Issues with PTT control

[Elisha]

Hello, Good day to all here in this group. I just recently purchased this Hl2 main board, N2ADR board, and IO Board from Makerfabs online. I am using the hl2 with my XPA125b running Thetis. After i put everything together using M0AWS guidelines as posted on https://m0aws.co.uk/?p=3768 and am using the Xeigu L4001 6 pin mini din to trrs cable for PTT control and band switching, Everything went great. Easy. After i got everything together i tested my connections end to end. Everything tested great. Then i plugged my XPA125b into the trrs jack and turned the XPA125b on, No PA and No ATU just main power. NO PTT control. I can transmit in Thetis but it doesn't key up the xpa125b. Band switching works great but no PTT control. I tested the xpa125b with my Icom 705 and found no issues with the XPA125b. So i then using a multimeter tested the PTT control on the Pico, Nothing on transmit, so i tested the EXTTR, to see if it was pulling to ground, still nothing. At Q5 gate pin on the MOSFET reads .00v on receive and .05v on transmit. The R125 Resistor is good. Both the MOSFET and resistor or 100% electrically working, There is no 3.3v output signal from the FPGA to Q5. I literately just took it out of the box, put it together and turned everything on. I never got to key up the XPA125b. Someone please help. Thanks guys   -----KR4OMB

["Christoph v. Wüllen"]

I do not understand your setup. The HL2 trrs jack is Key/PTT *INPUT* but if you want to key the PA
you need the RCA jack which is PTT *OUTPUT*.

> Am 09.10.2026 um 14:55 schrieb Elisha <corni...@gmail.com>:
>
> Hello, Good day to all here in this group. I just recently purchased this Hl2 main board, N2ADR board, and IO Board from Makerfabs online. I am using the hl2 with my XPA125b running Thetis. After i put everything together using M0AWS guidelines as posted on https://m0aws.co.uk/?p=3768 and am using the Xeigu L4001 6 pin mini din to trrs cable for PTT control and band switching, Everything went great. Easy. After i got everything together i tested my connections end to end. Everything tested great. Then i plugged my XPA125b into the trrs jack and turned the XPA125b on, No PA and No ATU just main power. NO PTT control. I can transmit in Thetis but it doesn't key up the xpa125b. Band switching works great but no PTT control. I tested the xpa125b with my Icom 705 and found no issues with the XPA125b. So i then using a multimeter tested the PTT control on the Pico, Nothing on transmit, so i tested the EXTTR, to see if it was pulling to ground, still nothing. At Q5 gate pin on the MOSFET reads .00v on receive and .05v on transmit. The R125 Resistor is good. Both the MOSFET and resistor or 100% electrically working, There is no 3.3v output signal from the FPGA to Q5. I literately just took it out of the box, put it together and turned everything on. I never got to key up the XPA125b. Someone please help. Thanks guys -----KR4OMB
>

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[Elisha]

See the https://m0aws.co.uk/?p=3768 website. GPUO13 on the pico to the j6 header is also PTT. My setup is as follows exactly from https://m0aws.co.uk/?p=3768   XPA125b to Xiegu L4001 mini din/trrs cable directly to the trrs jack i installed on the back of the hl2. 3 wires. Yellow is PTT, blue is band switching voltage, black is ground. The black ground wire is going to J3 fan ground. Blue is going to header j6. I could have ran my PTT control to the RCA EXTTR output but it doesn't work. It doesn't switch to ground during transmit. Nothing does. I tested the main hl2 board at Q5 Mosfet to see if that i was getting a signal from the FPGA to pull the EXTTR to ground. I got nothing. I tested the mosfet, it works perfectly fine, no shorts. I tested for 3.3v signal going to Q5 mosfet resister and got nothing on transmit. The whole EXTTR circuit is dead. It was like that when i got it. Please read the google groups post i made.https://groups.google.com/g/hermes-lite/c/XMPDknbDdEI/m/mgXOTcbrAQAJ. Thank you -- KR4OMB 

[Elisha]

[Elisha]

I get 3.1v output from the EXTTR on receive and 3.1v on transmit. It doesn't pull to ground. Same on the IO board. 

To view this discussion visit https://groups.google.com/d/msgid/hermes-lite/37c4d79d-db8c-423d-907b-199b2072e8a7n%40googlegroups.com.

[Steve Haynal]

Please post the full story which was on Facebook, and which included the picture of the blown Q5. This was deleted when you started the warranty claim. I can not recommend any warranty replacement or exchange without all details. 

73,

Steve

kf7o