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RE :KPA100 upgrade and KAT100 problem

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Ron ZL1TW

RE :KPA100 upgrade and KAT100 problem

Hi John,
Your problem is a mirror image I had with an upgrade here a
while ago.
On 80 and 160m bands the tuner would NOT tune 160 and 80m bands ...even
into a Dummy load. It would go through a TUNE cycle...report a 9.9:1 SWR
and lock into transmit. ( and not on a "in band" frequency)
I eventually found ( after being told to "think outside the square) that
caps C80 and C81 in the KPA100 had been installed with .047uf caps instead
of the 0.1uf they were supposed to have.
Fixing that made the amplifier stable when attached to a resonant antenna,
but I still had trouble with it not tuning and locking up in TUNE when
attached to the KAT100 ( but once again only on 80 and 160m) .....I
subsequently found that the parasitic oscillation had destroyed the SWR
bridge diodes in the KAT100...even though I had checked them earlier as
being OK. Changing them and rechecking the balance of the bridge
completely cured my problem.
So.....the main problem was in the input of the amplifier causing it to
oscillate , and it in turn damaged the KAT100. The alteration to "REV" D in
the amplifier made the problem of wrong componentry show itself .......so I
would be checking the input area of your KPA100....and double checking the
bridge diodes in the KAT100 when you find it.
There is actually nothing wrong with the modifications. I have altered 5
K2/100s here now and only been stung by that one with a prior component
misplacement.
Hope this helps?
73............Ron ZL1TW

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John Huffman-2

Re: RE :KPA100 upgrade and KAT100 problem

Ron -

I suspect the same has happened to the KAT100. I did replace the diodes
and it worked for a bit, but the problems quickly returned. Probably
blew up the second set of diodes. Setting the KAT100 aside until the
KPA100 behaves.

In C80 and C81 I have caps marked "562". The revision D manual says
these should be 472's, as do prior manuals.

I then found the "KPA100 Cap Kit Upgrade" which replaced C80 and C81
with 562's (5,600 pF).

Should I go back to 472's?

You use .01 uF. Would that be better? How did you arrive at .01 uF for
C80 and C81?

All help greatly appreciated.

73 de K1ESE
John

Ron Willcocks wrote:

> Hi John,
> Your problem is a mirror image I had with an upgrade here a
> while ago.
> On 80 and 160m bands the tuner would NOT tune 160 and 80m bands ...even
> into a Dummy load. It would go through a TUNE cycle...report a 9.9:1 SWR
> and lock into transmit. ( and not on a "in band" frequency)
> I eventually found ( after being told to "think outside the square) that
> caps C80 and C81 in the KPA100 had been installed with .047uf caps
> instead of the 0.1uf they were supposed to have.
> Fixing that made the amplifier stable when attached to a resonant
> antenna, but I still had trouble with it not tuning and locking up in
> TUNE when attached to the KAT100 ( but once again only on 80 and 160m)
> .....I subsequently found that the parasitic oscillation had destroyed
> the SWR bridge diodes in the KAT100...even though I had checked them
> earlier as being OK. Changing them and rechecking the balance of the
> bridge completely cured my problem.
> So.....the main problem was in the input of the amplifier causing it to
> oscillate , and it in turn damaged the KAT100. The alteration to "REV" D
> in the amplifier made the problem of wrong componentry show itself
> .......so I would be checking the input area of your KPA100....and
> double checking the bridge diodes in the KAT100 when you find it.
> There is actually nothing wrong with the modifications. I have altered 5
> K2/100s here now and only been stung by that one with a prior component
> misplacement.
> Hope this helps?
> 73............Ron ZL1TW
>
>

Don Wilhelm-3

RE: RE :KPA100 upgrade and KAT100 problem

John,

I had forgotten about C80 and C81 - yes change them to .0047 uF (472) - and
change R19 and R20 to the new non-inductive resistors.

I believe Ron made a mistake in his email - C58 and C59 which are nearby are
the 0.1 uF (104).

