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S-100 backplane project

Hi! I've partially built one of the unit for testing. I've gone as far as I can go but some parts are on back order. I may try to pick up some locally next weekend. What I am missing are the power connectors (0.200" spaced headers male and female). My plan is to finish assembly and test the active terminator section before installing the S-100 connectors.

Two of the eight units for initial testing have already been spoken for. If you would like your own S-100 backplane please contact me. The PCBs are $32 each plus $2 shipping in the US. Shipping overseas is typically $5 per PCB.

Some people have been concerned about availability of the S-100 connectors but they are plentiful and relatively cheap. At Mouser you can get EDAC parts which should work for $5 each. You can also substitute wire wrap connectors which sometimes can be found on eBay for $3 each.

There are photos at the wiki here

Thanks and have a nice day!

Andrew Lynch
 
Hi! Well today has been a great day for the N8VEM S-100 backplane project! My parts arrived and I was able to finish construction except for the bus connectors. In addition, I finished making the power supplies and hooked everything up... No Magic Smoke Released! Yahoo! Also the active terminator circuit appears to be working. I can adjust the trimmer pot to get exactly 2.7v on the bus signal lines which is really great! All the proper voltages are appearing on the bus at the supply rails so that is cool too.

My kludged power supply is 8VDC @10A regulated, +15 @6A regulated, and -15VDC @6A regulated. Its a bit on the light side for S-100 requirements but there are only 6 slots so it should be OK at least for more testing. The good news is that I made the power supply for less than $40 including shipping.

I uploaded three new pictures of the updated partial assembly to the N8VEM wiki. The next step is to get a power strip and also mount all the pieces on a piece of plywood for more testing. Then install the bus connectors and start testing with S-100 boards. This is going to be fun!

http://n8vem-sbc.pbworks.com/browse/#view=ViewFolder&param=S100

Any comments, suggestions, questions appreciated! Thanks and have a nice day!

Andrew Lynch
 
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Hi Bill! Well, its kind of hard to say. The design is an amalgam of various ideas and designs floating about. Clearly the active terminator is similar to the early Godbout designs. I used a home brew S-100 chassis, motherboard, with active terminator as my reference. Terry and Erik sold me the home brew S-100 chassis a couple of years ago and I got familiar with it during its repair. Obviously the original designer was a big fan of the Godbout stuff!

I am also working on an S-100 board "blank" to capture the basic outline of the card. I looked into IEEE-696 and also compared several S-100 boards and prototype boards but there is a *lot* of variation between units. Its a wonder anything works! I'll upload a PDF of what I have so far.

Of the eight S-100 backplane boards for the initial round of testing, I have shipped four. I still have four left if anyone would like to join me in testing this unit. I have mine basically assembled except I've only installed two bus connectors while in testing. I am finding some little things to make better in future versions but no show stoppers. KiCAD gave me some troubles in keeping some nets straight but nothing fatal.

I'd be glad to help anyone with S-100 power supply considerations. The kludged unit I rigged up is working OK so far.

Thanks and have a nice day!

Andrew Lynch
 
Hi! Well, I've been working on making the male card edge connector to fit the S-100 female card edge connector on the N8VEM S-100 backplane. I've been puttering with it for a while. Its along story but I started with something simple and ended up with a S-100 prototype board design. Please check it out and as always your comments, questions, and suggestions are welcome!

If there is sufficient interest I may go with a small PCB manufacturing production run. Please contact me offline. I don't know what the price per PCB would be but I'd guess it'd be in the $25 each neighborhood maybe less if there is enough interest.

BTW, I have basically finished my S-100 backplane assembly and it seems to work OK with the kludged power supply. I still have 4 of the 8 test boards and my confidence in this working has increased dramatically. If you'd like help making a power supply I can help with that too. My next project was going to be a linear power supply PCB but I got side tracked on this prototype board project.

Thanks and have a nice day!

Andrew Lynch

PS here is the URL http://n8vem-sbc.pbworks.com/browse/#view=ViewFolder&param=S100

Its the board named "Printing S100_Blank-full-brd.pdf"
 
Hi! Of the 8 units for initial testing, I have shipped 4 to testers and 1 is committed. I still have 3 remaining units so if anyone would like to build their own home brew S-100 system with this backplane this is great opportunity to start. A lot of the testing is basically done and the backplane is checking out fine. I think the S-100 backplane would make a good bench unit for fixing, testing, repairing, and prototyping your own S-100 boards as well.

