7320Re: Tracker2 not keying radio - Update -
- Apr 30, 2009Randy,
It does sound like something has been trashed on the OT2, so I will defer to Scott on how he wants to handle this from here. But these are my thoughts.
The gate of the FET is the only node you should see a change in voltage from the microprocessor. It will be at ground until it is keyed with 5V. The gate is isolated from the source and drain so no voltage should get through.
You should not see any voltage on the PTT unless Yeasu itself has a residual 5V from a "pulled up" line when it is plugged into the OT2. The FET gate only lowers the Source to Drain resistance from almost infinity to something very low. Since the source is at ground the drain (PTT) will also be at near ground when the FET is on. Otherwise it will be a high impedence and will be at whatever voltage the Yeasu might put on that line.
It is extremely rare that an LED would burn out unless an excessive voltage was applied directly to the anode without a voltage dropping resistor. However, I have accidently applied 5V to LEDs and had them survive. The microprocessor pins will be at ground until it wants to turn on the LED with 5V.
--- In email@example.com, "Randy Pryor" <Photo@...> wrote:
> Well I finally was able to get some more info on this wayward Tracker2. The voltage on the PTT is always low. There is 5 volts to the FET but nothing getting through.
> I tried shorting the pin to ground to key the radio, but the Yaesu apparently needs to see the 5 volts prior to going low to key, so no joy on that test.
> I also noted while swapping good tracker2 for suspect one that the Green RX led lights on the known good one when connected to the computer in tuning and diagnostics, but the suspect one does not.
> Good voltage appears to be at the leads to the LED, but it looks like it is also bad.
> I have no thoughts on what could have caused this combination of failures, but would love to hear yours.
> At this point repairing the Tracker2 is beyond my abilities, so I will be getting it back to the owner to contact Scott for his options.
> Thanks to all who helped out and shared their thoughts. They are much appreciated.
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