Here is what happened on C80 and C81 - for a short time after the 20 and 17
meter low power output problem, it was thought that the C80 and C81
capacitors had to be a higher value. Well as things turned out the problem
was really that the resistor manufacturer had changed R19 and R20 (1.6 ohms)
to an inductive design without notifying Elecraft. So a few (but very few)
KPA100 kits went out with the 5600 pf capacitors. You should replace R19
and R20 at the same time just to be certain you have the non-inductive
resistors. A note to Elecraft (mailto:[hidden email]) asking for 2
E530102 4700 pF capacitors and 2 E500130 1.6 ohm 2 watt resistors should
have the required parts to you in short order. While you are at it, get 2
1N5711 diodes PN E560004 just in case the high power oscillation zapped your
KAT100 wattmeter diodes again.

73,
Don W3FPR

> -----Original Message-----
>
> Ron -
>
> I suspect the same has happened to the KAT100. I did replace the diodes
> and it worked for a bit, but the problems quickly returned. Probably
> blew up the second set of diodes. Setting the KAT100 aside until the
> KPA100 behaves.
>
> In C80 and C81 I have caps marked "562". The revision D manual says
> these should be 472's, as do prior manuals.
>
> I then found the "KPA100 Cap Kit Upgrade" which replaced C80 and C81
> with 562's (5,600 pF).
>
> Should I go back to 472's?
>
> You use .01 uF. Would that be better? How did you arrive at .01 uF for
> C80 and C81?
>
> All help greatly appreciated.
>
> 73 de K1ESE
> John
>
>

Ken Wagner K3IU

RE: RE :KPA100 upgrade and KAT100 problem

The correct part number for the "good" 1.6 ohm resistor is E500177 per
errata sheet for KPA100UPKT.
73, Ken K3IU

-----Original Message-----
From: [hidden email]
[mailto:[hidden email]] On Behalf Of Don Wilhelm
Sent: Sunday, November 19, 2006 4:27 PM
To: John Huffman; [hidden email]
Subject: RE: [Elecraft] RE :KPA100 upgrade and KAT100 problem

John,

I had forgotten about C80 and C81 - yes change them to .0047 uF (472) -
and change R19 and R20 to the new non-inductive resistors.

I believe Ron made a mistake in his email - C58 and C59 which are nearby
are the 0.1 uF (104).

Here is what happened on C80 and C81 - for a short time after the 20 and
17 meter low power output problem, it was thought that the C80 and C81
capacitors had to be a higher value. Well as things turned out the
problem was really that the resistor manufacturer had changed R19 and
R20 (1.6 ohms) to an inductive design without notifying Elecraft. So a
few (but very few) KPA100 kits went out with the 5600 pf capacitors.
You should replace R19 and R20 at the same time just to be certain you
have the non-inductive resistors. A note to Elecraft
(mailto:[hidden email]) asking for 2
E530102 4700 pF capacitors and 2 E500130 1.6 ohm 2 watt resistors should
have the required parts to you in short order. While you are at it, get
2
1N5711 diodes PN E560004 just in case the high power oscillation zapped
your KAT100 wattmeter diodes again.

73,
Don W3FPR

> -----Original Message-----
>
> Ron -
>
> I suspect the same has happened to the KAT100. I did replace the
> diodes and it worked for a bit, but the problems quickly returned.
> Probably blew up the second set of diodes. Setting the KAT100 aside
> until the KPA100 behaves.
>
> In C80 and C81 I have caps marked "562". The revision D manual says
> these should be 472's, as do prior manuals.
>
> I then found the "KPA100 Cap Kit Upgrade" which replaced C80 and C81
> with 562's (5,600 pF).
>
> Should I go back to 472's?
>
> You use .01 uF. Would that be better? How did you arrive at .01 uF
> for C80 and C81?
>
> All help greatly appreciated.
>
> 73 de K1ESE
> John
>
>

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Vic K2VCO

Re: RE :KPA100 upgrade and KAT100 problem

In reply to this post by Don Wilhelm-3

Don Wilhelm wrote:

> Here is what happened on C80 and C81 - for a short time after the 20 and 17
> meter low power output problem, it was thought that the C80 and C81
> capacitors had to be a higher value. Well as things turned out the problem
> was really that the resistor manufacturer had changed R19 and R20 (1.6 ohms)
> to an inductive design without notifying Elecraft.

How well I know this! Without going into detail, I have 5600 pf
capacitors installed. Is this a possible cause of instability on 21 MHz.?

