I am doing some layout on that last circuit we were discussing. Did you get a chance to review the schematic?
I did review it, and thought I had left a reply on
this thread, but it's not there. Schematic looks good except some components are labeled twice (capacitors) and some are not labeled at all (resistors). Not sure why you would want to place capacitors across the resistors in series with the two push-button switches. MCLR doesn't need it. Other switch can be (should be) de-bounced in software. Want to re-post the latest schematic in this thread?
Did you make any progress on your toner/printer resurrection?
Well, it's a Hewlett-Packard Laserjet III, and I think I remember the scan mirror failed sometime in the previous century. I haven't tried to turn it on.
Tried using the Canon laser copyier and discovered that some plastic-foam strip stuff, used as either a light-trap or maybe as a cushion, had disintegrated. Left a black smudge on the back of the paper I sent through it. And now it jams when I try to make a copy. The toner cartridge is dead. Shaking it didn't help. I am not sure it would be worth the money to replace the toner cartridge (assuming replacements are available) because there may be some more of that rubbery foam stuff falling apart inside.
I talked to my oldest son, who had journeyed this week-end from Atlanta to attend a funeral tomorrow in Cincinnati and decided to stop by Dayton to visit me... he said when he was a student at The Ohio State University working in their Physics Laboratory making PC boards, he used transparency film loaded in a laser printer to make "negatives" that he taped to photo-resist covered boards. After exposure to light, the boards were developed and etched. He said he never tried the toner transfer method of creating a resist pattern on un-coated boards.
However, I did look at some inexpensive laser printers, some for less than $100, so I might try that unless I can find a source of pre-sensitized PC board stock at a reasonable price. Then I could try the transparency "negative" or maybe "positive" method (depending on which type of photo-resist the board has) using my high-resolution ink-jet printer to print on transparency film. Pretty sure I will need a mirror image of the artwork, so I can lay the side with the printing against the photo-resist for a contact exposure.
Not looking forward to this messy chemical process. The ferric chloride etch is bad enough, but IIRC the positive photo-resists use sodium hydroxide solution for the developer. I could apply positive photo-resist myself, maybe get some from my former employer if they haven't discarded their now-outdated supply of it. It was used many moons ago to coat semiconductor wafers, but I think this out-dated stock was also used a few years ago to make some superconducting Josephson junction arrays. The PhD who did that left UES, Inc. right after that when the contract ended.
Well, off to bed for now...