Crist, the crt in my set is a 17HP4 "C" as labeled by the rebuilder, most likely to show that the jug has a straight gun. Old_coot88 is correct that a width sleeve is needed to control the width on your set. The brass or copper is 1/2 to 3/4 the dia. of the neck and is sealed in thin sheet hi-temp plastic. Try to find a sleeve from a junker or make one. All the best,Tom.J

I've never done it, but wonder why not put a low resistance in series with the horiz yoke winding? Maybe try 20 ohms and go from there..? Seems like it wouldn't screw with the resonant point of the HV systen enuff to matter.

:nerd:

Regarding your concern of not being able to duplicate your earlier focus problem - It's possible the internal electrode connected to pin 6 is retaining a charge(because of capacitance) even after you remove the wire. :scratch2:

Could you go into more detail as to a "HV Doubler" circuit? Thanks.

See the 3 HV rects in this circuit? They constitute an HV trippler. Saw off the third HV rect tube (and everything right of the second HV rect), and you have an HV doubler.
http://www.earlytelevision.org/pdf/RCA-8PCS41-9PC41-648-741-Sams-90-9.pdf

There were also SS HV doublers, tripplers, and quadrupplers in 70's SS color sets that could be used if period correct look is not a concern.

Any doubler will increase load on the flyback and reduce width....Monitor H Out tube cathode current and flyback temperature over an extended test run and if it gets excessive power down and try something else.

Tube doublers will draw more power due to the tube heaters.

Tom,
I increased R63 (pin 8 of the 25DN6) to 6.8K and it finally made a difference in width, however my HV went from 13.5Kv to 10Kv. That won't work. Did I get the right resistor?

http://i1060.photobucket.com/albums/t458/crigotti/Tech-Master%20TV%20Kit%205516/100_5677a_zpsvkhhd8vh.jpg (http://s1060.photobucket.com/user/crigotti/media/Tech-Master%20TV%20Kit%205516/100_5677a_zpsvkhhd8vh.jpg.html)
Increasing the screen resistor to 6.8K is way too much of an increase. Maybe a 1.5K or so. Try putting the 25CD6 back in. :scratch2:

Here's a quickie tutorial on voltage multipliers.
http://www.electronics-tutorials.ws/blog/voltage-multiplier-circuit.html

I don't think a doubler would be the way to go in the case under discussion, though.:no:

If going back to the 25CD6 doesn't cut the width enough try dropping B+ to damper and output only,try +125 volts and see if width coil reduces screen size enough remember there is going to be some over scan on CRT television unlike Crt 'puter screen where the isn't over scan. All the best,Tom.J

Crist, the crt in my set is a 17HP4 "C" as labeled by the rebuilder, most likely to show that the jug has a straight gun. Old_coot88 is correct that a width sleeve is needed to control the width on your set. The brass or copper is 1/2 to 3/4 the dia. of the neck and is sealed in thin sheet hi-temp plastic. Try to find a sleeve from a junker or make one. All the best,Tom.J

Tom,
Thanks for the info on the CRT.

I'll look for one of those sleeves.

I've never done it, but wonder why not put a low resistance in series with the horiz yoke winding? Maybe try 20 ohms and go from there..? Seems like it wouldn't screw with the resonant point of the HV systen enuff to matter.

:nerd:

I'll think about that. It'll be easy to do.

Regarding your concern of not being able to duplicate your earlier focus problem - It's possible the internal electrode connected to pin 6 is retaining a charge(because of capacitance) even after you remove the wire. :scratch2:

Maybe. I left it disconnected for several minutes with no change. I wonder if there would be a way to discharge it?

See the 3 HV rects in this circuit? They constitute an HV trippler. Saw off the third HV rect tube (and everything right of the second HV rect), and you have an HV doubler.
http://www.earlytelevision.org/pdf/RCA-8PCS41-9PC41-648-741-Sams-90-9.pdf

There were also SS HV doublers, tripplers, and quadrupplers in 70's SS color sets that could be used if period correct look is not a concern.

Any doubler will increase load on the flyback and reduce width....Monitor H Out tube cathode current and flyback temperature over an extended test run and if it gets excessive power down and try something else.

Tube doublers will draw more power due to the tube heaters.

OK, thanks for the info. I'll look it over and we'll see.

Increasing the screen resistor to 6.8K is way too much of an increase. Maybe a 1.5K or so. Try putting the 25CD6 back in. :scratch2:

I tried from 1K on up. 6.8K finally made a noticable difference. 10K was too much.

I did put back in the 25CD6 and the width was reduced. But the HV went down to 11Kv IIRC.

If going back to the 25CD6 doesn't cut the width enough try dropping B+ to damper and output only,try +125 volts and see if width coil reduces screen size enough remember there is going to be some over scan on CRT television unlike Crt 'puter screen where the isn't over scan. All the best,Tom.J

Tom,
I'm going to try the sleeve first. It seems the least intrusive way. Then maybe try other methods.

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 20Kv 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.

