Tech-Master NIB TV Kit #5516

[dieseljeep]

Originally Posted by Crist Rigott

OK here is what I did. I connected a 20 ohm 25W resistor in series with the heater string. This allowed me to increase the B+ from 124V to 135V. Going from 124V to 135V the picture just got bigger and not any clearer. My variac could only bring the mains up to 132vac.

You can alter the heater string by replacing the damper with either a 19AU4 or a 17DE4, same heater current, 600ma.
I hate to say this, I feel, there's a problem with that CRT. If there was a problem with insuffient HV, there would be blooming and a change of focus with a change brightness and contrast settings.
I would refrain from realigning the IF, until the other problem is resolved. IF alignment problems are normally exposed when turning the fine tuning and double images are shown in the picture and other IF ringing.

[old_coot88]

I gotta concur, all signs thus far do point to the CRT re. the focus problem. Also, messing with video IF alignment would be like adjusting the brakes hoping to fix the carburetor. And while not a big deal, there's still the hourglassing problem indicating power supply ripple.

[Electronic M]

The hourglasing may also be from a large line transformer too near to the CRT...If you got one near the set move it away a few feet if you can.

[Crist Rigott]

Originally Posted by dieseljeep

You can alter the heater string by replacing the damper with either a 19AU4 or a 17DE4, same heater current, 600ma.
I hate to say this, I feel, there's a problem with that CRT. If there was a problem with insuffient HV, there would be blooming and a change of focus with a change brightness and contrast settings.
I would refrain from realigning the IF, until the other problem is resolved. IF alignment problems are normally exposed when turning the fine tuning and double images are shown in the picture and other IF ringing.

Yeah, I'll hold off on the alignment. I was just looking for a change of pace.

I varied the contrast and brightness and there is a very slight change of focus, but still way bad.

[Crist Rigott]

Originally Posted by old_coot88

I gotta concur, all signs thus far do point to the CRT re. the focus problem. Also, messing with video IF alignment would be like adjusting the brakes hoping to fix the carburetor. And while not a big deal, there's still the hourglassing problem indicating power supply ripple.

I was thinking of doing the IF alignment because I changed the caps and resistors of the IF strip, plus I wanted to do something a little different. Not because I think it will help my out of focus problem.

[Crist Rigott]

Originally Posted by Electronic M

The hourglasing may also be from a large line transformer too near to the CRT...If you got one near the set move it away a few feet if you can.

No line transformer near the CRT.

[Crist Rigott]

Tomorrow I should have my HV probe for my VTVM. Only then will I know what kind of HV I have.

[dieseljeep]

Originally Posted by Crist Rigott

Tomorrow I should have my HV probe for my VTVM. Only then will I know what kind of HV I have.

I have the same model Knight-Kit VTVM, bought and built in 1962. I never had the HV probe.
The meter still works great.

[Crist Rigott]

Originally Posted by dieseljeep

I have the same model Knight-Kit VTVM, bought and built in 1962. I never had the HV probe.
The meter still works great.

Cool! The probe is the Knight-Kit probe for the KG-625.

[dieseljeep]

Originally Posted by Crist Rigott

Cool! The probe is the Knight-Kit probe for the KG-625.

By the time, I needed a HV probe, I ended up buying a Pomona HV probe. It was the most common at the time. I mainly used it for color sets.

[Crist Rigott]

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.

[Crist Rigott]

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.

[Crist Rigott]

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.

[dieseljeep]

Originally Posted by dieseljeep

I have the same model Knight-Kit VTVM, bought and built in 1962. I never had the HV probe.
The meter still works great.

I did change the original probes with an Eico Uniprobe, much more convenient.
About 20 years ago, I replaced the "C" battery and rechecked the calibration.

[Crist Rigott]

I found the focus problem...most likely.

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



Unfortunately, I broke a filament wire in the process.