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Questions about RCA 5751tubes

I am needing some help..

I ordered a pair of Sylvania 3 mica Black Plate 5751s for $150
and was sent RCA JRC-5751s instead. Please bear with all my questions.

1. I was told these were better tubes and matched within 2.5%
One tube has a sticker with 1.5/1.5 and the other says 1.6/1.7
Can I tell if these are matched from these values?

2. What do these values mean? Are they an indication of life left
on the tube? If so what values are considered NOS and what
values are considered 50% and 75% life left?

3. Are RCA JRC-5751 Black Plate, 3 mica, (smooth edge top mica)
as good as Sylvania 3 mica Black Plate 5751s?

I was surprised to get a different tube than I ordered but wanted
to ask everyone if this really is a better tube? Anything you can
tell me about this tube would be very appreciated..

More info on these tubes:

The top of the tube (nipple of the tube)is painted half green/half red.
I assume these are military markings..??? What do they mean?

The silk screening is all white but 90% worn off so you can't
read anything but part of the RCA logo, 5751, and JRC

2 black plates

Each tube seems to have 2 paper clip looking supports (one at each
end) to tighten up and better secure all 3 mica disks.

square halos.
tom92602

Showing 1 response by amandarae

amandarae
512 posts
 
Me, if I ordered and paid for a Sylvania 5751 triple Mica tubes, I should get a Sylvania 5751 triple Mica tubes, period!

I do not need someone telling me that the RCA is better sounding than the Sylvania etc. etc. The bottom line is, you should get what you paid for. What if the Sylvania sounds better to you than the GE or the RCA? Only you can tell in your system.

Oh, the label(1 and 2) is the Gm measurements of the tube where (first one indicates triode 1 and the second triode 2 for the 5751 which is dual triodes) which, in most instances, many confuse as an indication of the tubes being the numbers to match so that the tube pair can be called "match pairs".
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