Any chance you can adjust the aspect ratio or the zoom level of your signal source?

Any chance you can adjust the aspect ratio or the zoom level of your signal source?

Kevin,
Good thought, but no I can't.

How much overscan have you actually got? On that size tube, a quarter-to half inch on either side wouldn't be unreasonable.

A quickie way to check is- turn the set off for several seconds and back on, and watch the fill-out.

How much overscan have you actually got? On that size tube, a quarter-to half inch on either side wouldn't be unreasonable.

A quickie way to check is- turn the set off for several seconds and back on, and watch the fill-out.

I tried but couldn't get a good look at how much. I'm thinking at least an inch or several inches on each side.

If you make a width sleeve DO NOT over lap or let the ends of your metal to touch! If there is over lap you will have a shorted turn and you will kill the horizonal stage. Learned that one, decades ago the hard way. All the best,Tom.J

If you make a width sleeve DO NOT over lap or let the ends of your metal to touch! If there is over lap you will have a shorted turn and you will kill the horizonal stage. Learned that one, decades ago the hard way. All the best,Tom.J

Tom,
I plan on using some .003 brass shim stock that I have. I plan on making it about 3/4" wide and about 4 inches long. The 4 inches come from the length that I need to push it in from the aft side of the yoke and long enough to clear the centering rings. I'll cover it with some packing tape for now for this experiment, till I can get high temp tape. Does this sound right to you?

Not exactly sure about your warning. This will be more like a strip rather than a sleeve.

This morning I scoped out the Horizontal Oscillator to adjust the frequency and to have the waveform peaks match.

Here is the result.

http://i1060.photobucket.com/albums/t458/crigotti/Tech-Master%20TV%20Kit%205516/100_5681a_zpsceaeclbn.jpg (http://s1060.photobucket.com/user/crigotti/media/Tech-Master%20TV%20Kit%205516/100_5681a_zpsceaeclbn.jpg.html)

It seems that the vertical hold is pretty touchy. But for right now, I'll address the width issue with a strip and then move on to a full IF/Video alignment. Oh boy.

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.

http://i1060.photobucket.com/albums/t458/crigotti/Tech-Master%20TV%20Kit%205516/100_5682a_zpsemhyanzi.jpg (http://s1060.photobucket.com/user/crigotti/media/Tech-Master%20TV%20Kit%205516/100_5682a_zpsemhyanzi.jpg.html)

Crist, ya did good. The warning was about causing a AC short through transformer action,mainly current overload. Read up on transformers to learn more on this. By the way did the HV stay up when you did the adjustment. All the best,Tom.J

The HV went from 14.5Kv to 10.2Kv! I pulled the strip out about an inch and its back up to 11.8Kv. Both voltages produce a very good picture.

Why does that happen?

The HV drop is caused by the de-tuning of the retrace freq. which is around 75 khz. Suggest reading books on horizonal sweep systems. Books by the late Jesse Dines are very good indeed. All the best,Tom.J

The HV went from 14.5Kv to 10.2Kv! I pulled the strip out about an inch and its back up to 11.8Kv. Both voltages produce a very good picture.

Dadburn. :worried: L'arn sumpthin new every day. Next question is would a resistor in series with the horiz yoke winding affect the HV. :saywhat:

Dadburn. :worried: L'arn sumpthin new every day. Next question is would a resistor in series with the horiz yoke winding affect the HV. :saywhat:

We'll see later.

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:

http://i1060.photobucket.com/albums/t458/crigotti/Tech-Master%20TV%20Kit%205516/100_5683a_zpsseq3gbpv.jpg (http://s1060.photobucket.com/user/crigotti/media/Tech-Master%20TV%20Kit%205516/100_5683a_zpsseq3gbpv.jpg.html)

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:
http://i1060.photobucket.com/albums/t458/crigotti/Tech-Master%20TV%20Kit%205516/100_5689a_zpssgwhd8mp.jpg (http://s1060.photobucket.com/user/crigotti/media/Tech-Master%20TV%20Kit%205516/100_5689a_zpssgwhd8mp.jpg.html)

Here is the pip at 26.4MC:
http://i1060.photobucket.com/albums/t458/crigotti/Tech-Master%20TV%20Kit%205516/100_5684a_zpsacxwhzpt.jpg (http://s1060.photobucket.com/user/crigotti/media/Tech-Master%20TV%20Kit%205516/100_5684a_zpsacxwhzpt.jpg.html)

Here is the pip at 23.1MC:
http://i1060.photobucket.com/albums/t458/crigotti/Tech-Master%20TV%20Kit%205516/100_5685a_zpsdbsrddza.jpg (http://s1060.photobucket.com/user/crigotti/media/Tech-Master%20TV%20Kit%205516/100_5685a_zpsdbsrddza.jpg.html)

Here is the pip at 21.9MC:
http://i1060.photobucket.com/albums/t458/crigotti/Tech-Master%20TV%20Kit%205516/100_5688a_zpshhipnryy.jpg (http://s1060.photobucket.com/user/crigotti/media/Tech-Master%20TV%20Kit%205516/100_5688a_zpshhipnryy.jpg.html)

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.

