Welp, killed my hermes a little.
Bill Berzinskas (WW1H)
I experienced a failure while bench testing an amplifier, specifically an oscillation during neutralization. Sadly, my hermes was the transmitter at the time.. Since then, the HL2 shows no RF output and according to the software draws 2A, and closer to 3A on my bench supply display during TX.
Below is a summary of my troubleshooting steps following the official guide. I used GPT to keep track of details, I hope we covered it all. For the purpose of not blowing anything up, the input voltage was restricted to ~11v.
✅ Software and Initial Behavior
-
Was the HL2 previously working and transmitting correctly?
→ Yes, confirmed working before the amplifier incident. -
Does the TX LED illuminate when transmitting?
→ Yes -
Do the relays click when switching to TX?
→ Yes -
Does the temperature rise during TX?
→ Yes, according to software 2-4C per 1 second PTT click -
Is any RF output seen on the ANT port during TX?
→ No -
In full duplex mode, is a single RF spike visible in the waterfall?
→ No
⚠️ Power and Bias Voltage Checks (10V PSU)
-
Vpa during TX:
→ 6.0V (should be 8.0V) -
Vop during TX:
→ 7.0V (should be 10.15V) -
Vbias during TX:
→ 3.0V (should be 10.0V) -
PSU behavior under TX load:
→ Drops from 10V to ~9V -
Bias current shown in software:
→ Reads 2A during TX
❌ Low Power Output Chain (PA Disabled)
-
With PA disabled, any signal on RF1 port?
→ No output -
Full duplex spectrum with PA disabled?
→ No spike or visible signal -
Oscilloscope reading on DB3 pin 3/4 during TX (CW mode, 80m):
→ ~240 mV p-p, sinusoidal
→ Seems low, not a clean "strong" 80m sine wave
✅ Physical Inspection
-
Any visible damage (J31, J32, B106, L34, AD9866 area)?
→ No physical damage seen -
Applying light pressure to AD9866 during TX changes anything?
→ No noticeable change
Conclusion / Theories
-
RF path upstream of the PA appears compromised
-
Vop, Vpa, and Vbias rails all undervolted
-
PA may have partially shorted FETs pulling rails down
-
DB3 DAC output appears weak; possible AD9866 damage?
-
PSU sag and 2A draw suggest hard fault on TX key
Any feedback or advice for next steps? I'm prepared to test or isolate components (e.g., PA FETs or regulators) as needed. And obviously, I'd like to minimize my chance of blowing things up in the feature as well.
Thanks in advance!
Bill - WW1H
