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8008guy
May 13th, 2017, 11:56 AM
Hi guys,

With no one coming up with up with an expansion board for the Altair buss I laid out a board. Here is the first pass. If any of you are interested take a look and see if everything appears correct. It is laid out for the original connectors used on the Altair. (.140 spacing.) Signal runs are .025" Edge connector holes .043", wire holes .029, except for power .043 and .061. Edge connector holes .125 and card edge guide .150. The PDF printed at 100% on legal paper is a 1:1 rendering of the board. (11 x 3.4)

Around the first of June I plan to have a run made. If you are interested in one, or more, please let me know. They will be made from .125? thick material. Probably will go 2oz copper.

Cheers,

len

http://chronworks.com/Altair/Altair_MB_0.pdf

http://chronworks.com/Altair/Altair_MB_1.pdf

8008guy
May 31st, 2017, 05:09 PM
Bump

I'm placing an order for these this week. Is anyone interested in a board?

len

Marty
May 31st, 2017, 06:36 PM
Hi All;

Can I make a suggestion, I think that the Boards from Grant, which I have one of, were .150 instead of .125 and the Extra thickness Is a Great Help in the strength of the Board..

THANK YOU Marty

8008guy
May 31st, 2017, 06:52 PM
Hi All;

Can I make a suggestion, I think that the Boards from Grant, which I have one of, were .150 instead of .125 and the Extra thickness Is a Great Help in the strength of the Board..

THANK YOU Marty

I'm looking at using PCBcart which offers only up to .125 thick, the same as the origial Altair boards.

8008guy
June 14th, 2017, 09:12 AM
My two boards came into day. Visually they look good, holes all line up. Over the weekend I hope to get one built and installed in my Altair.

http://chronworks.com/Altair/IMG_3677.JPG

len

Corey986
June 14th, 2017, 10:11 AM
What are you guys doing about the wire between the boards. As I recall MITS had a bunch of pre-cut ones with some sort of metal ends on them.

Or are you just going to cut them one at a time? That sounds tedious :-)

Chuck(G)
June 14th, 2017, 11:48 AM
Looks very nice--even has the holes for the (probably unobtainium) blue card guides.

If you want to be authentic, cut 100 pieces of the crappiest white stranded wire that you can find, strip the ends and start soldering.

8008guy
June 14th, 2017, 12:14 PM
What are you guys doing about the wire between the boards. As I recall MITS had a bunch of pre-cut ones with some sort of metal ends on them.

Or are you just going to cut them one at a time? That sounds tedious :-)


Hi Corey... You crack me up. A few years back I built a 4' x 4' modular analog synth from the ground up. You should try wiring a Klee sequencer, now that is tedious. I don't think I have the completed picture on here, but this will give you an idea.

http://knobhell.com/


I'm just going to cut individual wires. I have an "ok ST-500" wire stripper that makes the stripping painless. I'm on my second ST-500 in this lifetime, they last a long time. They have a stop so each wire will be consistent. I'll just measure the pieces off with a ruler. On this wires this short you need to grab them with needle nose.

len

8008guy
June 14th, 2017, 12:16 PM
Looks very nice--even has the holes for the (probably unobtainium) blue card guides.

If you want to be authentic, cut 100 pieces of the crappiest white stranded wire that you can find, strip the ends and start soldering.

On the Altair Yahoo group there was just a posting of files for 3D printing the guides. If they can be done cheap enough I would be interested.

len

8008guy
June 14th, 2017, 12:18 PM
Wiring on the Klee

http://knobhell.com/Pictures/klee-rear.jpg

p.s. I solder 100% of the connections on the MTA connectors.

glitch
June 14th, 2017, 12:47 PM
I'd rather do 100x jumpers than wire data/address busses across a bunch of ICs, especially soldered point-to-point!

Board looks good!

Chuck(G)
June 14th, 2017, 01:37 PM
Wiring on the Klee

http://knobhell.com/Pictures/klee-rear.jpg

p.s. I solder 100% of the connections on the MTA connectors.

Why? Aren't those supposed to be insulation-piercing connectors?

God gave us IDCs and ribbon cable for a reason... :)

8008guy
June 14th, 2017, 06:10 PM
Why? Aren't those supposed to be insulation-piercing connectors?

God gave us IDCs and ribbon cable for a reason... :)

They tend to not be reliable. When you build something that costs as much as a high end car you strip and solder every connector. Saves a whole lot of time if you have to debug...

