tubes age 9
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From: David Ross <ross@...>
Date: Mon Oct 18, 1999 11:17 am
Subject: Re: [R-390] WTB 26A7,26A6,26C6
Looks like Francesco is re-tubing an R-392. My R-392 book lists the 26FZ6 as
a sub for the 26A6, and AES used to sell the 26FZ6 a bit cheaper than their
26A6s. I tried a set of 26FZ6s in my R-392 and saw no difference from the
original 26A6s.
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Date: Fri, 15 Jan 1999 22:34:22 -0600
Subject: Re: [R-390] MTBF (was tubes and 3TF7 ...)
Every six months, I pull the tubes out of the R-1051B's and install new ones.
They'll last longer than that but I've got plenty of them. I think that I paid .25 a
piece for the 6AN5WA's when I bought them and only about .70 each or so for
the 6BZ6's. At the current rate of consumption I think that I have enough for 30
years or so. :-) It costs me about 4 dollars a year to retube both receivers.
Cheap, huh? And, yes I can notice a difference in sensitivity before and after
retubing. The performance differance and the low cost of the tubes is the
reason that I don't even bother to test them.
The antenna couplers, have a switchable meter on the front panel that monitors
the ten pairs of 6922's in each one. When I see the numbers drop to a level a
little below the recommended reading, for one pair, I replace that pair. I used to
just replace all of them but my supply of good quality Amperex 6922's is getting
low and they now cost more than the coupler is worth thanks to the golden
eared audio crowd. When they're finally gone, I'll have to start using the Jan
6922's but in the mean time, I'll cook Bugle Boy's in the couplers.
I've make little cards up that I keep on each of the receivers. On the card is the
testing date, the location (V#) in the receiver, the SN of the tube tester, and the
tested value of the tube expressed as xx/yy, where xx is the tester reading and yy
is the minimum value of the tube. I try to test the tubes about every six months.
After a couple of decades, you see trends. It's been my experience that for the
R390A's the tubes that seem to have to be replaced the most often are the
26Z5W's, and the 0A2WA's. I typically let them run 24/7. I don't trust the regulator
tubes as far as I can throw them. I hate the damn things. Anytime I install new
rectifier tubes in an R390A, I select and install a new regulator tube. Amazing
how many are a couple of volts or so "off". I've also had "noise" problems in the
receiver that I've traced to them. It's amazing the difference in sensitivity the the
tubes in the RF section make as they start to deteriate. Since it's a gradual
thing and you don't notice.
(14 pages)
(10 pages)
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