SOLVED Pots "wiggling" on Shruthi-1

I just sold my old Shruthi-1 (SRM-4, second batch if I’m not mistaken) to a guy, who now complains the pots are wiggling, i.e. the pots are causing fluctuations in the parameters. Is this possible? has anybody ever had the problem?

One possible cause for this could the fact that the knobs fit really tightly… I had to open the case and adjust some things before sending it, can it be that after some time that you have to remove and put back on the knobs on the pots these get a bit damaged?

If some parameter changes while tweakin another Pot there might be a short somewhere…

Did you sell a power supply with it? Looks like a shitty / underrated power supply causing a fluctuation of the ADC reference and pots voltages.

@ fcd72 So far the guy told me the parameters are “moving” without him touching anything.

@ pichenettes no I didn’t, so that might be the problem, since I’ve tested the unit thoroughly before shipping it and it worked just fine. thanks, I’ll the guy know, let’s hope that was it.

I think just about all my Shruthi’s (5 so far!) at times changed their settings a little bit, on their own.
Without touching it, the display would update to the setting that changed. But it was only ever by a minuscule amount, so it never bothered me.
I do only tend to use 1 Shruthi at a time though, with the same power brick… I recently got some new, beefier power bricks, so perhaps I will try with those, and see if there is any difference.

The pots themselves are mostly the same, right? Alps. Although some I got from digikey have longer shafts.
No problems with wobbliness on any of them though.

he told me that he will try a different power supply, btw. if you attach one with 1A instead of the suggested 300mA is this going to harm the Shruthi-1? I’ve always been told that it’s not a problem… but just to be sure…

That should never be a problem as long as we use voltage supplies and not current supplies…

That should never be a problem as long as we use voltage supplies and not current supplies…

ehm… sorry, I don’t really get it… does a power supply not always have both a voltage and a current, I mean, it’s just two ways of measuring one thing, isn’t it?

Most of the power supplies we are dealing with are voltage supplies - they guarantee a constant voltage. The current is variable, and depends on the load (what the circuit “sucks”). If you plug a 9V 1A supply to the Shruthi, the current flowing into the Shruthi won’t be 1A! 1A just means that the supply can feed the circuit up to 1A - but it’s always the load which is determining how much is fed!

Current supplies work differently - they “force-feed” the circuit with the selected curren - irrespectively of the load. As a result, the voltage increases with heavy loads.

Regarding voltage supplies that was basically what I knew about it, but I wasn’t that sure anymore. I didn’t know there existed current supplies as well, you never stop learning :slight_smile:
I don’t think he has a current supply, but I’ll check to be sure. Thanks a lot for explaining this to me!

I’m sorry for being so vague in my answer. Most power supplies are of the voltage supply variety meaning that these will deliver the current, within specification, to maintain a specific voltage or voltage range to be more precise. Current supplies on the other hand will deliver the voltage, within specification, to maintain a specific current or current range. These are getting more common as for example LEDs are preferably driven by a specific current and not a specific voltage. In your case we can be pretty certain that the buyer is using a voltage supply as these are the more common wall warts and being such the amperage of the supply is just number telling us how much current the supply can supply to keep the voltage within range, not how much current it will try to put thru your equipment at any given time.

i’ve noticed this with dodgy supplies on my shruthi.

It’s sound like he is in Programmer mode without a programmer plugged…

It’s sound like he is in Programmer mode without a programmer plugged…

well I had checked the setting and it was on 4CV… and I don’t think he changed that by himself

well, it’s not that hard to change, after all

problem was solved, it was the power supply after all…
thanks a lot for your help!