Elecraft

K2 Was Fine Now Dead?

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Allan Bacon-2

K2 Was Fine Now Dead?

K2 4670 with 100W and all options was working fine.

Per the recommendation of Microham, I added a speaker jack from J5 to a
stereo plug on the back of the case and now the unit will not power up on
the KPA-100

When I plug in power to the low power jack, the unit is OK, but will not go
to high power.

Any ideas?

Thanks,

73,

Allan Bacon

W6GBG

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Don Wilhelm-3

Re: K2 Was Fine Now Dead?

Allan,

Was that J5, the 3 pin connector point (no header is normally installed
there) on the RF Board near the front center (near the control board)?

If you did everything correctly, it should have no effect on the K2
power-up condition. If you wired to some other place than the 3 pin J5,
remove what you added and try to discover what the error is.

It may have been something that inadvertently happened, and not at all
associated with your additions - in that case, voltage measurements are
in order. You may have had a pin pushed back on the AUX DC connector
from the KPA100, and it is no longer making contact with P3 on the RF
Board - insert the crimp pins into the housing correctly if you find
that to be the problem.

Is the KPA100 ribbon cable properly attached to the control board?
These are but a few starter questions.

73,
Don W3FPR

Allan Bacon wrote:

> K2 4670 with 100W and all options was working fine.
>
>
>
> Per the recommendation of Microham, I added a speaker jack from J5 to a
> stereo plug on the back of the case and now the unit will not power up on
> the KPA-100
>
>
>
> When I plug in power to the low power jack, the unit is OK, but will not go
> to high power.
>
>
>
> Any ideas?
>
>
>
> Thanks,
>
> 73,
>
> Allan Bacon
>
> W6GBG
>
>
>
> _______________________________________________
> 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
>
>

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Allan Bacon-2

RE: K2 Was Fine Now Dead?

Yes, it was the J5, 3 pin connector point on the RF board near the front
center.

Ribbon cable is connected.

I will check the AUX DC connector and start voltage tracing.

Thanks,
Al

Allan Bacon
W6GBG

-----Original Message-----
From: Don Wilhelm [mailto:[hidden email]]
Sent: Thursday, May 24, 2007 9:27 PM
To: Allan Bacon
Cc: [hidden email]
Subject: Re: [Elecraft] K2 Was Fine Now Dead?

Allan,

Was that J5, the 3 pin connector point (no header is normally installed
there) on the RF Board near the front center (near the control board)?

If you did everything correctly, it should have no effect on the K2
power-up condition. If you wired to some other place than the 3 pin J5,
remove what you added and try to discover what the error is.

It may have been something that inadvertently happened, and not at all
associated with your additions - in that case, voltage measurements are
in order. You may have had a pin pushed back on the AUX DC connector
from the KPA100, and it is no longer making contact with P3 on the RF
Board - insert the crimp pins into the housing correctly if you find
that to be the problem.

Is the KPA100 ribbon cable properly attached to the control board?
These are but a few starter questions.

73,
Don W3FPR

Allan Bacon wrote:

> to high power.
>
>
>
> Any ideas?
>
>
>
> Thanks,
>
> 73,
>
> Allan Bacon
>
> W6GBG
>
>
>
> _______________________________________________
> 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
>
>

Allan Bacon-2

RE: K2 Was Fine Now Dead?

In reply to this post by Don Wilhelm-3

I started tracing 13.8 V from the power source

Input 13.8 V

Diode D10 Cathode 13.8 V Anode 0 to ground as per specifications

Diode D9 Anode 0 V Cathode 0 V

So, it seems power is not getting to the D9 Diode

>From the schematic on page 64, it looks as those are the only components on
the trace from power injection to the KPA-100 to the "Aux 12V" at J4

Here is where my lack of knowledge shows up -

1. Since voltage is not present on either side of the diode, should I pull
the heat sink and check the trace on the board?

2. Or - Does a bad (not even sure what that means) diode prevent voltage
from showing up?

3. Or - What

Allan Bacon
W6GBG

-----Original Message-----
From: Don Wilhelm [mailto:[hidden email]]
Sent: Thursday, May 24, 2007 9:27 PM
To: Allan Bacon
Cc: [hidden email]
Subject: Re: [Elecraft] K2 Was Fine Now Dead?

Allan,

Was that J5, the 3 pin connector point (no header is normally installed
there) on the RF Board near the front center (near the control board)?

If you did everything correctly, it should have no effect on the K2
power-up condition. If you wired to some other place than the 3 pin J5,
remove what you added and try to discover what the error is.

It may have been something that inadvertently happened, and not at all
associated with your additions - in that case, voltage measurements are
in order. You may have had a pin pushed back on the AUX DC connector
from the KPA100, and it is no longer making contact with P3 on the RF
Board - insert the crimp pins into the housing correctly if you find
that to be the problem.

