Prototype set is here - Page 34 - Videokarma.org TV - Video

ctc17 · #**496** 07-26-2012, 06:42 PM

So far I have had a 6GH8, 6JE6 and 21FJ crack and go to air after returning a retired set to service. None of these tubes were being touched, they just went to air while the set was off after I started using the set again.

***Eric H*** · #**497** 07-26-2012, 10:20 PM

Quote:

Originally Posted by ctc17

So far I have had a 6GH8, 6JE6 and 21FJ crack and go to air after returning a retired set to service. None of these tubes were being touched, they just went to air while the set was off after I started using the set again.

I suppose Glass ages just like anything else, maybe after 50 or 60 years minor flaws become fatal flaws.

kvflyer · #**498** 07-27-2012, 10:00 AM

And I too have had tubes crack after lengthy power off. The CTC-9C that I have had a cracked audio output tube, I think, 6AQ5. Had a 7591 crack and give a really nice purple show as the air leaked in. Now THAT was an expensive tube...

*zenithfan1* · #**499** 07-27-2012, 01:40 PM

I guess I've been lucky, I've never had a tube go to air. I've found a few in sets that I picked up but never while I've owned them. I better go knock on wood now. I just looked behind me and the CTC 11 that was dropped down the stairs is running in the living room. I use it every day....

I woke it up from a very long sleep.

joemama99 · #**500** 07-27-2012, 11:11 PM

I knew you would get that one going,Mark.

colorfixer · #**501** 07-30-2012, 12:37 AM

judging from the basket case 15g that RACS resurrected, I wouldn't think that this tube would be an issue since they would need to redo the neck of the tube to rebuild it in any event.

tvcollector · #**502** 07-30-2012, 05:00 AM

Isn't there a place in France that still rebuilds picture tubes? if so, I'm sure the shipping alone would be outstanding..

miniman82 · #**503** 07-30-2012, 10:41 AM

Yes, it's just a simple neck weld. The problem comes from the fact that if the planar dot plate and mask are heated at a different rate than the rest of the tube, the plate can crack or the mask can bend. This is the same issue as with the 15G, but it's worse because the prototype tubes have more thermal mass than a 15G does because its internal supports are heavier. This means even longer bake out times, and more cost. I've read notes from early books on the developmental tubes that state the face should be shielded during cooldown, to avoid cracking.

miniman82 · #**504** 04-22-2013, 08:15 AM

Just a reminder to all convention goers, Steve will be talking about the proto set this year and I assume there will be a demo of it working for all to see. Should be an interesting speech, hope I can be there to see it.

47'Plymouth · #**505** 04-22-2013, 01:36 PM

Heyboer Transformers 616-842-5830.they could you one from scratch if you had all of the specs on the power tranformer to run the set..ask for Phil...tell him i sent you..he could make you the filter choke(s) also if the specs on them also... Jody

Mal Fuller · #**506** 04-22-2013, 10:48 PM

I also endorse Heybour Transformer. Here's what I have for contact information:

miniman82 · #**507** 04-23-2013, 09:08 AM

What's all the hubbub about transformers?

Steve McVoy · #**508** 04-24-2013, 11:57 AM

I think someone confused the comments about the power supply chassis being missing. The problem is not a missing power transformer - we don't even have the schematic for the power supply chassis.

47'Plymouth · #**509** 04-24-2013, 04:23 PM

Then make one my friend,
Steve,... they've designed me one for 1927'Colonial 31 AC highboy console radio, that the power supply and speaker was missing
when i bought her,..he 's came up with the power transformer, chokes and audio transformers from using my schematic that I've got,...sent a copy to Phil and the rest is history,now you said you've got no schematic of it....what about you're having the voltages requirements and currents i.e.(milliamps) of the tubes and other goodies reqired to operate the set...you could get close enough to build it within 20 % tolenece of operating the set...have sheet metal fabber make up the missing chassis....just and idea!
Jody

Steve McVoy · #**510** 04-25-2013, 07:47 AM

We did make a supply some time ago. See the report on restoration of this chassis:

http://www.earlytelevision.org/rca_cpa_restoration.html

Designing a power supply isn't rocket science, and we used transformers we had pulled from junk chassis.

The problem, however, was that we don't have a schematic for either the main or power supply chassis, and don't have documentation of the supply voltages. We had to guess and experiment to come up with what we think are the correct voltages.