[Elecraft] again: CAL tPa problem

[Marcus Busch [DL1EKC]]

Don,

> If you can record and report the conditions (band, operational data before the
> occurrance, etc.) you observe each time it happens, you may be helping others
> and the real cause just might be found and corrected.

this is my problem. It seems there are no specific conditions to trigger 
this behaviour.

The effect seems to be ...

- band independent
- VSWR independent (but never happened with a dummy connected)
- only happens during high power keydown times

About one second before tPa "jumps" to 255 ("PA HOT") the sidetone becomes 
garbled (some kind of pulsing noise or maybe short interruptions in the 
sidetone). Maybe the garbling is caused by AuxBus activity during 
transmit, overloading the main MCU ?

If I'm quick and do stop my transmission immediately, K2/KPA100 stay fine. 
But if I'm late "PA HOT" comes up and locks the unit. tPA calibration then 
has to be re-done.

Once a while ago I set up my oscilloscope connected to the AuxBus to see, 
whether the KPA100 receives a command to reset tPa, or the KPA100 resets 
the value autonomously. Unfortunately the error didn't happen during the 
testing period.

The last four months nothing happened, last weekend however tPa was reset 
two times within hours. No changes in my station setup were done 
beforehand.

I know the above information doesn't help much, but I can't find the 
system behind the effect. I think some more in-depth knowledge of the 
design is necessary, especially about the AuxBus communication regarding 
the CAL tPa procedure.

I hope one of the experts here can solve this one day.

VY 73 de Marcus, DL1EKC