MOTM

I wonder if some bright, literate person on this list might accept the challenge to really, clearly (and with pictures!) explain the options for properly and safely powering a large MOTM system, now that the power requirements have changed. Moe has a pretty nice essay on his 'Hot Rod' site about power, but now the playing field has changed a bit.

It was really only a matter of time before the need for a 5v reared its ugly head; let's face it-we live in a 5v world. Now that day is here. I have an MOTM-900, and I also have several large linear +/- 15v supplies and now three +5v supplies on order. But I'm not 100% sure what to do with them in order to power several cabinets of modules.

I *thought* I could figure it out on my own, frankly... I had intended on rigging a single 1u panel on the front with a power switch; this would activate the multiple supplies internally... connectors to run power to wing cabinets...

However, a few months ago someone on this list posed a very similar question about wiring a front-panel switch, and several people whose opinions I trust a lot jumped up and yelled, *"What!?! Are you nuts!?! That's AC power - you will certainly be killed!!!"*

So, *wow*, I got scared. Now I'm sitting here with boxes of power supplies and 14 gauge wire and fuses... and I'm terrified to start tinkering.

Moe & Larry have photos of their cabinets' power runs on their sites, but it's not clear to me exactly how the terminal strips are wired, etc. And of course, the new 5v issue is not addressed, and perhaps cannot be until we get our hands on a few of these modules and the new power distribution boards. But I'm really hoping that maybe someone can undertake a kind of "mini-manual," with all the requisite warnings and "I take no responsibility if you fry yourself" notices of course. But some kind of guide to how to collect all of this mess into a coherent power system that, a) will not kill someone, and, b) not cause ground loops and other such nonsense.

Are there any takers? I'm the kind of DIY person who has added electrical sub-panels to their home circuit box, with the help of a Time-Life book, so I'm careful, I can follow instructions, and I haven't blown up or burned down my house yet. But I'm still not 100% clear on how you can take multiple power supplies, tie their grounds together (or not?), add a fuse (or two or three?) and get the whole thing working properly.

Anyway, long rant, but let's face it: power is a CRITICAL part of the synthesizer, and we have to address it. In fact, the first two modules I bought were a VCO and a power supply, because Paul rightly convinced me that without handling power properly, you have nothing. But it's also the part of the synthesizer design that is left most hazy, because we all have different cabinetry/mounting systems, many of us don't want to take up 3u, 6u, 9u, 12u of front panel space for power supplies, and now we have the new issue of adding a 5v rail to existing systems.

Thanks in advance for advice on this!

Ken (Mr. T)

Thanks Ken for posing that question to the list. I'm currently having the 
exact same feelings of concern. I was thinking of powering multiple supplies 
by wiring a double pole power switch (with a suitable amperage rating) to a 
terminal strip and then from there to my new power supplies. That way 
everything can be switched on and off with one go.  I just don't know if this 
is the correct way to do things. 

 Thanks in advance to anyone that can help,
  Andrew


In a message dated 12/3/02 8:55:26 AM Central Standard Time, 
ken.tkacs@... writes:

> I wonder if some bright, literate person on this list might accept the
>  challenge to really, clearly (and with pictures!) explain the options for
>  properly and safely powering a large MOTM system, now that the power
>  requirements have changed.

Mr. T wrote:

> But I'm really hoping that maybe someone can undertake a kind of
>"mini-manual," with all the requisite warnings and "I take no responsibility
>if you fry yourself" notices of course. But some kind of guide to how to
>collect all of this mess into a coherent power system that, a) will not kill
>someone, and, b) not cause ground loops and other such nonsense.

Yes, Yes, Yes!  I second, third and fourth that motion!

Those of us who are relatively new to the electronics game would really
appreciate this kind of thing.  Even basic stuff like "How does a terminal
block/strip work?" would be great.

