Rollz-5+ Kit from Meng Qi (2014 Revision 3)

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Waz
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Post by Waz » Fri Aug 09, 2019 10:14 am

I am pretty much done with this build, just waiting on the 1uF caps to come in from Mouser. I had simple question; Is the power switch for this unit a SPDT ON/ON switch?

*Edit
It's on/on

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Waz
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Post by Waz » Fri Aug 16, 2019 12:33 am

So I finished. It took me a while to figure it all out and get it making sound. After a year of slowly piecing things together, it actually works... 8-)

I only have one issue; the power supply. I have a box of over 100 wall warts saved from various electronics over my life. This will not work properly with any of them. It only works with my bench supply. My bench, unfortunately, is outside of my studio space. I assume it plays best with linear or regulated supplies. Is there some sort of “hack” I can do so I can use these wall warts? Any wall warts on the cheap the play well with this synth?

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GrantB
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Post by GrantB » Fri Aug 16, 2019 11:00 am

12V DC center positive should work

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Post by rmro » Fri Aug 16, 2019 11:44 am

I bought a bunch of these https://cpc.farnell.com/powerpax/std-12 ... 20supplies they're the same as the patch point ones

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Waz
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Post by Waz » Fri Aug 16, 2019 2:26 pm

GrantB wrote:12V DC center positive should work
You'd think but I have dozens of 9 - 12VDC center pos wall warts and all of them have a hum with only this gear. I found a beat-up Meanwell laptop PSU in my garage and this is the only one that works. I looked it up and it seems to be regulated. I think this is the issue? I really don't know the EE theory behind why this is happening. Would love to know why if someone wants to drop some knowledge.

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Post by GrantB » Fri Aug 16, 2019 9:40 pm

I'm using 3 of the DA36J12 regulated adapters for my Ciat gear. Cheap on Ebay.

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Re: Rollz-5+ Kit from Meng Qi (2014 Revision 3)

Post by flx » Sat Feb 01, 2020 12:06 pm

I just realized that the voltage starve feature on my secondhand Meng Qi Rollz-5+ doesn't work at all and I was not too stupid for the device after all :party: So I desoldered the 1k pot and it looks as if it's broken and "stuck" at around 1k resistance. Maybe that was also the reason why I couldn't run the device properly with a 9V PSU and had to use a 12V one?!

I temporarily added a new pot and also tried out various fixed resistors and finally had the desired voltage starvation effect. Of course I then tried out the vactrol, and it had almost no effect. You could only hear a very very faint effect when the voltage was already starved almost to death by the pot/resistors. I tried various voltage source from other Ciat Lonbarde gear, even the Sidrax, like in the Instagram video form the OP.

Can anybody help me troubleshoot this? Maybe the vactrol is broken too, I thought. My temporary voltage starve resistors got quite warm quickly, so maybe the original pot was burnt out by taking too much heat from the resistance/starvation process?


Edit: I see that a burnt out voltage starve section is actually not that uncommon here. Has there been a fix for this, or is it still a bit hit and miss? If so, I might just bridge the circuit and remove the section. Anything else that one could put there instead easily? :mrgreen:
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GrantB
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Re: Rollz-5+ Kit from Meng Qi (2014 Revision 3)

Post by GrantB » Sat Feb 01, 2020 2:17 pm

flx wrote:
Sat Feb 01, 2020 12:06 pm
Has there been a fix for this, or is it still a bit hit and miss? If so, I might just bridge the circuit and remove the section.
This feature was fixed in the last revision of the PCB by removing it. :foul:

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Re: Rollz-5+ Kit from Meng Qi (2014 Revision 3)

Post by flx » Sat Feb 01, 2020 2:25 pm

GrantB wrote:
Sat Feb 01, 2020 2:17 pm
This feature was fixed in the last revision of the PCB by removing it. :foul:
Hah, alright then :lol: Thanks!
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Re: Rollz-5+ Kit from Meng Qi (2014 Revision 3)

Post by jimmie » Sun Feb 02, 2020 12:16 am

flx wrote:
Sat Feb 01, 2020 12:06 pm
I just realized that the voltage starve feature on my secondhand Meng Qi Rollz-5+ doesn't work at all and I was not too stupid for the device after all :party: So I desoldered the 1k pot and it looks as if it's broken and "stuck" at around 1k resistance. Maybe that was also the reason why I couldn't run the device properly with a 9V PSU and had to use a 12V one?!
Mine (sold but missing now cuz some sounds from it can't be covered by PB) also had starve circuit broken but I didn't have a problem using a 9v adopter. I preferred using 9v to 12v for tamed feeling.

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Re: Rollz-5+ Kit from Meng Qi (2014 Revision 3)

Post by flx » Mon Feb 03, 2020 8:51 am

While I’m here, I’ve got another question:

On the Plumbutter there is a frequency pot for each Roll. Does anybody know how this is achieved? I’m looking at Pugix’ 2-Roll circuit here:
https://pugix.com/synth/rollz-5-schematics/

Where/how would one integrate a pot in this schematic?
You can also find and contact me here:
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