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KPA100 Problem

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Mark Flavin

KPA100 Problem

Well, I wanted to change the bridge diodes in the KPA 100 cause I was getting some wierd readings and hi swr readings so I decided to upgrade it while I had it apart. I did the whole upgrade and now as soon as I put it in high power, even at only 15 watts, I get PA HOT readings. I have checked all the parts values twice and did the calibration again including the C6 adjust, the r26 and 27 adjusts and even pulled the finals to make sure they weren't shorted or anything. Q3 and Q4 seem fine and are not cracked. The voltages seem to be fine and I readjusted R6 bias as per book. Whats wierd is as soon as I hit the key, even at 15 watts the fan comes on with the keying. A dot gives a short fan wiggle and an dash gives a loneger fan activation. Eventually it comes on and then I get the PA HOT. The fan even responds to my voice on SSB. I mean it comes on almost instantly. I have checked the archives and am starting to suspect the finals. I put on new pads on the transisto
rs and checked it all twice. Resoldered all connections. All works fine at 10 watts. Im sure Im missing something but I dont seem to be able to find it. Any ideas where I can check before I order new finals and go through that work again. Thanks MarkN5MF
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Don Wilhelm-4

Re: KPA100 Problem

Mark,

Have you checked the setting of the K2 CAL TPA menu? It should read the
same as the actual temperature of the PA transistor cases.

Let everything acclimate to the ambient room temperature (power off for
30 minutes should do it), then turn power on and set CAL TPA to the room
temperature in degC.

73,
Don W3FPR

On 11/26/2011 11:44 AM, Mark Flavin wrote:
>
>
>
> Well, I wanted to change the bridge diodes in the KPA 100 cause I was getting some wierd readings and hi swr readings so I decided to upgrade it while I had it apart. I did the whole upgrade and now as soon as I put it in high power, even at only 15 watts, I get PA HOT readings. I have checked all the parts values twice and did the calibration again including the C6 adjust, the r26 and 27 adjusts and even pulled the finals to make sure they weren't shorted or anything. Q3 and Q4 seem fine and are not cracked. The voltages seem to be fine and I readjusted R6 bias as per book. Whats wierd is as soon as I hit the key, even at 15 watts the fan comes on with the keying. A dot gives a short fan wiggle and an dash gives a loneger fan activation. Eventually it comes on and then I get the PA HOT. The fan even responds to my voice on SSB. I mean it comes on almost instantly. I have checked the archives and am starting to suspect the finals. I put on new pads on the transis
to
> rs and checked it all twice. Resoldered all connections. All works fine at 10 watts. Im sure Im missing something but I dont seem to be able to find it. Any ideas where I can check before I order new finals and go through that work again. Thanks MarkN5MF
>

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Mark Flavin

Re: KPA100 Problem

Yeah. I did that too. Im dreading changing the finals lol

T-Mobile. America's First Nationwide 4G Network.

-----Original message-----
From: Don Wilhelm <[hidden email]>
To: Mark Flavin <[hidden email]>
Cc: [hidden email]
Sent: Sat, Nov 26, 2011 17:45:04 GMT+00:00
Subject: Re: [Elecraft] KPA100 Problem

Mark,

Have you checked the setting of the K2 CAL TPA menu? It should read the
same as the actual temperature of the PA transistor cases.

Let everything acclimate to the ambient room temperature (power off for 30
minutes should do it), then turn power on and set CAL TPA to the room
temperature in degC.

73,
Don W3FPR

On 11/26/2011 11:44 AM, Mark Flavin wrote:
>
>
>
> Well, I wanted to change the bridge diodes in the KPA 100 cause I was
getting some wierd readings and hi swr readings so I decided to upgrade it
while I had it apart. I did the whole upgrade and now as soon as I put it
in high power, even at only 15 watts, I get PA HOT readings. I have checked
all the parts values twice and did the calibration again including the C6
adjust, the r26 and 27 adjusts and even pulled the finals to make sure they
weren't shorted or anything. Q3 and Q4 seem fine and are not cracked. The
voltages seem to be fine and I readjusted R6 bias as per book. Whats wierd
is as soon as I hit the key, even at 15 watts the fan comes on with the
keying. A dot gives a short fan wiggle and an dash gives a loneger fan
activation. Eventually it comes on and then I get the PA HOT. The fan even
responds to my voice on SSB. I mean it comes on almost instantly. I have
checked the archives and am starting to suspect the finals. I put on new
pads on the transisto
> rs and checked it all twice. Resoldered all connections. All works
fine at 10 watts. Im sure Im missing something but I dont seem to be able
to find it. Any ideas where I can check before I order new finals and go
through that work again. Thanks MarkN5MF >

