[R-390] F102 FUSE BLOWING

[Walter Wilson]

In addition, there is an excellent section in the TM 11-856A, p. 102,
section 90, regarding how to check for B+ shorts.  Unplug the AC power cord
from the outlet, set the MC knob below 8MC, remove rectifier tube XV801, and
connect an ohmmeter between pin 3 (or 8) and ground.  You should have
greater than 15000 ohms.  Check with the BFO switch both on and off, and
with the function switch in all power-on positions.  If the reading is below
15000 ohms, remove the power connectors from the decks in the following
order:
AF deck (P199 and P120)
IF deck (P112)
RF deck (P108)
VFO (P109)
Crystal Osc deck (P110)
Power Supply (P111)

If removal causes the ohmmeter reading to suddenly jump when disconnected
(and it started below 15000 ohms), thoroughly check this deck for problems.
In the aforementioned manual, paragraph 119 gives DC resistance checks for
each subchassis.  You'll need to check tubes for shorts, and then bypass
capacitors for shorts.

If the short persists after all power connections are removed (prior to
P111), the short may exist in the chassis wiring harness (if no problem
found in the power supply subchassis).

There are further details in the manual for those cases when the B+ short
only exists intermittently or when B+ voltage is present.  I did not find a
similar troubleshooting section in the R-390A Y2K manual, but someone else
on the list may be able to find it and point to it there as well.

Walter Wilson - KK4DF
http://r-390a.us
(REAL Radios: R-390A, R-390, T-368E, Ranger, Thunderbolt, KWM-2A)

----- Original Message -----
From: "william ohlsson" <wohlsson@comcast.net>
To: <r-390@mailman.qth.net>
Sent: Sunday, December 08, 2002 8:47 PM
Subject: [R-390] F102 FUSE BLOWING


> Hi guys,
>
> Just picked up a r-390a from the estate of a silent key...I wanted one
because I loved them when I was in the navy. Figures that I would have
problems right from the start. The F102 1/4 amp fuse blows. I need some
direction on where to start and who is a good source for parts to replace
all the bad ones that your going to tell me I need. I'm not a real expert
when it comes to repairing radio's, but I'm will to give it a shot.
Especially don't really want to ship this for repair, just to have it
destroyed en route.
>
> Thanks and 73'S......Bill Ohlsson....WA8BDA
>
>
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