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".

http://i1060.photobucket.com/albums/t458/crigotti/Tech-Master%20TV%20Kit%205516/100_5690a_zpstixielwl.jpg (http://s1060.photobucket.com/user/crigotti/media/Tech-Master%20TV%20Kit%205516/100_5690a_zpstixielwl.jpg.html)

http://i1060.photobucket.com/albums/t458/crigotti/Tech-Master%20TV%20Kit%205516/100_5692a_zpsmti1tfly.jpg (http://s1060.photobucket.com/user/crigotti/media/Tech-Master%20TV%20Kit%205516/100_5692a_zpsmti1tfly.jpg.html)

http://i1060.photobucket.com/albums/t458/crigotti/Tech-Master%20TV%20Kit%205516/100_5693a_zps0capplgu.jpg (http://s1060.photobucket.com/user/crigotti/media/Tech-Master%20TV%20Kit%205516/100_5693a_zps0capplgu.jpg.html)

http://i1060.photobucket.com/albums/t458/crigotti/Tech-Master%20TV%20Kit%205516/100_5694a_zpsolknkaun.jpg (http://s1060.photobucket.com/user/crigotti/media/Tech-Master%20TV%20Kit%205516/100_5694a_zpsolknkaun.jpg.html)

http://i1060.photobucket.com/albums/t458/crigotti/Tech-Master%20TV%20Kit%205516/100_5695a_zpsuwzajx4w.jpg (http://s1060.photobucket.com/user/crigotti/media/Tech-Master%20TV%20Kit%205516/100_5695a_zpsuwzajx4w.jpg.html)

http://i1060.photobucket.com/albums/t458/crigotti/Tech-Master%20TV%20Kit%205516/100_5696a_zpsyyyfbmkp.jpg (http://s1060.photobucket.com/user/crigotti/media/Tech-Master%20TV%20Kit%205516/100_5696a_zpsyyyfbmkp.jpg.html)

Verrry nice outcome. :) Virtually a 'brand new' 1955 TV manufactured on the spot. Man, you handled that alignment like a boss.

Re. the width sleeve, all the ones I've ever seen were not grounded. Just guessing it was assumed there'd be some potential for an arc to ground.

If you remove the ground connection on brass width adjuster you may get back some of the HV reason you will be getting rid of some stray cap. coupling to ground which will detune the retrace freq. plus get rid of a source of arching. All the best,Tom.J

This is the only kind of width sleeve I've ever encountered(admittedly not many). This particular one was never insulated, which is kind of scary knowing it was slid in between the CRT neck and the yoke, but I believe it was common for the yoke to have an internal paper sleeve when these were used in a production set. :scratch2:

http://i452.photobucket.com/albums/qq245/Kuehn/VK%20Pictures/Width%20Sleeve%20004_zps1chkneeg.jpg

If you remove the ground connection on brass width adjuster you may get back some of the HV reason you will be getting rid of some stray cap. coupling to ground which will detune the retrace freq. plus get rid of a source of arching. All the best,Tom.J

Ok, I took the ground off. I had it there thinking it would arc over when I touched it.

This is the only kind of width sleeve I've ever encountered(admittedly not many). This particular one was never insulated, which is kind of scary knowing it was slid in between the CRT neck and the yoke, but I believe it was common for the yoke to have an internal paper sleeve when these were used in a production set. :scratch2:

http://i452.photobucket.com/albums/qq245/Kuehn/VK%20Pictures/Width%20Sleeve%20004_zps1chkneeg.jpg

Thanks Kevin. The strip that I'm using seems to work well.

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.

http://i1060.photobucket.com/albums/t458/crigotti/Tech-Master%20TV%20Kit%205516/100_5704a_zpsuigrl15h.jpg (http://s1060.photobucket.com/user/crigotti/media/Tech-Master%20TV%20Kit%205516/100_5704a_zpsuigrl15h.jpg.html)

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.

http://i1060.photobucket.com/albums/t458/crigotti/Tech-Master%20TV%20Kit%205516/100_5707a_zpskvd9ni6c.jpg (http://s1060.photobucket.com/user/crigotti/media/Tech-Master%20TV%20Kit%205516/100_5707a_zpskvd9ni6c.jpg.html)

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

http://i1060.photobucket.com/albums/t458/crigotti/Tech-Master%20TV%20Kit%205516/100_5708a_zpsmdol6hlu.jpg (http://s1060.photobucket.com/user/crigotti/media/Tech-Master%20TV%20Kit%205516/100_5708a_zpsmdol6hlu.jpg.html)

http://i1060.photobucket.com/albums/t458/crigotti/Tech-Master%20TV%20Kit%205516/a_zps750dgbsk.jpg (http://s1060.photobucket.com/user/crigotti/media/Tech-Master%20TV%20Kit%205516/a_zps750dgbsk.jpg.html)

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.

