KPA100 oscillation during IARU Reg 1 Field Day

[Jukka Tarvainen]

Hello!

Sunday afternoon my KPA100 started oscillating, I believe. It happened just
when heavy rainshower hit our site. I was using a Spiderbeam on 20 meters
and running small CW pileup with 100 watts. Rig was performing well for 18
hours on various bands and it was running quite hot. I put fan running high
continuously in the beginning of contest.

When this happened I disconnected power supply. K2 seem to work normally
when KPA100 is not active. When KPA comes on it shows "Hi refl" immediately
when transmitting and draws 20-30 amps from 30 amp power supply. Power
supply starts to limit and cuts power.

There was some smoke smell coming from K2. Can't see any blown away parts.
Couple of 2 and 3 watts resistors have been warm, they are bit brownish. Any
ideas what and where to start looking for? I built my K2 and options, but
I'm technically challenged :)

Jukka Tarvainen, OH4MFA
K2/100 #4293
[hidden email]
http://personal.inet.fi/koti/oh4mfa


_______________________________________________
Elecraft mailing list
Post to: [hidden email]
You must be a subscriber to post to the list.
Subscriber Info (Addr. Change, sub, unsub etc.):
 http://mailman.qth.net/mailman/listinfo/elecraft   

Help: http://mailman.qth.net/subscribers.htm
Elecraft web page: http://www.elecraft.com

[NR5A]

Has anyone used there T-1 on 6m?  I just tried mine and it does nothing.
Using a PAR-50 antenna.

Ok has anyone had problems with it not working on certain bands?? I did
yesterday, use to I could get it to tune my 20m hamstick on the car on 30,
and 17. Yesterday it did nothing. I used it mobile on 30m and 17m last
winter and it worked fine.

I just tried it in the house with my vertical and it would only tune on 20m,
nada on the other bands. Any ideas on whats going on?

 K2 gives me a hi cur message on somedays, and works just fine on other
days.  I give up. hi  Problems problems

Jerry _-NR5A _ South Dakota

_______________________________________________
Elecraft mailing list
Post to: [hidden email]
You must be a subscriber to post to the list.
Subscriber Info (Addr. Change, sub, unsub etc.):
 http://mailman.qth.net/mailman/listinfo/elecraft   

Help: http://mailman.qth.net/subscribers.htm
Elecraft web page: http://www.elecraft.com

[Stephen W. Kercel]

Fellow Elecrafters:

I've had my K2 for only a short while, and I find that Jukka rises a
point that I've been wondering about. Can the K2 transmit at 100
Watts (into low SWR) CW (say 20-30 wpm) in a continuous session for
tens of hours on end without damage?

I usually use my rig in QRP mode, and only occasionally go to 100 W.
It always bothers me when the fan comes on even though I realize that
it is normal and desirable behavior. Thus far, I've only made one or
two extended "rag chew" QSOs where I've made long CW transmissions at
full power.

Consequently, I have not much feel for how the rig should work while
transmitting CW at full power for extended periods of time. (As we
see from Jukka's post, running the rig until one smells smoke is not
a good idea.) What is a reasonable operational cycle? What is the
line between acceptable operation and abuse?

Any insight from experienced K2 QRO operators would be most welcome.

73,

Steve
AA4AK




At 04:21 AM 6/5/2006, Jukka Tarvainen wrote:

>Hello!
>
>Sunday afternoon my KPA100 started oscillating, I believe. It happened just
>when heavy rainshower hit our site. I was using a Spiderbeam on 20 meters
>and running small CW pileup with 100 watts. Rig was performing well for 18
>hours on various bands and it was running quite hot. I put fan running high
>continuously in the beginning of contest.
>
>When this happened I disconnected power supply. K2 seem to work normally
>when KPA100 is not active. When KPA comes on it shows "Hi refl" immediately
>when transmitting and draws 20-30 amps from 30 amp power supply. Power
>supply starts to limit and cuts power.
>
>There was some smoke smell coming from K2. Can't see any blown away parts.
>Couple of 2 and 3 watts resistors have been warm, they are bit brownish. Any
>ideas what and where to start looking for? I built my K2 and options, but
>I'm technically challenged :)
>
>Jukka Tarvainen, OH4MFA
>K2/100 #4293
>[hidden email]
>http://personal.inet.fi/koti/oh4mfa
>
>
>_______________________________________________
>Elecraft mailing list
>Post to: [hidden email]
>You must be a subscriber to post to the list.
>Subscriber Info (Addr. Change, sub, unsub etc.):
>  http://mailman.qth.net/mailman/listinfo/elecraft
>
>Help: http://mailman.qth.net/subscribers.htm
>Elecraft web page: http://www.elecraft.com

