Scor­pio News

to CP/M and look at the directory....​very tedious if you have forgotten the name of the file you want to edit.

The manual gives some useful help on what to do with the printer or plotter dumps but does not mention a simple technique for using the printer or plotter output directly in photo-etching.

The “touched-up” dump, after cutting to size, is sprayed with Isodraft which renders it highly translucent (for suppliers, contact Cannon and Wrin, __ ____ ______, Chislehurst, Kent. __ ___ ____) and smoothed onto a piece of photo-resist-coated board after which it is exposed to UV light (you must wear protective goggles). The exact time would have to be found by experiment – it is about 5 – 10 minutes at 30 cm from a 300 watt “sun lamp”. Full instructions on processing are normally provided with the ready-coated board or the resist spray. After development, the board is etched in your favourite mixture, followed by a good wash and clean-up prior to drilling. Readers of Elektor (the electronics magazine) will have seen this technique mentioned in the 1985 and 1986 issues. It works quite well, with very little tidying up needed.

The instructions are a little vague on how to handle dumps for double-sided boards – and the need to get the registration of the holes exactly right. I placed the top track/​pad dump on the pcb, centre-punched and drilled the 4 holes in the corners, turned the pcb over and placed the bottom track/​pad dump on the copper and pencilled in very lightly the orientation needed. Sounds complicated but try it out for yourself – it gets easier with practice.

Comparisons with other PCB programs (odious or otherwise)

In the last issue of Scorpio News, Robert Pearce (who is the author of this program) reviewed the pre-release version of an upgrade of the simple PCB program which is available on Scorpio’s SVC-03 disk. His comments were fairly dismissive but I notice that Mr Pearce acknowledges that some of his routines owe their origins to the program that he was criticising. I would have liked to compare the SVC-03 program with this one.....

I understand that the program will sell for about £20-25 which is pretty reasonable for a simple CAD package. I expect that it would be of interest to 80-BUS users with an interest in the design and manufacture of short-run or one-off PCBs of low to moderate complexity.

It would be possible, provided one had the appropriate level of knowledge to design one’s own answer to Gemini or MAP’s RAM or FDC boards, but I wouldn’t like to tackle something as complicated as a redesign of the GM813 CPU!