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RE: [N8VEM-S100:2629] S-100 Bus Extender V2 and reversed Q1 transistor

I think you are correct Fabio, thanks for pointing that out.   The schematic at the bottom of the page is the way it should be.

If you have time perhaps you could fine tune the values for R14 and R15 and let us know. Perhaps temporally using two pots.


BTW, as best I can keep up,  the “most current” schematic (at the bottom of each page) on all the S100Computers.com pages are the ones to use.   

There are various schematic links to prototypes (+/- errors) in the pages for these boards as we fine tune the layouts and go through various versions.   

Unless you wish to follow progress/the evolution of these boards (e.g. the 80386 board for example), always use the .pdf’s at the bottom of the page.





From: n8vem...@googlegroups.com [mailto:n8vem...@googlegroups.com] On Behalf Of Fabio Battaglia
Sent: Monday, March 3, 2014 2:31 PM
To: n8vem...@googlegroups.com
Subject: [N8VEM-S100:2629] S-100 Bus Extender V2 and reversed Q1 transistor


Hello everyone,
I almost finished building my S-100 bus extender, the first board that will go into my S-100 system to help me debug future boards.
I'm left with only one piece to install: the Q1 PNP transistor, which is leaving me some doubts.
The extender board page (http://www.s100computers.com/My%20System%20Pages/Extender%20Board/Extender%20Board.htm) states that there is an error in the schematics and that Q1 is reversed. It's not clear to me if this is a problem of the V1 board/schematics only or if this is present in V2 too.

Adding to my confusion is that I see three schematics in the page:
1) Schematics of the V1 version (http://www.s100computers.com/My%20System%20Pages/Extender%20Board/Printing%20S100_Bus%20Extender-sch%20(FINAL%20V1).pdf) which i suppose has the reversing error.
2) A picture of what i think is the V1 version schematics, with a correction drawn in red (http://www.s100computers.com/My%20System%20Pages/Extender%20Board/Extender%20Board%20V3b%20Schematic.jpg)
3) The V2 schematics (http://www.s100computers.com/My%20System%20Pages/Extender%20Board/Printing%20S100_Bus%20Extender-sch%20(V2-1-FINAL).pdf), which has the transistor in the same position as the picture of point 2.

If the schematics of V2 are correct Q1 should have the collector tied to GND, and with my PN2907A (http://www.mouser.com/ds/2/149/PN2907A-191970.pdf) this means the transistor would actually be oriented the same way shown on the silkscreen, but in the very first picture of the extender board page i see the opposite: the transistor is still reversed on V2 card.

Anyone can shed some light on the matter?


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