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Logical approach to Pedal problem

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Logical approach to Pedal problem

Postby ManFromGlass » Wed Aug 12, 2020 8:15 pm

I have a Tensor pedal from a small boutique manufacturer. I contacted them about an issue with the pedal and I’m trying to take a logical approach to help narrow down what the issue can be. I might have it figured but if you have any further suggestions I’m all ears.

I would be using the pedal when suddenly all sound would burst into serious full volume digital hash. If I unplugged the power to the pedal for 10 seconds and replug all would be fine for a short while. A few days of this and now the digital hash stopped occurring, but the audio would just go dead. Bypassed sound was not affected.

My latest tests showed the sound stopping after a minute or so, power off/wait/on and the pedal is fine for another few minutes. The time between audio stopping gets longer each time until after 15-20 minutes the pedal is working fine with no issues. I don’t have an electronics background but does this sound like a possible cold solder joint? I know we are all only guessing. If it’s something on the chip then that’s another issue. I have been tempted to open up the pedal to see if there was something unseated that needs to be pushed back in (pedal unpowered while doing this). I did do a factory reset a few times - no luck. Anything else I might consider?
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Re: Logical approach to Pedal problem

Postby Martin Walker » Wed Aug 12, 2020 11:27 pm

Hmm... It could be a cold joint, although they tend to show up due to temperature changes during use, and I wouldn't personally have thought that a pedal would draw enough current for its circuitry to change temperature appreciably.

Having said that, the fact that the problem goes away after 15-20 minutes does suggest that the circuitry has stabilised in some way, and the voltages at various points around the circuit will no doubt vary a little for the first few minutes after switch-on.

You could try opening up the pedal before using it, and then gently wiggling various components to see if this starts up the digital noise again, which might identify a dodgy component or solder connection.

Hopefully someone else can suggest something else you can try, but without a circuit diagram it's more tricky to narrow down possible causes.


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Re: Logical approach to Pedal problem

Postby grab » Thu Aug 13, 2020 5:04 pm

Digital hash in my experience (as someone paid to interface processors with DACs and other stuff) is usually down to one of three things.

One is connection faults. If the signals to the DAC are dodgy, all bets are off. The only way to check this is to open it up; and with anything digital you're unlikely to be able to find the dodgy connection yourself unless you have the schematics and appropriate tools. If it was a larger system like a mixer then you might be able to trace a loose ribbon cable or something, but on a pedal it's all going to be on one PCB (or perhaps two with a hard connection between) and you're unlikely to be able to do much with that. You also risk not being able to return it if you do open the box to have a poke around. If they ask you to check it, fine. If not, leave well alone.

One is reset issues, which usually relate to the power supply and the associated electronics which dishes out hopefully-smooth power to the various chips. DACs usually have to be set up somehow after things are powered up, and the processor will do that at startup and then assume everything is working OK. If the power supply droops such that the DAC resets itself but the processor keeps going, then the DAC will come back up with dodgy settings, and whatever the processor subsequently throws at it will result in duff outputs. If you're running on batteries, try changing them. If you're running off a wall wart, try a different one (checking that the voltage and plug polarity is correct, of course).

If none of that helps, there could be something more fundamental going wrong. It's not unknown (I speak from experience!) that the circuit designer may have placed too much faith in everything starting up cleanly, and if that's the case then it's almost inevitable that it sometimes won't start up, and it might be worse for some devices than others, and the First Law of Sod says that the designer's one just happens to work perfectly every time. If there's a problem with the design, you need them to fix it.

And the last reason is bugs in the code. It's software. Excreta occurs. And sadly with small companies, they generally have less testing to intercept that excreta before it reaches the ventilation system. Not infrequently too, smaller companies may have their electronics and code done by people who are keen players, and possibly even are keen DSP coders on Windows, but aren't as experienced with the kind of problems you get in embedded systems. In my time I've seen some horror-show code written by well-meaning amateurs where, like Doctor Johnson's performing dog, the wonder is not that it does its job well but that it does anything at all.
:headbang:

Honestly, my advice would be to return it to them, get a replacement, and let them figure it out. As a small manufacturer, I'd definitely expect them to be responsive to customer issues. They can't afford the bad publicity, for starters. And like I said, if you have limited resources in a small company, it's not uncommon for testing or bugfixing to be pushed back until someone complains about it.
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Re: Logical approach to Pedal problem

Postby ManFromGlass » Fri Aug 14, 2020 1:36 am

Thanks for that, grab.
I’m waiting for them to say send it back, but the plague is slowing things down.
I have tried 2 different power supplies, proper polarity, 9Vdc, one is 200 mA the other 500mA. No battery compartment on board.
I will ask them if there is something I can prod inside but other than that I’m out of my depth.
Maybe I’ll get a T-shirt - “We are all Beta testers!”
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Re: Logical approach to Pedal problem

Postby Arpangel » Fri Aug 14, 2020 7:13 am

If this was bought from a retailer then you should take it back to them, and let them deal with it, not sure about where you are, but the responsibility is with the retailer here in the UK.
Of course, contact the manufacturer first, to see if they can help, but anything beyond that go back to the shop.
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Re: Logical approach to Pedal problem

Postby ef37a » Fri Aug 14, 2020 10:02 am

Martin, a digital pedal will pull a watt or so and in a small box that will result in the chip getting quite warm. (even NE5532s get warm on 17-17V)

I would wrap the pedal in a poly bag and stick it in the fridge for an hour or two then time how long the fault takes to occur. If that seems to extend the period of fault free use, try the freezer next time.

N.B. The pedal may not work at all straight out of a freezer! Most domestic electronics are only specce'd down to 0C. Don't panic, it will work when warmed a little.

That will prove if the fault is temperature related and may assist a repairer.

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Re: Logical approach to Pedal problem

Postby ManFromGlass » Fri Aug 14, 2020 6:30 pm

Brilliant - I will try this.
Thanks.
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Re: Logical approach to Pedal problem

Postby ef37a » Sat Aug 15, 2020 7:16 am

ManFromGlass wrote:Brilliant - I will try this.
Thanks.

Welcome: and if 'significant other' complains say "You are lucky I am not an angler!"

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Re: Logical approach to Pedal problem

Postby ManFromGlass » Sat Aug 15, 2020 12:28 pm

or a taxidermist!
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Re: Logical approach to Pedal problem

Postby ManFromGlass » Wed Sep 02, 2020 12:36 pm

Update -
After leaving the unit in the fridge for 2 days (I was busy) I fired it up and got 15 minutes of play before the unit stopped. From then on I would be lucky to get 1 minute of play before it stopped. Pulling the power supply and reinserting it woke the pedal back up as usual.
I made a realtime video and sent it off to the company. I received the “we are swamped due to the plague” email response.
So now I wait. And wait.
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