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Monotech

@MonotechPCs

Vintage computer enthusiast. Designer of new parts for vintage PCs. Here you will find my vintage PC adventures, and news/details about my products!

 New Zealand
monotech.fwscart.com
Joined May 2019
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8-layer PCBs for $2. What a time :D
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Some more results. Someone kindly provided a BASIC program that works on Commodore machines and Apple II. I ran it on a PET 2001, and discovered some of my samples are 65C02, which I suspected as they crash on C64 demos (when in my MOS CPU Replacer).
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Image from Monotech (@MonotechPCs)
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They really cranked the laser up to 11 when re-marking these 6502s. 6 out of 10 work. The bottom sides seem untouched (faulty on left, working on right).
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Image from Monotech (@MonotechPCs)
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New in box IBM 5140 power supply. I smelled the smell of cat pee as I closed the cardboard box after pulling it out. The smell is so bad up close. It's gonna be full of leaking caps :'D
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I have released the source files for the MOS CPU Replacer on my GitHub so you can build your own or help improve: github.com/monotech/MOS_CPU_… And I have some for sale: monotech.fwscart.com/MOS_CPU…
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Have just uploaded the design files for the Osborne 1 DD floppy upgrade replica. github.com/monotech/Osborne1…
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A new upgrade for the 386DX-40. What HDD should I pair with it?
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Through-hole SOIC...
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FPGA shortage that bad huh!
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What's a proper null modem cable? Every D"B"9 cable on Aliexpress is null modem apparently. Most show their wiring, so you can dismiss the straight-through ones. The other ones only have RX/TX crossed. Null modem diagrams online show more crossings and other shenanigans.
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Found an issue with my modified 5150 BIOS. It plays dead with an IBM EGA card, but is fine with MDA/CGA. The mod makes it always start as a warm boot, so as to skip the RAM test. Anyone know where this may be failing? Something that happens during cold boot that IBM EGA needs..
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A teaser for prototype 2 of the MOS CPU Replacement. - it will be open-source - uses standard logic ICs and a cheap, common 6502 - 29x57mm - replaces: - - 6510/8500 (C64) - - 6510T (1551 floppy) - - 7501/8501 (C16, Plus4) - - 8502 (needs 6502A) (C128) Let's hope it works :P
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Image from Monotech (@MonotechPCs)
Image from Monotech (@MonotechPCs)
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An update on this: Tested working well in a C64 and a C16 so far (after fixing some PCB mistakes). Now to borrow/buy a Plus4, 1551, and C128.
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A prototype for a new doodad (final version will be small, with SMD parts). It's a 6510/8500 replacement, using a cheap+abundant 6502 and some logic. The final version will also replace 6510T, 7501/8501, and 8502. Tests well in a C64 with all the tests I could think of for now.
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Have mostly finished the revised schematic intended for SMD and supporting those other chip models. One little roadblock before I finish that, is to figure out what the Gate-IN pin of the 8501 does exactly. It's something to do with latching of AEC and RW I think.
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I have a PAL Commodore 1084S-P. This is the same as Philips CM8833. (Not the same as 1084S-P1 which = CM8833-II) It's a very handy monitor, supporting digital CGA (including brown!), Analog RGBS, S-video, and Composite with good quality. And with built in speakers!
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Image from Monotech (@MonotechPCs)
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I then put the Samsung yoke on the tube. I just threw it on without wedges, just to see if the electronics would like it. Haha, better result than I expected for just throwing it on, and the electronics seems happy. Just needs a pincushion adjustment. Now... convergence time :D
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Image from Monotech (@MonotechPCs)
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Getting there! The dynamic convergence is difficult. That involves moving the yoke along the neck and tilting it horizontally and vertically, so the convergence is uniform. Unfortunately, moving the yoke also affects purity so it's quite tedious.
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