K2, HiCurr, and power output

Hi!

I encountered a problem during the Alignment and Test Part III of my K2 n°4018
(p71 of Rev E, Feb. 20023).
When I hold the TUNE button, I read in the display HiCurr , I can't adjust L1
and automatically HiCurr disapeares after few seconds.

I red a lot of post on the server, and I concluded that it coulds be due to the :
1/ R/T switching circuit
2/ oscillating PA
3/ a problem in VRFDET or V PWR or VALC circuits.

First I checked the T/R circuit , especially 8R and 8T lines :
I found :
on 8R : in RX, 8V and in TX : 7 V (!!) instead of 0V !!
on 8T : in RX : 0V and in TX : 7,40 V

SO I changed the 2N7000 (Q3 and Q4 and also Q23) as many guys encountered
problem with failed 2N7000 .
The new measures are the following, with a DMM :
RX TX
Q1 E 8V [OK] 8V [OK]
B 8V [OK] 7,17V [OK, I think]
C 0V [OK] 7,41V [OK, I think]

RX TX
Q2 E 8V [OK] 8V [OK]
B 7,22V [OK] 7,21V [OK, I think]
C 7,88V [OK] 5,61V [WRONG !I think it should be ZERO]

RX TX
Q3 S 0V [OK] 0V [OK, I think]
G 0V [OK] 5V [OK, I think, from pin 27/U6]
D 8V [OK] 0V [OK, I think]

RX TX
Q4 S 0V [OK] 0V [OK, I think]
G 5,1V [OK, from pin28/U6] 0V [OK, I think]
D 0V [OK] 4V [OK, I think]

In transmit I have always the HiCurr displayed and I can't adjust L1.
So please <<<<HELP!!!!!!!!!>>>>>>>

What I have to do now ?

Thanks.

73'

Jean-Claude
F1TTW
Grenoble
FRANCE




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[Don Wilhelm-3]

Jean-Claude,

>From those voltage measurements, I would believe you have a bad transistor
at Q2.  You are correct that 8R should go to zero during transmit.  BUT
before changing Q2, look at the orientation of D6 and D7 (compare with the
parts layout diagram in the back of the manual).

The inability to tune L1 is likely a different problem.  Is everything in
the 40 meter bandpass well soldered?  Do you have the proper inductor
installed (long slot on the adjustable core)?  Are all the capacitors the
correct value - particularly C4 (820pf - 821) and C5 (100pf - 101)?

Usually a High Current display is an indicator of something wrong with the
Low Pass filter, but resolve the problem with the L1 tuning first before
looking at the LPF.  Can you obtain a peak on L1 during receive?  If so, the
setting for the transmit alignment will not be very far away from the peak
obtained during receive (within 1/2 turn).

73,
Don W3FPR

> -----Original Message-----
>
> I encountered a problem during the Alignment and Test Part III of
> my K2 n°4018
> (p71 of Rev E, Feb. 20023).
> When I hold the TUNE button, I read in the display HiCurr , I
> can't adjust L1
> and automatically HiCurr disapeares after few seconds.
>
> I red a lot of post on the server, and I concluded that it coulds
> be due to the :
> 1/ R/T switching circuit
> 2/ oscillating PA
> 3/ a problem in VRFDET or V PWR or VALC circuits.
>
> First I checked the T/R circuit , especially 8R and 8T lines :
> I found :
> on 8R : in RX, 8V and in TX : 7 V (!!) instead of 0V !!
> on 8T : in RX : 0V and in TX : 7,40 V
>
> SO I changed the 2N7000 (Q3 and Q4 and also Q23) as many guys encountered
> problem with failed 2N7000 .
> The new measures are the following, with a DMM :
> RX TX
> Q1 E 8V [OK] 8V [OK]
> B 8V [OK] 7,17V [OK, I think]
> C 0V [OK] 7,41V [OK, I think]
>
> RX TX
> Q2 E 8V [OK] 8V [OK]
> B 7,22V [OK] 7,21V [OK, I think]
> C 7,88V [OK] 5,61V [WRONG !I think it should be ZERO]
>
> RX TX
> Q3 S 0V [OK] 0V [OK, I think]
> G 0V [OK] 5V [OK, I think, from pin 27/U6]
> D 8V [OK] 0V [OK, I think]
>
> RX TX
> Q4 S 0V [OK] 0V [OK, I think]
> G 5,1V [OK, from pin28/U6] 0V [OK, I think]
> D 0V [OK] 4V [OK, I think]
>
> In transmit I have always the HiCurr displayed and I can't adjust L1.
> So please <<<<HELP!!!!!!!!!>>>>>>>
>
> What I have to do now ?
>
> Thanks.
>
> 73'
>
> Jean-Claude
> F1TTW
> Grenoble
> FRANCE
>

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