Is the KPA100 ribbon cable properly attached to the control board?
These are but a few starter questions.

73,
Don W3FPR

Allan Bacon wrote:

Don Wilhelm-3

Re: K2 Was Fine Now Dead?

Alan,

You are reading the schematic correctly - yes there should be a
connection between the cathode of D10 and the anode of D9 (check to be
certain they are connected with an ohmmeter first).

If you find the path open, you could install a TEMPORARY jumper between
D10 cathode and D9 anode on top of the board to see if everything comes
back to life. If that restores full function, then remove the board to
find the damaged PC board trace or (more likely) the bad solder connection.

Nothing in your measurements indicate a bad diode to me. A diode
conducts positive voltage from the anode to the cathode (hint: follow
the arrowhead on the diode symbol), but blocks a positive voltage in the
opposite direction.

73,
Don W3FPR

Allan Bacon wrote:

> I started tracing 13.8 V from the power source
>
> Input 13.8 V
>
> Diode D10 Cathode 13.8 V Anode 0 to ground as per specifications
>
> Diode D9 Anode 0 V Cathode 0 V
>
> So, it seems power is not getting to the D9 Diode
>
>>From the schematic on page 64, it looks as those are the only components on
> the trace from power injection to the KPA-100 to the "Aux 12V" at J4
>
> Here is where my lack of knowledge shows up -
>
> 1. Since voltage is not present on either side of the diode, should I pull
> the heat sink and check the trace on the board?
>
> 2. Or - Does a bad (not even sure what that means) diode prevent voltage
> from showing up?
>
> 3. Or - What

Allan Bacon-2

RE: K2 Was Fine Now Dead - getting interestring?

Don,
Thanks for your help. When I checked for continuity between the cathode of
D10 and the anode of D9 it came up negative - problem.

So I temporarily jumped the cathode of D10 and the anode of D9 and the rig
powered up correctly.

Then I took the heat sink off and I see trouble, not sure if these are the
right words, but it is what I see.

The board between D9 via R-14, R-13, FRC-11 almost to R7 is delaminated, no
green material, just copper and there is evidence of charring.

Allan Bacon
W6GBG

-----Original Message-----
From: Don Wilhelm [mailto:[hidden email]]
Sent: Friday, May 25, 2007 10:40 AM
To: Allan Bacon
Cc: [hidden email]; [hidden email]
Subject: Re: [Elecraft] K2 Was Fine Now Dead?

Alan,

You are reading the schematic correctly - yes there should be a
connection between the cathode of D10 and the anode of D9 (check to be
certain they are connected with an ohmmeter first).

If you find the path open, you could install a TEMPORARY jumper between
D10 cathode and D9 anode on top of the board to see if everything comes
back to life. If that restores full function, then remove the board to
find the damaged PC board trace or (more likely) the bad solder connection.

Nothing in your measurements indicate a bad diode to me. A diode
conducts positive voltage from the anode to the cathode (hint: follow
the arrowhead on the diode symbol), but blocks a positive voltage in the
opposite direction.

73,
Don W3FPR

Allan Bacon wrote:

> the trace from power injection to the KPA-100 to the "Aux 12V" at J4
>
> Here is where my lack of knowledge shows up -
>
> 1. Since voltage is not present on either side of the diode, should I pull
> the heat sink and check the trace on the board?
>
> 2. Or - Does a bad (not even sure what that means) diode prevent voltage
> from showing up?
>
> 3. Or - What

Don Wilhelm-3

Re: K2 Was Fine Now Dead - getting interestring?

Allan,

Fine that you found it - somewhere along the line, the base K2 was
drawing excessive current and the trace acted like a fuse. I can't say
what the original problem was - maybe the power connector was plugged in
backwards, or something 'dumb' like that.

In any case, it is a simple matter to remove the delaminated PC board
trace and any charred material then repair it with wire. I would
recommend that you use #20 or larger wire for that replacement trace (or
use 2 pieces of #22 side by side). If you use bare wire, you can dress
it along the old path and encapsulate it in a small bit of epoxy which
will also glue the wire down to the board - it will be just as good as
new (you can even color it green with a permanent marker and few folks
will spot the repair).

73,
Don W3FPR

Allan Bacon wrote:

> Don,
> Thanks for your help. When I checked for continuity between the cathode of
> D10 and the anode of D9 it came up negative - problem.
>
> So I temporarily jumped the cathode of D10 and the anode of D9 and the rig
> powered up correctly.
>
> Then I took the heat sink off and I see trouble, not sure if these are the
> right words, but it is what I see.
>
> The board between D9 via R-14, R-13, FRC-11 almost to R7 is delaminated, no
> green material, just copper and there is evidence of charring.
>