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K2/100 Extreme high Power Out - What did I do?

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Bob Mallory

K2/100 Extreme high Power Out - What did I do?

Experimenting the other day, I had used my RS232 cable to connect a Icom
Radio to my PC. When I reconnected my K2, I forgot to disconnect the
Icom. I let smoke out of the K2!.

Everything seemed to work, PC control, receive, etc. Except on
Transmit, (with Tune button) with a dummy load I have either '0' out on
low power or 148 watts on high power, nothing in between. No modulation
out.

Before I dig in, any suggestions? I tried to search for smoked
components, but nothing obvious.
Why would the RS232 port have an impact on the Transmit circuitry.
Thanks for any suggestions as a starting point.
Bob - KD8HXT

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Don Wilhelm-4

Re: K2/100 Extreme high Power Out - What did I do?

Bob,

The first thing I want to mention is that the K2 does *NOT* have an
RS-232 port connector! You will do yourself a big favor by thinking of
that 9 pin connector by the name that is on the K2 - AUX I/O.
The connector does contain 3 RS-232 defined signals, but the rest are
internal K2 signal lines that can be damaged by connecting a standard
computer serial cable. Use only the special cable (instructions in the
KIO2 and KPA100 manuals) between the K2 and the PC.

In order for us to better understand what may have been damaged, please
tell us what type cable(s) you had connected at which points when it
failed - please include the Icom, the K2 and the PC, how the cables were
connected and what type cables were connected at all points.

It may be that the interconnections had nothing to do with the K2
failure, and you had a static discharge that damaged the wattmeter in
the KPA100 (or KAT100). Please tell us whether this is a K2/100 and
with or without the KAT100.

73,
Don W3FPR.

Bob Mallory wrote:

> Experimenting the other day, I had used my RS232 cable to connect a Icom
> Radio to my PC. When I reconnected my K2, I forgot to disconnect the
> Icom. I let smoke out of the K2!.
>
> Everything seemed to work, PC control, receive, etc. Except on
> Transmit, (with Tune button) with a dummy load I have either '0' out on
> low power or 148 watts on high power, nothing in between. No modulation
> out.
>
> Before I dig in, any suggestions? I tried to search for smoked
> components, but nothing obvious.
> Why would the RS232 port have an impact on the Transmit circuitry.
> Thanks for any suggestions as a starting point.
> Bob - KD8HXT
>
>

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Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

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Bob Mallory

Re: K2/100 Extreme high Power Out - What did I do?

Thanks Don,
Your right on target, I was thinking that it was a standard RS232
connection, that probably what got me in trouble.
I have the correctly built I/O cable for use with the K2/100 and a
KAT100 to the serial port on my PC. Has been working with HRD for quite
some time.
I recently acquired a ICOM R75 Receiver and without thinking much about
it, unplugged the K2/100 and KAT100 connectors and placed the KAT100
connector on to the R75. This was my 'thoughtless' attempt to use the
ICOM R75 with HRD. It wouldn't communicate. With no real concern to
attempt to troubleshoot, I decided to re-connect the K2/100 to the I/O
cable but inadvertently left the R75 connected to what should have been
the KAT 100 connector. Powered on the K2 and had instant smoke. Smoke
wasn't visible but you can't mistake that distinct smell. (took about 10
sec to notice)

I powered off, disconnected the R75 and tested the K2 connection to
HRD. Everything seemed to work.

I felt it necessary to pop open the K2 and take a look around the AUX
I/O port circuitry and everything 'appeared' ok. Not until I later
attempted to Transmit, did I notice a problem. Yes, I could have
injected a problem when I removed the cover of the K2.

I built the K2/100 and the KAT100 about one year ago and the build went
flawlessly. Now I think my momentary lapse of common sense has caused
some problems.

The Tuner will tune the separate bands to give an appropriate SWR but my
Watt meter (LP-100A) is showing 147 watts when using the 'Tune' button.
It normally only shows approx 17 watts.

I plugged in the Elecraft Dummy load (20 watt) and the Elecraft W1 Power
meter and a QRP 'Tune' shows NO Power out. Turn the Power Dial up to
activate the KPA100 and the Wattage immediately jumps to 140+ on the W1
watt meter. Obviously the 20Watt Dummy Load is not happy with that :)
Bob KD8HXT

Don Wilhelm wrote:

