K2 Original problem of High Current and Low Power

[Jimithy66]

Other problems discovered along the way with this partially
assembled kit.

Hi Don,

Thank you so much for sticking with me on this.

K2  #2438 Ver. A with no updates.

I had measured 1.48V at bases of Q7 and Q8. (installed.)

And as you suggested I removed the PA transistors

and now measure 0.63 at base terminals with PAs out.

I don't know how you figured that it was PA Q7 and Q8

that were bad Don but you were spot on !

It looks like the PA bias circuit is working but would

like your opinion.

The table in the manual for Q13 says:

E = 0.6V

B= 1.3V

C= 7.5V (With PA transistors in)


My voltages are :

E= 0.63

B= 1.2

C= 8.17 (With PA transistors out)


Think I should go ahead and put the new PA

transistors in leaving the old bias transistors

Q11 and 13 in place ?

Thanks

73,

Jim / W1FMR

PS... The 8T transmit voltage is 8.19v.
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[Don Wilhelm]

Jim,

Your PA transistors had some collector to base leakage which increased
the voltage on the base.  The usual case is that the base voltage goes
much higher and destroys Q11 and Q13, but it seems you are OK.

I have seen that condition many times over the years (I have over 1000
repairs under my belt).  So when you indicated high base voltage on the
PA transistors I knew where it was coming from.

The Q13 voltages you measured are within reason.
So yes, install the new Q7 and Q8 transistors and you should be good.

73,
Don W3FPR

On 6/18/2019 7:32 PM, Jimithy66 wrote:

> Other problems discovered along the way with this partially
> assembled kit.
>
> Hi Don,
>
> Thank you so much for sticking with me on this.
>
> K2  #2438 Ver. A with no updates.
>
> I had measured 1.48V at bases of Q7 and Q8. (installed.)
>
> And as you suggested I removed the PA transistors
>
> and now measure 0.63 at base terminals with PAs out.
>
> I don't know how you figured that it was PA Q7 and Q8
>
> that were bad Don but you were spot on !
>
> It looks like the PA bias circuit is working but would
>
> like your opinion.
>

______________________________________________________________
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Help: http://mailman.qth.net/mmfaq.htm
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Please help support this email list: http://www.qsl.net/donate.html
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