Resistance checks - check your meter too!

[Bill N2BC]

Just did a quick scan of the K3 assembly manual - wonder how many downloads
so far..?? !!     The following will likely apply to the K3 also - I'll find
out next year for sure.

I'm at the end of day one of assembling my second K2, just finished the
Control Board.  Used my trusty (old) auto ranging Fluke DMM to perform the
resistance checks and went down the tubes on the 8V regulator output,
measures 500 ohms - should the 3 to 4 Kohms.

To make a long story short....   be careful.  I did a simple test with the
Fluke connected across a 3K resistor - my handheld DMM says the Fluke is
applying almost 0.5V.  "Flipping" the meters, the handheld DMM only applies
about 60mV - and the 8V bus resistance check is fine measured on the
handheld DMM.

Clearly the Fluke's 1/2V is on the hairy edge of some of the active devices
on the 8V bus.  It's interesting that the lead polarity makes no difference
in the resistance measurement at all.

Now I'll carefully read the K3 assembly manual, then start the K2 front
panel.  Hmmm... I wonder.  Nah, I'll still end up with a K2.

73 all,  Bill N2BC


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[Brett gazdzinski-2]

 
I think I saved myself a lot of trouble by NOT
doing the parts inventory or any of the resistance
checks except the final output transistor short
to ground checks.

Not sure if that is smart for other folks, but I have
no patience to count parts, and I would rather trouble shoot
something that I know has a problem, rather then check stuff
that may be ok.

You can slip with a probe, get mixed readings, or introduce
damaging voltages to sensitive parts.

Maybe I was lucky in that everything worked fine, and the
kits had no missing parts.

For people with limited soldering skills, its likely a REAL
good idea to do the checks, it's a lot harder to remove
bad chips from a board then it is putting them in...

Brett
N2DTS

> -----Original Message-----
> From: [hidden email]
> [mailto:[hidden email]] On Behalf Of Bill
> Coleman N2BC
> Sent: Tuesday, September 11, 2007 8:23 AM
> To: [hidden email]
> Subject: [Elecraft] Resistance checks - check your meter too!
>
> Just did a quick scan of the K3 assembly manual - wonder how
> many downloads
> so far..?? !!     The following will likely apply to the K3
> also - I'll find
> out next year for sure.
>
> I'm at the end of day one of assembling my second K2, just
> finished the
> Control Board.  Used my trusty (old) auto ranging Fluke DMM
> to perform the
> resistance checks and went down the tubes on the 8V regulator output,
> measures 500 ohms - should the 3 to 4 Kohms.
>
> To make a long story short....   be careful.  I did a simple
> test with the
> Fluke connected across a 3K resistor - my handheld DMM says
> the Fluke is
> applying almost 0.5V.  "Flipping" the meters, the handheld
> DMM only applies
> about 60mV - and the 8V bus resistance check is fine measured on the
> handheld DMM.
>
> Clearly the Fluke's 1/2V is on the hairy edge of some of the
> active devices
> on the 8V bus.  It's interesting that the lead polarity makes
> no difference
> in the resistance measurement at all.
>
> Now I'll carefully read the K3 assembly manual, then start
> the K2 front
> panel.  Hmmm... I wonder.  Nah, I'll still end up with a K2.
>
> 73 all,  Bill N2BC
>
>
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> You must be a subscriber to post to the list.
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>
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>

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