It does seem more common to not have enough width. I suppose you could experiment with a 50 degree yoke, but hard telling what that will do to linearity and high voltage. Overall you have a very successful project. :thmbsp:

I went through most of the pages and noticed the set uses a width coil, but don't remember reading that you tried to adjust it. It does affect the tune of the flyback. It's amazing, that there is excessive width using a 21" CRT on a low B+ chassis.

It does seem more common to not have enough width. I suppose you could experiment with a 50 degree yoke, but hard telling what that will do to linearity and high voltage. Overall you have a very successful project. :thmbsp:

Kevin,
Yeah, I thought of substituting the yoke.

Another though I had was seeing if I can find a 90 degree CRT instead of the 70 degree that I have now. These were just some thoughts I had but I never followed up on.

Thanks. I am pleased on how it turned out.

I went through most of the pages and noticed the set uses a width coil, but don't remember reading that you tried to adjust it. It does affect the tune of the flyback. It's amazing, that there is excessive width using a 21" CRT on a low B+ chassis.

Like most width coils, there isn't much change when adjusting them. I adjusted the coil to the most minimum width.

Might help to re-tune that coil for max HV with the sleeve now installed.

Remember it was not uncommon to have 2-4" per side of overscan in sets of that size back then....Line voltages varied a LOT (and could be freaky low on farms), and the programming content lacked indicators of over-scan (so consumers would always complain of underscan, but never notice overscan).

What I'd prefer to see is a test pattern on the screen that was intended for a 4:3 aspect ratio display.

What I'd prefer to see is a test pattern on the screen that was intended for a 4:3 aspect ratio display.

Preparing a new HD 4:3 Indian Head Test Pattern DVD. Will post a picture when I have it ready and playing.

Kevin,
Here is a 4:3 Test Pattern without the sleeve:

http://i1060.photobucket.com/albums/t458/crigotti/Tech-Master%20TV%20Kit%205516/100_5710a_zpsfeau2en7.jpg (http://s1060.photobucket.com/user/crigotti/media/Tech-Master%20TV%20Kit%205516/100_5710a_zpsfeau2en7.jpg.html)

Here is a 4:3 Test Pattern with the sleeve:

http://i1060.photobucket.com/albums/t458/crigotti/Tech-Master%20TV%20Kit%205516/100_5713a_zpsewwvrive.jpg (http://s1060.photobucket.com/user/crigotti/media/Tech-Master%20TV%20Kit%205516/100_5713a_zpsewwvrive.jpg.html)

Boy that first picture is so close to being good. What happens if you slide the yoke back just a hair?

Conventional wisdom for underscan is to add capacity to the yoke (or across the damper with a "cookie" cap) - perhaps reduce the cap value in the yoke? Most are 24-68pf in parallel with one horiz winding.

Cookie Cap:http://www.videokarma.org/showpost.php?p=3140875&postcount=10 (and no, I don't have one anymore)

Likewise, how about the feedback cap from on side of the width coil to the HOT - reduce it by a factor of 1/10th?

Just my thoughts....:nerd:

Conventional wisdom for underscan is to add capacity to the yoke (or across the damper with a "cookie" cap) - perhaps reduce the cap value in the yoke? Most are 24-68pf in parallel with one horiz winding.

Cookie Cap:http://www.videokarma.org/showpost.php?p=3140875&postcount=10 (and no, I don't have one anymore)

Likewise, how about the feedback cap from on side of the width coil to the HOT - reduce it by a factor of 1/10th?

Just my thoughts....:nerd:

I would leave it, the way it looks with the circle almost perfectly round.
Using a different yoke would affect the flyback action because of an impedance mismatch. :thumbsdn:

I think the first pattern is fine. You've got left side underscan in the second....Granted you might be able to fix it in the second by adjusting the centering.

Some overscan is the natural state of the design, I'd keep the overscan to look authentic....Plus unless you grossly underscan on all sides you are going to cutoff parts of network logos, news tickers, and sports score boxes....Programming directors now squeeze those things into the very corners assuming every viewer has a flatpanel set...

What I see is a small amount of un-linearity(stretch) on the left side of the picture without the sleeve, also a little stretch in the vertical at the top. I think if those could be eliminated the width and overall symmetry would be almost perfect. But it's so close the way it is.

Or maybe the bottom vertical is compressed? Regardless when you adjust the vertical linearity those two(top to bottom ratio) tend to equalize.

Wow, guys. I appreciate the comments.

I'll work on getting the picture where it should be without the sleeve.

I was playing with it last night some and it seemed that with the sleeve, the test pattern was straighter. In other words, the vertical lines were straighter than without the sleeve.

Just a note here. The sleeve seems to "compress" the whole picture, thus it fits into the viewing area of the CRT. It does not cutoff any portion of the picture.

I'll spend some time tweaking the picture to see what I can get without the sleeve and post the results here.

I did consider that maybe changing some cap might be an improvement.

