I would also have recommended the GE black plates as the best 5751. However, the RCA JRC is a very sought after NOS 5751 made in the 50's - 60's and was also made as a grey plate version. Vacuum Tube Valley sells the RCA grey plates for $100 per tube, so price wise you did okay. The numbers are demonstrating that the tubes are closely matched, meaning they should have equal strength and current draw, which is what you want. I believe that matching is probably more essential for Power tubes. There isn't any true test that can determine how long any tube will last. These are military grade and more rugged to last longer. I have had 5751's last as long as 7,000 hours and had others die much sooner. My advice is to decide whether you feel the RCA's are equal to or better than the Sylvania's you ordered. If not, you should be able to return them without questions asked.
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.
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.