Early Sylvania Roundie on the 'Bay
 

Oh my! This is not something that you see everyday!

http://cgi.ebay.com/1957-SYLVANIA-CO...item27b192419c

I am not affiliated with this auction,
jr

Amazing! What are those red sticks on the back of the crt?

There are only two of those known to exist. This one and the "Saratoga" 31C606MU IIRC, which is a floor model. I owned that one for a short time. I had to sell it to a friend because of a major home repair that I had no money for. Now I wish I had the set back but oh well, it's got a great home. The red sticks are the purity magnets. The chassis is of a Sylvania design with circuits licensed through RCA. The HV section is almost identical to a CTC2B but uses a corotron tube for regulation. VERY interesting set to play with. I'm bidding but I doubt seriously that I'll win.

Mark, do you mean the set in the auction is one of the two which were previously known?

That's really close to where I grew up.

Too bad the 21AXP22 is dead.

John

Isn't the corotron the one that's impossible to find and difficult to sub?

John

David, you are correct! :D:smoke: These came from a Sylvania employee that had them forever, he lived in Pa. I think he's passed now IIRC. The set I got made it's way to Detroit and then to my house and now, not very far away.


John, It is almost if not impossible to find one. The good news is that it can be modified to use a 6BK4 like an RCA.

Did you win it??

I guess if your going to get the crt rebuilt you got a few more weeks to get it in to Hawkeye.

Guess it was rare! I didn't expect it would go that high. And no, I didn't bid.

John

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We have a 21C609 at the museum, which is a CTC4 clone. It is in Sams 352, while the 31C606 is in 391. I guess they sold the 21C for a few months until they could get their own design to the market. Strange that it uses a gas regulator tube when the shunt regulator had been in use in almost all sets for 2-3 years.

That didn't take long.

Who can explain those controls above the screen? I'm guessing that's a channel indicator in the center, but can't make out the rest.

Those red stick magnets kill me. Looks like something I would come up with. Let's see, all I need is a pack of soda straws, some little dime store magnets, and a roll of duct tape :)

Phil Nelson

No, I didn't win, I WISH! Since I already owned one of them I should have just kept it. I thought his BIN was stupid, that set would have gone higher in bids. As far as design, that set used everything that was already outdated like the corotron tube, a lot of the circuits were throwbacks to RCA's of previous years. They just incorporated them into their own design. The slide "ratchet" controls on top are for changing the channel, at least the right one is, the other one is the power switch. It sounds like a regular ratchet when you change channels, it's pretty neat. The color, tint, contrast and brightness are located below the screen. The controls are barely visible even when you are in front of the set. The purity assembly is of their own unique design, hence the weird looking "straws" for the magnets, you twist them to make an adjustment. Let me tell you that I would have STOLEN that at $1,700 if I had it to spare. It is worth much more. You will find ten CT-100s with good CRTs before another one of these shows up. SOMEONE did steal it at that price, I hope they are a member here.

I Was in touch with the seller before it went up for sale on ebay. As I already own the other Sylvania which Mark had, I was not interested in buying this one.

The set I have is the floor model, and someone converted the set to an all glass crt at some point. I was fortunate to obtain the only hard to get part that was missing, the odd purity ring assembly, and so I will be able to convert my Sylvania back to the 21AX crt at some point. The only items I will need are some red plastic straws and a large piece of polyethylene to create a HV insulator shell for the crt.

I think it probably used a coretron because of the simplicity. Just clamp it to ground and connect the HV lead and you're in business. May have even been more cost effective (no tube socket, no high megohm voltage divider resistors etc) This chassis also used the same flyback that is in the RCA 21CT55, relabeled as a Sylvania part number. The only reason I know they are the same, is because I had to do a lot of work on my CT55 HV section and I would recongize that flyback anywhere. I have not tested the coretorn in my Sylvania yet, but I would bet it is crap like most of them are.

Would it be possible to use high voltage zeners to make a replacement coretron? I see 300v 1w zeners available for about 10 cents each at Mouser. The 70 or so needed for 20kv could fit in the old can.

That's an interesting thought - even if the regulator had to draw 3 ma max, that would be 0.9 watts each. I assume that would require heat sinking? The hardest thing might be assembling the string in such a way as to avoid arcing over or gradual carbon tracking of whatever you mounted the diodes on.

3 ma can't be right. That would be 60 watts at 20 kv. Since the voltage drop across each diode would only be 300, I don't see a problem with arcing except maybe at the ends where the diodes would have to be looped around to fit. HV insulating cambric would solve that.

About a year or two ago I met a man who said he has a metal cone color tube...
 

so I suspect it must be a 21AX. He has a radio repair shop close to Fort Lauderdale. He seemed to be the sort that would be very difficult to deal with but I have been wrong many times before. So, I suspect others wil have one but I would try to find him again if anybody would like me to do so.

I would, I need a 21AXP22 like crazy!:)

It's back and the BIN is up by $100.

http://cgi.ebay.com/1957-SYLVANIA-CO...-/170484029517

Rough calculation (real current will be less, since it will be limited by max red gun current):
21AXP22 spec says absolute max average current 500 microamp per gun. I was just doing the calculation to show that the zeners could withstand more than enough current to handle a black screen. (To stay in regulation, they should still be taking some current on a max white screen, when the CRT draws less than 1.5 ma. So, the flyback has to supply something slightly above the max designed CRT current, and that value has to be less than 1.5 ma. (maybe 1 ma? maybe 1.2 ma? maybe less) Then, when the CRT anode current goes between 0 and 1 ma, the regulator goes between 1.2 and 0.2 ma.

Something like that, although I don't know what the fly is capable of and what typical beam currents are in this set.

It's back, wonder if the first buyer was overseas?

In big red letters:

"THIS ITEM IS FOR CONTINENTAL U.S.SALE ONLY"

Edit, I guess it said that the first time, wonder what went wrong?

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I heard indirectly that the buyer was trying to back out. I guess he did.

Wasn't me. I wonder what happened? Why click BIN when you can't afford it or whatever happened. I'm bidding again but like I said before, slim chance I'll win.
GAWD it would be cool though. That's a hole in my collection that will probably never be filled up again. Sure was cool while it lasted........

Hey Mark,

What the hell. Go for it. I know you're still smarting from having the console version and selling it. This table model sold for $595.00 in 1957. A fair piece of change back then.

-Steve D.

WOW! Who stole it for $555? I was bidding until $500 but spaced on the end of the auction today because I was busy at work. I can't believe how cheap it went for! If I'da payed attention, it could have been mine!

Not I, I'm a console guy. :)