[Elecraft] RE: Help, I think I've killed my K1

[Morrow, Michael A.]

> Good news for Mike if it is the regulator.

Hi Stuart.  That was John/N6JW who had the problem.  The quoted message you
saw with my name at the top was quoting part of John's inquiry and my
response to it.

> Might see if there is room to bypass the input of the regulator
> with a disc cap of say 0.01 for RF protection.  Just place it
> voltage bus to ground, flat on the back of the board or where
> convenient.

The front panel PCB 6 volt regulator FP-U4, the likely failed component in
John's case, has FP-C4 and FP-C5 as RF bypass caps on the output.  Its 12V
input side has a bypass cap, **BUT** it is located on the RF PCB (RF-C34).  

Perhaps a cap similar to RF-C34 installed on the front panel PCB would be
more effective for RF bypass of the input to FP-U4.  The assumption here is
that, in the presence of a strong RF field, the front panel metal may not be
at RF ground potential with respect to the rest of the K1 case and
circuitry.  I was not satisfied with the possibility of my K1's front panel
metal "RF floating" with respect to the remainder of the K1 case.  There was
quite a lot of paint covering the points where it joined the rest of the
case.  Therefore, I used a Dremel tool steel brush to remove the paint from
the inside of the case metalwork at *all* points, on all pieces of the K1
case, where there is a fastener to hold that piece to some other case part.
This made several bare metal patches on each piece in addition to the
several that were originally provided inside the K1 case.

The only K1 regulator which seems not to have an input RF bypass cap is the
input to the VFO 6V regulator RF-U6, which is the output of 8V regulator
RF-U5.  I suspect adding a bypass cap there wouldn't hurt, but I doubt that
had anything to do with John's K1 problem.

So how about it, John/N6JW?  Have you located the problem yet?  Inquiring
minds want to know.

73,
Mike / KK5F