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MOTM pcb in frac rack format?
MUFF WIGGLER Forum Index -> Modular Synth General Discussion  
Author MOTM pcb in frac rack format?
BBlack
I'm looking at kits on Bride Chamber, and there are quite a few I'm drawn to, but I'm interested in piecing together a frac format setup.

Just curious if the size of the PCB has to do with the format of the system, in other words, can I load a MOTM-intented PCB behind a frac-sized panel?

Thanks!
decaying.sine
Most of the MOTM PCBs are 4.5" x 5.5" ish.

You could easily make a bracket and mount the PCB with longer side out the back.

It's all about your case. If you have a big case (basically about just under 6 inches depth), then go for it. Just fly wire everything to the panel. It really only means the addition of four more sets of pot wires to the board, mostly. No big deal at all.

...and, welcome to Muff's! w00t
e-grad
MOTM pcbs have panel mounted pots. Any board with 4 pots won't fit behind a frac panel. At least not if you keep the mounting scheme. To my best knowledge any board with 3 pots will fit.

I've built several modules actually designed for 5U in frac: MOTM190 VCA; MOTM485 VCF; Oakley Dual Noise (old version); Oakley S&H; Oakley Overdrive; Oakley MulitMix.

With some patience you'll be able to spot them here (2nd pic):
https://www.muffwiggler.com/forum/viewtopic.php?p=173801&highlight=pic #173801
decaying.sine
Here's a pic of what I was talking about. It's just a MOTM-485 (<---It's really a 480 and Paul just busted me drinking on the job) PCB sitting like I would mount it behind a euro panel (Synth Tech e350 for demonstration purposes).

VR1-VR4 on most of the PCBs would just be "flyed" to the panel and you would mount the PCB with, say 1/4" standoffs, with bent aluminum. You can drill the holes your self and then secure this to the panel with a nut. You still get a nut on both sides of the panel and the PCB should be secure.

sduck
Sure, it can be done. Depends on how creative you are with mounting the pcb how neat it turns out. Don't worry about the pcb mounted pots - just run wires between the holes and the pots. That's a good idea even in motm format - those pots breaking off during shipping or whatever is the one weak spot in these designs.
paults
Just to be picky: that's a MOTM-480 pcb.
paults
And, I have shipped over 65,000 pots and I think maybe 1 ever "broke off in shipping". They are bolted to the front panel as well as soldered (Euro pots are soldered in 5 places). The one that broke was hit quite hard straight on from the front, and poped the back off when the shaft slammed into the element.

That was like 2003.
decaying.sine
paults wrote:
Just to be picky: that's a MOTM-480 pcb.

True True. I did have a couple Guinness ftw! Guinness ftw! Guinness ftw! Guinness ftw!
fluxmonkey
i've built quite a few in frac format, works fine. you have to work out the mechanicals for each module, but a general approach of having a line of pots on the one side (right if you want to be consistent w/ blacet) and using those to hold an perpendicular angle bracket, then mount the board to the bracket. works well for me.
Norman_Phay
This is actually pretty straightforward to do. You have to mount the board to the panel lengthways on standoffs. The clearance is quite tight, so wires run from the board to the panel are best not run below the board. As mentioned above, do not mount the pots to the board, run flying wires instead. I have converted my 5U MOTM300 and MOTM440 to frac and plan to do so w the rest of my modules:


MOTM440 filter behind frac panel by kay_wrad, on Flickr


Rear of MOTM440 filter by kay_wrad, on Flickr
#
Paul, I'm sure, is appalled by this....
sduck
paults wrote:
And, I have shipped over 65,000 pots and I think maybe 1 ever "broke off in shipping".


That's because people are sending those ones to me to fix! razz

No, actually the existing MOTM design is seriously robust, as long as you follow the instructions as per mounting the pots/pcbs/brackets. It's much less likely to pop a pot off than virtually any other design. And I've never had a problem with the actual motm modules, or even heard of anyone having such a problem.

The problem can become acute when you start mounting the pcb in other ways, as suggested by an earlier poster. These are fairly large, heavy pcbs - if only the pots are supporting it, or if they are only augmented with a flimsy bracket, that's when you can get problems, especially when using the pots with those tiny wire connectors like the spectrol ones. I've had to fix 2 motm style things that have had this problem - a Blacet Time Machine, and something else which is escaping my mind - but both of these were obviously really jostled in shipping.
paults
Certainly, if you depend on the soldered pot leads to support a stuffed board witout a bracket, you are asking for trouble.
Tubeampguy
paults wrote:
Certainly, if you depend on the soldered pot leads to support a stuffed board witout a bracket, you are asking for trouble.


Bananalogue LPFA comes to mind zombie
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