[K2] Q7/Q8 base voltage

[Jukka Tarvainen-2]

Hello!

While raining and after solar flares it is time to look into my friend's K2
(#3169). It had other PA transistor blown. I am in process of replacing all
K2PAKIT components. After changing Q11 and Q13 I am checking Q7/Q8 B
voltage. On RX it is 0 volts, but on TX seems to be 0.65 V with my
multimeter (Meterman 37XR). How to lower it to recommended 0.62-0.63 volts?
Or should I check with other meter?


73 de Jukka OH4MFA, OG4T
K2/100 #4293, K2 #5267
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[Don Wilhelm]

Jukka,

Measure the values of R59 (4.7k), R60 (100 ohms), R61 (120 ohms), and
R62 (2.7k).
If this is a K2 with a serial number below 3000, R60 will be a 100 ohm
potentiometer - set it to full counterclockwise rotation or replace it
with a fixed 100 ohm resistor.

Even though 0.65 volts is slightly higher than I like to see it, that
voltage will be OK.

73,
Don W3FPR

On 9/8/2017 11:31 AM, Jukka Tarvainen wrote:

> Hello!
>
> While raining and after solar flares it is time to look into my friend's K2
> (#3169). It had other PA transistor blown. I am in process of replacing all
> K2PAKIT components. After changing Q11 and Q13 I am checking Q7/Q8 B
> voltage. On RX it is 0 volts, but on TX seems to be 0.65 V with my
> multimeter (Meterman 37XR). How to lower it to recommended 0.62-0.63 volts?
> Or should I check with other meter?
>
>
> 73 de Jukka OH4MFA, OG4T
> K2/100 #4293, K2 #5267
> ______________________________________________________________
> 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
> Message delivered to [hidden email]
>

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[Jukka Tarvainen-2]

Thank You Don and others who replied directly!

I checked those resistors to be correct value. This K2 is >3000, so 100
ohms on R60. Then I continued with PA transistor installation. K2 works
now, a bit low output on 20 and up. Low bands easily ten watts. I will
check BPF tuning later.

After I will install options one by one and check operation after each add
(Rework eliminators are in use now). KPA100 I will change 1N5711 diodes
just to be safe.


73 de Jukka OH4MFA, OG4T


2017-09-08 19:27 GMT+00:00 Don Wilhelm <[hidden email]>:

> Jukka,
>
> Measure the values of R59 (4.7k), R60 (100 ohms), R61 (120 ohms), and R62
> (2.7k).
> If this is a K2 with a serial number below 3000, R60 will be a 100 ohm
> potentiometer - set it to full counterclockwise rotation or replace it with
> a fixed 100 ohm resistor.
>
> Even though 0.65 volts is slightly higher than I like to see it, that
> voltage will be OK.
>
> 73,
> Don W3FPR

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