[Elecraft] RF Probe again

[Gary Montalbine]

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?

> TP2
> D36 anode (small fragile glass diode on the bottom of the board)
> D36 cathode
> J11 pin 12
> J11 pin 7
> U10 pin 1
> 
> That is the entire path between the BFO and the transmit mixer input, 
> and you should be able to locate the point where the signal disappears.
> 
Gary, WA4SZI
> 
> Gary Montalbine wrote:
>> Don Wilhelm wrote:
>>> Gary does not work weekends, and you can likely have it isolated by 
>>> then.
>>>
>>> If you have no output from U10-4, then how about the input at pin 1? 
>>> That should be the BFO signal fed to the transmit mixer. (you do have 
>>> the KSB2 plugged in correctly do you not?).
>>
>> Pin 1 also reads 0. Per the troubleshooting instructions the KSB2 was 
>> removed. I installed temporary jumper pins between 1 & 3 of J9 and J10 
>> and installed a .001mf cap between pins 7 & 12 of J11. I can reinstall 
>> KSB2 if you think it will help.
>>
>>   The only other signal that
>>> must be present is the TX VFO which should have at least 70 mV RF on 
>>> U10 pin 6.
>>
>> I have .16V
>>
>>   You must be in TUNE or otherwise keydown to get RF to U10-1.
>>
>> Tried both.
>>>
>>> If you have RF at both U10-1 and U10-6, you shoudl also have RF at 
>>> U10-4.  Check the DC voltage at pin 8 (it will only be present during 
>>> TUNE or other transmit periods).
>>
>> Pin 8 voltage is 6V in tune.
>>
>> Thanks,
>>
>> Gary WA4SZI
>>>
>>> 73,
>