[Elecraft] [K2] No Transmit Power

[Brian Denley]

Don:
I brought home a DSO5054A (very nice 500 MHz Agilent scope!) and I was able 
to take the better measurements.  My measurements were in P-to-P but I have 
divided them by 2.8 for RMS comparison:\
(all measurments Keydown)

1.)    VPWR line (pin 2 of U8 on control board):    5.0 volts        this is 
HIGH

2.)    Xmit Mixer Output (pin 4 of U10):    28 mV

3.)    Buffer Output (pin 6 of U9):    121 mV

4.)    Band-Pass Filter Output (W6):    42 mV

5.)    T-R Switch #1 Output (anode of D1):    41 mV

6.)    Pre-Driver Output (collector of Q5):    34 mV           this seems 
LOW

7.)    Driver Input (base of Q6):    34 mV

8.)    Driver Output (collector of Q6):    179 mV                this is 
VERY LOW

9.)    PA Inputy (base of Q7):    80 mV                               this 
seems HIGH

10.)    PA input (base of Q8):    80 mV                              this 
seems HIGH

11.)    RF Detector Input (anode of D9):    143 mV          this is VERY LOW

on my own I also measured:

12.)    base of Q5:    43 mV

13.)    out of C107    43 mV

all of the DC voltages in column 1 on page 17 are normal

Anything look new?

Thanks for any help!!
Brian

http://home.comcast.net/~b.denley/index.html
----- Original Message ----- 
From: "Don Wilhelm" <w3fpr at embarqmail.com>
To: "Brian Denley" <b.denley at comcast.net>
Cc: "Elecraft Reflector" <elecraft at mailman.qth.net>
Sent: Tuesday, September 07, 2010 12:59 AM
Subject: Re: [Elecraft] [K2] No Transmit Power


>  Brian,
>
> Since you are unable to measure any RF voltage, I am going to start at the 
> beginning - proper assembly of the RF Probe.
>
> The RF probe voltage is not read "across" the 4.7 meg resistor, it is read 
> between the end of the 4.7 meg resistor and ground.  That is an important 
> difference.  In other words, the 4.7 megohm resistor is in series with the 
> detector.  Since the nominal input resistance of a DMM is 11 megohms 
> (established in the "old days" of VTVMs), that resistance in series with 
> the 11 megohms will cause the DMM to indicate the RMS value of the RF 
> voltage being measured.  There are other techniques that will provide DMM 
> readings that indicate the zero to peak RF voltage, but the RF probe parts 
> provided with the K2 will indicate the RMS voltage values when used with 
> most DMMs.