The Shop > Electronics & IC Programing
EasyPIC-6 Development Board by MikroElectronica - Take"2"
cidrontmg:
Hi, finally got my EasyPic6 yesterday. Not all of the stuff I ordered, but at least the main board. Rest coming later (hopefully). Tried compiling some (Basic) code, and got it to do funny flashing LEDs, and text on the COG2x16 display. This is a neat thing. Reminds me strongly of the first computer I built, many years ago. S-100 bus, Z-80 CPU, 2 boards of 8k of static RAM, a cassette tape for mass storage, and a B/W TV, where I fed the output directly to the cathode. No keyboard, just toggle switches on the front panel.... And an enormous amount of ICīs on the boards (all TTL logic). Powered with an old IBM transformer, also would be good for spot welding. And two Mallory 25000 mF (not micro-F, - thatīs really 25 Farads...) caps... Admittedly, EasyPic6 is a bit more sophisticated. Thereīs a learning curve looming ahead, I hope itīs not a vertical wall when I hit it.
:wave:
Bluechip:
Hi Olli
Doubt if they're really 25 farad ... On some German PSU's I worked on some caps were marked as 68,000 mF.
However, in The Parts Listing they were described as 68mF, and on the wiring diagram as 68,000uF.
I've no idea why they should be so marked, 'cos it's not correct. But not unknown.
Cannot imagine why anyone would want a cap. of that size for ripple rejection?
Tried a search on the type number, probably on it?
Dave BC
DMIOM:
--- Quote from: Bluechip on December 15, 2010, 06:15:27 PM ---...... On some German PSU's I worked on some caps were marked as 68,000 mF
--- End quote ---
Possibly that'll be the difference is symbology - the Brit . for decimal and comma for thousands - versus the continental European use of the comma for decimal separator?
Dave
cidrontmg:
Hi Bluechip, I canīt be sure they really were 25F, I had no way of testing/measuring them. But Iīm fairly sure they were. They came from a scrapyard (as did the transformer), and they looked more like car batteries than ("normal") electrolytes. In a rectangular plastic case (there was metal underneath, but not exposed). And with copper screw-on terminals instead of the leaden studs. And nowhere near as heavy as batteries. Quite huge things. I donīt think they ever were in a (mainframe) computer PSU, or even near a computer (or a PSU of any sort), but they came cheap (same as any ali scrap), and had all the capacitance I could ever wish for. 25000 mF, 25 volts.
Theyīre not with me any more, a friend was building a capacitor discharge welder, and he talked me into giving them away for that project. I donīt know how successful the project turned out, but if not, it certainly was not because of too small caps.
BTW. The same scrapyard had lots and lots (several hundred, I imagine, in a huge pile) of keyboards, which were practically unobtainable elsewhere then (1977-78). But he couldnīt sell them, he had a list from IBM about what bits he could sell, and what not, that really had to be crushed and scrapped. And no matter how nicely I tried to convince him of letting me have one, no way. Same thing with ribbon (flat) cables. Not one meter could I pry off him.
:wave:
Bluechip:
Dave
I'm aware of the , / . thing. They were in fact 68,000 uF. We had to change a good few. Why? Because they were rated at 40VDC Wkg. Fine. Except the off-load DC volts of that PSU @ 240VAC input was >51V. Not much 'Vorsprung Durch Technik' about those then .... The Spec called for 63VDC Wkg. so how someone thought 40VDC was OK is anyones guess. Entertaining bang when they let go anyway .. :lol:
Olli
Only said it was unlikely, not impossible .. :thumbup:
If they were as big as a car battery, it may be that's what they were. I worked for IBM for 16 years. Biggest I ever saw on a CPU , IIRC, was 250,000 uF @ 7.5 VDC. There were 6 in parallel on a 2.18V (?) PSU fitted to the System 7 CPU. About 70mm dia. x 150mm . May well have been larger caps. on machines I had no dealings with.
The narkiest ( not IBM ) was 2200uF @12kV. Like a young Wheelie Bin. Off some sort of Radar transmitter IIRC. Not the sort of thing to discharge with a screwdriver ..
IBM were/are very sensitive about spare parts going walkies. I think they don't want them to go to third party maintainers .. Naturally ..
If they were the transparent ribbon cables, they have a fair bit of silver in them ... IIRC.
Off to my freezing shop ... finish sorting out the screw junk pile ... I can feel the excitement and enthusiasm building up now ... NOT
Dave BC
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