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I have had my U3S running (nearly) non-stop for a couple of years with no issues.? WSPR spots reported from Japan to Germany.

Recently...nothing.

The QRP-Labs Dummy Load reports:
? 80 meters: 0.022 volts (yes, that's two one-hundredths of a volt)
? 40m: 0.03
? 30m: 0.09
? 20m: 0.05
? 10m: 0.04

I will appreciate hearing from others who might have experienced something similar.? Where did you start troubleshooting? Were you successful in returning your U3S to operation?? What was the fault?

I was running at 5 volts, with a single BS170, 5x switched filter board, GPS mounted in the top of the standard enclosure (patch antenna fed through).

Thanks.

Just a bit more background:? everything else seems to be working fine...start-up screen (v3.12), gps reporting, transmissions starting and stopping appropriately.

On 30/08/2023 22:04, KI7MWA via groups.io wrote:

The QRP-Labs Dummy Load reports:
? 80 meters: 0.022 volts

My guess is the BS170. Seems most likely (assuming the relays are switching.)

Check for RF voltage at C5, input to LPFs.

73 Alan G4ZFQ

?KI7MWA

This may help you troubleshoot

To measure? "rf"? I use this circuit and a common dc Volt meter (DVM)

At 10 mHz and 5 Volts and one BS170
Measure at output of C5 with filter removed

?? IF????? R5 is set to measure much over 1.5 V rms at C5 with filter removed?
THEN? one BS170 goes from warm to hot

P = (E^2) / R
(1.5 X 1.5) / 50? =? 0.045 W?? (45 mW)

72 73
John
N3AAZ

p.s.
N3AAZ