Resistance Checks During Front Panel Assembly

[Michael Cook-2]

Hi all. I just got my K2 in the mail this morning (hooray!) and I've  
been busily assembling. I did the control board and all checked out  
there. Now I've soldered most all of the front panel and I got to the  
resistance checks and ran into a problem.

Now when doing the resistance checks so far, when the manual says a  
range, things have been in that range. When the manual says ">50k" or  
">1M", things have been fine. My meter reads something (usually about  
4-6M). So I went through the resistance tests three times but I'm  
running into problems.

The first 40 test points (the pins on the LCD driver IC, U1) worked  
fine. Everything was as expected.

Then I got to the 20 tests on J1. The first 7 pins of J1 (measured at  
the solder point) are all "OL" which is my meters way of telling me  
that the probes aren't connected. In other words, infinite resistance.

Most of the rest of J1 works. Pin 8 measures zero, pin 10 measures  
4.4M (should be >50k), pin 12 and 14 both work (6.6M), and everything  
15 and above checks out too.

Pins 1-7, 9, and 11 all register as unconnected. I've even tried  
measuring from other pads that are connected by traces (for example,  
some of those connect to where the shaft encoder will go) but they  
still register unconnected.

Everything looks soldered well, I see no bridges, etc. I've build  
tons of kits, I'm quite confident in my skills. I just need to know  
what to check.

-- Michael Cook
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[Vin Cortina]

Michael,

OL may also mean "out of range".  Take the auto ranging off your DMM.  OL
may just mean resistance is higher than current range allows, or something.

Vin Cortina  KR2F

K1-4 s/n:1977
KX1  s/n:1476


-----Original Message-----
From: [hidden email]
[mailto:[hidden email]]On Behalf Of Michael Cook
Sent: Thursday, July 13, 2006 9:22 PM
To: [hidden email]
Subject: [Elecraft] Resistance Checks During Front Panel Assembly


Hi all. I just got my K2 in the mail this morning (hooray!) and I've
been busily assembling. I did the control board and all checked out
there. Now I've soldered most all of the front panel and I got to the
resistance checks and ran into a problem.

Now when doing the resistance checks so far, when the manual says a
range, things have been in that range. When the manual says ">50k" or
">1M", things have been fine. My meter reads something (usually about
4-6M). So I went through the resistance tests three times but I'm
running into problems.

The first 40 test points (the pins on the LCD driver IC, U1) worked
fine. Everything was as expected.

Then I got to the 20 tests on J1. The first 7 pins of J1 (measured at
the solder point) are all "OL" which is my meters way of telling me
that the probes aren't connected. In other words, infinite resistance.

Most of the rest of J1 works. Pin 8 measures zero, pin 10 measures
4.4M (should be >50k), pin 12 and 14 both work (6.6M), and everything
15 and above checks out too.

Pins 1-7, 9, and 11 all register as unconnected. I've even tried
measuring from other pads that are connected by traces (for example,
some of those connect to where the shaft encoder will go) but they
still register unconnected.

Everything looks soldered well, I see no bridges, etc. I've build
tons of kits, I'm quite confident in my skills. I just need to know
what to check.

-- Michael Cook
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[Michael Cook-2]

> OL may also mean "out of range".  Take the auto ranging off your  
> DMM.  OL
> may just mean resistance is higher than current range allows, or  
> something.
>
> Vin Cortina  KR2F

I just tried that, as well as my other DMM, and the same thing is  
still happening. For what it's worth, I think the guts of my second  
meter (sold by Radio Shack) are actually made by the same company as  
my first meter (Metex Instruments).

I tried both auto ranging (as I keep the meter on) and the highest  
range (dual digit mega-ohm, so it could show 37.5 M for example).

I have installed the parts on the board that you install for the  
KSB2, for what it's worth. I don't think that would change anything,  
but there you go.

There is a tiny chance I have an old analog meter somewhere, I'll  
hunt for it tomorrow.
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[Michael Cook-2]

On Jul 13, 2006, at 8:36 PM, W6NEK wrote:

> Hi Michael,
> I get the same type "Open Circuit" resistance readings as you and  
> my K2's worked just fine.  All it means is the series resistance  
> between J1 Pins 1 - 7 is greater then 10 megs to ground which my  
> DMM reads as Open Circuit.  If I were you, I would proceed with the  
> build.  I think all is fine with your build so far.
>
> 73,
> Frank - W6NEK
> PS - I have built 11 K2's so far and they all acted the same as far  
> as high resistance readings are concerned.

Thanks, that is kind of what I was thinking. I saw the note that >50k  
can read as open, but it threw me for a loop because up to that point  
everything that said >50k had read something, but all of a sudden  
some of the pins weren't doing that.
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[Ron D'Eau Claire-2]

WATCH OUT, WATCH OUT! Do NOT dig out that old analog meter unless you KNOW
it's designed for modern solid state gear. Making a single measurement with
it can fry more I.C.s, diodes and transistors than you may care to count!