_______________________________________________
Elecraft mailing list
Post to: [hidden email]
You must be a subscriber to post to the list.
Subscriber Info (Addr. Change, sub, unsub etc.):
 http://mailman.qth.net/mailman/listinfo/elecraft   

Help: http://mailman.qth.net/subscribers.htm
Elecraft web page: http://www.elecraft.com

[Darwin, Keith]

And a related question.  At what power level does the fan come on?  If I
wanted the fan to rarely come on, how low would I have run the
transmitter's output?  50 Watts?

I'm QRP thinking about going QRO but am not a fan of fans and their
noise.

- Keith KD1E -
- K2 5411 -

-----Original Message-----

It always bothers me when the fan comes on even though I realize that it
is normal and desirable behavior. Thus far, I've only made one or two
extended "rag chew" QSOs where I've made long CW transmissions at full
power.
_______________________________________________
Elecraft mailing list
Post to: [hidden email]
You must be a subscriber to post to the list.
Subscriber Info (Addr. Change, sub, unsub etc.):
 http://mailman.qth.net/mailman/listinfo/elecraft   

Help: http://mailman.qth.net/subscribers.htm
Elecraft web page: http://www.elecraft.com

[Chuck Gehring]

---- "Darwin wrote:
> And a related question.  At what power level does the fan come on?  
> -----Original Message-----
> It always bothers me when the fan comes on even though I realize that it
> is normal and desirable behavior.

IMHO
It  is my understanding the the Power transistors in the KPA-100 (2SC2879) are rated for 100W SSB PEP for each, and with that HUGE heat sink I would expect the KPA-100 to loaf along fine at 100 watts CW, 30 wpm for two minutes.  I have seen a few posts where folks have added additional fans.  The fan is temperature controlled it will turn on high when the heat sink temp goes above 40 degrees C and turn off two minutes after the temp goes below 37 degrees C.  For me, I like it when the fan turns on, it is letting me know that my KPA-100 is functioning as it was designed.
73 KI4DGH
Chuck G.
_______________________________________________
Elecraft mailing list
Post to: [hidden email]
You must be a subscriber to post to the list.
Subscriber Info (Addr. Change, sub, unsub etc.):
 http://mailman.qth.net/mailman/listinfo/elecraft   

Help: http://mailman.qth.net/subscribers.htm
Elecraft web page: http://www.elecraft.com

[Vic K2VCO]

Stephen W. Kercel wrote:

> I've had my K2 for only a short while, and I find that Jukka rises a
> point that I've been wondering about. Can the K2 transmit at 100 Watts
> (into low SWR) CW (say 20-30 wpm) in a continuous session for tens of
> hours on end without damage?

I've done this in various contests, and I'm sure others have also.
Several DXpeditions have used the K2 intensely.
--
73,
Vic, K2VCO
Fresno CA
http://www.qsl.net/k2vco
_______________________________________________
Elecraft mailing list
Post to: [hidden email]
You must be a subscriber to post to the list.
Subscriber Info (Addr. Change, sub, unsub etc.):
 http://mailman.qth.net/mailman/listinfo/elecraft   

Help: http://mailman.qth.net/subscribers.htm
Elecraft web page: http://www.elecraft.com

[Jukka Tarvainen]

I took closer look into K2 and KPA100. Can't find any source of smoke. Only
thing that looks like it could give some smell are the thermal pads of final
transistors. The black stuff has partly stuck or melt into heatsink. Pads
seem to be aluminium and they are clear where that "blackness" has gone
away. I will do more testing tomorrow.

