tubes age 64
See Skip, Its simple, all you have to do is.......
Strange, brand new tubes are noisier than used tubes. It can help to leave the
R390/A on for about 3 months after you install a mess of new tubes. Even 1
month will help. We would get a year out of a new tube and some times 18 to
24 months for the IF Audio and non signal path chain (AGC, Cal oscillator). ASA
was running 24 x 365 and some times 366 days a year. So there a lot of hours
in a tube for the casual user. If you do put in some new tubes I would let the
receiver stay on for at least 2 weeks. It does seem to help. Of course the 6DC6
right up front would always be the biggest noise factor. We just swapped those
every 6 months. At the next two monthly the receiver would get a in rack
operational check. At the 3rd monthly (quarter) we would redo the RF
alignment. fourth, and fifth monthlies were in rack operational checks. Then
again at 6 months we did the full service. This was 4 to 8 hours on the bench. I
was doing a pair per trick shift. Both receivers spared out and returned to the
rack before the end of the shift. I would load 2 receivers on a cart and do them
both together. I now take a whole Saturday to do a receiver. It takes time to find
the right tubes. I just can not go to the supply room and get them off the shelf.
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Date: Mon, 5 Feb 2001 18:56:50 EST
Subject: [R-390] correction to earlier post on tube noise test etc.
The group, An earlier post of this was wrong, I slipped on the tube socket to
use on the test for the 6C4's, the below is correct.
Here's an easy method of checking for noisy/weak tubes in the R-390A using
the receiver.
1. Selecting 5749/6BA6 tubes for noise....remove the tube from V-501. Turn on
line level meter adjust to vU mark, or a mark you make note of. Try the various
5749/6BA6's in V-502. Note the meter readings after a two minute warm up.
Then use the quietest as V-501 and second quietest as V-502.
(14 pages)
(10 pages)
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