[R-390] Trouble shooting the R390A

[Barry]

I had a similar thing happen.  After the fuse blew, I hooked up an ampmeter
across the fuse and monitored the current, making sure it didn't exceed
125mA while bringing the radio up with a variac.  Oddly, the current never
went much over 80 or 90mA.  I replaced the fuse and it has worked okay ever
since.

I suspected one or both of the filter caps may have been drawing excess
current, but if I remember the circuit correctly, the 1/8A fuse comes
"after" the caps so I don't know what was causing the current draw.  Maybe
the fuse was old?  Don't know.

Did the radio work before you worked on the front panel?

Barry - N4BUQ

----- Original Message -----
From: "Jon" <jonklinkhamer at comcast.net>
To: <R-390 at mailman.qth.net>
Sent: Tuesday, August 23, 2005 8:05 PM
Subject: [R-390] Trouble shooting the R390A


> To the Group:
>
> I have been going thru the IF and audio stage with respect to recapping,
> taking resistance measurements, checking tubes, cleaning, etc, being very
> careful and taking notes along the way. I recently just received the front
> panel back from painting it and I decided before I continue to go thru the
> RF, xtal and PTO stages, I wanted to put it all back together and make
sure
> I didn't break anything. (I really wanted to see how the panel looked.)
> Well, as of tonight, I fired it up and noticed right away no audio.
> Immediately, I played around going from 1 to 20Mhz and I also switched in
> the CAL but noticed again no audio. The lamps however lite up.  I turned
the
> receiver off and checked the fuses and notice the 1/8 fuse has blown. My
> thinking is to first see if it blows again and if so then take out both
the
> Audio and IF stage and power cycle again. I'm hoping to isolate it to one
of
> these stages with the assumption I mess something up. I'm just shooting
this
> out to see if the group has another preferred way of debugging or knows
the
> cause(s) when this particular fuse blows.
> I would like to thank everyone in advance for their comments. I am as
always
> much indebted.
>
> 73's,
> Jon, KB1DC
>
>
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