again: CAL tPa problem

[Marcus Busch [DL1EKC]]

Hi folks,

I'd like to again point Your attention to an old problem with my K2 setup.

My setup includes: K2 s/n 2360 with all official mods and newest firmware,
KPA100/KAT100 in EC2 enclosure with KPA100 F/W V1.10 and the newest shield
upgrade.

After making the last F/W updates the problem seemed to have vanished
away. But I was wrong.

>From time to time KPA100 looses its tPa setting resulting in an odd
behaviour. Most offen this bug results in a PA HOT display, locking out
the rig (usually in the middle of a contest). Today tPa jumped to "0 C",
which was a new version of this bug for me.

I do not have a RF-in-the-shack problem. In fact I have run out of ideas
how to overcome the issue! Maybe I should go for the dirty way and replace
the EEPROM with a ROM ?! Is there any way to lock out the WRITE function
of the EEPROM on hardware level? I have a programming device available.

But there should be a better solution for this. I do not understand
exactly what is happening in the unit. Maybe high SWR on the feedline is
causing fluctuations on the AuxBus, which are interpreted as a WRITE
command?

Did anyone finally overcome this problem? Maybe Wayne could implement a
new (more complex) communications procedure for writing the tPa value.
This would make it more unlikely to trigger a WRITE command by random
AuxBus activity.

Any ideas? Any help?

VY 73 de Marcus, DL1EKC

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[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

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