Boy that first picture is so close to being good. What happens if you slide the yoke back just a hair?

No help, but a good thought.

Just a note here. The sleeve seems to "compress" the whole picture, thus it fits into the viewing area of the CRT. It does not cutoff any portion of the picture.

I'll spend some time tweaking the picture to see what I can get without the sleeve and post the results here.

I did consider that maybe changing some cap might be an improvement.

But as someone pointed out you're actually under-scanning the screen in your second picture(the left edge of the picture is in view). Also the difference in width between the two picture seems to be about half of one square on each side, so it's not really a dramatic change in width. The idea behind over-scanning the screen was to make sure the edges of a 4:3 ratio picture never showed when the line voltage fluctuates.

Guys, I've just spent hours trying to adjust this TV with and without the sleeve. I just deleted the pictures by mistake that I wanted to post.

As of right now, I'm burned out on this thing.

Time to take some time off!!!!!

CRT televisions are all about the art of compramise. They are not like todays' digital sets. Do not beat your self up trying to get perfection. All any of us can do is get it as close as we can and leave it alone. All the best,Tom.J

CRT televisions are all about the art of compramise. They are not like todays' digital sets. Do not beat your self up trying to get perfection. All any of us can do is get it as close as we can and leave it alone. All the best,Tom.J

Truer words...


It is really easy to go off and fight windmills that are baked into the design when you want to optimize a tube set...Knowing when to declare good enough, or balance between two incurable issues that can not be fixed together is important to staying sane.

I gotta concur with the last two postings. Any B&W tube TV, especially a low B+, minimalist design, is gonna have very fluid parameters in its performance, like tubes and components aging, low and/or fluctuating line voltage etc. The design has built-in 'headroom' to allow for this. And very few sets if any will display perfect linearity, either horiz or vertically. Even If you set everything as near 'perfect' as possible, it's gonna change on its own.

The results you've already attained with this project have knocked everybody's socks off, and achieved performance beyond any typical BW set of the period.

(Edit) There's an old adage relating to model aircraft design, but it applies here as well: "Perfectionism is the manic form of fuddyduddy-ism.":D

I would be 110% happy with what you have there now.

The pic in the other post without the sleeve to me and others look great and these old sets were far from perfect aside from today's sets, no comparison, but these old sets were not engineered to be perfect that's why there is 20% built in but today's sets may have 1 or 2% built in, that's it. I say leave it alone looks great without the sleeve, you hand built it , lot of work now just enjoy it. It took me a long time to realize that these old sets are not perfect with all my annoying questions to a lot of members but not I'm cured, lol.

Very true about trying to get things to look exactly like the schematic wave forms or voltages spot on.

Now if you really want to beat yourself up, do a purity and then convergence on an old round CRT color set, say from 1959 or so! I remember reading that you should concentrate on the center of the picture and the edges will be as good as they will be (read, not always perfect).

Good time for a coffee (or beer, depending on the time of day :music:)

I don't know about 21AXP22 sets, but the 15GP22 CT-100 can indeed achieve truly perfect convergence, viewed at 3 feet. Mine showed that last night.

What's not easy, and perhaps impossible without at least one mod, is
keeping it near perfect at all average brightness levels (up to blooming of course.)

I got a great improvement by regulating the focus voltage (at the bottom end
of the focus pot only) with a big chain of Zeners and checking all the parts
including the pot in the 20kV regulator circuit and replacing ones
even a little off. It helps to be sure your
HV probe is calibrated right and setting the HV right at the top limit.

I don't know about 21AXP22 sets, but the 15GP22 CT-100 can indeed achieve truly perfect convergence, viewed at 3 feet. Mine showed that last night. ...
HV probe is calibrated right and setting the HV right at the top limit.

Oh, I hate you and you had to rub that in!

Just kidding of course and glad that you have a CT-100 with a good 15GP22. I doubt that I will ever have one. But I do have a CTC-9 that is in queue and hope to get to it soon.

So, please do enjoy that CT-100. There are not many out there, let alone ones with a good CRT. I am sure you understand and appreciate that!

Thanks for all the good comments guys. It is appreciated.


Here is a video of what I'm dealing with. This is without the sleeve and using my OTA and converter.

https://youtu.be/uQW7s4tmZM0

Later on from that recording, I tried a 17LP4 CRT with pretty much the same over scan.

Well, I gotta retract my earlier pontification.:sadwave::( It looks like you do have some excessive overscan. Startin' to sound like a broken record, but have you considered trying a bit of resistance in series with the H yoke winding? Dunno if it'll affect the HV as I've never tried it. But it might be worth a shot. Maybe 20 ohms to start out.

That is odd...Was the earlier test pattern somehow letter-boxed and pillar-boxed, or is the DTV box set to zoom?...There is a clear difference in apparent over-scan between the two signals you've shown.

Well, I gotta retract my earlier pontification.:sadwave::( It looks like you do have some excessive overscan. Startin' to sound like a broken record, but have you considered trying a bit of resistance in series with the H yoke winding? Dunno if it'll affect the HV as I've never tried it. But it might be worth a shot. Maybe 20 ohms to start out.

