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John,
That advice of using a decoupling capacitor .1uf near the regulator output pin is important. I have seen regulators go into oscillation without it. Joe, Big electrolytic capacitors don't work well at high frequencies, so a decoupling capacitor must be used next to them. The big caps are great storage caps, but very sloppy at stablizing the voltage on the rails. My 2 cents, Josh From: mon...@vitasoft.org To: n8vem...@googlegroups.com Subject: RE: [N8VEM-S100:2383] Z-80 V2 component questions Date: Sun, 9 Feb 2014 22:09:52 -0800 Hi Joe, On C3 I have seen it done both ways. Most old S100 boards have a large cap here typically 20-30 uF, however often they skimp of board 0.1uF’s around the board. Somewhere I seem to remember in a Voltage regulator book it was important to have a small ~0.1uF cap near the regulator output pin. Honestly on these boards it probably does not matter since Andrew has a 0.1uF cap for almost every IC on the board.
Yes no D2, D7 & D8. These boards go through many revisions where items are dropped/added etc. (often from circuits on other boards). Once or twice Andrew and I tried to clean up the terminology - IC numbers etc. Got badly burned with tracer errors, so right now it things work we leave them alone.
Yes any numbers in boxes are ohms. The 220 ohms resistors can be moved up to 420 or greater if you don’t like a bright LED burning your eyes out!
Good luck with the board.
John
From: n8vem...@googlegroups.com [mailto:n8vem...@googlegroups.com] On Behalf Of Joe Herdler
Hi All,
I have been slowly working on my Z-80 V2 board. I am taking my time, as the end is not the goal, rather the journey is the fun part. I solder each part in place after checking three times to make sure it is the right one, then I inspect the solder joint with a high power magnifying loupe to make sure it is up to standard. If not, it is fixed. As I assemble each component to the board, I check it off on the bill of materials list that I printed off. This way, I hope to minimize mistakes.
Thus, here is my questions...
First, is C-3 really a 0.1 uf ceramic cap? It is next to three (the only three) electrolytic caps, and the mounting area for it is a circle with a polarization indicator.
The second question is about the LEDs... D 1,3,4 and 5 are listed but not D 2,7 and 8. I just want to be sure that those are LEDs as well. (no assumptions here :-) Also, on the subject of LEDs, am I correct in that the flat side of the LED goes toward the little notch in the circles?
The third and last question that I have concerns two rectangular boxes near U 9 and U 29 that have the number 220 inside of it. Is this a 220 Ohm resistor? There is no "R" number in the boxes.
Thank you very much! This is really a neat project. When I was a kid, and the IMSAI machine came out, I did not have the means to get one. So I am now building one 40 years later as I type this on my Dell notebook right next to my work area where I am building this board. Couldn't ask for any more! :-)
Best,
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