[Elecraft] K2 Was Fine Now Dead - getting interestring?

[Allan Bacon]

Don,
Thanks for your help. When I checked for continuity between the cathode of
D10 and the anode of D9 it came up negative - problem.

So I temporarily jumped the cathode of D10 and the anode of D9 and the rig
powered up correctly.

Then I took the heat sink off and I see trouble, not sure if these are the
right words, but it is what I see.

The board between D9 via R-14, R-13, FRC-11 almost to R7 is delaminated, no
green material, just copper and there is evidence of charring.

Allan Bacon
W6GBG


-----Original Message-----
From: Don Wilhelm [mailto:w3fpr at earthlink.net] 
Sent: Friday, May 25, 2007 10:40 AM
To: Allan Bacon
Cc: w3fpr at arrl.net; Elecraft at mailman.qth.net
Subject: Re: [Elecraft] K2 Was Fine Now Dead?

Alan,

You are reading the schematic correctly - yes there should be a 
connection between the cathode of D10 and the anode of D9 (check to be 
certain they are connected with an ohmmeter first).

If you find the path open, you could install a TEMPORARY jumper between 
D10 cathode and D9 anode on top of the board to see if everything comes 
back to life.  If that restores full function, then remove the board to 
find the damaged PC board trace or (more likely) the bad solder connection.

Nothing in your measurements indicate a bad diode to me.  A diode 
conducts positive voltage from the anode to the cathode (hint: follow 
the arrowhead on the diode symbol), but blocks a positive voltage in the 
opposite direction.

73,
Don W3FPR

Allan Bacon wrote:
> I started tracing 13.8 V from the power source 
> 
> Input 13.8 V
> 
> Diode D10 Cathode 13.8 V Anode 0 to ground as per specifications 
> 
> Diode D9 Anode 0 V Cathode 0 V
> 
> So, it seems power is not getting to the D9 Diode
> 
>>From the schematic on page 64, it looks as those are the only components
on
> the trace from power injection to the KPA-100 to the "Aux 12V" at J4
> 
> Here is where my lack of knowledge shows up - 
> 
> 1. Since voltage is not present on either side of the diode, should I pull
> the heat sink and check the trace on the board?
> 
> 2. Or - Does a bad (not even sure what that means) diode prevent voltage
> from showing up?
> 
> 3. Or - What