Don,
You asked:
Did you have the front panel board isolated from the other boards when
you made those resistance measurements?
If not, that is sufficient reason for the low resistances.
73,
Don W3FPR
Yes, the Front Panel board was by apart from the rest of the radio when the
measurements were taken.
After further investigation, I noted that /BANK2 is shorted to ground. On a
hunch, I cut the CCW pin of R5 (the leftmost pin), thus isolating R5 from
/BANK2. Now, with R5 isolated, all of the problematic measurements taken
before are spot on. See the table below (from the K2 Owners Manual, Rev I,
page 29):
Test Point Signal Name Res. (to GND) First Meas Meas with R5
(CCW) cut
U1 pin 1 IDAT 25 - 35 k 8.84 k 29.3
k
U1 pin 2 ICLK 25 - 35 k 8.93 k 29.3
k
U1 pin 3 /SYNC 40 - 60 k 28 k 48 k
U1 pin 5 5A 15 - 40 k 4.1 k
24.4 k
U1 pin 12 2V 9 - 11 k 6 k 10
k
J1 pin 15 VPOTS 10 - 60 k 4.3 k 28 k
J1 pin 16 ICLK 25 - 35 k 8.9 k 29.3
k
J1 pin 17 IDAT 25 - 35 k 8.7 k 29.3
k
J1 pin 18 5A 15 - 40 k 4.1 k 24.4
k
I still need to find the /BANK2 short to ground. There is nothing obvious on
the board here, though.
Another odd behavior to note. Prior to cutting R5 (CCW), and with the radio
assembled and R5 set to midpoint, upon applying power, I got simply "ELE" on
the display. Then, turning R5 completely CW, the display changed to
"Elecraft". Turning R5 CCW a bit then back fully CW, I got "7100.0c". Have no
idea why this is happening.
I tested all of the /BANK2 switches (S9 - S16) and they all appear to be
working. Orientation of D4, D5, and D6 are all correct.
Would appreciate any further thoughts.
73,
Dan, K7DJK
On 11/26/2017 6:01 PM, Dan, K7DJK via Elecraft wrote:
> Now that the busyness of the Thanksgiving holiday is over, I was able to get
> back to the K2.
>
> First of all, thank you all for your help and suggestions.
>
> I first, for both the Front Panel and the Control Board, verified that all
> the proper components were \
> installed and in their proper orientation. No problems found here.
> I then went and reflowed all of the solder joints (well, all of those I could
> actually access).
>
> After reassembling the radio, I turned it on and got past the INFO 201.
> Good! Reflowing the solder \
> must have fixed something somewhere.
> Now I have the INFO 080 message.
>
> Referring to Appendix E of the K2 manual, I quickly found the problem to be a
> bad solder connection on \
> U1’s (RF board) 4 MHz resonator (RF-Z5).. Easily fixed that and checked all
> other solder connections \
> of the RF board.
> Applied power. Ah, the wonderful sound of clicking relays!
>
> Looked at the display, and saw...gibberish.
>
> Decided to reset the radio again (4+5+6 then power-on).
>
> Got the INFO 201, followed quickly by ELECrAFt, followed then by 7100.00c.
>
> All tests and functions as outlined in Alignment and Test, Part 1, worked as
> expected. Happy to see \
> that!
> Something still bugs me though. After reflowing the solder connections, I
> re-measured the resistance \
> checks (per pg. 29 of the User Manual). I only list below the measurements
> in question:
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