[Elecraft] K2 Build Question

[EricJ]

It would have done the same with an analog meter, Tom. The circuit you were
probing undoubtedly contained semiconductors (ICs, transistors, diodes,
etc.), not just pure resistors. With the leads one way, the internal battery
in the DMM causes some of those semiconductor junctions to be forward biased
and some of them to be reverse biased (depending on what they are and how
they are connected). So the readings one way are different than the readings
the other way...just like when you use an ohmmeter to check a diode.

Have a great 4th. And enjoy the K2. It is a great rig.

Eric
KE6US

-----Original Message-----
From: elecraft-bounces at mailman.qth.net
[mailto:elecraft-bounces at mailman.qth.net] On Behalf Of tom.w3qs
Sent: Saturday, July 02, 2005 11:43 AM
To: 'Margaret Leber'
Cc: Elecraft at mailman.qth.net
Subject: RE: [Elecraft] K2 Build Question

Hi Maggie,

Thank you so much for responding, I was afraid everyone was out fourthing.

I seriously hoped you were wrong about checking the soldering on U1 as the
pins are hidden by the glass-thing on the front side.

But, I dutifully checked everything again and made an absolutely ghastly
discovery!!!

I can't operate a DMM!

Seriously, I wouldn't have thought it would make a difference on resistance
checking, but I guess that is not the case.

I had done the checking by probing with the common lead while the other lead
was grounded.   I reversed the connections, and now all checks are within
normal range.  Many of the other checks are different, now, but they had
been in-range before.

Well, I guess you're never too old to learn something.  This is my first
DMM, always done it with analog meters before.

Thanks and have a great fourth!

On to the rest of the adventure!

Tom, W3QS

-----Original Message-----
From: Margaret Leber [mailto:maggie at voicenet.com]
Sent: Saturday, July 02, 2005 11:51 AM
To: tom.w3qs
Cc: Elecraft at mailman.qth.net
Subject: Re: [Elecraft] K2 Build Question

tom.w3qs wrote:

> 1.  Resistance checks for U1 pins 1 & 2 are out of spec.  Chart says
> 25 - 35 K for both pins.  DMM reads 17 K for both.  Old analog meter 
> reads 8 - 9 K for both.
> 
> 2.  Resistance checks for J1 pin 15 is out of spec.  Chart says 10 - 60 K.
> Analog meter reads 80 K.
> 
> Perhaps the resistance chart does not take the added SSB stuff into
account?
> U1 pin 1 and J1 pin 15 are both associated with this added circuitry.

I did the same build you did (well, on S/N 1641 anyway)...and noted the
resistance check values after adding the KSB2 components using a Triplett
2030A DMM.

U1 pins 1 & 2 : 30Kohm
J1 pin 15: 31Kohm

So whatever the reason for what you're seeing, I don't think we can blame it
on the KSB components being present. You might want to inspect things again.
It's *very* easy to overlook soldering a pin or two on the LCD or one of the
processor chips, and have things sorta almost work anyway because the pin's
in a plated-through hole making intermittant contact. I did that more than
once.

  73 de Maggie K3XS

-- 
-----/___.   _)Margaret Stephanie Leber CCP, SCJP/"The art of progress /
----/(, /|  /| http://voicenet.com/~maggie SCWCD/ is to preserve order/
---/   / | / |  _   _   _    `  _  AOPA 925383/ amid change and to  /
--/ ) /  |/  |_(_(_(_/_(_/__(__(/_      K3XS / preserve change amid/
-/ (_/   '        .-/ .-/        ARRL 39280 /order."-A.N.Whitehead/
/________________(_/_(_/_______AMSAT 32844_/<maggie at voicenet.com>/




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