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Anyone know what a DLDB Tube is?

Wharfcreek

Wharfcreek

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I had this odd-ball tube laying around.......tested it as a 12AX7, AT7, EU7, etc.....and tube didn't even light up......so I thought I toss it out. As it turns out......I just found it again....this time in the input position of a small push-pull EL-84 mono amp. Actually, I looked at the amp and saw it said 6EU7 on the chassis......so I just pulled the tube and stuck in another little amp I was working on.....and amazingly......it fired up and worked!! Considering this tube was 'supposed' to have been trashed, I don't really recall just how or when it got into the PP amp. I only use the PP amp as a platform for matching EL84 tubes while under a working load. I suspect I accidentally stuck this tube in the PP amp by mistake.....and this whole thing has resulted in my now finding that the tube actually works. My question is: What is it? I've looked it up on Duncan and NJ7P and can't find any record of the tube. It 'looks' just like any other 12AX7 type 9-pin. Any help w/ this would be appreciated.

Thanks,

Tom D.
 
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I can't help you with this one, but I also have some Tung-Sol made tubes that I can't find any references to which also resemble the 12AX7 & 5687 types. I bet they're useful somewhere, but I have no idea where I could use them.

Larry
 
Jay,

No pic....and not sure that I could actually get one that would reveal anything significant since my camera is really pretty lame. I'd have to be 2 feet away from the tube.....and at that distance, I don't think I could even pick up on the markings. But, it VERY CLEALY says "DLDB" and underneath it has USA on it. Halo getter....and otherwise looks just like a 12AX7 in virtually all ways. Perhaps GE or RCA? No paint and no other markings anywhere. Also, the fact that it works in the spot for a 6EU7 has got to account for something. At least it means it's internally 'wired' like the 6EU vs the 12AX as far as pin-out goes.

Ya know......I could send it to ya if you've got a 'stock' 6EU7 I can use......lol.

Thanks for responding Jay. Hope you're doing well!!


Tom
 
Buck, did that post indicate that the DLDB was a direct sub for the 6EU7? Thanks, Tom D.
 
Nope, just that it was a miniature 9-pin and between 3 tubes he had it could make out that it was DLD_ and the last letter looked like either a 'B' or an '8'. The link is in my post above.
 
Wharfcreek said:
Buck, did that post indicate that the DLDB was a direct sub for the 6EU7?
Click to expand...


One way to figure out if it's the same as a 6EU7 is to measure the voltages on the cathodes, plates and grids of the 6EU7 and then the other tube in the same circuit, and if they come out close, then you can say that it is a 6EU7. "DLDB" may have been a pre-production experimental tube designation. Which probably got loose in the wilds when a company lab got cleaned out and someone dumpster dived.
 
Good thought!! I'll give that a shot in the next day or so. Amp has been moved to the proverbial 'back burner' for now. But.....tomorrow I'll have some time, and I'll give that a shot. Thanks for the suggestion. Tom
 
I posed the question to a local cabal of tube arcanists :-) "What's a DLDB tube?" (plus a link to this thread).
One of them answered back that it is a 20EZ7. That is not implausible; it appears to be a 20 volt version of an ECC83... although I don't know for sure if he was pulling my leg or not! :-)

http://tdsl.duncanamps.com/show.php?des=20EZ7
 
20EZ7 DOES match the pinout of the 6EU7... but I wouldn't expect it to light up (or conduct) on less than 1/3 of rated heater voltage.
 
Well, I guess this is a testament to the PT in my little old Magnavox 8901 amp then, since it delivered enough juice to the filaments of all the tubes, including the DLDB, to make the amp function. But, if we're talking 20 volts on the filaments here, then I doubt I'll EVER have a use for a tube like that. Nice to know what it is though.......Thanks guys!! Tom D.
 
I have a tabletop stereo radio that uses a pair of 20EZ7s... one in the multiplexer, one for drivers - needless to say, it has series string heaters. Actually TWO series strings, 100 mA and 150 mA. 9 tubes in total.
 
Remarkable, Tom! I had never even heard of this tube until this morning...
If you don't mind disclosing - what radio is it?
 
Tom,

I'll include my DLDB w/ my payment for the Stromberg!! Looks like you're about the only one who could use the tube!! TSD
 
Tom Bavis said:
Not really necessary - I have a few spares and a whole spare radio...
Click to expand...

Now you're talkin'! As immortal B-more Orioles skipper Earl Weaver (if memory serves) would put it, ya gotta have "deep depth".

:-)

PS That is a nice looking "modern" radio - from the very tail end of the first vacuum tube audio era.
 
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