Reverse Engineering 15 yr old electronics

[Gordon JC Pearce]

Douglas Taylor wrote:

> What I don't have is circuit schematics that tell me how to connect 
> power to these parts and what voltages, and how to cable the electronics 
> to the interferometer portion.
> 
> Any tips on how to efficiently reconstruct circuit diagrams from 
> inspection of the electronics?  There are two cards, with standard TTL 
> and analog parts.  The printed circuit has a design date of 1985, while 
> the IC's have 88-89 dates.

Well, you could start by tracing out the power pins from the chips, and 
working out what they connect to.  Obviously the TTL will want 5v 
(possibly at quite a high current).  The analogue supply voltages would 
be more difficult, but have a look at the voltage ratings of power 
decoupling capacitors - that will give you an "absolute maximum" idea. 
The "real" voltage will probably be somewhat less.

Gordon.