As an aside, isn't it nice that we have a forum for questions like this?
I recall some electronics newbies being berated regularly on AH for
asking this kind of stuff!  I hope our list never becomes that useless!

Thanks!

-Chris-

Larry the AC power man!

He brings up 1 important (and overlooked) point: the current (pun alert!) AC power switch in the
MOTM-900 is NOT RATED for the MOTM-950. A larger, different AC power switch is needed.

OK, back to writing the '190 manual.......

Paul S.

Request for Knowledge: Powering the MOTM SynthesizerOriginal Message -----

From: Tkacs, Ken
I wonder if some bright, literate person on this list might accept the
challenge to really, clearly (and with pictures!) explain the options for
properly and safely powering a large MOTM system, now that the power
requirements have changed.

--LH--
I will be happy to take on this challenge.  Since I just finished wiring the
NAMM cabinets (which include 5 volt power) and questioning Paul at length
about the new 990 power board, I "think" I have it all together  But, let me
take 5 minutes to throw out some basics incase someone wants to disagree and
shed some lighb on the subject I had not seen.

1.  There is NOTHING wrong with running AC power to the front panel switch.
Loads of consumer equipment on the market with UL and CE approval does just
that. The MOTM 900 does just that.  However, lets select an appropriate
switch for the job.  I suggest a nice 250 volt AC 10 amp minimum rated
rocker if you plan to switch multiple supplies.  And, many of them are rated
for high in-rush to cover the initial spike while charging them big 'ole
caps.  Sure, using the standard MOTM toggle would look nice.  And, you could
get by with that kind of switch for a single supply.  But, its just not
appropriate application in my opinion.

2.  Fusing.  For maximum protection of your supplies, each should be fused
independently at the lowest value that allows you to load your supply.  If
you gang 4 supplies on one fuse and increase the size accordingly, you are
compromising the protection of the supply.  If any old fuse big enough was
good enough, they would only make one size.  Now, that means the fuses are
downstream electrically from the switch.  So, you need another fuse, large
enough to carry all loads right where the power enters the synth.  It is to
the the FIRST thing on the hot leg after the AC connector.  Otherwise, if
you switch fails, you have a small fire until the house breaker trips.
Notice the MOTM power switch has the fuse built in.

3.  Use big wire to the distribution boards.  Get some stranded copper 12 or
14 gauge.  Nuff said.

4.  Connect earth ground to the power supply case.  Lug the wire, pick or
drill a hole, take a #6 to # 8 machine screw and locking nut and tie earth
ground to the power supply case(s).  This is not optional, it is absolutely
required.  Don't tell me it works fine without it because I can show you why
it is bad (not to mention a code violation).

5.  When  adding the 5 volt supplies (or for some supplies with 5 volt
output (built in) bond the bipolar ground for the +/- 15 and the separate 5
volt ground together AT or VERY NEAR the supplies.  Run separate grouns
wires from the 5 volt ground and the 15 volt ground to the distribution PCB.
BUT, do not assume that on a triple supply that these two ground points are
common.  They are not on the power one supply that Paul sent me for the NAMM
cabinets.  Don't cheat and run ome wire to the PCB and jumper them at the
PCB.  Jumper at the supplies and run two ground wires.  If you are adding
the little 5 volt add on supplies, bonding the two DC grounds between the
supplies is also required.

OK, my 5 minutes is up and my day gig is calling.  I'll do some PDF drawings
and such later.

Larry Hendry

Thank you Larry...thank you Ken

Gary

In reality it is a 3.3 V, 2.5 V and 1.8 V world.  Synth module design is
still fighting off the lower voltage ranges.
John Loffink
jloffink@... 
It was really only a matter of time before the need for a 5v reared its
ugly head; let's face it-we live in a 5v world. Now that day is here. I
have an MOTM-900, and I also have several large linear +/- 15v supplies
and now three +5v supplies on order. But I'm not 100% sure what to do
with them in order to power several cabinets of modules.