______________________________________________________________
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Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
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Don Wilhelm-4

Re: KPA100 Problem

Mark,

I don't think the finals are the problem. I would check Q3 for good
soldering and the value and soldering of R5 - make certain you used the
1k trimmer at R6 rather than the 100k trimmers for R26 and R27.
The soldering at U1 pin 5 should also be checked, and be certain U1 pin
5 is not bent under the socket or sticking out the side. Make certain
there is 5 volts on one end of R5 - if not, find out why.

The temperature of the heatsink is sensed by the conduction through Q3
from the base to the emitter (and collector), that resulting voltage is
sent to U1 pin 5 for calculation by the firmware - it has nothing to do
with the actual PA transistors, just the temperature of the heatsink at
the Q3 location.

73,
Don W3FPR

On 11/26/2011 1:04 PM, Mark Flavin wrote:

> Yeah. I did that too. Im dreading changing the finals lol
>
> T-Mobile. America's First Nationwide 4G Network.
>
> -----Original message-----
> From: Don Wilhelm<[hidden email]>
> To: Mark Flavin<[hidden email]>
> Cc: [hidden email]
> Sent: Sat, Nov 26, 2011 17:45:04 GMT+00:00
> Subject: Re: [Elecraft] KPA100 Problem
>
> Mark,
>
> Have you checked the setting of the K2 CAL TPA menu? It should read the
> same as the actual temperature of the PA transistor cases.
>
> Let everything acclimate to the ambient room temperature (power off for 30
> minutes should do it), then turn power on and set CAL TPA to the room
> temperature in degC.
>
> 73,
> Don W3FPR
>
> On 11/26/2011 11:44 AM, Mark Flavin wrote:
>>
>>
>> Well, I wanted to change the bridge diodes in the KPA 100 cause I was
> getting some wierd readings and hi swr readings so I decided to upgrade it
> while I had it apart. I did the whole upgrade and now as soon as I put it
> in high power, even at only 15 watts, I get PA HOT readings. I have checked
> all the parts values twice and did the calibration again including the C6
> adjust, the r26 and 27 adjusts and even pulled the finals to make sure they
> weren't shorted or anything. Q3 and Q4 seem fine and are not cracked. The
> voltages seem to be fine and I readjusted R6 bias as per book. Whats wierd
> is as soon as I hit the key, even at 15 watts the fan comes on with the
> keying. A dot gives a short fan wiggle and an dash gives a loneger fan
> activation. Eventually it comes on and then I get the PA HOT. The fan even
> responds to my voice on SSB. I mean it comes on almost instantly. I have
> checked the archives and am starting to suspect the finals. I put on new
> pads on the transisto
>> rs and checked it all twice. Resoldered all connections. All works
> fine at 10 watts. Im sure Im missing something but I dont seem to be able
> to find it. Any ideas where I can check before I order new finals and go
> through that work again. Thanks MarkN5MF >
>
>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
>

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

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Please help support this email list: http://www.qsl.net/donate.html

Mark Flavin

Re: KPA100 Problem

Thanks Don. This thing worked before I did the upg kit. I will check that
again but I didn't really touch those. Perhaps I will remove the Q3 and
check that area. Best I can tell the upgrade didn't really address any of
that but I don't know. The finals don't get hot at all. I even took the
heatsink off to make sure there were no shorts or anything and its the same.
The weird thing is how the fan starts and stops as I key even at low (11
to 15 watts) power. I just hope its not the finals. I don't think so
either but I want to try everything else first. Could Q3 just be too
sensitive due to something. I could try changing it I suppose.

T-Mobile. America's First Nationwide 4G Network.