Please contact me if interested. Thanks!

Andrew Lynch
 
Hi! Its been a while since I've done anything with the S-100 backplane. There are several builders waiting for another PCB run and a lot of feedback on how to improve the board. I am doing a PCB respin at the moment and addressing several issues.

The S-100 backplane PCB will have active termination like the first one and retain the same form factor. It has a power supply connector for +15V, +8V, and -15V. Those voltages can vary somewhat since the boards use local voltage regulators. I am using scrap laptop and printer "power bricks" on mine but you can use anything you'd like.

The new S-100 backplane will have 8 slots instead of 6 and the spacing between slots is reduced to the IEEE-696 standard of 0.75". I am also adding power LEDs for the three power inputs. There is a reset button and 2 pin connector for external reset including a jumper for CPU reset and/or external clear (peripheral reset).

The S-100 backplane retains its mounting holes and as many traces as possible will be on the component side. The copper side will be all ground plane to improve EMI performance. The PCB will be double thick (0.125") and use double weight (2oz) copper. All signal traces are 17 mils wide and the power related traces are 51 mil. Ground pins will have thermal relief pads to ease soldering issues.

I don't have a price or an ETA yet but this board will be in the queue for another PCB manufacturing order. New boards have higher priority and since there are several coming out soon they will probably be dominating the PCB manufacturing orders for a while. However when I get a chance the plan is to make another run of the S-100 backplane.

If anyone has ideas or suggestions regarding the S-100 backplane respin now would be a good time to discuss. However, I am not interested in making this backplane a 12, 18, 22, or even larger multi slot unit due to cost issues involved. Also one of the main purposes of this board is to be small, cheap, and relatively portable for benchtop work in repairing and restoring vintage S-100 bus systems. 8 slots is sufficient for build and test of small systems and a few vintage boards. The S-100 backplane will work as a main system backplane but that is not my primary goal.

One thing I am curious about is if there were ever any standards for S-100 backplane mounting holes. There doesn't seem to be any and placement varies quite a bit among the S-100 backplanes I've seen.

Thanks and have a nice day!

Andrew Lynch
 
Hi! I've partially built one of the unit for testing. I've gone as far as I can go but some parts are on back order. I may try to pick up some locally next weekend. What I am missing are the power connectors (0.200" spaced headers male and female). My plan is to finish assembly and test the active terminator section before installing the S-100 connectors.

Two of the eight units for initial testing have already been spoken for. If you would like your own S-100 backplane please contact me. The PCBs are $32 each plus $2 shipping in the US. Shipping overseas is typically $5 per PCB.

Some people have been concerned about availability of the S-100 connectors but they are plentiful and relatively cheap. At Mouser you can get EDAC parts which should work for $5 each. You can also substitute wire wrap connectors which sometimes can be found on eBay for $3 each.

There are photos at the wiki here

Thanks and have a nice day!

Andrew Lynch

Andrew,

Could you give some more info on your kludged power supply. I have several notebook and printer power supplies and would like to (finally) put together an S-100 system. I have a Cromemco 21-slot motherboard with cage and card guides (in great shape - it is available for trade for a smaller system) but would hook up a kludged power supply to it to test out some of my cards and throw together a simple system (start with my Cromemco SCC and then add a 64K memory board and then maybe one/some of my other boards.

Thanks,

Art
 
Hi! You can use any sort of SMPSU although for small loads you can use repurposed laptop and printer power bricks. Obviously only use scrap units. What you need is at least one rather beefy brick that can generate 7.5V-10V for the 8V rail (pins 1 & 51). The closer to 7.5V the better but not less than since the 7805 voltage regulators (or equivalent) have to have some "headroom" to generate 5V. However any voltage above 7.5V is wasted heat so 7.5V is ideal.

Similarily you'll need a pair of 14.5V-18V power bricks for the +15V and -15V rails. The +15V rail is (pin 2) obvious but the -15V rail (pin 52) is powered by a two conductor power brick I just flipped the positive lead and ground. This trick only works with isolated ground power bricks (there are only two lines coming out of the brick and neither is electrically common with the ground input power to the brick).

