Alesis DM Pro surgery 1; internal memory battery

Distinction:

I have a long and complex history with the Alesis DM Pro. It’s a uniquely powerful and expressive device, specifically in how one can custom-program both natural and novel drumming expression between modulation Sources

  • hit velocity
  • hit rate (think “swells”)
  • random variation
  • many others…

…and the resultant sound controls.

  • pitch
  • amplitude gain and envelope controls
  • filter cutoff and envelope control
  • many others…

I spent a LOT of time programming and personalizing it to get the most flexible e-drum system I could out of it, and as it’s outputs started to fail, I realized I could keep the unit and dump all my hard-earned programming into a new (likely cheaper) unit.

In fact, I picked up a second DM pro that was in rough shape for spare parts or frankenstein-ing.

The Brain’s brain fails:

However, when I booted it up this month, I started seeing scrambled patch names, and when I tested it’s saving of trivial changes, it failed to retain them. I immediately (re)backed up all my DM Pro kits and Globals into SoundDiver.

In this unit, like most programmable gear from the 90s, patches are stored in (non-flashing) memory chip(s)  powered by a coin-sized battery that keeps them charged while the unit is powered down. Whenever a unit (especially from 80s and 90s) starts wiping all the presets, check for a little coin battery.

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many units come stock with single-use batteries which solder directly to the board. These are often designed to only last a few years (often RIGHT past manufacturer warrantee).

 

To the Bench 

Opening the DM pro up is tricky.

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the unit’s main “hood” is a full-width panel with hoods to the sides: be careful with those recessed screws.

 

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once open, we can see how the battery is on the motherboard, with two ribbons to a Front Panel UI board, and a a ton of I/O

 

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getting lined up to try with battery, initially buying another of the exact “single use solder in” battery found inside.

 

Spec:

for reference: this project involved.

  • initial purchase of a Panasonic BR-2325-HG panel-mounted battery
  • upgrade to CR2025 coin-button battery holder

 

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before proceeding, I chose to upgrade to a battery housing for easier future service.
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in order to do soldering on that battery, you have to pull out the motherboard, which requires removing EVERYTHING around it. be careful to sort all the nuts, screws, etc on your way in.
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the Front Panel UI board was tricky, as it has criss-crossing ribbon cables that should not be confused.
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once disconnected, the Front Panel can come right off
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careful in dismounting the MotherBoard from the main chassis

Practical Problems of Polarity

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I metered the existing battery for polarity

 

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Mark the polarity on the PCB, just to be idiot-proof, because…
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…the out-going battery had 3 tabs, so you could only install it “right way in” polarity…

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…but the incoming battery only has two, so I have to “get it right”

Making it fit:

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the solder-tabs on the incoming Battery Holder were too wide to fit the open holes on the motherboard, so I used a file…
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…making the battery-case
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now the battery case fits nicely for a fresh LiOn battery.

 

 

Power ON ?

after reversing the process to re-assemble the parts enough to power on, I found the unit suddenly showed symptoms WORSE than “memory wipe”

it Showed NO screen or response to front panel board.

Before panicking, checked my work and realized I’d mis-mounted a standoff.

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After remedy of that mistake, I everything worked fine, and it could now save patches through  power cycles (again), so I reassembled the unit for future use.

back to “normal” (for now)

 

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