Reverse Engineering 15 yr old electronics

[Tony Duell]

> 
> Thanks for the hints, I was uncertain whether to use a continuity tester, 
> but it sounds safe.

I must have traced out over 100 boards in my life. I've always used a 
continuity tester (firstly a homebrew one, then the Fluke 85), and have 
never damaged anything. The chips on the boards have been a mix of TTL 
(plain, L, H, LS, S, F, HC, HCT at least), 4000-series CMOS, NMOS and 
PMOS LSIs, bipolar and FET-based analogue, etc (not all on the same 
board, of course ;-)). AFAIK I've never damaged a single chip.

I would be wary if there were tunnel diodes on the board (from what I've 
read, those are easy to damage), but I doubt that will be the case on 
your boards.

> 
> The circuit boards are multi-layer and from what I can see, looking at one 
> side you can see writing on the layer below that says either +5 plane or 
> ground plane depending on which side you are looking at.  I have never seen 
> this before, the buried ground and +5 buss, is this normal?

Yes, it've fairly normal to have the signal traces on the outside layers 
and the power/ground planes inside. 

-tony