Jul - The R-390A Frequently Asked Questions Page

$4000 (maybe $5000, I don't remember). Of course, it was probably better than new in many ways.
> My 390 is cleaning up nice Roy. I can't wait to have it finished so it can kick some 390A butt. :-) Fair
Radio's knobs are nice, but don't look original because they have no casting marks. They are too perfect.
There are some cast knobs that don't have significant casting marks. I don't know which contract made
them. Paul
From cbscott@ingr.com Thu Jul 11 15:15:07 2002
Subject: [R-390] OT
Can someone give me some advice concerning some optoisolators? I built an interface to go between
the computer to my Knwd TS440. It uses a MAX232 level converter and four NEC PS2501
optoisolators. The project did not work and, after finding a bad solder joint, the MAX232 seems to be
doing what it should, but all the optoisolators seem to be blown.
I was careful handling them (assuming they are somewhat static sensitive), but all of them appear to be
bad. The diode part checks okay with the Fluke DMM's diode-checker mode, but the EC junction
doesn't seem to be working. I've ordered replacement isolators, but before I start playing with them I
have a couple of questions.
Is it possible (or safe) to check the EC junction using the Fluke's diode-checking function? Unless the
LED is forward biased, should I see anything across this junction with the Fluke?
How "rugged" are these devices? Given that I strap a ground wire around my wrist and have my feet on
the concrete floor, should this be sufficient to keep from "blowing" them? Are they as rugged as, say, a
2N2222? Thanks, Barry(III) - N4BUQ SAND
From R390A@r390a.com Thu Jul 11 15:57:21 2002
Subject: [R-390] Filter Caps
Several had written me over the past few months asking if I would rebuild their filter caps. I had
responded that I was out of the Mallory 350V elements and had to decline.
I found a small cache of caps at a supplier out west. I now have enough in hand to rebuild 12 sets of
caps. I also have enough parts on had to build 4 solid state 3TF7 replacement modules. If you are
interested, let me know. Chuck Rippel, WA4HHG
From drewmaster813@hotmail.com Thu Jul 11 17:47:04 2002
Subject: [R-390] Re: Miltronix EAC
Barry (Hauser),
The single "tube" you refer to on the modified power supply unit is probably a thermal time delay relay.
This would allow sufficient time for tube warm-up then would apply B+. An example of an R-390A
power supply modified this way can be found at: members.aol.com/ac5zt/r390a.html
One opinion holds that application of B+ before cathode warm-up causes deterioration ("stripping") of
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