I'll try that. It'll be a week or so till I can get back to the TV.

That is odd...Was the earlier test pattern somehow letter-boxed and pillar-boxed, or is the DTV box set to zoom?...There is a clear difference in apparent over-scan between the two signals you've shown.

Tom,
Not sure what you mean by letter-boxed or pillar-boxed. The DTV does not have a zoom feature.

Maybe I can borrow another converter box.

Tom,
Not sure what you mean by letter-boxed or pillar-boxed. The DTV does not have a zoom feature.

Maybe I can borrow another converter box.

https://en.wikipedia.org/wiki/Letterboxing_(filming)

https://en.wikipedia.org/wiki/Letterboxing_(filming)

The test pattern is one I made from a hi res 4:3 pattern. I converted a jpg to a 30 minute movie and saved it to a DVD.

The test pattern is one I made from a hi res 4:3 pattern. I converted a jpg to a 30 minute movie and saved it to a DVD.

There is enough variance in digital processing implementations that I can't comment based on that info as to whether your system generated a good pattern or not.

The best advice I can think of to confirm things is to connect another 4:3 display (such as a modern CRT set) that is known NOT to have excessive over scan to both signal sources in the same manner as your Tech-Master and see if there is a black bar wrapped around that test pattern, or if the DTV picture is excessively zoomed (I suspect one of those is occurring).

With changing aspect ratios and poorly standardized means of dealing with it flooding consumer and broadcast markets alike, there is good argument to keep a VCR or pre-2000 test pattern generator on hand...So you know you have a signal source that will always give you an accurate measure of over-scan...

Too many modern signal sources are capable of distorting things and giving a misleading signal.

The test pattern is one I made from a hi res 4:3 pattern. I converted a jpg to a 30 minute movie and saved it to a DVD.

I'm guessing your digital TV signal is broadcast in wide screen format, don't you think? It does fill out the width on a modern wide screen set, no? But when you made your 4:3 aspect ratio test pattern DVD, the machine plays it back as it was originally formatted.

If you put your digital TV box in letterbox mode it should shrink the picture width down and put a black bar at the top and bottom, although I don't have such a device so I have no idea if they even have that feature these days.

From this screen shot it looks like you have some pretty severe Horizontal linearity issues on the left side of the screen.

The "through the scope" shot here should be perfectly round, it's egg shaped with the point to the left of the screen, I also noticed all the credits were cut off on that side too.

As has been mentioned, it may just be a shortcoming of the sets design.

Is it adjustable so the stretch is equal on both sides? If you can do that you may then be able to reduce the width to bring it into a circle.

Oddly enough it doesn't look as bad with the test pattern.

http://videokarma.org/attachment.php?attachmentid=193466&stc=1&d=1484537957

Oddly enough it doesn't look as bad with the test pattern.
Yeah, the test pattern display was what threw me off too.

Here are a couple of pics with another TV next to it. I just used clip leads to connect the antenna inputs together. The other TV is a non-HD 9" RCA.

http://i1060.photobucket.com/albums/t458/crigotti/Tech-Master%20TV%20Kit%205516/100_5741a_zps7y8c73eq.jpg (http://s1060.photobucket.com/user/crigotti/media/Tech-Master%20TV%20Kit%205516/100_5741a_zps7y8c73eq.jpg.html)

http://i1060.photobucket.com/albums/t458/crigotti/Tech-Master%20TV%20Kit%205516/100_5739a_zpsarl1gtdf.jpg (http://s1060.photobucket.com/user/crigotti/media/Tech-Master%20TV%20Kit%205516/100_5739a_zpsarl1gtdf.jpg.html)

Well guys, I found the problem with the over scan using the converter for OTA programs. It was the zoom feature. I looked for the zoom feature in the instruction manual, but no mention of the word zoom. But I did find out how the "Picture Format" button works. One thing though, it works real well on other channels, but is very sporadic on MeTV!

With the format in "normal" I have black bars along the bottom and top of the picture. I'll but my video generator on it and adjust the linearity and I'll be done.

Thanks for hanging with me and all your suggestions.

http://i1060.photobucket.com/albums/t458/crigotti/Tech-Master%20TV%20Kit%205516/100_5745a_zpsxbhpnin8.jpg (http://s1060.photobucket.com/user/crigotti/media/Tech-Master%20TV%20Kit%205516/100_5745a_zpsxbhpnin8.jpg.html)

DTV stations send signals that dictate format to the box. Some stations handle it better than others and some boxes give the user better control of format/zoom than others.

Glad you got to the bottom of it.

When watching TV, I have to have the "Contrast" 99% all the way up. I'm considering adding or taking away some resistance in the contrast circuit. Here is the schematic and the contrast when watching TV the resistance is almost all the way down and the wiper is moved closer to the tube.

I'm thinking of reducing the R53A from 1K to something like 680 ohms. Would this put the contrast control more off all the way? If not, what could be done.

