As some of the original components are difficult to source, here is a list of known working substitutions

Capacitors

The majority of relevant capacitors are still easy to source. However, this might not be the case for every capacitance value. As a rule of thumb, a substitute capacitor should have at least the nominal voltage rating, higher voltage ratings are uncritical. For the capacitance value, a daviation of approximately +- 20% should still be fine. For all capacitors that are indicated in the schematics as decoupling/ filtering capacitors, a (slightly) higher value is even better. One example is the 200nF capacitor, which was sucessfully replaced with an 220nF value without issues.

(work in progress)

Transistors

The following transistors might be difficult to source, but where sucessfully substituted as follows:

• Original value 2N3643, known good substitute is 2N3904
• Original value 2N3644, known good substitute is 2N3906

Be aware of the different package-types and double check the right pin alignment:

IC's

The original boards used TTL-types. While LS-Types should work in general, there are reports that indicate issues, using 74LS161 on the motion board. At the time of this writing, there is no information regarding experience using HS-types available.

Relay

The default circuit design requires a SPST Relay with a release time of 250µs or faster to work properly.

Options for relays:

• SPST Relay, Compac 2187 P/N 150-5, 5V DC Coil (or replacement with similar properties)
• Alternative Relay, SPST, 5V DC Coil, release-time >250µs with increased capacitance on C9 (e.g. 3.5µF for release-time of 3ms)
• Optocoupler replacement
• Bypassing Credit Management by pulling UE3:B pin 3 to ground (bodge wire on UE3:B from pin 3 to pin 7 (gnd), results on an all time present credit). (work in progress)