73 Jukka, OH4MFA

_______________________________________________
Elecraft mailing list
Post to: [hidden email]
You must be a subscriber to post to the list.
Subscriber Info (Addr. Change, sub, unsub etc.):
 http://mailman.qth.net/mailman/listinfo/elecraft   

Help: http://mailman.qth.net/subscribers.htm
Elecraft web page: http://www.elecraft.com

[w6jd]

I  wonder if Jukka remembered to re-tighten the screws holding the transistors to the heat sink after the first 10 hour "break in" period?

Doug
W6JD

-------------- Original message --------------
From: "Stephen W. Kercel" <[hidden email]>

> Fellow Elecrafters:
>
> I've had my K2 for only a short while, and I find that Jukka rises a
> point that I've been wondering about. Can the K2 transmit at 100
> Watts (into low SWR) CW (say 20-30 wpm) in a continuous session for
> tens of hours on end without damage?
>
> I usually use my rig in QRP mode, and only occasionally go to 100 W.
> It always bothers me when the fan comes on even though I realize that
> it is normal and desirable behavior. Thus far, I've only made one or
> two extended "rag chew" QSOs where I've made long CW transmissions at
> full power.
>
> Consequently, I have not much feel for how the rig should work while
> transmitting CW at full power for extended periods of time. (As we
> see from Jukka's post, running the rig until one smells smoke is not
> a good idea.) What is a reasonable operational cycle? What is the
> line between acceptable operation and abuse?
>
> Any insight from experienced K2 QRO operators would be most welcome.
>
> 73,
>
> Steve
> AA4AK
>
>
>
>
> At 04:21 AM 6/5/2006, Jukka Tarvainen wrote:
> >Hello!
> >
> >Sunday afternoon my KPA100 started oscillating, I believe. It happened just
> >when heavy rainshower hit our site. I was using a Spiderbeam on 20 meters
> >and running small CW pileup with 100 watts. Rig was performing well for 18
> >hours on various bands and it was running quite hot. I put fan running high
> >continuously in the beginning of contest.
> >
> >When this happened I disconnected power supply. K2 seem to work normally
> >when KPA100 is not active. When KPA comes on it shows "Hi refl" immediately
> >when transmitting and draws 20-30 amps from 30 amp power supply. Power
> >supply starts to limit and cuts power.
> >
> >There was some smoke smell coming from K2. Can't see any blown away parts.
> >Couple of 2 and 3 watts resistors have been warm, they are bit brownish. Any
> >ideas what and where to start looking for? I built my K2 and options, but
> >I'm technically challenged :)
> >
> >Jukka Tarvainen, OH4MFA
> >K2/100 #4293
> >[hidden email]
> >http://personal.inet.fi/koti/oh4mfa 
> >
> >
> >_______________________________________________
> >Elecraft mailing list
> >Post to: [hidden email]
> >You must be a subscriber to post to the list.
> >Subscriber Info (Addr. Change, sub, unsub etc.):
> > http://mailman.qth.net/mailman/listinfo/elecraft 
> >
> >Help: http://mailman.qth.net/subscribers.htm 
> >Elecraft web page: http://www.elecraft.com 
>
>
> _______________________________________________
> Elecraft mailing list
> Post to: [hidden email]
> You must be a subscriber to post to the list.
> Subscriber Info (Addr. Change, sub, unsub etc.):
> http://mailman.qth.net/mailman/listinfo/elecraft 
>
> Help: http://mailman.qth.net/subscribers.htm 
> Elecraft web page: http://www.elecraft.com 

_______________________________________________
Elecraft mailing list
Post to: [hidden email]
You must be a subscriber to post to the list.
Subscriber Info (Addr. Change, sub, unsub etc.):
 http://mailman.qth.net/mailman/listinfo/elecraft   

Help: http://mailman.qth.net/subscribers.htm
Elecraft web page: http://www.elecraft.com

[Tom Althoff]

Yes Jerry...had my first 6M QSO with my FT-817 and internally mounted T1
last night in preparation for the upcoming VHF contest.   It tuned my 80M
dipole on 6M just fine.

