Posted by
Wiley Kling on
Jul 14, 2012; 8:25pm
URL: http://elecraft.85.s1.nabble.com/K2-RF-Board-resistance-check-failure-U6-Pin-8-tp7559095.html
I am building a recently purchased K2, serial # 7313. In the past few years
I have built 6 or 8 solid state kits, including a K1, without a hitch.
However, I am now having a problem that is really making me feel like a
"newbie".
I am on page 62 of the manual and things have gone swimmingly until now.
All of the resistance checks (RF Board) are fine except for U6 pin 8 which
is supposed to read >100 ohms. My reading is 38.3 ohms and I cannot locate
the problem. I have searched the Elecraft Reflector and many folks have
suffered the same problem. Problem is, I can't find a reference as to how
anyone resolved the issue. I have done the following things:
1. Reversed the leads on my DMM.
2. Performed the resistance checks with a second DMM. Same results.
3. Checked polarities on all devices.
4. Spent 2 full days looking for cold or bridged solder joints.
5. I have not "lifted" and checked the resistance of all resistors as I
am in the habit of testing them before installing.
6. I have checked the schematics and have given special attention to
the soldering and polarity of all "8B" components. (I locate 5 schematic
areas fed from U6 Pin 8).
7. I have checked the "Thermistor Board" to the extent I can without
removing it. It looks to be OK visually.
8. I have not applied power and looked for heat or smoke but I have
been tempted.
9. I have checked for a reversed U8 regulator.
I would appreciate any advice that anyone might offer. I would be truly
thankful. Would it be helpful for me to know what resistance others show
between U6 Pin 8 and each of the 8 pins on the "Thermistor Board"? I'm
thinking that might allow me to eliminate that board as a source of the
problem but not sure I am thinking correctly. Thanks.
73, Wiley, KG4UPO
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