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 <[EMAIL PROTECTED]> 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: Elecraft@mailman.qth.net 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
