By DjDiskmachine
Sun Mar 04, 2018 9:38 pm
Hello MPC-lovers!
I've realized there are quite many posts on the subject about MPC 500 being noisy either on inputs when sampling or outputs or both of the above. I had this problem myself, and I did some detective work on determining the cause of this. As a few users reported their unit wasn't noisy and the previous owner of my unit hadn't said anything about it, I considered the possibility that my unit had gotten worse with time. I managed to solve it with an audio probe, new caps and my trusty soldering iron. I write this guide hoping that this post will be helpful to some of you that are experiencing the same problems. Also, if you find my description confusing, please drop a line and I'll explain a bit more and/or update the guide. =)
TLDR; so what's wrong with it?
I came to the conclusion that AKAI used a few components of lower quality to save manufacturing costs when constructing this unit. In short terms, this causes the power supply lines in the machine to have a dirty DC supply which in turn appears in the parts that handle audio amplification etc.
Causes
-Reason 1:
The behaviour is caused by using a (cheap) switched power supply that itself has a noisy voltage output.
-Is this a problem with my unit?
Might be! Get yourself a pack of fresh batteries (not the cheapest brand u can find for this excercise). Put em in, start the machine without a PSU.
Inputs / outputs still noisy? Read on further down. Noise gone - great! Get yourself a good PSU from your local music shop, doesn't need to be anything fancy but at least you can go back and swap it out easily if it doesn't help. Try another brand before continuing.
-Why does this happen?
This means your PSU is struggling to keep a constant voltage output due to the current draw being to high from the machine. Not uncommon for cheap PSUs that have a current rating lower than the value stated on the sticker. This is actually a bit hazardous for your work flow and might cause stuff like hanging while loading, reboots and corrupted saves.
-Reason 2:
Bad capacitors. A more tedious solution, but if performed correctly will produce great results. See guide below.
Note! Please let someone with quite a habit of soldering stuff do this, this is a bit more fiddly than soldering jacks to your audio cables.
Also, always unplug all power supply sources and ground yourself while operating the bare PCB of the machine or you might risk breaking something that is very hard to repair.
So- your unit seems to display the same symptoms as mine did. Don't worry, let's get engineery.
MPC500 service manual, a useful read for everyone interested in maintaining a unit of good health: http://www.synfo.nl/servicemanuals/Akai ... MANUAL.pdf
See this thread for my notes on diagnosing the problem: viewtopic.php?f=26&t=183490&p=1731157#p1731157
References below containing the form "C9##" are references to Electrolytic capacitors, an electrical component that is common in filtering circuits.
I suspected the capacitors that are associated with decoupling the output voltage from the power regulators to be the cause of my problem. The caps are all by the brand Lelon, after doing some measurements as well as consulting with a friend that does a lot of Amiga re-capping, I made the conclusion that the electrolytic caps were starting to go bad. This is a common phenomenon in cheap capacitors and a bit of a nuisance.
My friend made the recommendation to get a japanese brand, and I decided to go with a brand called Nichicon that was available from my goto electronics store.
Check Mouser, Elfa or similar retailer web page for your options.
The type you need to get is called Radial electrolytic capacitor, I picked this type: https://www.mouser.se/ProductDetail/Nic ... mA9VOTs%3d
The caps that need to go are C907-C912 and can be seen on the last page of the MPC service manual.
Both the power jack and the battery line will be led through three Integrated Circuits; IC901-903. These are LM2674M-ADJ, adjustable step-down switching voltage regulators that produce the 1.7, 3.3 and 5V power lines that all need filtering. These can be seen in the top right corner, last page of the MPC service manual.
C907-C909 are of the value 100uF (100 microfarads,16V) and C910-C912 are of the value 220uF/16V (220 microfarads/16V). The Volt tolerance doesn't matter so much, the MPC operates on 5V logic level so just pick any value as long as it's not a lot more than 16V as the caps you recieve on the mail will be huge and might nog fit in there.
It's not necessary to replace all of these blue cylindrical caps, just check the PCB next to the components, there will be a C9##-marking next to the cap to show which one it is.
These can all be seen in this picture here: https://www.instagram.com/p/BY_oUn0nSuF ... iskmachine
And after re-capping: https://www.instagram.com/p/BZCS0jpH9cw ... iskmachine
There's a dissassembly guide on how to screw the MPC here: viewtopic.php?f=26&t=184022
..aand here is a great tutorial on capacitors and how to replace them:
GLHF!
