Old Muntz TV for sale Locally to me, Should I pick it up?

[vortalexfan]

Originally Posted by old_coot88

Dang. How'd I miss this post earlier? (Thumps forehead)

Is it honestly labeled 5KV? It should be rated at least 20 KV.

Temporarily disconnect this cap and see if the HV comes up.

It's the original doorknob capacitor to the set, look at the parts list in the Sam's for this set, it says 500 mmf 5kV.

[old_coot88]

Originally Posted by vortalexfan

Here's a picture of what the picture looks like now.

Izzat pic with the doorknob in circuit?

[vortalexfan]

Originally Posted by old_coot88

Izzat with the doorknob in circuit?

Yes. And I still haven't replaced the 1 meg 1 watt resistor in line with the high voltage anode yet, as I'm still waiting for that part to arrive in the mail.

[Kevin Kuehn]

Wow, whether this TV is working or doesn't is making my head spin. That's a respectable picture you have there right now, although it could be a tad brighter. Where was the brightness set for that picture?

[Kevin Kuehn]

BTW my sams says that HV cap is rated 15,000v. I think we need a different informer.

[vortalexfan]

Originally Posted by Kevin Kuehn

BTW my sams says that HV cap is rated 15,000v. I think we need a different informer.

Mine says 5,000 Volts I think what you're reading as a 1 in front of the 5 is actually the double cross symbol that references to the double cross symbol at the bottom of the capacitor parts list that said that some models use a 210 MMF capacitor in this position.

As for the brightness control it's in the middle or thereabouts to get the picture where I have it now.

[Kevin Kuehn]

Originally Posted by vortalexfan

Mine says 5,000 Volts I think what you're reading as a 1 in front of the 5 is actually the double cross symbol that references to the double cross symbol at the bottom of the capacitor parts list that said that some models use a 210 MMF capacitor in this position.

Are we talking about C80? It sure looks like 15k to me.

[vortalexfan]

Originally Posted by Kevin Kuehn

Are we talking about C80? It sure looks like 15k to me.

OK, you're right it is 15,000 Volts, I confirmed it with the Sam's Folder I had of the Meck Model XL750 which was basically the model that my TV took the place of, and that one had a 10,000 Volt Capacitor listed, and seeing as my manual was a copy it was hard to read the details because the copy wasn't very clear, also when I was reading the value of the cap when I had the high voltage cage apart to check that 1 Meg 1 Watt Resistor that capacitor looked like it said 5kV on it but the writing on it was kind of worn so it may have actually said 15kV but the 1 was probably worn off.

And if that door knob capacitor were to go bad, where would one acquire one of those capacitors? I don't think anyone makes those anymore, seeing as they quit using those in TVs around the time TVs went solid state which was in the mid 1970s for some of the companies like GTE/Sylvania, and early 1980s for the rest so that's over 35 years that those Door Knob style High Voltage caps have been out of production for.

Also I had a very shocking experience last night when I was trying to adjust the horizontal size adjustment on the TV, the Horizontal Size adjustment slug was turning rather hard and so when I was turning it with my screwdriver, the screwdriver slipped and my hand hit one of the terminals on the Flyback Transformer and I got a good jolt out of it and a couple of tiny burn marks on my ring finger on my left hand.

[old_coot88]

Some doorknob resources here - https://www.bing.com/search?q=doorkn...BLH&sp=1&ghc=1

Actually doorknobs in TV sets fell out of vogue in the early '50s, as all-glass CRTs phased out the old metal bell types. Glass tubes, by dint of inner and outer dag coatings, provided their own HV filtering, so doorknobs weren't needed. But out of convention, some mfrs continued using doorknobs for a while anyway.

