[Elecraft] RF Probe again

[Don Wilhelm]

Gary,

Possibly Q24 could need replaced, but it is too quick to judge.
Certainly V ALC is not up to the normal DC level - BTW, that listed 
voltage is nominal for a setting of 5 watts out with the K2 actually 
delivering 5 watts.  Since you have no power out, the voltage on V ALC 
should be quite a bit higher.  If the K2 senses no ouput, the V ALC 
voltage should increase in an effort to increase the power - that is not 
happening in your case.

V ALC comes from the Control Board - the emitter of Q8 drives that 
signal.  Check the 2 capacitors added on the back of the Control Board 
(this circuit deals with the keying waveshape control).  With the 
information you have provided so far, Control Board U10A, Q8 and their 
associated components are the prime suspects.

73,
Don W3FPR

Gary Montalbine wrote:
> Don Wilhelm wrote:
>> Gary,
>>
>> You should have signal at U10 pin 1 but you don't - you had a signal 
>> at the BFO output if I recall correctly, so something is broken 
>> between those two points.
>>
>> Since you jumpered the KSB2 headers correctly, leave things that way 
>> for now.
>>
>> Set the K2 to TUNE and recheck to be certain you have RF at the 
>> following points (in order):
>> U11 pin 6 
> 
> .36V
>> Q24 gate
> .04V
> 
> Rest are all 0V. The voltage was present at U11 and Q24 without going 
> into tune. The voltages did not change in tune. Don't know if this is 
> significant.
> 
> Q24 D shows an input from V ALC. I cannot find this source. Voltage on D 
> is 0. The DC voltage table shows that the following transmit-mode 
> voltages for Q24 should be G - 0, S - 1.2, D 1.3. I got the following DC 
> voltage with key down, not RF probe, G - 0, S - .86, D .94.
> 
> Would replacement of Q24 be in order?
>