about. I'd really like to reduce the overall width. Yes, I adjusted the "Width Coil" but it is still too big.

Any ideas?


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 Post subject: Re: Tech-Master NIB TV Kit #5516
PostPosted: Jan Sun 01, 2017 11:28 pm 
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The width being too wide is the only "problem" I have left. The picture is very watchable and the too wide picture is more of a preference than a problem.

With that said, I'd like to list the errors etc found when building the kit. Overall when following the 6 instruction sheets step-by-step will give a working TV.

1) Yoke brown and red numbers doesn't match between the schematic and the yoke plug drawing on Instruction Sheet 6. I corrected the numbers on the schematic.

2) On the schematic, C43A shows a chassis ground. Should be shown as going to B-.

3) On the schematic, R61 a 220K resistor should be labeled R61C.

4) On the schematic, C15A 470pf cap should be labeled C15.

5) On the assembled RF Strip, R33 and R34 are 12K. The schematic, parts list, and Instruction Sheet IF Strip lists them as being 15K. When I was replacing all the resistors, I used 15K.

6) The shielded cable shown on Instruction Sheet 1 has red and black. The cable supplied with the kit, the colors are orange and yellow.

7) On Instruction Sheet 3, R80 should be drawn going all the way to V6-3.

8) Parts List and IF Strip Instruction Sheet missing the 68pf cap across L8.

9) I rotated TB20 90 degrees due to the close proximity to C43.

10) T5 on Instruction Sheet 5 didn't match the physical T5. I removed the can and rotated it to match the Instruction Sheet.

11) On the schematic, C42 in the yoke, is listed as 51pf. The parts lists it as 47pf. A 52pf cap was installed.

12) I installed a 10 Ohm 25 watt chassis mount resistor in the filament string due to my voltage being 124Vac.

13) I replaced the selenium rectifier with a 1N4007 diode.

14) I replaced R69 a 5 Ohm 5 watt resistor with a 15 Ohm 50 Watt chassis mount resistor.

15) I added a 220uf 250V E-Cap to each C44A and C44B. Each now are rated at 440uf 250 volts. This might not have been needed, but it did seem to stabilize the picture a bit more.

16) I'm using a new rebuilt 21FP4C CRT that is aluminized with a straight gun. No ION trap is used.

17) I'm using a polarized line cord without an interlock. The "Hot" side goes to the fuse.

18) I replaced the HV lead with a 20K wire and modern boot.

19) I replaced the 25CD6 tube with a 25DN6. This gave me at least 1Kv more HV.

I plan to install a CL-90 thermister to prevent surges to the filament string during turn-on.

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 Post subject: Re: Tech-Master NIB TV Kit #5516
PostPosted: Jan Mon 02, 2017 7:49 pm 
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This morning I scoped out the Horizontal Oscillator to adjust the frequency and to have the waveform peaks match.

Here is the result.


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 Post subject: Re: Tech-Master NIB TV Kit #5516
PostPosted: Jan Mon 02, 2017 7:51 pm 
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Next up is the width issue. I'll make a strip from .003 brass shim stock about 3/4 wide and 4 inches long. I'll use some packing tape for now to see how this experiment works.

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 Post subject: Re: Tech-Master NIB TV Kit #5516
PostPosted: Jan Mon 02, 2017 8:35 pm 
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I made a "sleeve" using .003" brass shim stock 1" wide and 6" long. I then covered each side with packing tape. I then shoved it in between the CRT neck and the yoke at the top. I figured this would be the place because the horizontal yoke windings are on the top and bottom. I also placed the centering rings back on the neck and in the same position as before. I then connected a clip lead from the sleeve and chassis ground.

Turned on the TV and here is what I got. Wahoo! Now to clean it up and play it for awhile to see how hot it really gets.


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 Post subject: Re: Tech-Master NIB TV Kit #5516
PostPosted: Jan Tue 03, 2017 12:48 am 
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Well, I just finished an IF alignment.

I followed the procedure as in the Instruction Booklet on page 4. Basically it went like this:

1) Hook up a VTVM - I used my Knight KG-625

2) Hook up a signal generator - I used my Eico 322. I know, I need to get a better generator. Maybe a BK E-200D.
I did use my 6J6 with pin 1 cut off to eliminate any incoming signal.

3) Connect a 3V bias battery

4) Preset all 5 coils either full in or full out.

5) Set signal generator to a specific frequency and tweak a coil to a max reading on the VTVM.