Older meters put way too much voltage on the circuit and allowed way to much
current to pass for modern devices.

Open circuit is > 50 K, or whatever so your find with any such readings.

Ron AC7AC

-----Original Message-----
From: [hidden email]
[mailto:[hidden email]] On Behalf Of Michael Cook
Sent: Thursday, July 13, 2006 7:24 PM
To: [hidden email]
Subject: RE: [Elecraft] Resistance Checks During Front Panel Assembly


> OL may also mean "out of range".  Take the auto ranging off your
> DMM.  OL
> may just mean resistance is higher than current range allows, or  
> something.
>
> Vin Cortina  KR2F

I just tried that, as well as my other DMM, and the same thing is  
still happening. For what it's worth, I think the guts of my second  
meter (sold by Radio Shack) are actually made by the same company as  
my first meter (Metex Instruments).

I tried both auto ranging (as I keep the meter on) and the highest  
range (dual digit mega-ohm, so it could show 37.5 M for example).

I have installed the parts on the board that you install for the  
KSB2, for what it's worth. I don't think that would change anything,  
but there you go.

There is a tiny chance I have an old analog meter somewhere, I'll  
hunt for it tomorrow. _______________________________________________
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[Don Wilhelm-3]

Michael,

A resistance reading stated as >50k can indeed be an open circuit.
Infinitity is greater than 50k.
One reason they are should not listed in the manual as open circuit is that
many meters will respond to just the resistance of your body should you make
contact with the probes.

If you follow the schematic, you will indeed find that at this point of
assembly, those points are really open circuits.  The resistance check is
mainly to find any solder bridges or other assembly errors - since your
meter reads as though they are open circuits, all is well.

There is a statement that the high resistance readings may actually indicate
infinite resistance, exactly as you have found to be true.  No need to use
another meter to check anything.

73,
Don W3FPR

> -----Original Message-----
>
> Hi all. I just got my K2 in the mail this morning (hooray!) and I've
> been busily assembling. I did the control board and all checked out
> there. Now I've soldered most all of the front panel and I got to the
> resistance checks and ran into a problem.
>
> Now when doing the resistance checks so far, when the manual says a
> range, things have been in that range. When the manual says ">50k" or
> ">1M", things have been fine. My meter reads something (usually about
> 4-6M). So I went through the resistance tests three times but I'm
> running into problems.
>
> The first 40 test points (the pins on the LCD driver IC, U1) worked
> fine. Everything was as expected.
>
> Then I got to the 20 tests on J1. The first 7 pins of J1 (measured at
> the solder point) are all "OL" which is my meters way of telling me
> that the probes aren't connected. In other words, infinite resistance.
>
> Most of the rest of J1 works. Pin 8 measures zero, pin 10 measures
> 4.4M (should be >50k), pin 12 and 14 both work (6.6M), and everything
> 15 and above checks out too.
>
> Pins 1-7, 9, and 11 all register as unconnected. I've even tried
> measuring from other pads that are connected by traces (for example,
> some of those connect to where the shaft encoder will go) but they
> still register unconnected.
>
>

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[Tom McCulloch]

 -------------- Original message ----------------------
From: "Ron D'Eau Claire" <[hidden email]>
> WATCH OUT, WATCH OUT! Do NOT dig out that old analog meter unless you KNOW
> it's designed for modern solid state gear. Making a single measurement with
> it can fry more I.C.s, diodes and transistors than you may care to count!
>
> Older meters put way too much voltage on the circuit and allowed way to much
> current to pass for modern devices.
>
Hi Ron - Well I learned something today.  Never thought about that--thanks
Tom
WB2QDG

ps - for what its worth this question about open circuits and >50k ohm resistance checks seems to comes up all of the time, I wonder why they don't mention it in the manual...just wonderin'
t
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[Nick Waterman]

[hidden email] wrote:
> ps - for what its worth this question about open circuits and >50k
> ohm resistance checks seems to comes up all of the time, I wonder why
> they don't mention it in the manual...just wonderin'

Yeah, probably at the top of page 21, just above the first resistance
checks, they should maybe say something like "your resistance reading
may be much higher or even infinite. This is typical when using a DMM
(digital multimeter)"

You could maybe add some notes about analog meters, and maybe something
like "Note: Some digital multimeters will flash their display to
indicate an infinite resistance"

What do you reckon?   ;-)

--
"Nosey" Nick Waterman, G7RZQ, K2 #5209.
use Std::Disclaimer;    [hidden email]
Keep the wind in your solar sails... -- Glenn Clapp
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[Stuart Rohre]

Most of the older meters were OK on the X100 Resistance scales.   Two things
you watch out for, a few VOMs used a higher voltage on some Resistance
scales, and some used high current on low Resistance scales.  Spend a little
time with the schematic for your test equipment, and you will be OK.

Stuart
K5kVH


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