Tom K2TA
----- Original Message -----
From: "nr5a" <[hidden email]>
To: <[hidden email]>
Sent: Monday, June 05, 2006 1:18 PM
Subject: [Elecraft] T-1 on 6m?


> Has anyone used there T-1 on 6m?  I just tried mine and it does nothing.
> Using a PAR-50 antenna.
>
> Ok has anyone had problems with it not working on certain bands?? I did
> yesterday, use to I could get it to tune my 20m hamstick on the car on 30,
> and 17. Yesterday it did nothing. I used it mobile on 30m and 17m last
> winter and it worked fine.
>
> I just tried it in the house with my vertical and it would only tune on
20m,

> nada on the other bands. Any ideas on whats going on?
>
>  K2 gives me a hi cur message on somedays, and works just fine on other
> days.  I give up. hi  Problems problems
>
> Jerry _-NR5A _ South Dakota
>
> _______________________________________________
> Elecraft mailing list
> Post to: [hidden email]
> You must be a subscriber to post to the list.
> Subscriber Info (Addr. Change, sub, unsub etc.):
>  http://mailman.qth.net/mailman/listinfo/elecraft
>
> Help: http://mailman.qth.net/subscribers.htm
> Elecraft web page: http://www.elecraft.com

_______________________________________________
Elecraft mailing list
Post to: [hidden email]
You must be a subscriber to post to the list.
Subscriber Info (Addr. Change, sub, unsub etc.):
 http://mailman.qth.net/mailman/listinfo/elecraft   

Help: http://mailman.qth.net/subscribers.htm
Elecraft web page: http://www.elecraft.com

[Jukka Tarvainen]

Yes, I did. And re-tightened again just before CQ WPX CW.

Jukka, OH4MFA

-----Original Message-----
From: [hidden email] [mailto:[hidden email]]
Sent: 5. kesakuuta 2006 22:53
To: Stephen W. Kercel; Jukka Tarvainen; [hidden email]
Subject: Re: [Elecraft] KPA100 oscillation during IARU Reg 1 Field Day


I  wonder if Jukka remembered to re-tighten the screws holding the
transistors to the heat sink after the first 10 hour "break in" period?

Doug
W6JD

_______________________________________________
Elecraft mailing list
Post to: [hidden email]
You must be a subscriber to post to the list.
Subscriber Info (Addr. Change, sub, unsub etc.):
 http://mailman.qth.net/mailman/listinfo/elecraft   

Help: http://mailman.qth.net/subscribers.htm
Elecraft web page: http://www.elecraft.com

[Jukka Tarvainen]

Hello again!

Started to check KPA100 after weekends failure. Voltage tests on page 43
(Appendix G, KPA100 manual).

D13 133 V
U4 pin 8 -23.9 V
TP1 0 V
J3 + lead 1.35 V

Last one failed, should be 0 volts.

What to look for to rectify this? Or should I just go ahead with receiver
tests?

73 Jukka, OH4MFA
K2 #4293, KPA100 out-of-order

_______________________________________________
Elecraft mailing list
Post to: [hidden email]
You must be a subscriber to post to the list.
Subscriber Info (Addr. Change, sub, unsub etc.):
 http://mailman.qth.net/mailman/listinfo/elecraft   

Help: http://mailman.qth.net/subscribers.htm
Elecraft web page: http://www.elecraft.com

[Ron D'Eau Claire-2]

I was one of the fellows who helped John test the PLL VCO temperature
stability mod. To do that I wanted to heat up the K2 to in internal air
temperature of my K2 up to about 120F or so for a period of time and then do
drift measurements.

I did that by loading a memory with CW, then putting the K2 into "repeat"
mode at 100 watts into a dummy load, then going away for half an hour or so
while it slammed out 100 watts of CW. I used no additional cooling - only
what the little internal fan provides.

Transmit times were at least 30 minutes, continuous CW, at 100 watts output.
There were no issues with the heat produced.

The CW speed doesn't matter, by the way. It's the duty cycle that determines
how much heat is produced. The duty cycle is the ratio of key down to key up
time. While higher speeds mean the key goes down more rapidly, the ratio of
key down to key up remains unchanged no matter what speed a given text is
sent.

