[R-390] R-390A help
Cecil Acuff
chacuff at cableone.net
Sat Mar 18 12:11:28 EST 2006
Barry, Tom and Group....
Barry you are absolutely correct....I was confusing my work on the
R-390/URR with that of the "A". Tom sorry for the confusion. I told you
guys I would have to go look. After checking three R-390A's that have the
three fuse rear panel all are indeed connected and should be again!
On the selenium rectifier....is it mounted on the power supply module or to
the rear panel? The rear panel mounted one is factory...beyond that it's
probably a mod!
They say your memory is the second thing to go......I can't remember what
the first is! :-)
Cecil...
----- Original Message -----
From: "Barry Hauser" <barry at hausernet.com>
To: "Cecil Acuff" <chacuff at cableone.net>; "TChirhart"
<sparks at codepoets.com>; <r-390 at mailman.qth.net>
Sent: Friday, March 17, 2006 10:23 PM
Subject: Re: [R-390] R-390A help
>
> Cecil wrote:
>> If I remember correctly one of the fuse holders never had anything
>> connected to one lead...I am working from memory here but I think it is
>> the one marked 20 amp....I'll have to go look.
>
> 20 amp? That's the DC fuse on the R-390/R-391, not on the R-390A.
> Probably not used on stock R-390's, but is used for the 28 vdc external
> supply for the autotune on the R-391, thus probably not connected in the
> R-390. (also might have been for some other 28 vdc equipment on the R-390,
> or for an alternate dynamotor supply -- but those have "@RARE@" encrypted
> into the contract number.
>
> All three fuses should be wired in to properly protect an R-390A. You're
> right Tom -- it makes no sense to bypass them, unless you feel lucky, very
> lucky. ;-)
>
>>
>> Pull the power supply out and look under the bottom side of the tube
>> sockets...I am guessing you'll find solid state rectifiers soldered onto
>> the tube socket pins. That was a military mod. Crushing the tube socket
>> bases was to ensure tubes were not placed in the sockets after the mod
>> was done. It's no big deal. You will find differences of opinion on the
>> list as to the suitability of the mod but personally it works fine. The
>> selenium rectifier is factory...it supplies a couple of things. The
>> break-in relay and the antenna relay. If it's not causing the relay to
>> buzz or chatter it's ok for now. I usually replace them with a silicon
>> bridge just to improve long term reliability...they are quite nasty if
>> they fail and spew their guts!
>
> I dunno, sounds like Tom was possibly referring to an _added_ selenium
> rectifier. If the previous owner jumpered out all the fuses (wore a
> sombrero and said at the time "wheee don' need no steeenkin' fuses. Hah
> Hah Hah Hah Hah. But wheee do need another maybe steeeking selinium
> rectifiers!") Could have felt fuses were superfluous but seleniums were
> the best thing since sliced bread -- and look something like a bread
> slicer. Probably not, but ya' never know. "Radio Bart does it again!
> Rare fuseless double-selenium Collins designed, almost-Mish-Rippel-like
> R-390A. So reliable was this model with it's rare Cosmos PTO and special,
> high reliability hermetically sealed molded capacitors, drift-proof carbon
> comp resistors, and mercury-laced MFP coating -- it didn't need the
> protection of common glass fuses ..."
>
> (Am I getting the hang of that? Sometimes I scare myself.)
>
> My 2 cents woith.
> Barry
>
>
>>
>> ----- Original Message -----
>> From: "TChirhart" <sparks at codepoets.com>
>> To: <r-390 at mailman.qth.net>
>> Sent: Friday, March 17, 2006 9:00 PM
>> Subject: [R-390] R-390A help
>>
>>
>> This is my first R-390A project. I have an Imperial 1963 vintage R-390A
>> and the previous owner may have modified it. First of all, all 3 fuse
>> holders are either missing or have been bypassed, the AC, B+ 1/8 amp and
>> B+ ¼ amp have been bypassed with F-102 B+ ¼ amp fuse holder missing..
>>
>> F-102 B+ ¼ amp fuse socket, near power supply is missing and two wires
>> soldered together.
>> F-101 AC 3 amp fuse has been bypassed, fuse socket broken
>> F-103 B+ 1/8 amp, fuse bypassed inside.
>>
>> In the power supply, the 2x 26Z5's are missing, the metal tube sockets
>> crimped and a selenium rectifier installed over the sockets and the
>> F-102 fuse holder is missing, apparently this is a modification.
>> But why would you bypass the AC and 1/8 amp B+ fuse?
>>
>> Am I missing something here?
>>
>> It makes no sense to bypass all 3 fuses, especially the AC fuse socket.
>> The fuse holders are damaged, but can easily be replaced. I would hope
>> that the previous owner had enough sense to replace a simple fuse
>> holder...but...
>>
>> I've pulled out all the tubes and found over half of them bad or very
>> weak.
>>
>> This is my first time going into an R-390A so I'll need some advice from
>> you experts.
>>
>> Also does anyone have the top and bottom covers for an R-390A?
>> Thanks in advance
>> 73
>> Tom K4NCG
>>
>>
>>
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>
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