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KPA 1500 Fan Speed not locking in at transition points

wb6bee
 

I have a KPA 1500.   According to Elecraft notes, the fans are to accelerate at 70C to level 2, returning to level 1 at 55C.  They are to accelerate to level 3 at 80C and return to level 2 at 75C.

When I got the amp,  the fans would not lock in.   For example, if you had the amp on a dummy load and held key down to 70C, the fan would go to level 2. But, if you immediately released the key, it would instantly drop back to level 1.   It would not hold level 2 until 55C.  Same at 80C.   Fans would jump to level 3, but if you released the key, it would instantly drop back to level 2 (still above 75C)

I talked to Support and then sent me a new sensor and capacitor modification kit.   I installed them both.   I ran the dummy load test described above and the amp fans worked perfectly.

Now a couple weeks later, it is back to the old problem.   It will not lock into the fan speed as it hits 70C or 80C.   It's really irritating in CW when you are keying and the spaces between characters allow the amp to cool ever so slightly.  At temperature transition points, the fans just oscillate back and forth between the two fans speeds.  Level three is bad enough, but have it jump back and forth and it will  run you out of the room

I have advised Support of the return of the problem.   Any comments or similar experiences

Don
WB6BEE

Drew Vonada-Smith K3PA
 

Has there been a resolution?

73,
Drew K3PA

Drew Vonada-Smith K3PA
 

Also, have you checked to see if this is band dependent?  AC0C and I found the issue to be worse on 40M than other bands.

73,

Drew K3PA

wb6bee
 

I have not checked "all" the bands, but I have not found a band where the problem didn't exist.   It also exists in the dummy load.    I also occurs at every transition point (fan speed zero to one, one to two, etc)

It was particularly bad before I installed a new temperature sensor and the capacitor modification.   I did the cap mod with the cap soldered on the two tabs of the sensor.   It seemed to be correct after that, only to return later.   I reheated the solder joints on the cap modification and it (again) seemed to go away.    

Elecraft support asked for a copy of my configuration file (for a second time).  I sent them one from end of August and the current one.   No response from them yet.

Don
WB6BEE

Drew Vonada-Smith K3PA
 

Don,

There is a new Beta firmware out to improve some of this. Did they get you a copy?

73,

Drew K3PA

wb6bee
 

Drew

They sent me two Beta updates.   The first one did not make any changes.   The second one (2.32) did.      Now, Fan 1 on at 50,off at 39.    Fan 2 on at 70, off at 54.  Fan 3 on at 80, off at 72.    

So far, continues to work with those thresholds.

Thanks

Don
WB6BEE

Drew Vonada-Smith K3PA
 

Thanks Don, I just wanted to make sure you knew about it.

73,

Drew K3PA