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What BUS do we take for RCA Microboards?

Joe Blackburn
 

What - if any - BUS standard do RCA Microboards (Microboard Universal Backplane) follow?

Specifications:

"Size: 4.5 inches x 7.5 inches (114.3 mm x 190.5 mm)

Backplane Connector: edge fingers, 44 pins (dual 22) on 0.156-inch centres"


Lee Hart
 

Joe Blackburn via Groups.Io wrote:
What - if any - BUS standard do RCA Microboards (Microboard Universal
Backplane) follow?

Specifications:

"Size: 4.5 inches x 7.5 inches (114.3 mm x 190.5 mm)

Backplane Connector: edge fingers, 44 pins (dual 22) on 0.156-inch centres"
Just like everyone else back then, RCA invented their own. "Standards? We don' need no steenkin' standards!"

The great thing about standards is that there are so many to choose from. :-)

--
In software development, there are two kinds of error: Conceptual
errors, implementation errors, and off-by-one errors. (anonymous)
--
Lee Hart, 814 8th Ave N, Sartell MN 56377, www.sunrise-ev.com

Joe Blackburn
 

Haha! I know exactly what you mean, Lee!

When I worked at Electrohome, we used to do CSA certifications for various brands.

Beyond that, standards were "project specific" - although we did do a number of fed contracts. Nobody beats the rigamarole of fed contracting, and compliance!

They even had "standards" for the billing cycle and project reports...

Was hoping to share loose something that help me narrow down what racks and perf boards are correct for using COSMAC MBDS boards like the 18S020 and 18S604...

I have a number of these, and I have the five-card chassis. For prototyping was thing to connect to protoboards in their own rack of compatible format.

"44 pins (dual 22) on 0.156-inch centres" semi just a bit "loosey goosey"!

cmdrcosmac
 

Look at the Vectorboard products at
https://www.vectorelect.com/plugbord-card-edge-44-contacts.html

This stuff is not cheap but if you have the card cage already it should do.
-Chuck

somaspack
 

RCA developed their own standard. RCA provided their own racks: one for the 5-card backplane and the MCS Development System rack that contained 25 cards. The pitch on the original slots was .4" pretty dang slim. Vector provided generic 44-pin cards but they were not Microboard sized.  I'm not aware of any commercial racks with correct width and pitch for Microboards.

Scott

Joe Blackburn
 

Hi, Scott!

Yes, I have the CDP-18S676 5-Card Chassis, no top. There were two forms of this, one was open ended, the other a full wrap. IIRC, there was a 18S675 earlier version. It was modified to increase air flow. I'll be using this for the 18S604B with the CDP18S640A Control & Display, and a CDP18S508 UART.

A few years ago a fellow in Australia had a MCDS with the 44-card Rack on eBay, but it was priced in the thousands, so out of my budget. Still, live and hope...

Joe Blackburn
 

On Fri, Jul 19, 2019 at 10:25 AM, cmdrcosmac wrote:
https://www.vectorelect.com/plugbord-card-edge-44-contacts.html

Thanks, Chuck!

There are a number of 4.5x6.5 boards that have workable layouts.

The rack I have will take these. It has no backplane, so I will need create something like Scotts or the CDP-18S676's to fill that gap. Being the Great White North. I suffer from a 30-50% increase in prices for most electronics (Thanks, Trudeau). If any of you have a Canadian source for stuff, with decent prices, please let me know. Thus far, I've been using Active or Digikey, or even Mouser.

We used to have a ton of decent, competitive electronics outlets in Kitchener-Waterloo, but alas, now down to one semi-surplus (Orion Electronics) and he doesn't stock most of this stuff.

thinkpast
 

On Fri, Jul 19, 2019 at 03:36 AM, Joe Blackburn wrote:

[RCA Microboard] Specifications: 4.5 inches x 7.5 inches ... 44 pins (dual 22) on 0.156-inch centres"
somaspack said
Vector provided generic 44-pin cards but they were not Microboard sized. I'm not aware of any commercial racks with correct width and pitch for Microboards.
I confirm the RCA specification, on two RCA Microboards I have. Also, a "standard" Vector 3662 plugboard I have, has the same connectors, spaced the same, located the same on the edge - I physically matched them.The width is the same; but the 3662 is 6.5 inches long. 44-pin boards like these, were not uncommon in the 1970's when the RCA Microboards were produced. They sometimes varied in length.

But... : I found some "Archer" (Radio Shack / Tandy) 44 pin protoboards in my stock. While the connector count and spacing are the same, the boards are four inches wide. They'd flop around in a cardcage for wider cards. - Herb