Posted by
Don Wilhelm-4 on
Sep 05, 2007; 1:12am
URL: http://elecraft.85.s1.nabble.com/K2-Low-output-during-initial-TX-alignment-tp452294p452304.html
JT,
Fine information. You have a problem between the collector of Q6 and
the bases of Q7 and Q8.
Your next step is to turn to the schematic RF Board sheet 4 of 4 and
locate Q6, Q7 and Q8 and all the components between them. Check all for
good soldering and be certain the 3 and 4 (green) leads of T2 are well
tinned and soldered.
You should have zero ohms between the end of R54 and the end of R53 (the
ends that are connected to the T2 winding) - if not, T2 is not well
tinned and soldered - if that is the problem, remove T2, re-strip the
leads and re-install it, it is next to impossible to correct a poor lead
tinning condition with the leads connected on the board (I have tried
that and failed many times). The T2 3/4 winding is the most likely
source of your problem.
If you want to check the components with your ohmmeter, you will have
to lift one end of many of the components (RF Chokes and resistors),
with the RF chokes paralleling the resistors it is just not possible to
check the actual resistance in-circuit, but you can usually trust the
color code markings - but be certain the correct resistor is in the
right place.
73,
Don W3FPR
JT Croteau wrote:
> On 9/4/07, Don Wilhelm <
[hidden email]> wrote:
>
>> If you have little or no RF output
>>
>
> Exactly, this is my problem. Continuing onward.
>
>
>> An added note - measure the RF voltage across your dummy load.
>>
>
> I'm not seeing any RF voltage across the dummy load. I am only seeing
> about 350 mV of DC voltage across the DL1 on key-down.
>
> I have just completed the Pre-driver, Driver, and PA signal tracing.
> Things are very interesting here. Driver voltages are very high,
> especially the output voltage but the PA Inputs and Detector Input are
> very low.
>
> Pre-Driver Output: 1.841 V (Expected: 0.120 V)
> Driver Input: 0.355 V (Expected: 0.026 V)
> Driver Output: 8.04 V (Expected: 1.8 V)
> PA Input (Q7): 0.030 V (Expected: 0.38 V)
> PA Input (Q8): 0.002 V (Expected: 0.38 V)
> RF Detector Input: 0.040 V (Expected: 2.0 V)
>
> Does this mean I have a problem between the Driver and PA or do I have
> a different problem area due the the high output of the Driver?
>
> Thanks
>
>
_______________________________________________
Elecraft mailing list
Post to:
[hidden email]
You must be a subscriber to post to the list.
Subscriber Info (Addr. Change, sub, unsub etc.):
http://mailman.qth.net/mailman/listinfo/elecraft
Help:
http://mailman.qth.net/subscribers.htmElecraft web page:
http://www.elecraft.com