Recently bought a batch of 6SL7GT, including National Union, Ken-Rad, RCA and Sylvania.
There also was one tube with no markings on the base, just the stop-sign 6SL7GT on the glass.
My thoughts went first to RCA, but it wasn't like the others in the batch.
Circular top mica, rectangular getter and black plates (probably). Does anyone recognize this structure/construction? All suggestions welcome!
There also was one tube with no markings on the base, just the stop-sign 6SL7GT on the glass.
My thoughts went first to RCA, but it wasn't like the others in the batch.
Circular top mica, rectangular getter and black plates (probably). Does anyone recognize this structure/construction? All suggestions welcome!
Right, that seems very likely. The round top mica differs from your example and my other RCAs. Is there a way to find out when the tube was manufactured, anyone?
No, that's the problem. I assume the base once had a print that has worn off after all these years. Also note that the getter's silver deposit is very low, hardly visible from the outside.
Ooop´s...Looks like my octagon logo idea is wrong. However, many tubes of the 1950´60´&70´s were cloned by other manufacturers around the globe. One cannot count the raft of numbers in Europe and former Eastern Block.
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those sure look lke RCA micas from the era, but i dont remember RCA having those mica supports like ken rad. i dont see any bottom flashing here.
before the small signal tubes the octagon was used by just about everyone. in small signal tubes its RCA, tung sol, westinghouse (cant remember atm), hitachi, and i forget who else.
before the small signal tubes the octagon was used by just about everyone. in small signal tubes its RCA, tung sol, westinghouse (cant remember atm), hitachi, and i forget who else.
Thanks for all suggestions. Have gone trough my own 6SL7GTs again and found similarities with two tubes. First an RCA VT-229/6SL7GT, tube on the right:
Round top mica and rectangular getter - but no top mica supports.
The second one is a Ken-Rad VT-229/6SL7GT:
Round top mica with supports, but - foil getter. The Ken-Rad octagon is also without breaks (difficult to see on the photo but it's uninterrupted), while the mystery tube "carries breaks indicating the year and month of manufacture, as shown in the Dowd brochure. A break in the corner gave
year; in the straight part, the month." (https://www.teltec.se/bocker/rcadates.pdf) I've never seen an instruction to those breaks, by the way.
In all, I would guess it's an RCA tube. Googling, I found this photo. The tube on the right is similar to the my unidentified tube, an old logo RCA, indicating the mystery tube is from the 1940s.
Any thoughts on this?
Round top mica and rectangular getter - but no top mica supports.
The second one is a Ken-Rad VT-229/6SL7GT:
Round top mica with supports, but - foil getter. The Ken-Rad octagon is also without breaks (difficult to see on the photo but it's uninterrupted), while the mystery tube "carries breaks indicating the year and month of manufacture, as shown in the Dowd brochure. A break in the corner gave
year; in the straight part, the month." (https://www.teltec.se/bocker/rcadates.pdf) I've never seen an instruction to those breaks, by the way.
In all, I would guess it's an RCA tube. Googling, I found this photo. The tube on the right is similar to the my unidentified tube, an old logo RCA, indicating the mystery tube is from the 1940s.
Any thoughts on this?
"In all, I would guess it's an RCA tube. Googling, I found this photo. The tube on the right is similar to the my unidentified tube, an old logo RCA, indicating the mystery tube is from the 1940s."
well, it indicates the tube you found in the google pic is frmo the 1940s.
notice the visible getter flashing on the tubes in that google photo you found--you dont have a match there. its also possible that yours wore off.
you have some good leads. continue examining photos of accurately identified tubes until you find several matching every characteristic of yours.
well, it indicates the tube you found in the google pic is frmo the 1940s.
notice the visible getter flashing on the tubes in that google photo you found--you dont have a match there. its also possible that yours wore off.
you have some good leads. continue examining photos of accurately identified tubes until you find several matching every characteristic of yours.