Tech-Master NIB TV Kit #5516

[Electronic M]

Originally Posted by Crist Rigott

Yes, please! Thanks.

After much futzing with a bad SD card; pictures at last!



The audio output transformer is not for sale, and will be trimmed off. The side with the transformer once mounted to a defunct speaker. If you don't want the cloth wire on the other end, then I'd like to keep that wire.

I'd do an even trade for that HV connector/cable you did not use that came with your kit.

PM me if interested.

[Crist Rigott]

Thanks for the pictures. Let me think about it for a while. If I did get it, I wouldn't need any wires and such. Just the connectors.

[Crist Rigott]

I've had a lot of suggestions from people on the ARF. While good suggestions, there is still no joy.

Everybody's help is appreciated and together we'll get to the bottom of this.

I think what I'll do next is to change out the rest of the caps and resistors that is left to do in the IF strip. Then look at the alignment procedure that is given in the instruction booklet and see if that will help. In the meantime, I might be able to round up another CRT that I could try. Another thing that is on my mind is to remove the CRT base and closely inspect and redo the leads going through the pins in the base.

I should have a good HV probe to go with my Knight KG-625 VTVM in a few days so then I'll know where I stand with the HV.

I just might need a smaller CRT. We'll see.

With Christmas here, my time in the shop will be limited for a bit.

With that I'd like to wish everybody a Merry Christmas.

[dieseljeep]

Originally Posted by Crist Rigott

The focus on the 5AXP4 is much better.

Boost the line voltage another 10 volts or so. See what the focus and brightness looks like then. You installed E'caps, that were rated for higher B+ so no worry.
I just looked at an old Sylvania tube manual for the specs on the 21FP4 and it shows the focus voltage, rated between -200 to 1KV on pin 6. I don't remember seeing, that kind of voltage used for E'stat focusing. It was always between ground and boost.

[old_coot88]

Originally Posted by dieseljeep

Boost the line voltage another 10 volts or so.

And if that shows promise, consider sticking a few 9V batteries in series in the B+ line feeding the H.out circuit. That would give it even more grunt, B Boost and HV without overstressing the heater string.

This would at least give a yes/no whether raising B+ further on the H.out circuit would help.

The battery string would go in the B+ line feeding the plate (pin 5) of the 12AX4. If it helps, then consider building a small dedicated supply in place of the batteries.

Just a thought FWIW.

[old_coot88]

P.S. If you're interested in trying the 9V battery trick, I have a ton of them which are pulls from smoke detectors in my building. They are Mallory Duracell and all test well into the green on a standard batt. tester. The pulls are always good since they're changed on one-year interval.
Free for postage. PM me if interested. Bill

[Crist Rigott]

Here is a video of the picture quality. The picture is a lot more focused just after turn on but then looses focus after that. Watch the SUN day of the weather to see what I mean.

https://youtu.be/DXsw8_pofTA

[Crist Rigott]

Originally Posted by dieseljeep

Boost the line voltage another 10 volts or so. See what the focus and brightness looks like then. You installed E'caps, that were rated for higher B+ so no worry.
I just looked at an old Sylvania tube manual for the specs on the 21FP4 and it shows the focus voltage, rated between -200 to 1KV on pin 6. I don't remember seeing, that kind of voltage used for E'stat focusing. It was always between ground and boost.

I could boost the line voltage by 10 volts. Would that hurt the filament string?

[Crist Rigott]

Originally Posted by old_coot88

And if that shows promise, consider sticking a few 9V batteries in series in the B+ line feeding the H.out circuit. That would give it even more grunt, B Boost and HV without overstressing the heater string.

This would at least give a yes/no whether raising B+ further on the H.out circuit would help.

The battery string would go in the B+ line feeding the plate (pin 5) of the 12AX4. If it helps, then consider building a small dedicated supply in place of the batteries.

Just a thought FWIW.

OK, it's worth a try. What, like 27 to 36 volts?

[Crist Rigott]

Originally Posted by old_coot88

P.S. If you're interested in trying the 9V battery trick, I have a ton of them which are pulls from smoke detectors in my building. They are Mallory Duracell and all test well into the green on a standard batt. tester. The pulls are always good since they're changed on one-year interval.
Free for postage. PM me if interested. Bill

Stand by for preliminary tests.

[old_coot88]

Originally Posted by Crist Rigott

Here is a video of the picture quality.
https://youtu.be/DXsw8_pofTA

The raster shows some 'hourglassing' from powerline ripple causing the slow bend on the sides that drifts up. What's the value of the two main filter caps (right after the rectifier)? The second one may need to be bigger to get rid of the ripple.

[dieseljeep]

Originally Posted by Crist Rigott

I could boost the line voltage by 10 volts. Would that hurt the filament string?

I forgot to mention using a Variac. Many will put out 140 volts.
You can boost the B+ by using a 12V heater transformer, rated at around an amp, connected boost. Connect it before the rectifier and you'll just increase the B+, without increasing the heater string.

[Crist Rigott]

Originally Posted by old_coot88

The raster shows some 'hourglassing' from powerline ripple causing the slow bend on the sides that drifts up. What's the value of the two main filter caps (right after the rectifier)? The second one may need to be bigger to get rid of the ripple.

Both are 220uf

[Crist Rigott]

Originally Posted by dieseljeep

I forgot to mention using a Variac. Many will put out 140 volts.
You can boost the B+ by using a 12V heater transformer, rated at around an amp, connected boost. Connect it before the rectifier and you'll just increase the B+, without increasing the heater string.

OK, I can do that.

[Crist Rigott]

Originally Posted by dieseljeep

I forgot to mention using a Variac. Many will put out 140 volts.
You can boost the B+ by using a 12V heater transformer, rated at around an amp, connected boost. Connect it before the rectifier and you'll just increase the B+, without increasing the heater string.

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.