I really don't want to take the board off the heatsink again unless I
know for sure that this is a likely cause of my problem.
--
73,
Vic, K2VCO
Fresno CA
http://www.qsl.net/k2vco
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Don Wilhelm-3

RE: RE :KPA100 upgrade and KAT100 problem

In reply to this post by Ken Wagner K3IU

Thanks for that info Ken. I pulled the part number from the manual proper.
When ordering parts, it is a good idea to include the part description in
addition to the part number - there is a much better chance that someone
will pick up on changes like that.

73,
Don W3FPR

> -----Original Message-----
>
> The correct part number for the "good" 1.6 ohm resistor is E500177 per
> errata sheet for KPA100UPKT.
> 73, Ken K3IU
>
>

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Don Wilhelm-3

RE: RE :KPA100 upgrade and KAT100 problem

In reply to this post by Vic K2VCO

Vic,

I would think that is a possibility, but can't be certain at this time - did
you change R19 and R20 when you added the upgade? If not, please change
them and see if that fixes it. With care, you can change the resistors from
the top of the board.

>From what I can recall, slightly higher value capacitors will only cause a
bit of a power output dropoff on the high bands. I once had a KPA100 here
that had severe power dropoff on 20 through 10 meters, and I overlooked C80
and C81 many times before discovering that they were .047 uF instead of the
4700 pf, so I know the amp will 'work' with much higher value capacitors.

BUT if you have the inductive resistors (the real problem behind the
temporary change to the 5600 pf caps), then they could be the cause of your
current problem.

I have 4 KPA100s to upgrade here, and one of them may have the 5600 pf caps
installed - yet to be checked, let's hope I am lucky enough to be able to
verify the problem situation.

73,
Don W3FPR

> -----Original Message-----
>
> Don Wilhelm wrote:
>
> > Here is what happened on C80 and C81 - for a short time after
> the 20 and 17
> > meter low power output problem, it was thought that the C80 and C81
> > capacitors had to be a higher value. Well as things turned out
> the problem
> > was really that the resistor manufacturer had changed R19 and
> R20 (1.6 ohms)
> > to an inductive design without notifying Elecraft.
>
> How well I know this! Without going into detail, I have 5600 pf
> capacitors installed. Is this a possible cause of instability on 21 MHz.?
>
> I really don't want to take the board off the heatsink again unless I
> know for sure that this is a likely cause of my problem.
> --
> 73,
> Vic, K2VCO
> Fresno CA
> http://www.qsl.net/k2vco
>

Ron ZL1TW

Re: RE :KPA100 upgrade and KAT100 problem

In reply to this post by John Huffman-2

Hi John,
Sorry...I had a "Senior moment" nominating C80 and
C81......what I meant was C58 and C59 were wrong in the PA I worked on. I
believe C89 and 81 *should* be 472's ...or are according to the latest
release of the circuit I have .....however....there could have been a
change, and if the latest instructions from Elecraft dictate otherwise I
would follow instructions.
Yes I think it is wise to fix the amp first. It might be wise to check the
HV you get at the junction of R11 and C77 . In the amp I mentioned, the
voltage there was falling to under 80v when the KAT100 was plugged in, so I
went back to the 39k resistor at R4 to bring the voltage back in range.
Good luck......and sorry for my mistake....
73.....Ron ZL1TW

At 03:59 p.m. 19/11/2006 -0500, you wrote:

