[vcf-midatlantic] MMJ cables for cheap

David Riley fraveydank at gmail.com
Sat Apr 23 16:33:26 EDT 2016

On Apr 23, 2016, at 3:11 PM, Dave Wade via vcf-midatlantic <vcf-midatlantic at lists.vintagecomputerfederation.org> wrote:
> Dave,
> I think several folks have the crimp tools and jacks/plugs needed to make MMJ leads. The problem I have had is finding 9 or 25-pin adaptors when I want to plug into a non-DEC terminal.  The last cables I made were "bodged" from a similar cable. I cut one RJ12 off and replaced it with an MMJ plug, so I ended up with an MMJ<->RJ12 lead. I then tweaked an RJ12 DE-9 Socket to connect to a laptop with serial port. In fact these leads are a cheap source 6-Way cable...

DE9 and DB25 to 8p8c adaptors with completely customizable pin selections are easily available from Monoprice, though they insist on calling them DB9 and RJ45 (you really DON'T want actual RJ45 going into your motherboard; those buffers are tolerant, but 50v is a lot):

http://www.monoprice.com/product?p_id=1152 <http://www.monoprice.com/product?p_id=1152>
http://www.monoprice.com/product?p_id=1159 <http://www.monoprice.com/product?p_id=1159>

Despite what it looks like in the picture, it comes with the pins uninserted into the D-sub socket, so you can pin them out however you like.  I like to pin mine out to the Cyclades specification, for two reasons: 1) I have a big Cyclades terminal server, so it's handy to be able to be able to move the cables between the two, and 2) it's actually a mostly 1-to-1 match for the MMJ pinout; you only have to bend down/snip one wire, and nothing has to cross over.  A Paladin crimp frame and the MMJ and 8p8c dies will set you back probably $80-$100 all told, but if you ever have plans to make even just Ethernet cables in the future, it's a really good thing to have.  The MMJ end plugs are pretty cheap in bulk (about 30 cents each) and still readily available; ask around on the list, and I'm sure you'll find people willing to split a bag of 100.

Making 8p8c->MMJ cables is really the best way to go, especially with the presence of these little D-sub adaptors.

- Dave

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