[hpsdr] Looks like I fried my PTT output

[Tim O'Rourke]

I have small extra relay stuffed in a box with Gerd's antenna switch as a precaution.
Have used it to activate a THP amp for long time now with no problems.
THP amp has an open transistor input for PTT input that was not compatible with open collector outputs on Penelope anyway.
I can send you the part number Gerd suggested.
Tim 


-----Original Message-----
>From: John Marvin <jm-hpsdr at themarvins.org>
>Sent: Dec 15, 2012 1:28 AM
>To: hpsdr at lists.openhpsdr.org
>Subject: [hpsdr] Looks like I fried my PTT output
>
>***** High Performance Software Defined Radio Discussion List *****
>
>  So PTT out seems to be permanently "on" now.  I'm not sure how it 
>happened, but I believe it happened when I was doing some "high" power 
>testing. High is in quotes since it was just the highest I had gone up 
>to then since I was maxing out my dummy load, but I believe the highest 
>I got was about 20W.  The PTT input of my amp is basically 12V through 
>an opto-isolator, so I'm not sure what went wrong.  The best I can come 
>up with is that the PTT input wire is in the same internal board 
>connector as the antenna output, so maybe some voltage was coupled into 
>the PTT circuit.
>
>Anyway, looking at the schematic it would appear that the best, and 
>perhaps only candidate for repair would be Q2, which is a 2N7002K FET. 
>So I'll have to order one (or more)_ of those and see if I can fix 
>this.  I think I may have to come up with some isolation on the Hermes 
>end to prevent this from happening again, i.e. I'll probably come up 
>with a circuit that I can fit in the case that has the PTT output drive 
>a relay.
>
>Anything I've missed or should check?
>
>Thanks,
>
>John
>AC0ZG
>_______________________________________________
>HPSDR Discussion List
>To post msg: hpsdr at openhpsdr.org
>Subscription help: http://lists.openhpsdr.org/listinfo.cgi/hpsdr-openhpsdr.org
>HPSDR web page: http://openhpsdr.org
>Archives: http://lists.openhpsdr.org/pipermail/hpsdr-openhpsdr.org/


Tim O'Rourke 
W4YN at ARRL.Net
Low Power Amateur Radio Rocks 
Member of Flying Pigs,ARCI,GQRP,RSGB,ARRL Life Member
NHRA Life Member

 1355571093.0