-----Original message-----
From: Don Wilhelm <[hidden email]>
To: Mark Flavin <[hidden email]>
Cc: [hidden email]
Sent: Sat, Nov 26, 2011 19:00:07 GMT+00:00
Subject: Re: [Elecraft] KPA100 Problem

Mark,

I don't think the finals are the problem. I would check Q3 for good
soldering and the value and soldering of R5 - make certain you used the 1k
trimmer at R6 rather than the 100k trimmers for R26 and R27.
The soldering at U1 pin 5 should also be checked, and be certain U1 pin 5 is
not bent under the socket or sticking out the side. Make certain there is 5
volts on one end of R5 - if not, find out why.

The temperature of the heatsink is sensed by the conduction through Q3 from
the base to the emitter (and collector), that resulting voltage is sent to
U1 pin 5 for calculation by the firmware - it has nothing to do with the
actual PA transistors, just the temperature of the heatsink at the Q3
location.

73,
Don W3FPR

On 11/26/2011 1:04 PM, Mark Flavin wrote:

checked
> all the parts values twice and did the calibration again including the C6
> adjust, the r26 and 27 adjusts and even pulled the finals to make sure
they
> weren't shorted or anything. Q3 and Q4 seem fine and are not cracked.
The
> voltages seem to be fine and I readjusted R6 bias as per book. Whats
wierd
> is as soon as I hit the key, even at 15 watts the fan comes on with the
> keying. A dot gives a short fan wiggle and an dash gives a loneger fan
> activation. Eventually it comes on and then I get the PA HOT. The fan
even

> responds to my voice on SSB. I mean it comes on almost instantly. I have
> checked the archives and am starting to suspect the finals. I put on new
> pads on the transisto
>> rs and checked it all twice. Resoldered all connections. All works
> fine at 10 watts. Im sure Im missing something but I dont seem to be able
> to find it. Any ideas where I can check before I order new finals and go
> through that work again. Thanks MarkN5MF >
>
>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
>

Don Wilhelm-4

Re: KPA100 Problem

Mark,

If there was a marginal solder connection, it may have worked but with
the movement involved with the upgrade, it may have finally failed.

Yes, investigate those components that I mentioned. If the temperature
is not being sensed, the fan will be turned on and off by the firmware
because the firmware is not getting correct information about the actual
temperature.

Are the thermal pads under Q3 and Q4 in good shape? It may be worth
replacing them if there is any question.

73,
Don W3FPR

On 11/26/2011 2:24 PM, Mark Flavin wrote:

> Thanks Don. This thing worked before I did the upg kit. I will check that
> again but I didn't really touch those. Perhaps I will remove the Q3 and
> check that area. Best I can tell the upgrade didn't really address any of
> that but I don't know. The finals don't get hot at all. I even took the
> heatsink off to make sure there were no shorts or anything and its the same.
> The weird thing is how the fan starts and stops as I key even at low (11
> to 15 watts) power. I just hope its not the finals. I don't think so
> either but I want to try everything else first. Could Q3 just be too
> sensitive due to something. I could try changing it I suppose.
>

Mark Flavin

Re: KPA100 Problem

Ok. I will do that. Anything is worth a try

T-Mobile. America's First Nationwide 4G Network.

-----Original message-----
From: Don Wilhelm <[hidden email]>
To: Mark Flavin <[hidden email]>
Cc: [hidden email]
Sent: Sat, Nov 26, 2011 20:05:50 GMT+00:00
Subject: Re: [Elecraft] KPA100 Problem

Mark,

If there was a marginal solder connection, it may have worked but with the
movement involved with the upgrade, it may have finally failed.

Yes, investigate those components that I mentioned. If the temperature is
not being sensed, the fan will be turned on and off by the firmware because
the firmware is not getting correct information about the actual
temperature.

Are the thermal pads under Q3 and Q4 in good shape? It may be worth
replacing them if there is any question.

73,
Don W3FPR

On 11/26/2011 2:24 PM, Mark Flavin wrote:
> Thanks Don. This thing worked before I did the upg kit. I will check
that
> again but I didn't really touch those. Perhaps I will remove the Q3 and
> check that area. Best I can tell the upgrade didn't really address any of
> that but I don't know. The finals don't get hot at all. I even took the
> heatsink off to make sure there were no shorts or anything and its the
same.
> The weird thing is how the fan starts and stops as I key even at low
(11
> to 15 watts) power. I just hope its not the finals. I don't think so
> either but I want to try everything else first. Could Q3 just be too
> sensitive due to something. I could try changing it I suppose.
>

______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html