Exchange tips and tricks for the Akai MPC4000
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By Telefunky Thu Jul 28, 2022 7:24 pm
Posts about pad sensors on this board generally agree that MPC 2k, xl, 2500, 4k use identical sensors and the MPD16‘s are identical to the 2k.
So I got an MPD16 (in top condition) to slaughter it and save on shipping and tax...
Opened the 4k, removed the pad holder chassis and couldn‘t believe the size of the flat cable :Sigh:
Twice as wide the the MPD‘s ribbon :shock:
Yes, electrically both are identical, same lines, but sometimes size does matter...
At least the 4k has brand new pads now (which doesn‘t change a thing, except they damp case noise slightly better)

If anyone has experience with remove of the sensor pad and the glue I‘d appreciate a hint.
Plan is to heat it up from the bottom to enable lifting and then try acetone or isopropanol (on an edge part first).

cheers, Tom
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By MPC-Tutor Thu Aug 04, 2022 9:22 pm
Hmmm, I had hoped to do the same as you with an old mpd16, but haven’t yet opened up my 4000 to perform the swap over. I won’t get a chance to do this for another few weeks so I’m interested to see if I experience the same issue. Based in old posts here I assumed it was a straight swap
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By Telefunky Thu Aug 04, 2022 9:51 pm
My brand new elcheapo desoldering gun arrived today and already served to remove the ribbon connector from the MPD circuit board. Flawless job, really enjoyed it...
The ribbon connector of the 4k can remain untouched.
There‘s a lot of space on it‘s back side to solder a short flat cable (20 lines needed) to the connector pins and the other end will receive the former MPD connector (an open/lock version), more convenient than the 4k‘s
A copper lines flat connector would have avoid the removal of the control circuit board, but I forgot to order. :WTF:
to be continued...
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By Telefunky Fri Aug 05, 2022 3:20 am
The flat ribbon cable was a fail for the angle required towards the smaller connector...
Replaced by single wires, wanted to test with the MPD chassis still under the sensors.
Oops, different frame position, put some foam under to avoid shorts.
And another surprise: stupid me centered the connector at the position of the original one, but of course it needs a shift to the rightmost side... :Sigh:
Still the construction seemed sufficient for some light finger banging and the thing responded... way more intense than before :smoker:

Learning by doing, tomorrow I‘ll do the stripping off by heat gun (thanks for confirming, Sense-A) and re-position the connector.
ps: the ribbon cable of the pad sensors does not fit at all, the MPD16‘s is only half the width of the 4k‘s, just the line arrangement is identical.
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By Telefunky Fri Aug 05, 2022 7:07 pm
The pads have a fairly low sensitivity, a full (!) bang may reach about 80 in velocity.
But I‘d rather not hit too hard, mainly to reduce noise.
The 4k is also intended as a synth midi controller, so good velocity response is much appreciated.

Atm it’s compensated by Pad Assign-Sensitivity and I get along with 160%, but my 4k doesn‘t remember the setting. After a power cycle it’s still displayed, but not applied.
Only after tapping each pad and dial 1 step up/down (or down/up) the screen setting becomes active again. :hmmm:
I‘ve checked if this changes with programs, multi, but no way.

Here are both sensor pads side by side

Image

let‘s see how this link works...
obviously it does, left is the MPD16, right the 4k
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By Sense-A Sat Aug 06, 2022 3:12 pm
You could still make it work. It's just a lot of work.

You could get two female socket connectors for the ribbons (lift part numbers out of service manuals), mount them on to a small breadboard, connect each pad from each ribbon with arduino cables, and try to squeeze your custom adapter assembly into the mpc 4000 box.

You could also see if you can modify the metal plate screwholes so that you can just mount the other one without trying to lift the pad sheet off of it.

That sounds like a lot of work just to get a pad sheet to work, though.
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By Telefunky Sat Aug 06, 2022 9:56 pm
Yes, Sense-A... looks like I‘m back to my senses again... :mrgreen:
On the flipside of the desaster there were a couple of small revelations (imho) about the sensor construction and why it wears out.

The electric line grid is printed with conductive ink, a fairly weak mechanical base.
I even suspect it‘s less the black pad‘s properties that change, but the conductive lines below. At least in my case the area under different pads looked rather inconsistent.
For a restoration to „state as new“ one would have to replace both the bottom layer and the pad sensor sheet.
And that’s the state I‘d like to put in the 4k again... it‘s a very unique piece of gear. :smoker:
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By Sense-A Sun Aug 07, 2022 1:35 pm
Someone suggested that the isla s2400 should have used the keyboard switch type tact switches that are easily replaceable and customizable among the keyboard enthusiasts and gamers.

Only problem is i'm not sure how much velocity feedback you could get from that type of tact switch.

I remember, back when trying to fix mpc 1000 shit pads, i even used conductive carbon out of an old Nintendo Power Pad which had plenty of it. LOL

You can buy flat, conductive copper tape and make your own circuit for the pads. https://www.youtube.com/watch?v=nKMhuQ2hq9E The 13 minute mark is how an mpc pad works.

This conductive copper tape is too wide but you get the idea https://www.3m.com/3M/en_US/p/d/b40067945/

You could just use 2-3mm wide conductive copper tape and bridge ribbon cables like that with a piece of clear plastic film with copper tape lining up each trace.
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By Telefunky Sun Aug 07, 2022 10:35 pm
Agreed - the construction of the sensors is indeed really primitive.
You find them as examples in countless Arduino applications: an FSR pad bridging conductive comb shaped lines.

I even considered a printed circuit board which allows a different type of connector.
But it would certainly need experimentation with various FSR materials to match the „decoding“ built into the MPC‘s firmware. (resistance and reaction time varies)
As I also need a couple of switches, I‘ll probably order a new one from MPC Parts and silently grumble about shipping and tax... unless another strange idea enters my mind :mrgreen:

The MPD-16 was a nice purchase (50 bucks), though. May serve as a standalone midi controller.
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By Telefunky Wed Aug 10, 2022 1:57 pm
Ordered a new sensor pad from MPC Stuff, arrived within 2 days (California/Germany)
Fedex performed as announced, great service, which also applies to MPC Stuff.
They are a bit on the expensive side, but deliver quality (imho).
The sensor pad is already mounted and works perfectly. :smoker:
... eh, isn’t it a bit too sensitive now ? :hmmm: just kidding :mrgreen: