Tech-Master NIB TV Kit #5516

[old_coot88]

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

I don't think a doubler would be the way to go in the case under discussion, though.

[tom.j.fla]

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 Rigott]

Originally Posted by tom.j.fla

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.

[Crist Rigott]

Originally Posted by old_coot88

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.

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

[Crist Rigott]

Originally Posted by Kevin Kuehn

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.

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

[Crist Rigott]

Originally Posted by Electronic M

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/R...-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.

[Crist Rigott]

Originally Posted by dieseljeep

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.

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.

[Crist Rigott]

Originally Posted by tom.j.fla

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.

[Crist Rigott]

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.

[Kevin Kuehn]

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

[Crist Rigott]

Originally Posted by Kevin Kuehn

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

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

[old_coot88]

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.

[Crist Rigott]

Originally Posted by old_coot88

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.

[tom.j.fla]

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

[Crist Rigott]

Originally Posted by tom.j.fla

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.