BTW, the schematic shows the pot value as 2K, but the kit came with a 5K pot.

http://i1060.photobucket.com/albums/t458/crigotti/Tech-Master%20TV%20Kit%205516/100_5746a_zpsakqam6ck.jpg (http://s1060.photobucket.com/user/crigotti/media/Tech-Master%20TV%20Kit%205516/100_5746a_zpsakqam6ck.jpg.html)

I would try a couple of things first. Run a jumper from the 12BY7 cathode (pin 1) to pins 3 & 9. See if contrast improves.

If it does*, check resistance from the wiper to the top lug of the contrast control when it's rotated to max contrast. It should be zero or near zero ohms. If it is, try shorting out the 39 ohm resistor R109. See if that gives more grunt.

*Be sure jumper is removed.

I would try a couple of things first. Run a jumper from the 12BY7 cathode (pin 1) to pins 3 & 9. See if contrast improves.

If it does*, check resistance from the wiper to the top lug of the contrast control when it's rotated to max contrast. It should be zero or near zero ohms. If it is, try shorting out the 39 ohm resistor R109. See if that gives more grunt.

*Be sure jumper is removed.

When I jumper pin 1 to 3 & 9 contrast improves. Not a whole lot but an improvement.

When I short out R109 (with the jumper removed from pin 1 to 3 & 9), the contrast improves just barely.

Because the contrast pot is 5K, it doesn't take a lot of rotation to really change the contrast. BTW, with the contrast all the way up, I read 94 ohms from wiper to the pot end.

When I jumper pin 1 to 3 & 9 contrast improves. Not a whole lot but an improvement.

When I short out R109 (with the jumper removed from pin 1 to 3 & 9), the contrast improves just barely.

Because the contrast pot is 5K, it doesn't take a lot of rotation to really change the contrast. BTW, with the contrast all the way up, I read 94 ohms from wiper to the pot end.

I jumpered a 3.3K resistor across the pot. This should give me 2K resistance and the rotation of the contrast pot is much better. I know it isn't linear, but very usable.

I jumpered a 3.3K resistor across the pot. This should give me 2K resistance and the rotation of the contrast pot is much better. I know it isn't linear, but very usable.
I think, I would've done the same.

I think my big problem is that the pot doesn't go to "zero" ohms. I don't think there is anyway around that except changing the control. I'll have to pull it from the chassis to see if there is a part number/mfgr that might help.

When you put that jumper from pin 1 (cathode) to pins 3 & 9, it shunts the contrast control and R109 completely out-of-circuit, giving the tube all the gain it's gonna deliver. The tube's at max gain and doesn't "see" the contrast control and R109 at all.

That may be all it's capable of with the low B+. What is the actual plate voltage BTW?

You might try raising the value of R87 a little, to allow the plate a little more 'swing'. For the heck of it, also try lowering the value a bit.

The set uses a very primitive, nonadjustable AGC. You could bump the IF gain up just a tad, by doing this:

Jump a 3.3 megohm resistor from B+ to the AGC bus (test pt. B). If no change is noted, work downward in value (like 2 meg, 1 meg, 470K etc until a gain increase is noted. (the 12BY7 grid also becomes a tad less negative, which will compensate for the contrast control's not going full on).

Too much gain will probably cause sync clipping. But there might be some usable gain-increase before clipping or sound buzz sets in.

I'll get to those suggestions later. I have some scanning to. Stay tuned.

Another suggestion if you happen to have a bias box (a low voltage variable DC supply): Put the positive lead to ground, the negative lead to: (schematic's too blurry to read) the Test Point on the AGC bus, below the 2nd IF tube. Vary the voltage to see if you can get optimal contrast with no clipping or overloading.

Some early low end sets had no AGC circuitry at all, and actually used this method in lieu of a contrast control, sometimes calling it the 'Picture' control.

Or you could rig a 'bias box' very easily with a 9V battery, a resistor and potentiometer. (Of course it will disable the set's regular AGC action.)

OK, here's what I did.

1) Jumper R109 so it is out of the circuit. I don't think it is needed because the contrast pot doesn't go all the way down to zero. It only goes to 93 ohms.
2) Placed a 56K resistor between pins 2 and 8 (B+) of V6 12BY7A.
3) Placed a 3.3K resistor across the 5K contrast pot to effectively make it a 2K pot per the schematic. This gives me a fair amount of rotation or range with the contrast knob.

These mods are fairly easy and give decent results. Would doing any of this cause harm to the TV?

Wow, I didn't know you'd have to go all the way down to 56K. That'll be making the 12BY7 grid too positive, causing it to conduct, which you don't want. So scuttle that idea.

Maybe try the bias box further down the AGC line, as suggested earlier. This doesn't involve the 12BY7.

What is the value of the resistor between Test Pt. B and the next test point (where the bias box would connect)?

Wow, I didn't know you'd have to go all the way down to 56K. That'll be making the 12BY7 grid too positive, causing it to conduct, which you don't want. So scuttle that idea.

