RCA mystery tube help

rotaspec · 13th January 2010, 04:48 AM

Anybody recognize this tube? Seller can only identify it as 7-29A on the base.
Looks a little like a 5R4 rectifier. If so, I am definitely interested.

Thanks in advance
Gary

JPeitzman · 07:25 AM

Looks to me like either a 5R4GY or 5U4G, though most of my 5U4G's have ribbing on the plates, not all. That would be my best guess.

If he looks really good at the glass at the right angle he should find the marking of what the tube is. I have found that on many tubes, even if the markings are rubbed off from age or cleaning they can still be faintly found under the right light at the right angle. Just something to try if he doesn't mind looking.

Geek · 13th January 2010, 07:49 AM

Plates are too short for any 5R/U4 I've seen.

My guess is a Type 80 or 5Y3G. Look at the pic on the right:
http://dmradios.com/280.jpg

Cheers!

azazello · 13th January 2010, 08:33 AM

I have 80 FIVRE Italy....looks me the same.

DigitalJunkie · 13th January 2010, 08:50 AM

filament is too small to be 5U4,looks 5Y3-ish to me.

JPeitzman · 13th January 2010, 01:56 PM

Hmmm... I may stand corrected. To me though it is a bit hard to tell at that angle if it is a ST-16 or close up of a ST-14 bottle. If he can provide a shot from straight on that would be better.

kevinkr · 13th January 2010, 05:06 PM

Looks suspiciously like a UX-4 4 pin base to me, (is it?) and the plate structure looks like an 80 to me as well.

HollowState · 06:46 PM

It looks a little cloudy down near the base. (mercury) And the plate structure is exactly the same as a NOS RCA type 83 complete with the two supporting rods up the middle.

rotaspec · 13th January 2010, 06:49 PM

Here's the only other pic from the auction site (a local eBay variant).
Looks like an octal base with only a few pins used.
Person selling is not into electronics judging by the wording of the auction.

Gary

boywonder · 13th January 2010, 07:01 PM

Quote:

Originally Posted by JPeitzman

If he looks really good at the glass at the right angle he should find the marking of what the tube is. I have found that on many tubes, even if the markings are rubbed off from age or cleaning they can still be faintly found under the right light at the right angle. Just something to try if he doesn't mind looking.

Try heavy breathing (on the glass). Fogging up the glass sometimes reveals the markings. A trick that Stan at the tube center showed me....

13th January 2010, 07:23 AM	#2
JPeitzman diyAudio Member Join Date: Jan 2007 Location: Iowa	Looks to me like either a 5R4GY or 5U4G, though most of my 5U4G's have ribbing on the plates, not all. That would be my best guess. If he looks really good at the glass at the right angle he should find the marking of what the tube is. I have found that on many tubes, even if the markings are rubbed off from age or cleaning they can still be faintly found under the right light at the right angle. Just something to try if he doesn't mind looking. Last edited by JPeitzman; 13th January 2010 at 07:25 AM.

13th January 2010, 05:06 PM	#7
kevinkr diyAudio Moderator Join Date: Sep 2004 Location: Boston, Massachusetts Blog Entries: 6	Looks suspiciously like a UX-4 4 pin base to me, (is it?) and the plate structure looks like an 80 to me as well. __________________ www.kta-hifi.net

13th January 2010, 06:44 PM	#8
HollowState diyAudio Member Join Date: Aug 2006 Location: Taxland, New Jersey	It looks a little cloudy down near the base. (mercury) And the plate structure is exactly the same as a NOS RCA type 83 complete with the two supporting rods up the middle. __________________ "The supercomputer is technologically impossible. It would take all of the water that flows over Niagara Falls to cool the heat generated by the number of vacuum tubes required." ~ Professor of Electrical Engineering, New York University Last edited by HollowState; 13th January 2010 at 06:46 PM.

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13th January 2010, 07:49 AM	#3
Geek diyAudio Member Join Date: Sep 2004	Plates are too short for any 5R/U4 I've seen. My guess is a Type 80 or 5Y3G. Look at the pic on the right: http://dmradios.com/280.jpg Cheers!

13th January 2010, 08:33 AM	#4
azazello diyAudio Member Join Date: Aug 2008 Location: Bulgaria	I have 80 FIVRE Italy....looks me the same.

13th January 2010, 08:50 AM	#5
DigitalJunkie diyAudio Member Join Date: Apr 2003 Location: Portland,Oregon Blog Entries: 4	filament is too small to be 5U4,looks 5Y3-ish to me.

13th January 2010, 01:56 PM	#6
JPeitzman diyAudio Member Join Date: Jan 2007 Location: Iowa	Hmmm... I may stand corrected. To me though it is a bit hard to tell at that angle if it is a ST-16 or close up of a ST-14 bottle. If he can provide a shot from straight on that would be better.

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