My only caution is that screwing around with repurposed power supplies can be extremely hazardous so please *BE CAREFUL* If you don't know what you are doing you can hurt or kill yourself quite easily. It may be easier to just get some inexpensive Meanwell SMPSUs off of eBay. The real trick here is to remove any boards from the chassis and when POWERED DOWN, connect each supply to the appropriate rails and measure the voltage available at the bus pins. The power down and connect another, measure, and repeat until it is all connected. Another good idea is to rig up an S-100 prototyping board with some voltage regulators and LEDs with resistors to make a bus power check tool. If the VRs or LEDs don't come on (or catch on fire) obviously something isn't right.

Seriously, be careful and you can reuse old scrap power supplies. This is certainly practical and can save a lot of money *and* find a use for some old junk headed to the e-waste dumping grounds.

Thanks and have a nice day!

Andrew Lynch
 
Andrew,

Ok, got that - been working with electronics for over 40 years, so if I screw up, I only get what I deserve (I do give electricity respect, not always enough, but...).

My question here is: what do you use to get the output of the p/s (most of mine are a bit above 8 VDC) down to the 7.5? I know of a lot of ways (regulators, resistor dividers, etc), but what is the way that you used to get them down to the required voltages - or did you just find the closest and let it run a bit hot?

Thanks again,

Art
 
Hi! OK good, I worry that sometimes giving advice might get a newbie killed so I tend to be overly cautious.

I just dug through the pile until I found a 7.5V power brick. There was one for a laptop of some type or maybe an old printer. I used a couple of the 15V Dell laptop power bricks. An 8V power brick would work fine. I would not exceed 10V though as that will run the 7805's too hot. Anything between 7.5V-10V would be fine. Many of the old S-100 chassis ran the 8V rail at 10V so most boards are ready for it.

You can also modify old AT power supplies. There are instructions on how to do it if you search. Basically it is replacing one of the feedback resistors with a potentiometer. Frankly, I haven't bothered since there are so many of these old orphan power bricks laying around looking for a use. As long as you aren't pulling huge current from them they'll work just fine. I wouldn't power a rack full of 8K SRAM boards for instance...

Thanks and have a nice day!

Andrew Lynch
 
hello,

I am considering doing a small PCB manufacturing run in the relatively near future to assess this prototype. What I am looking for is a small group of experienced S-100 builders who'd like to purchase one of these boards (at cost, PCB only, plus shipping) to help with building it and checking it out. I am trying to keep the costs low but the PCB will be in the $30-$40 range.

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Hi Karl,
Yes, the S-100 backplane PCB did go through as planned. Indeed it was popular enough that I will be making another PCB manufacturing run in the near future. This will be a respin of the PCB based on feedback I received from the first batch. The changes are simple but many builders requested them. As I remember they are:

Increase slots from 6 to 8
make slot spacing IEEE-696 compatible (0.75" center to center, was 1.0")
added reset switch and jumper
added power LEDs for +8V, +15V, and -15V rails
added inline fuses

All the other features are still intact like the active termination, power interface, etc.

I am not sure when the PCB manufacturing run will happen but hopefully soon. It has been a while and I think it would be helpful to have another batch for the builders to use.

Thanks and have a nice day!

Andrew Lynch
 
Hi! The good news is I did finally order a new batch of S-100 backplane PCBs. They are here but going fast to their new builders. I sent along most already but there are a few left if anyone is interested. They are $20 each plus $3 shipping in the US and $6 elsewhere. If these manage to run out I will order some more but probably after this batch settles in so I can get feedback.

There are several of the earlier S-100 boards that need reorder/respins so they are probably next in the queue. After looking at the waiting list, it looks like its the highly controversial S-100 Parallel ASCII keyboard boards turn next. That ought to be interesting and it needs a respin in a big way. It is a cool board but has several annoying bugs. There are no show stoppers and it works amazingly well. It's not for everyone though!

Thanks and have a nice day!

Andrew Lynch
 
Project Status:

Are these PCB's available ?

Where may I find the current doc's ?

I've read this thread and it was last mentioned that the
slot count is currently eight, but the pic's & pdf's on wiki are
of the original six slot design. I have a case in mind, but with
limited footprint, the PCB size important.

Any updated info would be great !

Todd
 
Hi! Thanks! Yes, there are a couple of PCBs still available. There is a folder on the N8VEM wiki called "S-100 backplane" with the latest schematics, PCB layout, and parts list. It is an eight slot backplane with active termination. There are a variety of other useful things like reset switches, power connectors, inline fuses, power indicator LEDs, etc.

Thanks and have a nice day!

Andrew Lynch
 
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