Maybe try the bias box further down the AGC line, as suggested earlier. This doesn't involve the 12BY7.

What is the value of the resistor between Test Pt. B and the next test point (where the bias box would connect)?

That would be R10 470K.

I removed the 56K from the 12BY7A tube.

I don't have a bias box.

Bad info. Disregard.

There's something else you could try in lieu of a bias box.

From that Test Point junction with R10, run a 10K resistor to ground. Add another resistor from the Test point to B+, using clip leads. Start with 2.2 meg for this resistor, working downward in value until the IF gain starts coming up. Find a value that gives good contrast without overloading. The regular AGC action will be largely disabled however.

With a constant level signal source, AGC might be less important than with over-the-air reception.

I need a little explanation. In your last statement about a constant signal source, are your referring to my converter box? And the same thing as my RF converter from my DVD player?

Would doing this mod disable the contrast control?

How would I know when the IF starts to overload?

Sorry for all the questions but as you know I'm weak on the theory and how all the components work together.

When you say take the 10K resistor to ground, you mean my B- rail?

Thanks.

Sorry for the bad info. Senior moment:twak: Please disregard.

Try shorting the Test point/R10 junction directly to ground, and see if gain improves. If it overloads, use a resistor; start with a 1K, working upward in values like 10K, 47K etc until the overload condition diminishes.

Sorry for the bad info. Senior moment:twak: Please disregard.

Try shorting the Test point/R10 junction directly to ground, and see if gain improves. If it overloads, use a resistor; start with a 1K, working upward in values like 10K, 47K etc until the overload condition diminishes.

I'll give that a try.

I have another thing that is a bit annoying. There is a very noticable "clicking" sound that varies with either the Vert. or Horiz. hold controls. It seems it is coming from the HV section, but tell for sure. I'm not sure it was there when I first got the TV going. It has been present for the last several weeks at least. Do I have something mis-adjusted? Any good way to find what the problem is or a way to eliminate it?

Thanks.

I think the sound is coming from the Vertical output transformer area.

Crist am sorry for replying to your request this way, couldn't get the system to post the reply, so here goes. 1) do not have a camera or smart phone 2)in my set the CRT is mounted to the cabinet so no need for chassis brackets. 3)chassis is mounted in vertical plane(knobs up/down).4) yoke back cover has means for centering and clamp. 5)Son wants the set so got to mod for 128vac, auto-transformer from a junk Pencrest color set, going to use the 98vac tap to get 113vdc for damper and output which gives 7/8 inch overscan,all the other circuits use the 130vdc supply. All the best,Tom.J

Thanks Tom.

Keep in mind that maximum contrast on these old sets is a bit of an illusion that relies heavily on the ambient lighting in the viewing room. Of course the screen can never get darker than it is when it's off for a given ambient light level. So considering the relatively bright room lighting in your below picture, I'd say your set is putting out about the best contrast it's capable of. The modern set next to it likely has a darker screen filter, yet to me it looks more washed out than your Tech Master. Also remember that the contrast of the old program material was not all that consistent. Your set has a darn good picture with your DVD test pattern on it, so just be careful that you don't go chasing rainbows in an attempt to correct for a lousy picture that your OTA converter box may be responsible for.

http://i1060.photobucket.com/albums/t458/crigotti/Tech-Master%20TV%20Kit%205516/100_5741a_zps7y8c73eq.jpg

Kevin,
Thanks for those thoughts. You are right about chasing rainbows!

What I eneded up doing is to eliminate R109, thus reducing the lowest value the pot can go to 93 ohms instead of 93 + 39 = 142 ohms. This gives me acceptable contrast when watching some of the older programs on MeTV. The contrast control is almost but not quite at its full stop. I live with it. What really helped was putting the 3.3K across the 5K pot to get the listed 2K. This gives me a little more dial to adjust the contrast.

Working on how to do the cabinet right now. I'm going back and forth on what I want to do. Once I settle on that then I can "lock" down the CRT mounting.

BTW, I've gone to a 17" CRT. I'm using a NOS rebuilt RCA 17LP4B. Thanks to El Predicta here on the forum. The reason is because I'm going to use the "sleeve" to control the width and when I do that, the HV goes down. So I thought the 17" CRT would handle the reduced HV better and thus give me better service for the life of the TV.

Just wanted to let you guys know that I borrowed a 17" CRT but instead of a 70 degree the borrowed one is 90 degrees.

When I tried it, sure enough the picture was well within the CRT screen. After some adjusting and such I got the picture close to the outer edges of the screen. Of course this is without the sleeve. The 90 degree CRT didn't quite work well enough, so back in went the 70 degree CRT with the sleeve.

Looks like I have a 80 degree yoke!

It's all adjusted and playing well now. Life is good.

Interesting. It's hard to say exactly what the specs are for the yoke that was included with your kit. And I wouldn't put it past a kit manufacture of that period to use some oddball combination of surplus components.