[AMRadio] R-390A Help

rbethman rbethman at comcast.net
Tue Jul 8 07:35:09 EDT 2014


There is one particular power chain failure that has become rather common.

Download the Y2K3 manual, and check the selenium rectifier right by the 
power transformer.  (The link escapes my mind at the moment - due to a 
shortage of coffee at this time of the morning.)

They smell like crap when they go.  They should be replaced by a diode 
and dropping resistor.

They tend to let out the magic smoke, stink up the place, and do damage.

Join the R-390 qth.net group.  You'll get a lot of detailed help, and 
the friendly group will assist you in tracking down the problem.

Bob - N0DGN

On 7/7/2014 6:45 PM, Bill Guyger via AMRadio wrote:
> Hi All
> I acquired a 390A over the weekend from a friend who can no longer see to work on his gear. He made me promise to not sell it or trade it while he was still alive which I wouldn't do anyway out of respect to a genuine gentleman, a fine ham and one hell of a builder of radio related gear. Returning it to the air is my way of honoring a long time friend.
> The last time he fired it up the line fuse blew preceded by a sound like one might experience after too much Mexican food and a wisp of smoke. He suggested something in the power supply which seems pretty basic other than Collins' use of 26Z5's for rectifiers. There's not much else there except for chokes and a couple of caps which date from the 1960's.
> I haven't had time to really dig into the unit, and those old caps seem a logical place to start in addition to suspecting one of the rectifiers. Hopefully lightning etc. didn't get into the radio and fry something when he wasn't looking.
> My question to some of you R-390 gurus out there is. Is there a history of Power Supply issues and does anyone know of a source of 26Z5's. Or....if it's not heresy could I replace them with Silicon rectifiers after doing something about the additional B+ that will create? Not sure I want to pillage a great radio by doing that anyway if I can find the correct tubes but it's a consideration.
> Many thanks and 73 Bill AD5OL

More information about the AMRadio mailing list

This page last updated 22 Jan 2018.