8008guy
June 14th, 2017, 06:14 PM
Ok, I got the edge connectors soldered in and the board washed. Here it is mounted in the machine so you can compare the difference between the original and new board. The main difference is that I used round pads. I did to a layout with rectangular pads at first. I made the trace routing a bit close, which was probably ok. In any case I feel back to the round pads.

len

http://chronworks.com/Altair/IMG_3678.JPG

http://chronworks.com/Altair/IMG_3679.JPG

http://chronworks.com/Altair/IMG_3680.JPG

http://chronworks.com/Altair/IMG_3681.JPG

Chuck(G)
June 14th, 2017, 10:31 PM
They tend to not be reliable. When you build something that costs as much as a high end car you strip and solder every connector. Saves a whole lot of time if you have to debug...

I've found that IDC connectors on ribbon cables to be perfectly reliable over 40-odd years. Of course, having the correct tools to do the job matters. Same goes for D-sub crimp pins over solder-cup.

Of course,the "correct" way to do the expansion backplane would be to terminate them in a card edge that mates with a connector on the previous board. The last connector would be fitted with a small terminator board.

Amazing how 20-20 hindsight works, isn't it? :)

8008guy
June 15th, 2017, 04:41 AM
You are talking apple and oranges... The mta's dont have a physical backing plate that holds the wires captive. Any flex on the wire causes movement directly on the joint. They are convinient but lousy connectors. OTOH ribon cable connectors have a lot of provision for stress relief. The wires also being monolithic helps a whole bunch as well.

Ans yes, i use the proper punch tool for mta's.


I've found that IDC connectors on ribbon cables to be perfectly reliable over 40-odd years. Of course, heaving the correct tools to do the job matters. Same goes for D-sub crimp pins over solder-cup.

Of course,the "correct" way to do the expansion backplane would be to terminate them in a card edge that mates with a connector on the previous board. The last connector would be fitted with a small terminator board.

Amazing how 20-20 hindsight works, isn't it? :)

Chuck(G)
June 15th, 2017, 08:10 AM
That's one thing that I'm puzzled about--I've certainly run into MTA's with backing plates (so-called "closed")--and even some with strain relief covers. Why not use them?

glitch
June 15th, 2017, 08:26 AM
I've always heard those called "Jaguar connectors" -- I don't know if that was a particular trade name or what. In any case, they have the same record of being unreliable IDCs, especially if there's a lot of plugging/unplugging or moving around of the wiring harness. The affected connectors we worked with *had* backing plates. We often replaced with Molex KK-156 housings and crimped terminals.

Backplane looks right at home in the Altair!

8008guy
June 15th, 2017, 09:16 AM
That's one thing that I'm puzzled about--I've certainly run into MTA's with backing plates (so-called "closed")--and even some with strain relief covers. Why not use them?

The open top with striped and soldered wires are easy to use, and open to inspection. Once a cover goes on I lose visibility into the connection.

The IDC connectors for ribbon cables I put together with a 1 Ton press. I feel pretty good about those when they snap together.

len

8008guy
June 15th, 2017, 09:36 AM
Backplane looks right at home in the Altair!

Thanks!

len

Chuck(G)
June 15th, 2017, 10:30 AM
The open top with striped and soldered wires are easy to use, and open to inspection. Once a cover goes on I lose visibility into the connection.

The IDC connectors for ribbon cables I put together with a 1 Ton press. I feel pretty good about those when they snap together.

len

I use a die and small arbor press for ribbon cables--designed for the application.

I have to admit to being puzzled about the MTA connector use in your photo. I've always considered MTA's most suited to power distribution. What made you choose them for what seems to be a signal application?

glitch
June 15th, 2017, 10:37 AM
I use a die and small arbor press for ribbon cables--designed for the application.

I use a small arbor press as well, but I don't have the right die, so for e.g. ribbon cable to DIP crimps I use a stack of perfboard :p

8008guy
June 15th, 2017, 07:13 PM
I use a die and small arbor press for ribbon cables--designed for the application.

I have to admit to being puzzled about the MTA connector use in your photo. I've always considered MTA's most suited to power distribution. What made you choose them for what seems to be a signal application?

It's pretty typical in the synth world to use mta connectors. Synthesyzers.com uses mta's on comercial modules. When you have a ton of pots and switches it is nice to be able to replace controls without a lot of soldering.

I use mta's on the power as well.

You can use regular molex but it is more labor crimping the individal pins.

gslick
June 15th, 2017, 07:41 PM
I use a die and small arbor press for ribbon cables--designed for the application.


I picked up a 3M Scotchflex 3640 manual press and a set of various connector locator plates on eBay a while back. I mangled a few 50-pin IDC card edge connectors trying to press on ribbon cables with the wrong tools before I got the right tool for the job.

Chuck(G)
June 15th, 2017, 10:06 PM
It's pretty typical in the synth world to use mta connectors. Synthesyzers.com uses mta's on comercial modules. When you have a ton of pots and switches it is nice to be able to replace controls without a lot of soldering.

I use mta's on the power as well.

You can use regular molex but it is more labor crimping the individal pins.

