On Thursday, July 18, 2019 at 12:37:49 PM UTC-4, John Foster wrote:
I'm in the process of building a new instrument panel in my glider and am at the point of hooking it all back up. When I have the power cable plugged in to the back of the CAI CPT 505 and turn the power on, the needle deflects to -10kt, and if I switch it to 2x, then the needle deflects to -5kt. None of the air hoses are connected to the back of the instrument, so it is all open to the ambient air. I wouldn't think that would make a difference though. Is there something else I need to do, or is the instrument broken? I don't have a manual for it, and haven't been able to find one online.. Thanks.

The CPT50S used a pressure transducer differentiated output; the DC part
is blocked by a 4 MF cap with a 20meg feedback; time constant 80sec
more than 10 mins is needed to settle to a usable value.
This was unacceptable and the design was dropped.
The CPT 50 was very susceptible to RF .( radio transmit)
JMF