K2/100 and Condensation

[Bill Coleman-2]

K2/100 #2548 made another trip to field day this year, at the N4N  
field day site.

Ran into the same problem as last year. K2 was working the night  
before, then in the morning I got INFO 080 upon switching it on. The  
KAT100 wasn't recognized, either.

After leaving it switched on for about a half an hour, it returned to  
normal operation.

The problem appears to be internal condensation building up in the  
K2. Is anyone else encountering this problem? What can be done about it?

Bill Coleman, AA4LR, PP-ASEL        Mail: [hidden email]
Quote: "Not within a thousand years will man ever fly!"
             -- Wilbur Wright, 1901

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[n5ib]

On Tue, 4 Jul 2006 10:05:47 -0400 Bill Coleman <[hidden email]> writes:
>The problem appears to be internal condensation building up in the  
>K2. Is anyone else encountering this problem? What can be done about
>it?


Moisture can only condense on a surface if the surface temperature is at
or below the dew point, and the dew point will be below (rarely, at) the
ambient air temperature.

So all you have to do to prevent condensation is to keep the surface ever
so slightly warmer than the ambient  air (glasses fog up when you get out
of the shower and put them on??    run hot water over them, they'll stay
clear as long as they're warmer than the bathroom air...)

In the case of radios the easiest fix, if you have the electricity to
spare in the field, is just leave the rig on. Even the QRP K2 consumes
and dissipates as heat a couple of watts (200 mA at 12 V = 2400 mW) in Rx
which should be enough to keep internals dry. Alternatively, put a couple
of those chemical hand warmers on the top cover (NOT inside the radio).
I'd put a sheet of plastic wrap or something between the rig and the
packs, because there is an oxidation reaction going on and perhaps
undesirable reaction products present. DON'T put the packs in a closed
zip-lock bag though, they need a supply of oxygen to work.

You could tuck a couple of those silica gel desiccant bags (like those
packed with cameras, etc) inside the case. That will help to lower the
dew point of the air trapped in the case. I'd take them out right after
use though.  My K2 is a temple, and I don't put no junk in the temple.
:^))

73
Jim N5IB
K2 #1233

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[Oscar F Hills]

Well, thanks to great forbearance on my wife's part over this little  
holiday vacation, K2 #5630 is coming right along. I finished up Part  
1, and all the tests are just fine _except_ that I have no backlight.  
The LCD reads fine, but there's no change in it or in the LED  
brightness when I switch between night and day. I haven't tied it in  
a darkened room, but I am assuming I should be able to tell whether  
the backlight is on even in normal room light.

At first I had the terrible fear that I should have taken the white  
film off the diffuser, but an archive search told me I was right to  
leave it there. But now I don't know why I don't have the back light.

Any advice on the most efficient way to troubleshoot this?

Thanks!

Oscar WV1C

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[Don Wilhelm-3]

Oscar,

If you want to troubleshoot it, look at the schematic and follow the path
for the voltages applied to D2 and D3 with your DMM, you can approximate 1.5
to 2 volts drop through each LED if it is conducting.

The most likely thing is that you have failed to solder a connection, check
R9, R10, R11, Q1 and Q2.  Be certain Q1 and Q2 are oriented properly, and be
certain U3 pin 17 has been soldered.

73,
Don W3FPR

> -----Original Message-----
>
> Well, thanks to great forbearance on my wife's part over this little
> holiday vacation, K2 #5630 is coming right along. I finished up Part
> 1, and all the tests are just fine _except_ that I have no backlight.
> The LCD reads fine, but there's no change in it or in the LED
> brightness when I switch between night and day. I haven't tied it in
> a darkened room, but I am assuming I should be able to tell whether
> the backlight is on even in normal room light.
>
> At first I had the terrible fear that I should have taken the white
> film off the diffuser, but an archive search told me I was right to
> leave it there. But now I don't know why I don't have the back light.
>
> Any advice on the most efficient way to troubleshoot this?
>
> Thanks!
>
> Oscar WV1C
>

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[Oscar F Hills]

Thanks very much to Don W3FPR and Jim W4ATK who pointed me on the  
right path, and now all is well with the backlight. A few minutes  
with my DMM isolated a cold joint on pin 17 of U3. It looked okay to  
the eye, but I guess it was the result of trying to solder quickly  
with minimum solder to protect U3!  Thanks again, guys! And, I  
learned a little more about schematics and troubleshooting too. I  
really appreciate it.
73,
Oscar WV1C

>> -----Original Message-----
>>
>> Well, thanks to great forbearance on my wife's part over this little
>> holiday vacation, K2 #5630 is coming right along. I finished up Part
>> 1, and all the tests are just fine _except_ that I have no backlight.
>> The LCD reads fine, but there's no change in it or in the LED
>> brightness when I switch between night and day. I haven't tied it in
>> a darkened room, but I am assuming I should be able to tell whether
>> the backlight is on even in normal room light.
>>
>> At first I had the terrible fear that I should have taken the white
>> film off the diffuser, but an archive search told me I was right to
>> leave it there. But now I don't know why I don't have the back light.
>>
>> Any advice on the most efficient way to troubleshoot this?
>>
>> Thanks!
>>
>> Oscar WV1C
>>
>

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