K2: Control Board Strangeness

[Tim Cailloux]

My Christmas project of the K2 build got started early (s/n 4539).

Here are the two problems I have right now:

* Display LCD (i.e. text readout) is very dim.  It's almost impossible
to read with the backlight off.  Everything displays as normal, but
just very dim text.  (The LED backlight comes right on and is great.)

* When adjusting the pot on the control board (R1) for 3.80V per the
alignment procedure during the checkout of the control board and
display board, the most I can get is 3.6V.

The measured and reported supply voltage is 14.7-14.8V and the current
draw varies between 80 and 100 mA.

Yes, I've checked the solder joints.  First item I looked at.  I was
using a pretty bad DMM (since I started the build much sooner than I
planned, I didn't have everything with me) but I *think* the
resistance checks were all normal (I'm stealing a better DMM from work
this weekend).

Thanks in advance,

tim

--
Tim Cailloux
[hidden email]
W4EGT
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[Mike, W8ENG]

Tim,  I had a similar problem with my K2.  I was not able to get the full
3.8 volts with the pot cranked all the way over.  Search 'Low AGC threshold"
on the e-mail list archive for more info.

I was getting full brightness on the LCD display.  I'm certinally no expert,
but sound like yuo may have a bad connection somewhere.   When you bet the
better DVM, check the input voltage to the 8v regulator.  It should be same
as the voltage at your power supply.

Good luck, and 73,

Mike, W8ENG



----- Original Message -----
From: "Tim Cailloux" <[hidden email]>
To: <[hidden email]>
Sent: Monday, November 29, 2004 10:28 AM
Subject: [Elecraft] K2: Control Board Strangeness

> My Christmas project of the K2 build got started early (s/n 4539).
>
> Here are the two problems I have right now:
>
> * Display LCD (i.e. text readout) is very dim.  It's almost impossible
> to read with the backlight off.  Everything displays as normal, but
> just very dim text.  (The LED backlight comes right on and is great.)
>
> * When adjusting the pot on the control board (R1) for 3.80V per the
> alignment procedure during the checkout of the control board and
> display board, the most I can get is 3.6V.
>
> The measured and reported supply voltage is 14.7-14.8V and the current
> draw varies between 80 and 100 mA.
>
> Yes, I've checked the solder joints.  First item I looked at.  I was
> using a pretty bad DMM (since I started the build much sooner than I
> planned, I didn't have everything with me) but I *think* the
> resistance checks were all normal (I'm stealing a better DMM from work
> this weekend).
>
> Thanks in advance,
>
> tim
>
> --
> Tim Cailloux
> [hidden email]
> W4EGT
> _______________________________________________
> Elecraft mailing list
> Post to: [hidden email]
> You must be a subscriber to post to the list.
> Subscriber Info (Addr. Change, sub, unsub etc.):

http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/subscribers.htm
> Elecraft web page: http://www.elecraft.com
>

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