Ah, that explains it. Years ago, a friend brought over a Prophet 5 (IIRC) synth that he was having trouble with and I helped him to get it going. The relatively unsophisticated layout surprised me.

MikeS
June 16th, 2017, 07:39 AM
I'd rather do 100x jumpers than wire data/address busses across a bunch of ICs, especially soldered point-to-point!

Try a Roadrunner or equivalent wiring pencil next time; just like drawing a schematic except for the soldering afterwards. Love 'em myself, especially for bus wiring.

Here's a DIY version:

http://www.instructables.com/id/Wiring-Pen/

Chuck(G)
June 16th, 2017, 08:45 AM
I thought the idea of a 4-slot expansion card was to be "authentic". The units of the time with the expansion card installed that I saw all had connections with the crappy white stranded wire. A wiring pencil, it seems to me, would be cheating.

I mean, why not just install a full backplane card if authenticity doesn't matter?

8008guy
June 16th, 2017, 11:08 AM
I thought the idea of a 4-slot expansion card was to be "authentic". The units of the time with the expansion card installed that I saw all had connections with the crappy white stranded wire. A wiring pencil, it seems to me, would be cheating.

I mean, why not just install a full backplane card if authenticity doesn't matter?

Hey! Mine are as crappy as I can make them... White wire and all. ;)

8008guy
June 16th, 2017, 12:57 PM
Ah, that explains it. Years ago, a friend brought over a Prophet 5 (IIRC) synth that he was having trouble with and I helped him to get it going. The relatively unsophisticated layout surprised me.

Chuck,

If you want to understand pull up this link, click on "enlarge the image". Your thoughtful analysis of the wiring harness would be appreciated. I love their modules, they work great, prices great, customer service can't be beat. But this single image is why I designed my own power distribution system.

https://www.synthesizers.com/power.html

MikeS
June 16th, 2017, 02:39 PM
A wiring pencil, it seems to me, would be cheating.

Well, I didn't mean for connecting pc boards, but for running address & data busses between ICs (which is what Glitch was talking about) the pencil can't be beat IMO.

Chuck(G)
June 16th, 2017, 03:38 PM
https://www.synthesizers.com/products/qdh/modulepowerboth_1000.jpg

I see that they use the closed MTA connectors. I dunno--maybe it works for synths--other than my ancient Casio WK-1200 keyboard (used as an input device), I haven't had much exposure. Since Sequential Circuits was just two buildings down from us on North First Street (ca 1981), I'd occasionally have lunch with the guys, but most of the talk was computer, not synthesizer.

8008guy
June 16th, 2017, 06:43 PM
https://www.synthesizers.com/products/qdh/modulepowerboth_1000.jpg

I see that they use the closed MTA connectors. I dunno--maybe it works for synths--other than my ancient Casio WK-1200 keyboard (used as an input device), I haven't had much exposure. Since Sequential Circuits was just two buildings down from us on North First Street (ca 1981), I'd occasionally have lunch with the guys, but most of the talk was computer, not synthesizer.


No, I was referring to the wire nuts on the harness...

8008guy
June 16th, 2017, 06:52 PM
Yea! got the new back plane wired in and tested. I put everything back in the case. Booted Martin's ROM monitor with two memory cards plugged in.

Lots of bitty wires:

http://chronworks.com/Altair/IMG_3682.JPG

Starting to connect the two back planes together:

http://chronworks.com/Altair/IMG_3683.JPG

Bottom side all complete:

http://chronworks.com/Altair/IMG_3684.JPG

Top view, view of the rebuilt power supply and new pre-regulator PCB. I relaced the harness. It is pretty tidy now.

http://chronworks.com/Altair/IMG_3685.JPG

Front angle view:

http://chronworks.com/Altair/IMG_3686.JPG

Back in the case. I think the original owner clear coated the front panel. The clear coat didn't fair to well.

http://chronworks.com/Altair/IMG_3687.JPG

And last a birds eye view in the case.

http://chronworks.com/Altair/IMG_3688.JPG

Last week I booted 4k basic. This weekend I have a new FDC+ to play with and see if I can get CPM booted. Wish me luck.

Cheers,

len

edale
July 2nd, 2017, 11:04 AM
Hi Len,

I got my Altair booted up with 48K of RAM but the 7805s on my 32K RAM board run *really* hot. So, my top priority now is to add an expansion board and get some spacing between the cards to keep them cool. Any chance you could email me your KICAD files?

8008guy
July 3rd, 2017, 11:39 AM
Hi Guys,

Here are the gerbers for the Altair buss expansion PCB. When I ordered from PCBcart I selected a single layer board and the .125 inch thickness. Be aware that the zip file includes ALL layers. If you order a single layer board pull out the top silk screen and top layer. (If not they will email you and tell you you included the extra layers...) Please let me know if you have any issues.

http://chronworks.com/Altair/BackPlane.zip

len