Machinedrum volume problem

Elektron Gear Machinedrum
#1

Hello, I’ve recently acquired (it was a bargain) a machinedrum MK2 uw, sold as not functioning.

Indeed, It Is not working properly: all the functions EXCEPT outputting audio seem to work great. It does send and receive midi, all the buttons and knobs work, it is just almost dead silent.
I say almost as if I crank the volume up (with gain after the unit) I can hear some faint clicks out of the machine, resembling what I can see is programmed.
Also the inputs (if driven extra hot) seem to work as I can hear it out of the machine with low volume. The volume knob has some issues and I can hear it crackle if moved, but there is no audio in any position.
Needless to say I’ve done all the possible factory resets and update to the latest firmware, I also opened the machine, unplugged and re plugged the cables, tried the others additional outputs, nothing. In test mode everything seem fine.

What can I do? I’m confident enough to open and check other things, or to solder reflowing the volume knob.

#2

anything from CDEF outputs?

swapping the volume pot is a good start.

#4

try to check signal before it goes through the pot to establish if there’s something wrong with it. as there’s no schematics probably you would need to try/figure out which pins are the incoming signal.
if the pot is ok/ok-ish next sensible step would be checking amp section. i do realise it is easier said than done.

edit:
i have checked photos i took some time ago so it seems that volume pot is connected via cable to the main board, which helps a bit
image

#5

I was typing this and I saw the edit live!
Yes it is. The connections seem good tho in my machine, so it is a weird behaviour.
One of the pin on my unit seem a little bit soldered worst than the others, but it doesn’t seem so bad… I’ll do pictures ASAP.
I think (from the research I’m doing on this forum) it could be a PSU problem, still I don’t think really know where to put my hands on.

#6

Sadly not! Any output doesn’t seem to work. From what I hear I can only hear faint clicks when overdriving externally the headphone output and listen carefully, but maybe if I exagerate more I can get similar results from the ABCDEF outputs as well.
Do you know where I can buy this pot?
Also, should I see some activity if I turn the volume pot in test mode? Because it doesn’t. Maybe is the only analog part in the machine

#7

i can’t recall how md is structured but found this

9133371995_f5d0a629cd_h
9133371995_f5d0a629cd_h900×1360 508 KB

so it seems that the connector from the pot feeds the output board. from the image i gather that the audio signal comes from the pcb with lcd, passes the pot and is carried to the output pcb

i would check the pot first, next output pcb and lastly (if first two items are ok) i would look into amp on pcb with lcd

edit:
I guess the above is not 100% correct. i found this

image
image1056×556 212 KB

which indicates that there is cpu board (below/beneath output board). it makes sense, as i couldn’t find an mpu/cpu on the control board

#8

This seem to be a MK1, and Is kinda the same but not quite as much I can recall.
I’m going back home in the evening, open it up and compare, but it seem that your deductions are right, the connections should be similar but I don’t remember jumper wires like in the first pic or a transformer of that kind (?)

#9

possibly if you could do photos of all the pcbs from both sides (apart from psu) that would help to approach the problem in a more educated way :slight_smile:

ps:
as you mentioned, checking output voltages from psu might be a good point to start with

#10

Finally I’m home and I opened the machine. Here’s the pics

IMG_20240403_144637
IMG_20240403_1446374000×3000 1.82 MB
IMG_20240403_144629
IMG_20240403_1446294000×3000 2.04 MB
IMG_20240403_144642
IMG_20240403_1446424000×3000 2.26 MB
IMG_20240403_144707
IMG_20240403_1447074000×3000 2.24 MB
IMG_20240403_144738
IMG_20240403_1447383000×4000 1.53 MB

As I can see it seem a little bit desoldered on the volume pot, I’ll try to reflow it.
Should I post a picture of the other side of the jacks PCB?

1 Like
#11

Also a note: I didn’t think about that, but I’ve tried to boost the gain of the master compressor at maximum, and I can hear the machine from both the main output and headphones out (obviously still pretty low and distorted) so the problem should be in the analog domain I guess?

#12

so there are 3 op amps on the output board. highly unlikely all 3 went down. that would make me think that potential issue could be related to audio codec ak4626

i included datasheet links above. i would check voltage on pins 14, 15.

image
image1081×200 78 KB

if they are within the range, i would check voltages at op amps pin 4, 11

image

2 Likes
#13

btw. did you try to reset the machine to factory settings via boot menu? taking it one step further, have you tried to reinstall the firmware? i suggest that in reference to your comment re changing compressor settings.

#14

I tried to boot up my multimeter to find out is dead… I’ll buy another one tomorrow to check the op amps. Thank you so much for the schematics!
Yes I did both factory reset and firmware updates, the only thing I didn’t try software side is to install the unofficial X firmware.

#15

x firmware would not anything. ok. so software wise you are in the clear.
have you changed the coin battery? it is very unlikely it has anything to do with the machines odd behaviour but changing it won’t make any harm.

#16

I didn’t cause my unit has it soldered so it wasn’t my first thought
I ordered a pot replacement from eBay, coming in a week or so and then I’ll see… Cracking a lot of volumes up I can finally hear better, and there are multiple “dead zones” on the pot, so I hear the same volume at both minimum and maximum value…
Hope the fix is that simple!

#17

fingers crossed :slight_smile: you may try to put a few drops of contact cleaner into pot’s shaft to see if there is any difference.

1 Like
#18

Check analog power lines. It’s not the pot as same issue with the individual outs.
It is a general best practice to start from the power supply.
If a voltage is missing or bad first try without load (plug all the boards from the power board) - to check if the problem within the power board itself or a short circuit somewhere else.

2 Likes
#19

Wait, the volume knob doesn’t affect the others external outputs?
I’ll try to check power lines then. Got a multimeter on my hands right know, let’s try

#20

SOLVED! it was a broken diode in the power supply. just swapped it out and now goes perfecty :wink: