K1 transmitter dead

[Alexandru Csete]

Greetings,

I finished my K1 last week and everything went fine. Both resistance
and voltage check were perfect and the alignment procedures were good,
too, both rx and tx but I have only used a dummy load on the tx and
didn't transmit into an antenna.
Today I finished and installed the KNB1 and that seemed to be good as
well, I could toggle between HI/LO/OFF. I connected the K1 to an
antenna via my T1, which I have used many times before with my FT817,
and the first time I set the K1 in tune mode my power supply tripped
because the K1 wanted more current then the power supply was set to,
around 1.5A I believe. I didn't manage to see whether the SWR was too
high, but there were plenty of loud signals in the receiver, so it
couldn't be too bad, could it?
I increased the current limit (the max is 3A) but after that, every
time I set the K1 into tune mode, it just displayed P0.1 no matter
what I set the output power to. The same happened when I used a dummy
load. The current consumption in tune mode is now 220mA and 70mA in rx
mode. The receiver seems to work as it did before.
Any ideas what can be wrong? Did I really manage to blow my final? Can
it be blown due to high SWR? The power was set to 2W.

Thanks in advance

Alex
OZ9AEC
_______________________________________________
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.htm
Elecraft web page: http://www.elecraft.com

[Alexandru Csete]

Hi,

Here is a followup on my problem with dead TX.
I have received two suggestions on checking D19 and R30, both turned
out to be fine. I have also done the TX voltage checks and they were
fine, too. Then I went on with TX signal tracing, as described in the
assembly manual, using a Velleman PCS500 PC based oscilloscope. I
obtained the following measurements:

PRE (0.04-0.09): 0.025 V
ATTN (0.02-0.05): 0.047 V
OSC (0.01-0.04): 0.019 V
MIX (0.1-0.2): 0.042 V
BUF (1.5-2.0): 1.74 V
TR1 (0.5-1.0): 0.66 V
BPF (0.5-1.0): 0.78 V
TR2 (0.5-1.0): 0.72 V
TR3 (<0.01): 1.5 mV
DRV (0.9-1.6): 3.7 V
PA (10-15): 0 V
ANT (10-12): 0 V
RFD (1.7-2.0): 0 VDC

That was enough to convince me that the PA transistor Q7 was bad. I
cut it out and checked it with my DMM and it did indeed seem dead. I
couldn't measure any resistance nor hfe of it.
I am, however, still puzzled by the too low voltages at PRE and MIX,
as well as the high voltage at DRV. Is there anything else I should
keep an eye on when I will try the K1 with a new PA transistor?

73
Alex OZ9AEC

On 3/18/06, Alexandru Csete <[hidden email]> wrote:

> Greetings,
>
> I finished my K1 last week and everything went fine. Both resistance
> and voltage check were perfect and the alignment procedures were good,
> too, both rx and tx but I have only used a dummy load on the tx and
> didn't transmit into an antenna.
> Today I finished and installed the KNB1 and that seemed to be good as
> well, I could toggle between HI/LO/OFF. I connected the K1 to an
> antenna via my T1, which I have used many times before with my FT817,
> and the first time I set the K1 in tune mode my power supply tripped
> because the K1 wanted more current then the power supply was set to,
> around 1.5A I believe. I didn't manage to see whether the SWR was too
> high, but there were plenty of loud signals in the receiver, so it
> couldn't be too bad, could it?
> I increased the current limit (the max is 3A) but after that, every
> time I set the K1 into tune mode, it just displayed P0.1 no matter
> what I set the output power to. The same happened when I used a dummy
> load. The current consumption in tune mode is now 220mA and 70mA in rx
> mode. The receiver seems to work as it did before.
> Any ideas what can be wrong? Did I really manage to blow my final? Can
> it be blown due to high SWR? The power was set to 2W.
>
> Thanks in advance
>
> Alex
> OZ9AEC
>

_______________________________________________
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.htm
Elecraft web page: http://www.elecraft.com