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Mates,Actually, I'm the silly one.
On putting back one of the 5881s in the power supply chassis of the ARC SP10, the centre locating pin broke away. Then I noticed that the pin had been re-attached previously with a gob of silicone. I realize the pin is only to direct the tube into the socket, but I began to wonder which of my several $XXX repairs paid for the breakage/repair without mention.
I have reglued this with "Krazy Glue", but this may be a subtle sign to get a new pair of 5881s.
I'm curious too who made these. They were in the SP10 when I bought it in 1986 and are RAM tested: single side getter, red/brown base, "USA" on the bottom, no etched dots or octagon. The upper mica has two "smiles" and two "frowns." Plates are quite plain with two subtle horizontal ribs and two narrow ones top to bottom on the ends. The bottle is certainly more compact than the nearest thing round the house- an old GE 6L6GC from the MC240. Any ideas?
The remaining getter flash is about 7/8" x 3/4" with slight iridescent rainbows on the edge. As I was also stupid with my Eico 666 while playing with an arced 6550, I can't test these presently.
The questions: what are these "power regulator" 5881s doing for their keep? Are these under much stress? Is there a reason to choose a tube in this situation for sonic reasons? Any recommendations for new ones: NOS or current production?
TA as always!
Cheers,
Bambi B
Follow Ups:
I've had good luck and decent sonic performance from these Russian tubes. I'm not sure what the name is... They are the "E" version of the 6n3c, which is the 6L6GC (I'm told). The "E" variant was made for military applications and is very rugged.Tim
Check out Antique Radio Supply, They sell a neet little device that replaces the broken key-pin. Trim any remaining pieces off and slip it on the pins, good as new. They have a link on the Asylum main page.Hasta...
Bambi-- in the mid 80s, RAM actually selected their tubes from very decent stock; I have a pair of RAM GZ34 that are Blackburn plant Mullards. That said, I can start by eliminating some of the usual suspects. Its not a tung sol, as they are all top getter and instantly recognizable.(Tung Sols have the red/brown base you describe, though) Your description of the mica and single plate getter says American Sylvania/Phillips of late 70s vintage, but again that base color would be atypical. What shape is the getter ring? If it is square, that would suggest GE or Raytheon, but they didn't make this tube; it is unlikely but not impossible that RAM would re-label a relabeled tube. Sylvania/Philips consumer (not JAN) is my best guess. BTW, you can easily get away with JAN Phillips or even Sovtek for this tube-- this is the one Sovtek tube that I truly have faith in, reliability and durability-wise; as it is voltage regulation, both would serve as well as even 1952-60 Tung Sols (they won't last as long, of course.) Chris
Chris,I gained a little more respect for RAM when I discovered that my 13 NOS 6DJ8s are graded Amperex A-frames from the early 70's. I still can not discover though which is this RAM 12AT7 marked 4/75.
The 5881 side getter is a medium size ring. The other models seem to also have some kind of additional shield inside the bottle, whereas mine are very plain.
Sylvania makes sense for the 5881, as it is the only one I have heard about that does not have a top getter, though I have not found a good photo of one on Ebay or from dealers.
It's amazing how poor the photos are on Ebay- one would think that it would be a great source to learn, but with all those foggy, spotty, dark, out of focus photogs from 11' away- it's a miracle anyone makes a bid. Strangely, the fakes seem to have the clearer snaps.
But for once, Sovtek to the rescue!
Thanks again for your time.
Cheers,
Bambi B
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