When done, I hooked up my O'scope and Eico 369 Sweep Generator to check the overall response curve. This was the waveform displayed. Picture #1

Not even close!

So, with my diddle stick in hand, I first set the middle frequency of 24.75MC on the marker and then started tweaking till the marker was near the middle of the hump. A quick check to see if the 50% frequencies were anywhere close. They were not. After a lot of adjusting and getting a feel for which coil did what to the waveform, I ended up with a very decent waveform with the 50% frequencies right on the mark. This only took me several hours of being patient. I can't imagine doing this with the grand kids over!

Here is a picture of what the response curve is supposed to look like. Picture #2

Here is the pip at 26.4MC. Picture #3
Here is the pip at 23.1MC. Picture #4
Here is the pip at 21.9MC. Picture #5

Overall this alignment went a lot better than the Admiral 14R12 I did a few months ago.

I haven't tried it yet because I have to do the sound alignment next even though I tweaked the coils by ear the other day.

Stay tuned for a report on that.
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 Post subject: Re: Tech-Master NIB TV Kit #5516
PostPosted: Jan Tue 03, 2017 2:20 am 
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In general, if you have not replaced any components that are directly part of the tuned circuits and have no reason to suspect that the alignment is way off, you can skip the presetting of the coils to specific frequencies and just go to the sweep alignment.

By the way, in your last picture it looks like you have some snow in the picture. :)

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 Post subject: Re: Tech-Master NIB TV Kit #5516
PostPosted: Jan Tue 03, 2017 3:52 am 
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Tom,
I followed the Instruction Booklet just to follow it. I did replace all the film caps and resistors in the IF Strip.

The last picture was an OTA picture and it wasn't the best. I don't think there was any snow. Maybe too much contrast.

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 Post subject: Re: Tech-Master NIB TV Kit #5516
PostPosted: Jan Tue 03, 2017 3:54 am 
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I accomplished the audio alignment per the instruction booklet. I then ended up doing it again by ear. Much better.

I reinstalled the CRT, here are some pictures of how it is mounted and secured. The strap works well but the bolt brackets are a bit hooky. But they do the job. My guess on smaller CRT's the brackets would "work" better.

I centered the picture and moved the width sleeve to achieve a very nice picture. I'm playing Walt Disney's "Pollyanna".


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 Post subject: Re: Tech-Master NIB TV Kit #5516
PostPosted: Jan Tue 03, 2017 4:11 am 
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Crist Rigotti wrote:
Tom,
I followed the Instruction Booklet just to follow it. I did replace all the film caps and resistors in the IF Strip.

I figured that you were doing all the steps just to do them. But I thought to mention the quicker way just in case.
Crist Rigotti wrote:
The last picture was an OTA picture and it wasn't the best. I don't think there was any snow. Maybe too much contrast.

At first glance it looked like a winter scene. Looking again, probably not.

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 Post subject: Re: Tech-Master NIB TV Kit #5516
PostPosted: Jan Fri 06, 2017 4:47 am 
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My CL-90 came in and I installed it between the line and the 10 ohm resistor in the filament string. I installed it with the long leads and in the open. It took the voltage from 117vac to 113vac for the 115vac filament string.

I then installed the 15 ohm 50 watt resistor from the line to the B+ supply. With the resistor installed and the TV plugged in the wall, the B+ is now 132 volts.

Then I installed my speaker disconnect using some RCA phono jacks and plugs.

This pretty much concludes the assembly of the chassis.

The thing that still bothers me is the too wide picture and I had to use the sleeve to reduce it. When using the sleeve the HV is reduced by a fair amount. I really didn't like reducing the HV from 14.5Kv to around 10.5 to 11Kv.


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 Post subject: Re: Tech-Master NIB TV Kit #5516
PostPosted: Jan Fri 06, 2017 5:45 am 
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I think that reducing the screen grid voltage on the horizontal output tube is the way I would go. It will reduce the current through the tube and flyback and I would not use the sleve. same results smaller width and unfortunately the hv wil go down too but as I stated lower current is a good thing lower temperature on components and no metal under the yoke for it to arc to and ruin the yoke.


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 Post subject: Re: Tech-Master NIB TV Kit #5516
PostPosted: Jan Fri 06, 2017 5:48 am 
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I noticed in your last photo of the screen that you have some black showing at the edges of the screen. CRT TV sets are designed to over scan, at least a little. The idea is that a momentary dip in line voltage should not cause any black to show at the edges. Perhaps you are trying to reduce the width too much. Just how much too wide is the picture? If you have other CRT TVs, how does it compare with the other sets?

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