MOTM

At 8:42 PM -0600 03/31/01, J. Larry Hendry wrote:
>
>Mark, I have three of the PCBs in my metal rack. The existing ones have 12
>MTAs and also some push-on faston lug connections that are designed to be
>the source.  You don't want to feed the PCB distribution board with # 18
>wire.  You want to use something larger if possible between the PCB and
>power supply.  I use # 14 stranded in all mine.

Really??  That seems a bit much.  Are you running them over a long
distance??  My entire studio is run off of two 12/3 cords going from the
wall outlets to the power conditioners.  Most gear uses 18/3, including
tube amps that draw so much current you can use them to heat up sandwiches.
Sure most people use a microwave, but you can taste the difference with
tubes ;)

I notice that motm uses four conductors, but do all three go to the power
supply??  Since that seems like two grounds, I assume the first one is
common to the supply voltage, but what is the second one -- local, earth,
or what??  I'm thinking of buying this cable at Home Depot (who do not sell
10/32 or 8/32 inserts, btw, in case anyone is wondering) since 14AWG is
more like electrical supply than electronics supply.  I'll have more
choices in three conductor cable than four conductor cable.

>Personally, I don't see that mounting the PCB wood is a big deal.  At 15
>volts, wood is a pretty good insulator.  At 15,000 it woudl be a bad idea.
>However, when I mounted mine in my metal rack, I just went to Radio shack
>and bough some of those shallow $3 project boxes with the screw-on lids,
>just big enough to hold the PCBs.  I tossed the lod and mounted the PCBs in
>these plastic boxes.  Worked out real nice.

Nor do I think the black paint I'm putting on the wood is all that
conductive either.  I have to see how I'm going to fit this PCB -- whether
I need stand-offs or have to mount it perpendicular to the board (like the
motm PCB's are perpendicular to the panel).

Also you could use a box like that and make it cable mounted!!  I have a
bag of clamp connectors to make clunkers, which will fit a plastic outlet
box.  Now the big question is whether the PCB will fit, how long is it??

>--Mark--
>and then build a cable with a MAT-1564
>(AMP#640426-4, right??) on one end and whatever
>on the other.
>
>--LH--
>Personally, I would not use the MAT-156 connector as the source to the PCB.
>The PCBs are set up for a better source connection.  I can send you a photo
>of one if you like.

That's a very good point.  Also, if I used anything bigger than 18AWG then
I couldn't use a MAT-156 anyway (at least not according to the Digikey
catalog).

>Amphenol makes some real nice round connectors too.  However, they are
>pricey also.  I would not consider Cinch-Jones for a power connector.  I
>would prefer something that is locking.  The last thing you want is your
>power supply cable popping out on you.

I finally found a circular plastics connector called the AMP "Series 1".
It takes 18-14AWG wire and isn't that expensive, but the four conductor
connector is .942" inches in diameter, which sounds huge!!  So all things
considered, I think your plastic box idea might be the best of all.  That
way if I need to move the system, I could disconnect the box from the rack,
cable and all.