K2 thermistor board check

[lstavenhagen]

Hi all,
Is there a procedure where I could check the K2 thermistor board for proper operation once soldered in? I just passed that step in my second K2 build, and I'm uncertain about one of the pins - it rocked out of place while I was soldering it to the RF board, but of course it's now soldered in. It's not just in there but it's IN THERE hi hi and I'd like to check it before tearing it up trying to pull it out of the board.

Visual inspection still shows the makeshift pin in place, but I'd just like to do some kind of measurement or continuity at the RP3 location just to be sure.

Thanks es 73,
LS
W5QD

[lstavenhagen]

PS: I've looked at the schematic but I've gone as far as putting the varactor diodes in, so I'm unsure if there's enough circuitry installed to mess up just going by the schematic for it...

Help Me, Obiwan!

Tnx es 73,
LS
W5QD

[Don Wilhelm-4]

LS,

The most common problem with the thermistor board is a solder bridge on
that board.
One quick check is the voltage at U6 pin 5 which should be 1/2 of the 8
volt supply.
Another check is to see if the voltage at U6 pin 1 is twice the voltage
at pin 3.  Those voltages will change as the VFO is changed over a 10kHz
range, so check with several positions of the VFO.

73,
Don W3FPR

On 4/1/2016 10:41 AM, lstavenhagen wrote:
> Hi all,
> Is there a procedure where I could check the K2 thermistor board for proper
> operation once soldered in? I just passed that step in my second K2 build,
> and I'm uncertain about one of the pins - it rocked out of place while I was
> soldering it to the RF board, but of course it's now soldered in. It's not
> just in there but it's IN THERE hi hi and I'd like to check it before
> tearing it up trying to pull it out of the board.
>
>

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[lstavenhagen]

Hi Don,
Ok, thanks for the info. Would a resistance check according to the schematic be reliable at this point (just finished the varactor diode installation steps)? I dont know if I want to try to power anything up in the half built state lol.

I'm pretty confident in the daughter board since I checked it over after flush cutting it, etc. One of the pins got hot enough to melt the solder on the daughter board itself while I was soldering it to the RF board (my fault for holding heat onto the pad at RP3 too long) and it rocked out of place a bit before I repositioned it.

It looks ok and I dont know if I dare try to get my soldering iron in there to try to "touch it up". So I'd just like to do a continuity check on that pin. And maybe the whole board while I'm at it?

Thanks kind sir,
LS
W5QD

[Don Wilhelm-4]

LS,

You can do a resistance check from the schematic if you are willing to
do all the series/parallel resisance calculations.

73,
Don W3FPR

On 4/1/2016 11:39 AM, lstavenhagen wrote:
> Hi Don,
> Ok, thanks for the info. Would a resistance check according to the schematic
> be reliable at this point (just finished the varactor diode installation
> steps)? I dont know if I want to try to power anything up in the half built
> state lol.
>
>

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[lstavenhagen]

Hi Don,
No problem, in fact going through those calcs would probably do me some good. Part of why I'm building K2 #2 is to learn something along the way. Especially when I have a problem or question I stop building and start reading, and am having a great time lol. All kinds of things I didn't pay attention to during K2 #1 a few years ago.

It occurred to me also that I could just do a continuity check with my DMM directly at the board, from the pin I'm worried about (pin #6) to some point at the board also. I'll get out the calculator!

You all are why I only do Elecraft rigs now!

thanks kind sir,
LS
W5QD