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Diablo Series 30 connectors

gwiley

Experienced Member
Joined
Nov 12, 2021
Messages
277
Location
San Diego, CA, USA
Is anyone aware of a source for the Winchester MRAC connectors used for the disk bus and power connections on the Diablo series 30 disk drives? Alternatively, has anyone built something compatible using pogo pins or an array of contacts mounted to a circuit board that could connect to the drive?
 
I think the last time I needed power connectors I just watched on ebay for them
someone on eBay is selling complete bus cable assys
Thanks! I saw this cable but wasn't certain whether it was the right one. It does say Cable model 30 though

I was hoping to find a reliable supply of connectors or means to make them so people could easily mix RK05 emulators with Diablo drives.
 
Thanks! I saw this cable but wasn't certain whether it was the right one. It does say Cable model 30 though
I was speaking with the seller separately and it sounds like he is getting ready to list an inventory of Diablo 31's and 33F's at some point and has a smaller assortment of cables and power supplies. I would not be surprised if that data cable is compatible with the lot.

Edited: Nevermind. Looks like he already has the drives listed in the store.
 
gwiley and I have been working the problem. I have a stash of winchester connectors. the problem is my cables are mostly in a building I won't have access to until the end of June now.
I have a couple on cables I'm going to desolder so he can prototype an adapter.
An outstanding question is how common is a plug on the drive end of the cable from the interface in the cpu as opposed to a socket. I think the Alto was weird using a socket. Terminators
with sockets seem much more common than plugs and my tester cables use plugs.

If the cables get down to where they are $25/connector end, it may be worth buying from the guy for all of the associated hardware like the thumb screws that you'd be nickel and dimed
to death on buying new as components.

I need to take better picture, but there are a few up for the diablo cables up now under http://bitsavers.org/pdf/diablo/disk/model_30/cables_terminators/
Pictures of the RK03 adapters are under http://bitsavers.org/pdf/dec/disc/rk03/RK11C-RK03-Connectors/ they use unibus cables for drive/drive cabling
 
attached is all of the info on male mrac42 plugs. they are expensive and the solder tail 8142 pins are hard to find and around 2$ PER PIN
 

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In addition to the adapter PCB, I/m looking into using one of the following types of pins to make the "P" side of the connector:

Have some in the Digikey cart to try them out to see how well they fit in the Diablo "S" side of the connector.
Pins on the Diablo MRAC42P are 0.062" diameter.

To make the "P" side of the connector, do something like this:
1. plug 42 pins into an actual MRAC42S, such as the socket on a Diablo Terminator​
2. fit the adapter PCB over the solder tail side of the pins​
3. solder all 42 pins​
4. unplug the soldered adapter from the MRAC42S​
It might be necessary to fit a thin plastic 3D printed piece with 42 holes over the base of the pins after soldering, not sure about that yet.

The mounting screws are a harder problem. A thumb screw, aka shoulder screw could attach one side. The part with the nut in the shaft I don't know yet. Maybe something like a shoulder screw permanently fixed to a round metal threaded standoff.

However, the first step is to just make a Diablo adapter using a real MRAC42P and confirm that it works.
 
I'm pretty excited about this MRAC discussion, gwiley's note above sounds very workable. Last year I did a template for an attempt workalike MRAC with scalable pin matrix for almost all of the sizes. The idea was to use regular PC power supply pin sockets instead of real pins as they require a special tool to insert and extract. This was were I left it, next step was/is to put the calculated shell perimeter on and position the jackscrew holes. This was how it looked (yellow CAD model)
https://forum.vcfed.org/index.php?t...o-diskinterface-on-ebay.1241324/#post-1294654
EDIT I ran the OpenSCAD script to generate the regular sizes
MRAC_pin_spacing_layout.png
 
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I took some better pictures of the Alto terminator plug
also, the plug and socket versions of the terminator connector pins are mirror images of each other
so you can't just put a socket on a pcb designed for a plug.
I'm going to tear down one of the socket terminators.

The rolled pins on the thumb screws are annoying to remove.

also MRAC is the 'compact' version of the MRA connector. MIL spec for the pins MIL-DTL-28748C
AMP makes a rolled-pin tin version of the pin 66471-3
 

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Yes, but I'd have to think a bit about the implications of the board being backwards for the 40 pin ribbon connectors.
Probably a moot point for the new adapter cables since you will be able to daisy chain w/o plug/socket cable pairs with the new pcb with a set of 'in' and 'out' ribbon cables

Making a plastic block drilled out for the AMP rolled-pin .062 pins is probably going to be the least expensive way to make those cards.
In that case, plug pins make the connector block thinner because the socket pins are recessed into the connector block.
All you'd have to do for the plug block is drill a smaller diameter hole for the solder-side pins and counter-sink for the plug end
and do the same for the block to pcb attachment screws.
Soldering the pins to the PCB holds the pins in place. The AMP pins are only .7" long while the MRAC is 1.3"
You want to make the plastic blocks out of something that doesn't melt at soldering temperatures.

