Sudden F4 F5 F6 failure

Hi you guys,

Long time MPC adept here with focus on the MPC1000 for the last 10 years.
I ran into a problem and hope will find some guidance here!

The MODE button failed on one of my machines so I replaced the button.
Closed the machine up and suddenly F4 F5 and F6 didn’t work anymore.
I guess it’s no failure of both three tactile switches. That would be quite a coincidence.
Eventhough I cleaned them en used some red Deoxit D5 but with no result.

There is nothing wrong with any connection visable in the machine.
I hesitant to open the part where the F buttons are situated.
Does anyone have a constructive suggestion to what caused this en what can be a solution?
I can replace the tactile switches but it doesn’t make sense to me that all 3 switches failed at the same time.

Thanks so much! Keep up the good work.

These devices are also getting older, and it is possible that the cable/pins on one of the connector boards has become oxidized.. a bit of Deoxit might help. Or just disconnect and reconnect the cables to the Function board a few times and see if it restores the connection. Given that fixing one board is unlikely to cause an issue on another board... I'd probably *start* with checking all the connecting cables/pins. I've got a 1k where somebody munged up the lower Q-Link cable, and it causes a poor connection to the board, causing the Q-Links to function somewhat inconsistently and require the cable to be reseated.


I'd check all of your solder joints... it's possible you bridged ground to something else on accident which could cause this kind of problem... it's been a while, but I believe that all of the switches work separately, especially across boards... so you may want to try desoldering/removing the replaced Mode switch and see if it restores the other F switches.


Beyond that... you might check the board for hairline fractures. It's unlikely, but possible that a screw was overtightened and sheered a connection/joint. I've seen goofier things happen on accident.

Good luck!

Hi, thanks for the reply.

The machine is in very good and clean condition.

I checked the cable/pins/ribbon connector, cleaned them: no result...F4 F5 F6 still not working.

Thoroughly cleaned all tact switches. No result.

Did the multimeter continuity test, there is nothing wrong with the tact switches.

This all started when i simply replaced a broken plastic MODE button so hey, replaced that again with another one: no result.

Did a full factory rest: no result.

Replaced the whole upper board (F1F2F3F4F5F6) with another one from an older 'Blue' MPC and....still F4 F5 F6 NOT working.

Re-installed 'Free JJOS' with the help of the footswitch assigned to F$ and F6 with no result.

So: it's not in the tact switches, it's not in the upperboard, it's not in the wiring from upper board to main board.
What on earth can i do to find the error and how do i fix this?

I am just using common sense here i am no electronics expert by far. I attack these sort op problems by ruling out options one by one.
And i ran out of options ...

If anyone has a clue to where this F4F5F6 error can come from and maybe how to solve this please, please let me know.

So you've done a lot of the common (and not so common) sense checks... here's a few additional thoughts
* Changing out the plastic mode button should have had *no* impact on the device
* This is unlikely to be a software issue, but definitely worth trying to reset and re-install
** It *might* be worth putting JJOS 3 on there, just so you can do the... I *think* SHIFT+F2 button combo for testing, just to 100% confirm it's not seeing the F4-F6 presses
* Using a second board showing the same problem good... *might* be worth putting the F board into the Blue MPC 1k just to double check the OG board works properly
* cleaning the cables is a good step, but doesn't guarantee fixing a continuity issue...

I feel like you've pretty much isolated the problem down to a handful of potential issues...
* There are two connection points between the Function board and the main board, through the cable... if either side has an issue it could cause this kind of issue... since you've already check continuity of the switches... and the Blue F board has the same issue... I'd check the continuity from the connector pins on the F board to the main board
* It's possible that the main board has something wrong with it that has caused it to no longer see some of the F board buttons.

Next time you've got the MPC 1000 apart, and the F board is unmounted, check to see if the buttons work... if they do, there might be a grounding issue causing this... similarly, you might unscrew the main board and see if the F board functions with the main board disconnected... overall there could be a grounding issue from any boards... but... I'd start with those two...

If you've got the time/patience... it might be worth going through all of the cables, and making sure that nothing got mashed/munged... something might've gotten pinched and mashed two (or more) wires together, or accidentally cut a wire. It can happen.

As dumb as this may sound... check the capacitors on your power supply. It's possible something went bad, though I find this highly unlikely to cause this kind of issue.

Beyond that... it might be worth trying to swap parts between your two MPCs... the more you can swap between the two (doing one at a time)... the more likely you can isolate the issue down to a single board or cable.

Good luck and take your time...

Had some help figuring it out (thank you Jazzcat). There was a hairline fracture in the right PCB. Onjly visable from the flipside. Allthough i never touched the plate it still got fractured so i guess buying the upgraded version from MPCstuff is the way to go..

If you're good with soldering, you could probably jump the fracture by soldering between the two points that have the issue. I've done this with completely smashed boards. It takes some time, but could save you a few $$$