Prophet x Freezing/Brick'd Up - Solution Found and Fixed! NOV2023

[kevinjonass]

Posting this so people can learn from my experiences! After hours of searching through forums and chatting with Sequential, we fixed it!

I sent this to SEQUENTIAL:
My prophet x has been working like a dream for the past 2 years, but all of a sudden it froze at the loading screen with the loading bar full, with nothing happening. No luck on turning off and on again. It was sitting in my studio, with no difference of power/lights/anything.
Reading through the forums (of people having this issue for years), I tried plugging a computer keyboard into the sample import USB port, and holding F1, or CTRL + F1 for the whole time, or just near the end, and about 40% of the time it somehow turned back on. I tried again, and it DIDNT WORK. Then tried again and it DID work. No consistency.
On one of the times that the keyboard turned on successfully using the computer keyboard, I updated the firmware from 2.2.0.0.0 to 2.2.2.0.0, and the "Cannot reach audio processor" message came up now when it froze.
Tried again with the USB keyboard with the F1 method and it turned on. Tried two more times without touching F1 and it worked fine. Unplugged the keyboard and it turned on fine. Tried one more time and it froze on the "cannot reach audio processor

I was heading on tour next day so no time to send it in, so they said (with pictures):

REPLY:
once inside, you will need to reference the 5v power line on the main board with your multimeter. Pull back the PSU safety cover and locate the trimpot in the upper lefthand corner of the PSU. This trimpot adjusts the +5VDC supply. Locate the GND and +5V test points, located in the bottom righthand area of the Main board, just above the keybed connectors. Power on the unit and allow a few minutes for the voltages to settle. Then, with a DMM
set to measure DC volts, probe between GND and +5V and turn the PSU trimpot CLOCKWISE until the DMM measures 5.20x.

I had my local tech take a look and he responded with:

LOCAL TECH:
The 5v test-point initially measured around 4.8v.
We adjusted this to the suggested 5.20x volts, and the system still does not boot on its own.
From here, I measured the other visible voltage test points on the board:
3.3v, +/- 5v, +/- 12v ect.
All measured stable and accurate.
When the system is tricked to load via the USB-F1-method - the Synth appears to operate fine.
With this need of a keyboard (HID) sending a message to the small computer system - My suspicion would lead towards an issue with the on-board computer.
Similar to a typical computer system's BiOS indicating an error - and requiring human interaction to continue loading.
Could a dying Bios Battery be known to cause this, or failing SSD drives?

REPLY:
It definitely seems like an issue with the motherboard as we've seen this behavior before. There is a current BIOS update on our support page that I would reccomend persuing as well. The instructions are very specific in regard to the file structure and USB version necessary for a clean update. I'll attach a link to the update here:
https://www.sequential.com/updating-prophet-x-os/
Additionally, I'm not too concerned about the clock battery but I do usually go ahead and replace those with a fresh one whenever I do a routine Prophet X repaird here in our shop. It is also reccomended to perform a passive clock reset by changing the pin bridge orientation briefly on the circled three pins on the attached image. You just need to move it from pins 2-3 to connect with 1-2 instead for about 20~30 seconds and replace it back to its original orientation.

so we opened it up one more time, and LOW AND BEHOLD WE FIXED IT, but something different.

LOCAL TECH:
When testing this Prophet again, the internal OS was already up-to-date with the newest version available online... So no fix there.
Before trying to do the 'Passive Clock Reset' as suggested - I pulled the Bios battery, and measured its voltage.  (What I should have done back in September!)
Very rarely do I see a CR2032 battery.... measuring 0.17 volts.
New battery - and it's done 20+ cold-starts with zero signs of issue. (*knocks on digital wood*)

HOLY SHIT. This entire thing (at least in my case) was all because of a CR2032 battery (a friggin watch battery), something you can get for a few bucks. So maybe just test the volatge of that little battery before sending everything in.

Best of luck, this synth is the best thing in the world.
P.S. I was able to borrow another prophet x for a tour across the ocean the next day from a stranger in a city an hour away from my home, THANKFULLY. 

[Derek Cook]

Thanks for sharing. All useful info for diagnosing if anybody has a similar issue

[thirteen_engines]

Thanks for this post. With all the horror stories about bricked PX’s over the past few years I’ve become very paranoid that the same will happen to my synth. Now I at least have a starting point to try and get it runnng again if it happens here.

Keith

[mildwest]

Where is this little battery located in the synth. I have one of the first ones and never changed it. No issues yet but over the holiday it sounds like it may be a good idea to swap it out for a fresh one.