Reverse Engineering 15 yr old electronics

Douglas Taylor dj.taylor at
Wed Nov 16 20:01:37 CST 2005

Thanks to all who responded, it is real food for thought.  To sum up, my 
project is to extract wiring diagrams from 2 boards.  The first has about 
25 TTL ICs and about a dozen op amps, lots of resistors and capacitors, 
etc.  On the first board only the IC's are numbered, the resistors and 
capacitors and diodes are not.  The second board only has a few components 
but all the parts are numbered, which is good. However, the second board 
has a large A/D convertor from 1985 that I know nothing about, it has no 
markings but I think it is an Analog Solutions model.

I will proceed by following some of the wisdom from the group:

1. If I can, put sticky labels on the IC's with diagrams of the functions, 
some of the IC's are, e.g., quad and gates, number the IC's and the gates 
individually.  Is it possible to print on some kind of Avery sticky 
paper?  Will I be able to see that small?

2. Label all resistors and capacitors, R1 C1 ....

3. Label all connectors also, J1 pin 2 ....

4. Oh, almost forgot, get data sheets on all the IC's.

5. Use a large sheet of paper for drawing.

6. Continuity tester is a must.

I'll post progress to my web space.


At 04:39 PM 11/12/2005, you wrote:
> >
> > 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.

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