I've realized there are quite many posts on the subject about MPC 500 being noisy either on inputs when sampling or outputs or both of the above. I had this problem myself, and I did some detective work on determining the cause of this. As a few users reported their unit wasn't noisy and the previous owner of my unit hadn't said anything about it, I considered the possibility that my unit had gotten worse with time. I managed to solve it with an audio probe, new caps and my trusty soldering iron. I write this guide hoping that this post will be helpful to some of you that are experiencing the same problems. Also, if you find my description confusing, please drop a line and I'll explain a bit more and/or update the guide. =)
TLDR; so what's wrong with it?
I came to the conclusion that AKAI used a few components of lower quality to save manufacturing costs when constructing this unit. In short terms, this causes the power supply lines in the machine to have a dirty DC supply which in turn appears in the parts that handle audio amplification etc.
Causes
-Reason 1:
The behaviour is caused by using a (cheap) switched power supply that itself has a noisy voltage output.
-Is this a problem with my unit?
Might be! Get yourself a pack of fresh batteries (not the cheapest brand u can find for this excercise). Put em in, start the machine without a PSU.
Inputs / outputs still noisy? Read on further down. Noise gone - great! Get yourself a good PSU from your local music shop, doesn't need to be anything fancy but at least you can go back and swap it out easily if it doesn't help. Try another brand before continuing.
-Why does this happen?
This means your PSU is struggling to keep a constant voltage output due to the current draw being to high from the machine. Not uncommon for cheap PSUs that have a current rating lower than the value stated on the sticker. This is actually a bit hazardous for your work flow and might cause stuff like hanging while loading, reboots and corrupted saves.
-Reason 2:
Bad capacitors. A more tedious solution, but if performed correctly will produce great results. See guide below.
Note! Please let someone with quite a habit of soldering stuff do this, this is a bit more fiddly than soldering jacks to your audio cables.
Also, always unplug all power supply sources and ground yourself while operating the bare PCB of the machine or you might risk breaking something that is very hard to repair.
So- your unit seems to display the same symptoms as mine did. Don't worry, let's get engineery.
MPC500 service manual, a useful read for everyone interested in maintaining a unit of good health: http://www.synfo.nl/servicemanuals/Akai ... MANUAL.pdf
See this thread for my notes on diagnosing the problem: viewtopic.php?f=26&t=183490&p=1731157#p1731157
References below containing the form "C9##" are references to Electrolytic capacitors, an electrical component that is common in filtering circuits.
I suspected the capacitors that are associated with decoupling the output voltage from the power regulators to be the cause of my problem. The caps are all by the brand Lelon, after doing some measurements as well as consulting with a friend that does a lot of Amiga re-capping, I made the conclusion that the electrolytic caps were starting to go bad. This is a common phenomenon in cheap capacitors and a bit of a nuisance.
My friend made the recommendation to get a japanese brand, and I decided to go with a brand called Nichicon that was available from my goto electronics store.
Check Mouser, Elfa or similar retailer web page for your options.
The type you need to get is called Radial electrolytic capacitor, I picked this type: https://www.mouser.se/ProductDetail/Nic ... mA9VOTs%3d
The caps that need to go are C907-C912 and can be seen on the last page of the MPC service manual.
Both the power jack and the battery line will be led through three Integrated Circuits; IC901-903. These are LM2674M-ADJ, adjustable step-down switching voltage regulators that produce the 1.7, 3.3 and 5V power lines that all need filtering. These can be seen in the top right corner, last page of the MPC service manual.
C907-C909 are of the value 100uF (100 microfarads,16V) and C910-C912 are of the value 220uF/16V (220 microfarads/16V). The Volt tolerance doesn't matter so much, the MPC operates on 5V logic level so just pick any value as long as it's not a lot more than 16V as the caps you recieve on the mail will be huge and might nog fit in there.
It's not necessary to replace all of these blue cylindrical caps, just check the PCB next to the components, there will be a C9##-marking next to the cap to show which one it is.
These can all be seen in this picture here: https://www.instagram.com/p/BY_oUn0nSuF ... iskmachine
And after re-capping: https://www.instagram.com/p/BZCS0jpH9cw ... iskmachine
There's a dissassembly guide on how to screw the MPC here: viewtopic.php?f=26&t=184022
..aand here is a great tutorial on capacitors and how to replace them:
GLHF!