[Premium-Rx] Racal RA6778C - Product Safety Advisory (Oh MY!!!)

[Steve Stutman]

Hi All,

Follow on question:

Any suggestions as to an AC "power strip" which has a switch/outlet?

Mains power switches made of unobtainium are not unique to 6778.

73,
Steve


Ben Dover wrote:

> Greetings, Group.
> 
> I had a rather odd incident occur this week that I think I
> should pass along to other owners of this rig. It COULD 
> possibly be an operator safety or fire hazard issue.
> 
> I was taking the rig out of it's usual shack location to haul
> it on a trip to visit another Premium Receiver fan. While it
> was sitting on the floor, I decided I wanted to check what I
> had programmed into the memories, and plugged it back in.
> 
> When I flipped the AC power switch, the shack's receiver
> isolation transformer gave an alarming grunt from overloading,
> and I saw the Premium Receiver Nut's Worst Nightmare; a BIG
> puff of smoke rolled out of the back of the radio, and the 
> isolation transformer's breaker tripped.
> 
> Quick investigation showed the radio's fuse to be OK, and the
> proper rating. An ohmmeter across the plug showed open in both
> AC switch positions.
> 
> Pop the dust covers and dig in deeper... The AC power switch is
> DPDT, and it showed a DEAD SHORT across the AC line in both
> positions!
> 
> Grabbed a screwdriver to pull the rear panel & allow removal of 
> the power supply module, and there was the source of the smoke;
> on each lead of the incoming AC line there are ferrite RF chokes
> and bypass capacitors. The plastic heat shrink tubing of one of
> the chokes was melted. Removing the choke & doing an ohmmeter
> check showed it was open; the choke had done a splendid job of
> sacrificing itself to protect the fuse!  ;o)
> 
> Quick, temporary repair was a simple matter; strip off the burned
> winding, clean the ferrite core, and put on a new winding... but
> the AC switch, the source of the problem, is a different matter.
> 
> 
> I've long been of the opinion that the RA6778C is a receiver that
> is designed to be turned on and LEFT on 24/7 for weeks or months 
> at a time. The AC switch is an oddball unit, made to fit the small 
> space available on the front panel. It is QUITE flimsy; essentially 
> a Rat Shack type mini toggle switch fitted with a large switch's 
> mounting bushing and bat handle.
> 
> As hams and SWLs we use the radio differently than the original
> owners; we turn them on and off a LOT, while the original users 
> might power them down once every 6 months or so. The switch is
> good enough for occasional useage, but daily? NO WAY!
> 
> Dissecting the switch it looks like the internal sliding contact 
> somehow rotated 90 degrees and wound up shorting out the AC line.
> 
> For the moment, the switch leads have been soldered together and
> covered with heat shrink tubing, and the rig is running fine.
> However, finding a more robust switch that will fit into the space
> provided is going to be a challenge. In the meantime until a
> solution to the problem shows up the receiver AC power is being
> controlled by the switch on an AC outlet strip.
> 
> Just thought I should pass this one along.
> 
> 
> 73's,
> 
> Tom, W9LBB
> 
> 
> 
> 
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