> Bob,
>
> The first thing I want to mention is that the K2 does *NOT* have an
> RS-232 port connector! You will do yourself a big favor by thinking
> of that 9 pin connector by the name that is on the K2 - AUX I/O.
> The connector does contain 3 RS-232 defined signals, but the rest are
> internal K2 signal lines that can be damaged by connecting a standard
> computer serial cable. Use only the special cable (instructions in
> the KIO2 and KPA100 manuals) between the K2 and the PC.
>
> In order for us to better understand what may have been damaged,
> please tell us what type cable(s) you had connected at which points
> when it failed - please include the Icom, the K2 and the PC, how the
> cables were connected and what type cables were connected at all points.
>
> It may be that the interconnections had nothing to do with the K2
> failure, and you had a static discharge that damaged the wattmeter in
> the KPA100 (or KAT100). Please tell us whether this is a K2/100 and
> with or without the KAT100.
>
> 73,
> Don W3FPR.
>
> Bob Mallory wrote:
>> Experimenting the other day, I had used my RS232 cable to connect a
>> Icom Radio to my PC. When I reconnected my K2, I forgot to
>> disconnect the Icom. I let smoke out of the K2!.
>>
>> Everything seemed to work, PC control, receive, etc. Except on
>> Transmit, (with Tune button) with a dummy load I have either '0' out
>> on low power or 148 watts on high power, nothing in between. No
>> modulation out.
>>
>> Before I dig in, any suggestions? I tried to search for smoked
>> components, but nothing obvious.
>> Why would the RS232 port have an impact on the Transmit circuitry.
>> Thanks for any suggestions as a starting point.
>> Bob - KD8HXT
>>
>
>

Don Wilhelm-4

Re: K2/100 Extreme high Power Out - What did I do?

Bob,

Thanks for answering the configuration/cable questions - that helps a lot.

Since the KAT100 was not connected at the time of the 'incident', it is
probably just fine. That is a good assumption for the time being, but
should be checked out later.

The reason the ICOM R75 would not connect with the cable plugging you
had is that the cable to the KAT100 does not have the 3 RS-232 signals
(RXD, TXD and Signal GND) installed on that part of the cable.

It is probable that the ICOM R75 has a 'loopback' connection between the
normal RTS and CTS signals (pins 7 and 8), so when you left the cable
(which is normally connected to the KAT100) attached to the ICOM R75,
and powered the K2/100 the internal 12CTRL line would have applied 12
volts to the VRFDET signal.
I highly suspect that you zapped U6 in the KPA100 by applying 12 volts
to its output pin. You can verify that by looking at the KPA100
schematic and mentally connecting J8 pins 7 and 8.

However - it is unusual for the condition that when VRFDET is not
functioning, to have max power out of the KPA100 (120 watts or more)
*and also* to have no power output when the power is set to less than 10
watts - normally you would have 120 watts or more if the power control
was above 10 watts and 12 to 15 watts if the power control is less than
10 watts.

As a result, I will ask you to physically remove the KPA100 from the
base K2 and test the power control on the base K2 alone. If the power
control is normal (can control between very low power and 12 to 15
watts), then the base K2 is probably unharmed and the problem is most
likely U6 of the KPA100. OTOH, if the base K2 power control is not
normal, the 'incident' created two failures and we need to tackle them
one at a time (base K2 first).

My guesses can be wrong, but try the tests that I inferred as first
order of business and let me know the results. If the troubleshooting
get too intense, we will take it off the reflector and you can report
the final results to the reflector after the problem has been solved.

73,
Don W3FPR

Bob Mallory wrote:

> Thanks Don,
> Your right on target, I was thinking that it was a standard RS232
> connection, that probably what got me in trouble.
> I have the correctly built I/O cable for use with the K2/100 and a
> KAT100 to the serial port on my PC. Has been working with HRD for quite
> some time.
> I recently acquired a ICOM R75 Receiver and without thinking much about
> it, unplugged the K2/100 and KAT100 connectors and placed the KAT100
> connector on to the R75. This was my 'thoughtless' attempt to use the
> ICOM R75 with HRD. It wouldn't communicate. With no real concern to
> attempt to troubleshoot, I decided to re-connect the K2/100 to the I/O
> cable but inadvertently left the R75 connected to what should have been
> the KAT 100 connector. Powered on the K2 and had instant smoke. Smoke
> wasn't visible but you can't mistake that distinct smell. (took about 10
> sec to notice)
>
> I powered off, disconnected the R75 and tested the K2 connection to
> HRD. Everything seemed to work.
>
> I felt it necessary to pop open the K2 and take a look around the AUX
> I/O port circuitry and everything 'appeared' ok. Not until I later
> attempted to Transmit, did I notice a problem. Yes, I could have
> injected a problem when I removed the cover of the K2.
>
> I built the K2/100 and the KAT100 about one year ago and the build went
> flawlessly. Now I think my momentary lapse of common sense has caused
> some problems.
>
> The Tuner will tune the separate bands to give an appropriate SWR but my
> Watt meter (LP-100A) is showing 147 watts when using the 'Tune' button.
> It normally only shows approx 17 watts.
>
> I plugged in the Elecraft Dummy load (20 watt) and the Elecraft W1 Power
> meter and a QRP 'Tune' shows NO Power out. Turn the Power Dial up to
> activate the KPA100 and the Wattage immediately jumps to 140+ on the W1
> watt meter. Obviously the 20Watt Dummy Load is not happy with that :)
> Bob KD8HXT
>
>