Steve
If you trace through the schematic you will see the forward and reverse voltages from the SWR diodes are fed to the PIC via a voltage divider using 68k and 34k resistors..
If you trace through it would seem to be there is a short on the line close to the PIC input effectively across the 34k resistor..
vk3pe
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On Mon, Nov 29, 2021 at 06:24 AM, g4edg wrote:
Hi
Ive just been given a faulty ATU 100 EXT (brand new ready built unit). The display remained dark on powering up, I happened to have a spare display so replaced it which resulted in a nice bright display. Test mode performs as expected, L and C can be adjusted up and down by the AUTO/BYPASS buttons.?
When I try to get the tuner to autotune the tuner refuses to react. I noticed that the power indicated on the display, showing only 0.2w even when driven with 50w from my transceiver.?
I have measured the voltage derived from the coupler when driven with 50w...around 1v on the forward diode, by the time this reaches pins 2 and 3 on the processor this is down to a few tens of millivolts. I wonder if anyone has measured these voltages??
It would seem the power detected by the processor is deemed too low to perform the tuning action at 0.2w
Any thoughts?
73 Steve G4EDG