IMPORTANT; It is very important to remember to tighten the final amplifier
mounting screws after an initial "run-in" period as described in the KPA100
manual. If your experience is like mine, you'll find them loose and in
danger of not maintaining good thermal contact with  the heat sink if you
don't go back and tighten them. Once I did the initial re-tightening per the
manual, I've not found them loose again. I've used my KPA100 for about three
years now.

Ron AC7AC


_______________________________________________
Elecraft mailing list
Post to: [hidden email]
You must be a subscriber to post to the list.
Subscriber Info (Addr. Change, sub, unsub etc.):
 http://mailman.qth.net/mailman/listinfo/elecraft   

Help: http://mailman.qth.net/subscribers.htm
Elecraft web page: http://www.elecraft.com

[Jukka Tarvainen]

Hello!

Short follow up on this. My KPA100 broke down during EU Field Day. Could not
find any burned parts visually at first. Later I find D12 and D14 to be
shorted. I have not yet found any replacements from my junkbox. I wonder
what else might be broken? How to measure those FETs in T/R switch? I need
to order components, I like to order same time all what might be necessary.

73 CU
Jukka, OH4MFA
K2 #4293

_______________________________________________
Elecraft mailing list
Post to: [hidden email]
You must be a subscriber to post to the list.
Subscriber Info (Addr. Change, sub, unsub etc.):
 http://mailman.qth.net/mailman/listinfo/elecraft   

Help: http://mailman.qth.net/subscribers.htm
Elecraft web page: http://www.elecraft.com

[Don Wilhelm-3]

Jukka,

Components are relatively inexpensive, so I recommend that you order all the
diodes in the KPA100 T/R switch and the FETs too - often the price break on
a quantity of 10 or 25 will be a better choice if you do any building at
all.  Arbitrary replacement of the T/R switch active components may be the
easiest way to attack the problem.  You might consider ordering some spares
while you are at it - having available components for replacement often
makes troubleshooting faster and easier.

If you think that the diode failure might have been due to a lightning
surge, consider replacing the 1N5711 diodes in the wattmeter section too (or
at least order them as spares).

I really hate to find my junkbox lacking in components and have to wait for
them to be ordered before I can proceed with a troubleshooting task - but
then I do a bit of building and experimenting, so excess parts will
eventually find a use.  You will have to make a trade off of convenience vs.
your ham radio budget, I consider the excess parts an asset, but your
situation may differ.

73,
Don W3FPR

> -----Original Message-----
>
> Short follow up on this. My KPA100 broke down during EU Field
> Day. Could not
> find any burned parts visually at first. Later I find D12 and D14 to be
> shorted. I have not yet found any replacements from my junkbox. I wonder
> what else might be broken? How to measure those FETs in T/R switch? I need
> to order components, I like to order same time all what might be
> necessary.
>
> 73 CU
> Jukka, OH4MFA
> K2 #4293
>
>

_______________________________________________
Elecraft mailing list
Post to: [hidden email]
You must be a subscriber to post to the list.
Subscriber Info (Addr. Change, sub, unsub etc.):
 http://mailman.qth.net/mailman/listinfo/elecraft   

Help: http://mailman.qth.net/subscribers.htm
Elecraft web page: http://www.elecraft.com

[Jukka Tarvainen]

Hello again!

Now KPA100 works OK. Just did all alignment tests. I replaced diodes 11, 12,
13, 14, 16 and 17 and transistors 3, 4, 6 and 7. Parts I got from Mouser,
one week delivery by mail. Now I need to order new thermal pads from
Elecraft, before I really use KPA100. Thank you Don W3FPR and Tom N0SS for
email support.

73 GL
Jukka, OH4MFA
K2/100 #4293


_______________________________________________
Elecraft mailing list
Post to: [hidden email]
You must be a subscriber to post to the list.
Subscriber Info (Addr. Change, sub, unsub etc.):
 http://mailman.qth.net/mailman/listinfo/elecraft   

Help: http://mailman.qth.net/subscribers.htm
Elecraft web page: http://www.elecraft.com