>Ron -
>
>I suspect the same has happened to the KAT100. I did replace the diodes
>and it worked for a bit, but the problems quickly returned. Probably blew
>up the second set of diodes. Setting the KAT100 aside until the KPA100
>behaves.
>
>In C80 and C81 I have caps marked "562". The revision D manual says these
>should be 472's, as do prior manuals.
>
>I then found the "KPA100 Cap Kit Upgrade" which replaced C80 and C81 with
>562's (5,600 pF).
>
>Should I go back to 472's?
>
>You use .01 uF. Would that be better? How did you arrive at .01 uF for
>C80 and C81?
>
>All help greatly appreciated.
>
>73 de K1ESE
>John
>
>
>
>Ron Willcocks wrote:
>>Hi John,
>> Your problem is a mirror image I had with an upgrade here a
>> while ago.
>>On 80 and 160m bands the tuner would NOT tune 160 and 80m bands ...even
>>into a Dummy load. It would go through a TUNE cycle...report a 9.9:1 SWR
>>and lock into transmit. ( and not on a "in band" frequency)
>>I eventually found ( after being told to "think outside the square) that
>>caps C80 and C81 in the KPA100 had been installed with .047uf caps
>>instead of the 0.1uf they were supposed to have.
>>Fixing that made the amplifier stable when attached to a resonant
>>antenna, but I still had trouble with it not tuning and locking up in
>>TUNE when attached to the KAT100 ( but once again only on 80 and 160m)
>>.....I subsequently found that the parasitic oscillation had destroyed
>>the SWR bridge diodes in the KAT100...even though I had checked them
>>earlier as being OK. Changing them and rechecking the balance of the
>>bridge completely cured my problem.
>>So.....the main problem was in the input of the amplifier causing it to
>>oscillate , and it in turn damaged the KAT100. The alteration to "REV" D
>>in the amplifier made the problem of wrong componentry show itself
>>.......so I would be checking the input area of your KPA100....and double
>>checking the bridge diodes in the KAT100 when you find it.
>>There is actually nothing wrong with the modifications. I have altered 5
>>K2/100s here now and only been stung by that one with a prior component
>>misplacement.
>>Hope this helps?
>>73............Ron ZL1TW
>
>
>
>--
>No virus found in this incoming message.
>Checked by AVG Free Edition.
>Version: 7.5.430 / Virus Database: 268.14.8/539 - Release Date: 19/11/2006
>7:10 p.m.

No virus found in this outgoing message.
Checked by AVG Free Edition.
Version: 7.5.430 / Virus Database: 268.14.8/539 - Release Date: 19/11/2006 7:10 p.m.

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Ron ZL1TW

Re: RE :KPA100 upgrade and KAT100 problem

In reply to this post by Ron ZL1TW

Great Scott......I am worse than I thought....make that C80 and C81 in the
second sentence ......
73 again...Ron
Hi John,
Sorry...I had a "Senior moment" nominating C80 and
C81......what I meant was C58 and C59 were wrong in the PA I worked on. I
believe C89 and 81 *should* be 472's ...or are according to the latest
release of the circuit I have .....however....there could have been a
change, and if the latest instructions from Elecraft dictate otherwise I
would follow instructions.
Yes I think it is wise to fix the amp first. It might be wise to check the
HV you get at the junction of R11 and C77 . In the amp I mentioned, the
voltage there was falling to under 80v when the KAT100 was plugged in, so I
went back to the 39k resistor at R4 to bring the voltage back in range.
Good luck......and sorry for my mistake....
73.....Ron ZL1TW

At 03:59 p.m. 19/11/2006 -0500, you wrote:

Brent Sutphin WB4X

Re: RE :KPA100 upgrade and KAT100 problem

In reply to this post by Don Wilhelm-3

I just ordered a new KAT100 for my K2/100. There seems to be a really big
problem with this combination, I'm almost afraid to build it.

Brent WB4X

----- Original Message -----
From: "Don Wilhelm" <[hidden email]>
To: "Ken K3IU" <[hidden email]>; <[hidden email]>; "'John Huffman'"
<[hidden email]>; <[hidden email]>
Sent: Sunday, November 19, 2006 5:07 PM
Subject: RE: [Elecraft] RE :KPA100 upgrade and KAT100 problem

> Thanks for that info Ken. I pulled the part number from the manual
> proper.
> When ordering parts, it is a good idea to include the part description in
> addition to the part number - there is a much better chance that someone
> will pick up on changes like that.
>
> 73,
> Don W3FPR
>
>> -----Original Message-----
>>
>> The correct part number for the "good" 1.6 ohm resistor is E500177 per
>> errata sheet for KPA100UPKT.
>> 73, Ken K3IU
>>
>>
>
> _______________________________________________
> Elecraft mailing list
> Post to: [hidden email]
> You must be a subscriber to post to the list.
> Subscriber Info (Addr. Change, sub, unsub etc.):
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>
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> Elecraft web page: http://www.elecraft.com

Don Wilhelm-3

RE: RE :KPA100 upgrade and KAT100 problem

Brent,

Not to fear. There are many more out there working just fine. You will
naturally hear about the exceptions here on the reflector.

73,
Don W3FPR

> -----Original Message-----
>
> I just ordered a new KAT100 for my K2/100. There seems to be a
> really big
> problem with this combination, I'm almost afraid to build it.
>
> Brent WB4X
>
>

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