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Prophet '08 Knobs behaving strangely / not working

Prophet '08 Knobs behaving strangely / not working
« on: December 11, 2020, 05:49:24 AM »
Hi all!

I'm new to the forums as I'm a first time Prophet owner! I recently purchased a second hand Prophet '08 from Reverb.com, and there seems to be some strange issues with the knobs.

- Most knobs don't do anything. For example, the 'Param 2' knob literally does not change the bank or any other values.
- Some knobs that do work act strangely. For example, the BPM knob does change the bpm, but no matter which way I turn it the value only goes up. If I touch it just after I turn the synth on, it jumps down to 128 or so, then only goes up.
- The master volume knob kind of works, but even at fully left, the volume does not go down to zero
- The setting shown on the LCD screen will sometimes randomly jump to something I have pressed/touched
- Sometimes it will randomly scroll through the programs list

To me this seems like some kind of dust or water damage, but it's odd that it's only the knobs (all buttons work perfectly so far), and the output is fine, sounds are all good.

Has anyone got advice for what could be the cause, or whether I just need to get someone to look at it?

Thank you!

Jake

Re: Prophet '08 Knobs behaving strangely / not working
« Reply #1 on: December 12, 2020, 08:26:10 PM »
This sounds like the first generation of Prophet '08s after a lot of neglect.  The instrument originally had all encoders, which could eventually become very erratic.  Your instrument sounds like an extreme case.  First two questions: how old is it and is it an encoder edition (EE) or a potentiometer edition (PE)?  The EE has endlessly rotating knobs, whereas the PE has knobs with white lines and rotate only to a point.
The Musical Synthesizer YouTube Channel:
https://www.youtube.com/channel/UChLGwGiRVs7rlZXnOG9_mUw

The Musical Synthesizer Blog: https://themusicalsynthesizer.wordpress.co

Re: Prophet '08 Knobs behaving strangely / not working
« Reply #2 on: December 13, 2020, 05:13:19 AM »
This sounds like the first generation of Prophet '08s after a lot of neglect.  The instrument originally had all encoders, which could eventually become very erratic.  Your instrument sounds like an extreme case.  First two questions: how old is it and is it an encoder edition (EE) or a potentiometer edition (PE)?  The EE has endlessly rotating knobs, whereas the PE has knobs with white lines and rotate only to a point.

Thanks for the reply, that seems about right.

I think it's quite old but not 100% sure. The previous owner said they barley used it, so makes sense it was neglected. Lots of dust on and in it when i got but since cleaned it and no noticeable change sadly.

It's an encoder edition.

I'm currently trying to get a return/refund via Reverb.com as it seems there's probably no easy fix without a serious service...

Re: Prophet '08 Knobs behaving strangely / not working
« Reply #3 on: December 13, 2020, 07:49:11 AM »
If you can get a return with full refund, that would be easiest.  In the future, get only the PE version.  I, too have been watching Reverb for a Prophet '08, but I would only buy a mint condition PE version.

If you can't get a refund, it is possible to convert the instrument with Sequential's help.  There's also the temporary fix of cleaning all the encoder housings with deoxit.  You can do it yourself in about forty minutes.  Many of us had to do it around 2009.  Either way, all is not lost.

 https://www.sequential.com/troubleshooting-prophet-08/
« Last Edit: December 13, 2020, 08:01:15 AM by Sacred Synthesis »
The Musical Synthesizer YouTube Channel:
https://www.youtube.com/channel/UChLGwGiRVs7rlZXnOG9_mUw

The Musical Synthesizer Blog: https://themusicalsynthesizer.wordpress.co

Re: Prophet '08 Knobs behaving strangely / not working
« Reply #4 on: December 13, 2020, 02:24:41 PM »
Thank you so much for your advice, really appreciate that. Feeling better now I know that there is a solution if worse comes to worse. Cheers!

Re: Prophet '08 Knobs behaving strangely / not working
« Reply #5 on: December 13, 2020, 05:46:07 PM »
You're welcome.
The Musical Synthesizer YouTube Channel:
https://www.youtube.com/channel/UChLGwGiRVs7rlZXnOG9_mUw

The Musical Synthesizer Blog: https://themusicalsynthesizer.wordpress.co

gdh

Re: Prophet '08 Knobs behaving strangely / not working
« Reply #6 on: December 15, 2020, 10:13:30 AM »
I have an early encoder version. DSI sent me some deoxit in 09, worked for a few weeks. Got back to DSI they sent a new bd with encoders. They had said that the first batch was problematic. No issues since. I quite like the encoders.