[vortalexfan]

Originally Posted by old_coot88

Some doorknob resources here - https://www.bing.com/search?q=doorkn...BLH&sp=1&ghc=1

Actually doorknobs in TV sets fell out of vogue in the early '50s, as all-glass CRTs phased out the old metal bell types. Glass tubes, by dint of inner and outer dag coatings, provided their own HV filtering, so doorknobs weren't needed. But out of convention, some mfrs continued using doorknobs for a while anyway.

OK, so that must of been the way it was with Meck I'm assuming, they were one of the companies that still continued to use doorknob capacitors in TVs even after they were no longer required in TVs...

[Electronic M]

Originally Posted by vortalexfan

OK, so that must of been the way it was with Meck I'm assuming, they were one of the companies that still continued to use doorknob capacitors in TVs even after they were no longer required in TVs...

The 10" and 12" glass CRTs didn't need the doorknob, but many chassis of the day were designed to drive both of those and a 16" metal cone CRT....it was less of a production hasto to make a chassis that drove some glass and some metal CRTs have the cap in the HV cage regardless of the CRT type than pick and choose a flavors of basically identical chassis off the line.

Doorknobs continued in color TVs (which had metal cones later) until around 1956...the RCA TM-21 broadcast monitor had one and was built into the 60s.

Doorknobs are still made today for X-ray machines (based on the datasheets) and we're stocked by mouser and digikey when I last need to order one a year ago....they are very expensive. Also there's really only 2 choices in physical mounting: ASE or metric thread on the bolt holes in the terminals...If you need a terminal to be a stem or something special you have to machine something that will do the job and thread into the cap you get....I had to do a good bit of clever fabrication to fit the 3 replacement doorknobs I installed in my RCA 21CT55...

If your CRT has outer dag and a ground spring making good contact between it and chassis you could probably get away with just flat out removing the doorknob and not replacing it...

[vortalexfan]

Originally Posted by Electronic M

The 10" and 12" glass CRTs didn't need the doorknob, but many chassis of the day were designed to drive both of those and a 16" metal cone CRT....it was less of a production hasto to make a chassis that drove some glass and some metal CRTs have the cap in the HV cage regardless of the CRT type than pick and choose a flavors of basically identical chassis off the line.

Doorknobs continued in color TVs (which had metal cones later) until around 1956...the RCA TM-21 broadcast monitor had one and was built into the 60s.

Doorknobs are still made today for X-ray machines (based on the datasheets) and we're stocked by mouser and digikey when I last need to order one a year ago....they are very expensive. Also there's really only 2 choices in physical mounting: ASE or metric thread on the bolt holes in the terminals...If you need a terminal to be a stem or something special you have to machine something that will do the job and thread into the cap you get....I had to do a good bit of clever fabrication to fit the 3 replacement doorknobs I installed in my RCA 21CT55...

If your CRT has outer dag and a ground spring making good contact between it and chassis you could probably get away with just flat out removing the doorknob and not replacing it...

My picture tube I believe does have an outer dag coating and some ground springs, so maybe I can just remove the doorknob capacitor in my tv altogether and just wire the new 1 Megaohm 1 Watt resistor from the 1B3 socket straight to the high voltage anode via a terminal strip bolted to the old doorknob capacitor hardware.
Because I looked at the price of a 500pF 15kV doorknob capacitor and they're over $100 a pop!

[bandersen]

Maybe, but if you do need a replacement, there are used and NOS on ebay for much less.

https://www.ebay.com/itm/500pF-20-00...S/333120846632

[vortalexfan]

Originally Posted by bandersen

Maybe, but if you do need a replacement, there are used and NOS on ebay for much less.

https://www.ebay.com/itm/500pF-20-00...S/333120846632

Ok, thanks I'll look into that.
But if my picture tube doesn't even really need that doorknob capacitor to function then I may as well remove it from the TV and be done with It and then save myself some trouble in the future.

[Kevin Kuehn]

One advantage of leaving it in place, is that if the springy dag contact becomes a bad connection you'll still have some filtering. Why not temporarily unhook it to see if it's dragging down your high voltage?