[R-390] Tube Info Needed..

[Roger L Ruszkowski]

Fellows,
I am looking for the following information.

That after you have checked all you tubes in the 390.

There is a list,  about tube placement.
It tells you where to put the best tube in the radio. Where you can put the
weakest tube. Where to put the most stable tube.

TKS
Gary
-----------------------------

Gary,

What is is the question here. after you have checked all you tubes in the
390

What did you check?
How did you check it.
All the tubes?
All of the tubes?

This is a 3 stage process.

Stage 1 find all the tubes you can and check them
on a tube tester. Throw the bad ones away.
What is a bad tube?
How will your tester know?
How will you know?

Stage 2 sub the tubes into the receiver to find the
best low noise tubes.

Start with the 5749 6AU6 IF Deck tubes.
Use the very first If amp.
Sub them all in to find some good ones.
Put the good ones into the deck.
Check all the tubes again to rank them.
Put the very best most quiet one in the first IF
put the second in the PTO
Put the 3rd in the BFO
Put the next best ones in to IF strip
down the IF chain.

Do the 6AK6's next.
Put the best one in the IF deck
Put the 2nd best one in the audio chain you will
listen to (may or may not be the phone output)
Put the 3rd best one over there on the other audio.

Do all the 5814's into the audio link.
Pick a socket where both sides of the of the tube
is being used. Do not use the limiter. Do not use
the diode detector.
Put the best ones in the audio chain.
fill the AGC and limiter last.
AGC is not listened to.
Limiter is mostly off.

Do the 6C4,
Do the 6AK5's
Do the 6DC6.

Turn the lights off and look for the pretty blue glow
inside the bottle. These will first become test spares
until you acquire enough tubes with out blue glow to test
your tube set. If you are desperate (who is not) there
is a zippo process to conduct on the pretty blue glow ones
to get the glow out of the bottle. Then these tubes become
trash. If you are desperate (who is not) there is a zippo
process to conduct on the pretty blue glow ones to get
the glow out of the bottle.

Stage 3 install the best of what you have.

All ways put the best tube to the front end.
Injecting a signal and metering signal plus noise to noise
will provide a better test than the tube tester will.

Start with 150 UV (what ever [need not be calibrated]) into the IF deck and
get
a 30 db difference in signal plus noise to noise in the
If audio deck. You can hang an AC volt meter and 600 ohm resistor
on the line out put. Do some math and determine what the
voltage should be and difference is.
signal plus noise is 455Khz with 30% mod at 400 - 1200 hertz.
noise is 455 Khz is CW on the signal gen.
455 Khz is peaked into the 100 Hz .1 crystal filter of the IF deck.

You need .5 watt into a 600 ohm line load.
You need -7 volts on the diode load.

If you can not set these 3 things up, the If deck and
audio deck are below space and nothing in the RF deck will
over come the problem.

In the RF deck, just use the best tubes you can get.
The first time you set the test up with 4 -5 UV
into the antenna and measure the line out with
the signal generator on and off to see the ratio,
and then swap a tube, any tube, and see what the difference is,
you become a believer for swapping tubes in socket for performance.

You can use WWV and watch the meter bounce between carrier and
tones if you do not have a signal generator.

Roger KC6TRU San Diego.