The AMP pins look like they are just their crimp pins with a solder pin crimped on

I went down the DIY rathole this morning because plug plastic blocks seem to be less available and more expensive than sockets.
Here is a plug block price https://www.mouser.com/ProductDetail/Amphenol-Positronic/GMCT42M0T0000-AA?qs=QpmGXVUTftG68fElJff6TQ==
 

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gwiley and I have been working the problem. I have a stash of winchester connectors. the problem is my cables are mostly in a building I won't have access to until the end of June now.
I have a couple on cables I'm going to desolder so he can prototype an adapter.
An outstanding question is how common is a plug on the drive end of the cable from the interface in the cpu as opposed to a socket. I think the Alto was weird using a socket. Terminators
with sockets seem much more common than plugs and my tester cables use plugs.

If the cables get down to where they are $25/connector end, it may be worth buying from the guy for all of the associated hardware like the thumb screws that you'd be nickel and dimed
to death on buying new as components.

I need to take better picture, but there are a few up for the diablo cables up now under http://bitsavers.org/pdf/diablo/disk/model_30/cables_terminators/
Pictures of the RK03 adapters are under http://bitsavers.org/pdf/dec/disc/rk03/RK11C-RK03-Connectors/ they use unibus cables for drive/drive cabling
Both of my terminators are plug-ends; I have one for the diablo 31 and one for the diablo 44.
That said, my DG 4047 also has a plug-end coming out of the controller, so I'd be willing to bet it's a matter of "both ways are equally valid"
In my opinion, with the prices the way they are for 'genuine' connector components, the only viable solution would be a reproduction. Gwiley seems like he has a good way forward for the 'P' contacts, but that still leaves the (last I checked) more difficult to acquire 'S' contacts.
 
S bodies (at least on eBay) are cheaper than P

you still have to source the solder pins at 1-2$ ea

https://www.ebay.com/itm/233868116699 is nice that it has the thumbscrews
 
Both of my terminators are plug-ends; I have one for the diablo 31 and one for the diablo 44.
That said, my DG 4047 also has a plug-end coming out of the controller
Guess we should swap one of my socket terminators for your plug terminator.
So far, all of the cables I have coming into the drives have been sockets.
I think there is a use case for having a terminator pcb that plugs into the two "out" 40 pin connectors of the adapter

Thinking about it, I think all of my socket terminators came out of DG environments...
 
Here's an attempt to record the likely use cases... tried to capture the most likely configurations.
Diablo Adapter Cases page1.jpg Diablo Adapter Cases page2.jpg

There could be two types of Diablo Adapter, a "pin version" (the most common configuration) and another with sockets. The socket version of the adapter is highlighted in yellow in the drawings.

Here's a possible adapter design. It connects to the dual 40-pin flat cables that connect the "A4" and "A6" accessories of the RK05 emulator and is almost the same signal set as the dual cables from the DEC RK8-E:
1716188261154.png 1716188289969.png
This is a "pin version" that uses the real MRAC 42P connector. I'm looking at a slight variant that could use contact pins mounted to the PCB and a small spacer between the PCB and the connector on the Diablo drive.
The pins would be something like this: https://www.digikey.com/en/products/detail/keystone-electronics/1362-2/2746382
and need larger holes (0.062") compared to 0.039" for the real MRAC 42P.

The "socket" version could be essentially the flip of the pin version, as @vrs42 mentioned. However, a unique board design for the socket version might be better so the silkscreen indicates where to mount things. The mounting holes are intended to attach a 3D printed cover, similar to the metal plate on the real Diablo cables.

I think there is a use case for having a terminator pcb that plugs into the two "out" 40 pin connectors of the adapter
I've also been thinking this might be useful. New owners of Diablo drives might not have Diablo terminators.
 
I remember reading about an issue not having an RK05 closest to the disk controller when mixed RK05 and Diablo drives are used. The Diablo drives don't generate AC Low and DC Low signals and the disk controller expects them.
 
you also have to be careful about addressing because Diablos treat the id pins as individual selects while the rk05 does a 1 of 8 decode
thinking about it, i that may also be an issue between the RK11-C and D
 
I remember reading about an issue not having an RK05 closest to the disk controller when mixed RK05 and Diablo drives are used. The Diablo drives don't generate AC Low and DC Low signals and the disk controller expects them.
Oh, Good point! The Diablo Adapter board connects the AC Low and DC Low through between the 40-pin flat cable connectors but any of the configurations in the use case diagrams in this post that loop through the Diablo won't work:

Another issue that is similar is that in the RK05 emulator design I hijacked pin J2-A on the RK8-E dual 40-pin flat cable interface to carry the BUS_RK11D_L signal. Clearly, that also won't loop through the Diablo, but that brings up the issue of the select lines. More on that in the response to Al's post.
 
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