Call for community help Edit

David from our forum's reported his Ion has stopped working. Turns our David lives in Manchester UK, I was going there on business, so we agreed to meet up and I would see if it was possible to bring the Ion back to life. Right now this task is beyond me but I wanted to share some pictures etc with the wider community - perhaps we can try to diagnose the issue together and/or if it really is beyond economic repair (or lack of spare parts) then folks can request spares from this and get their instrument working. Alternatively, Alesis UK may also like to scavange parts for potential reuse by others from our community.

Exterior Shot Edit

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Exterior shot of Alesis Ion on the bench

The Ion was in its original box. David had taken the external screws off leaving the Ion ready to be investigated.

First observations were the internals did have the characteristic "smoke" smell - so something clearly had gone wrong. I downloaded the Alesis Ion (Q01) Service Manual P/N: 8-31-0125-A from our files section.

Interior - Switched Mode Power Supply Edit

The first thing I checked was the SMPS.

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Switched Mode Power Supply

I try to know my limitations so I checked:

  1. Power Lead had continuity with plug pins via continuity meter
  2. Power Lead supplied 240VAC with AC meter
  3. Power off, check fuze is good.
  4. Carefully unplug the switch and check for continuity - good.
  5. Look at service manual.

Please find page 40 "BB SWITCH-MODE POWER SUPPLY" schematic. NOTE: this is "upside down" - ie the opto coupler highlighted at the bottom of the diagram in red is in the correct position relative to the "underside" of the PCB. Therefore the voltages highlighted in blue (V2, GND, V3, V1) are V2, GND, V3, V1 as we look at the power supply photo.

CAUTION: There is a nice 400V capacitor highlighted in a thick green - I bought myself a 5W 10k Ohm resistor that I carefully insulated to bleed the voltage out of this - and I am sure there are other nasty parts on this that might retain energy even after power is removed. Click on the image to enlarge it.

SMPS 001

SMPS schematic. Heavy green -> 400V cap. Discharge this via a suitable insulated resistor. I am interested to know the V1, V2, V3 and whether they are DC supplied from the SMPS.

I checked with Alesis UK - they no longer stock such parts. So my idea was can the community help us to work out:

  1. what voltages should be present at
V1 [RED, +15V]
V2 [BLACK, -15V]
V3 [ORANGE, +7V]
  1. are they fully rectified DC? (I dont see the typical 4 diode arrangement on the schematic)
  2. Is it possible to work out where DC is supplied on the main board and hence bypass this PS with a suitably rigged bench supply (for testing purposes)?

NOTE: I am moderately colour blind - but normally folks use black wires for 0V, red wires for positive, then a whole load of other colours on an ad-hoc basis - yellow is often -12V say. Alesis uses Red, Orange, Green, Black - and since black is on one end it for sure is NOT ground.

Steve Wahl points out ... Edit

"Why dont you look at page 27 of the Service manual? Good question other Steve. And he is right - great info.

MB 001

Follow 1, 2, 3, 4 to find the Vmax for each line

This I now do, then marked on schematic the values.

We see that:

MB pin 1 -> +15V     == V1 RED
MB pin 2 -> +7V      == V3 ORANGE
MB pin 3 -> ground   ==    GREEN
MB pin 4 -> -15V     == V2 BLACK

I took a picture with cable connected between defunc SMPS and Mainboard so you can see the colours too (please check my colours!)

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SMPS connected to Main Board with cables. NOTE: the schematic for the SMPS is "reversed" - that is turn PS upside down if you want the pins to correspond. Seems "right way" up on main board.

Main Board Edit

Moving to the main board I noticed some splatter on one of the capacitors and a lose cover for one of the components - look like C146 (see photo on right).

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MainBoard CapSplatter

Here's the schematic.

I noticed one of the LM7912s back waiting to fall off. I have some of these lying around the garage so I may replace this part (if I can find them).

Other than that the capacitors look in good working order. I did attempt to measure some capacitance with a meter but realised I need an ESR meter - and even then may need to desolder leg at a time.

I attach some extra photos - oh one chap in the forum noticed his Ion was playing the keys "wrong" - I suspect this is because the upper/lower keys were put wrong way. When I took these off David's Ion I added some tape - red for upper and green for lower (I find red and green tricky colours BUT RGB - so red is always my first choice, then green, then blue if I want to remind myself of an ordering. I also added tape to the main board so they two have to match). One experiment I did try - I put the Ion keybed into a Miniak - and it works ... for about 10 seconds then the Miniak raises an error - it knows it should not be able to find 49 keys :-(. I guess this is why MIDI was invented :-)

More internal photos Edit

If there were other internal photos that folks think may be of interest then please contact me (shooking_sybase) via the main Ion, Micron, Miniak group and if I still have the machine I will take photos.

Next Steps Edit

Ideally if we could work out what V1 - V3 is and make up a bench supply then it may be possible to get the machine working.

Thanks to Steve we have this info (will ask for a check from community).

Failing that, even to be able to verify that they mod wheels work, or the voice chips, display, knobs could be used by others - well this would be a fitting end to such a beautiful instrument. I had hoped I could use the Miniak PS somehow (because the architecture of these machines is so darned similar). I notice various test points on the schematic/board. It seems there are TP for +/- 12V, 5V, 3.3V, 2.5V and GND. I have an old ATX PS that can supply pretty much all of these.

Else if folks would like to request test parts then ONCE we exhausted all simple possibilities to resurrect David's Ion then it would be possible to split the parts.