OK PTT... managed to get it worked out using Rocky... using cw mode (feel like an idiot as had tried using SSB!) Anyway on PTT in Rocky I get 5V on pin3 of the AVR. Good so far.
With no PTT enabled on the galvanically isolated RF side at the opto output with R36 and R34 in place to tap into the 13.8V line I get 10.71V (13.8V supply) at R51, enable PTT and R51 drops to 0.09V. OK that seems fine.
However if I follow the voltage signals from R51 where connects to Q9 I get 8.73V and this drops to 0.09V on PTT, L4 on PTT I get 0V wrt ground PTT or not. C27 on PTT I get 0.27V on PTT and 0V PTT off. On RX I get zero connectivity through Q10 to the antenna and same on TX.
I suspect this means Q10 is fried?
As it stands on U10 the voltages when PTT is off are:
1 0V
2 2.45V
7 2.48V
8 0V
9 2.49V
15 0V
16 4.99V
On PTT 1+ 15 become 0.1V and 0.11V respectively...
Anyone?
Yes Q10 was duff. ESD?
ReplyDeleteReplaced now I get RX ant switching.
The oms across Q10 on PTT off is very low, PTT on is very high.
Now to work out the truth table for Q9 and Q11 to see if they are also duff.
OK the other BS170 are fine. I checked the others and couple were duff so grabbed a bunch bought from jabdog a while back and replaced the duff ones.
ReplyDeleteI put R36 back in place and on PTT Q9 and Q11 do as they are supposed to and Pin 1 & 15 on U10 go high... thanks for that.