Here is my first pass at BOM (bill of materials) for the SCELBI cassette interface.

Initial Cassette Interface BOM

This is taken from the schematics, with some reference to images and my PCB layout. I haven’t check all the resistors and capacitors to see if what is populated on the boards matches the schematics. The sum and count rows in the document compare the count of devices in the document (sum) with the number (count) that are found in images of the original circuit boards. The intention is too make sure that all devices are included in the document.

Other than the schematics, I haven’t seen any original documentation for the SCELBI cassette interface, though we do have the driver for MEA and there is some articles about the cassette interface in the SCELBI newsletters (available at scelbi.com).

The most unusual device is the 72741 opamp. This is a classic 741 opamp in a 14 pin DIP package. I have been able to find a few on eBay. If you want to use Ohmite carbon composition resistors, much to my surprise, it appears that Mouser has everyone of these values in stock.

I’ll have to research the capacitors a bit more, but I’m sure that something that will function, can be found for each of these values.

Since I haven’t built one and haven’t verified all the discrete components by examination of an original card, there could be some problems with this first pass BOM. In particular, I don’t know what specific transistors and diodes were used. Based on usage in the circuit, I expect that pretty generic versions will do the job, so that is what I listed in the BOM.

The last part that may cause you to scratch your head, is the DIP relay. In the past, I found a matching part is still made, but I failed to record the manufacturer and will have to dig around to locate it again.