Advice needed - I have done something very stupid

Valendom

I just accidentally plugged the wrong voltage power supply into my Nova Drive, 16v rather than 12v. All the lights on the unit flashed for second and then went off followed by a smell of burning. As you can imagine it now does not work.......have I managed to kill it?

d8m

At a guess yes.

Only way to really see would be to unplug it and take it to bits and examine the PCB.

If you are lucky you've blown a component that is easily replaced(diode would be likely to go from over voltage) so can fix it or get it repaired easily enough.

dano

Ah the joys of a mass market manufacturer not even fitting 20p zener for overvoltage protection !

Open it sooner than later and see if you can identify what has burned. Sniff around the board until you find it.

You are unikely to have blown any caps on the power input as they'll be rated to 16v as a minimum. I have no idea of the insides but id be looking at damage to a regulator which woould generate 3V3 or 1V8 (or something similar) that the processor runs on. I woild have though any ICs or trans on the audio path should tolerate 16v. But this is purely speculation with uou investigating the inside. good luck !

ICBM

I'd find it surprising if just that much overvoltage killed it - although it is possible - was the 16V supply the wrong polarity as well?

Valendom

Not sure about the polarity but will check. The other adapter was for a HT Dual which are usually 22v but this one is 16v I think.

ICBM

Valendom said:

Not sure about the polarity but will check. The other adapter was for a HT Dual which are usually 22v but this one is 16v I think.

And AC, not DC.

That explains why the lights flashed briefly, which they wouldn't have done if it was simply the opposite polarity.

If so, there is hope - it sounds like it might have burned out the protection diode. If the power supply is fairly beefy (the HT one is) it will fry the diode before the supply shuts itself down. If you're lucky the diode didn't completely burn away and leave the circuit unprotected.

Valendom

Thanks @ICBM. I'm going to let someone who knows what they are doing take a look at it during the week. Fingers crossed it didn't completely fry anything.

viz

Surely if the diode burns out the circuit is safe anyway? I once had reverse polarity on my old metalzone and one of the diodes at the beginning was fried, I thought that meant it was open circuit?

ICBM

viz said:

Surely if the diode burns out the circuit is safe anyway? I once had reverse polarity on my old metalzone and one of the diodes at the beginning was fried, I thought that meant it was open circuit?

It depends - usually a protection diode is in parallel across the supply, rather than in series with it.

If the diode is a parallel type it relies on conducting enough current to simply bypass the pedal, which is a fairly large current which can shut down the power supply if it has a regulator - or actually blow it, if it has a thermal transformer fuse or something non-resetting. But a heavier-duty supply can supply enough current to fry the diode as well.

If the diode shorts - they usually do fail like this initially - the circuit is still protected because no voltage of either polarity can reach the circuit, although you have to replace the diode before it will work again. But if the power supply is even heavier-duty, so that even a direct short doesn't shut it down, it can keep on supplying current until the diode actually burns away completely and becomes an open circuit, at which point it's no longer giving any protection and then the original reverse (or AC) voltage will cause the damage the diode was trying to stop.

Unfortunately this is getting more common - most old pedal power supplies were in the 200-500mA range and so would shut down before the diode (usually 1A-rated) burned out, but a lot of modern pedals use such high currents that supplies capable of well over 1A are now often found, and if you don't spot the problem quickly enough they will destroy the diode… and then the pedal. I've seen a few recently where something like a 1300mA Line6 power supply has been connected to the wrong pedal, and cooked it completely. The 'One Spot' type of high-current power supply are also a problem for this.

So really makers should be switching to using series protection diodes - which are better anyway since they 'block' rather than 'short' the wrong supply, but have the disadvantage of lowering the voltage slightly.

57Deluxe

...put it in a cool place and try again in an hour... (with the correct V of course!)

viz

ICBM said:

viz said:

Surely if the diode burns out the circuit is safe anyway? I once had reverse polarity on my old metalzone and one of the diodes at the beginning was fried, I thought that meant it was open circuit?

It depends - usually a protection diode is in parallel across the supply, rather than in series with it.

If the diode is a parallel type it relies on conducting enough current to simply bypass the pedal, which is a fairly large current which can shut down the power supply if it has a regulator - or actually blow it, if it has a thermal transformer fuse or something non-resetting. But a heavier-duty supply can supply enough current to fry the diode as well.

If the diode shorts - they usually do fail like this initially - the circuit is still protected because no voltage of either polarity can reach the circuit, although you have to replace the diode before it will work again. But if the power supply is even heavier-duty, so that even a direct short doesn't shut it down, it can keep on supplying current until the diode actually burns away completely and becomes an open circuit, at which point it's no longer giving any protection and then the original reverse (or AC) voltage will cause the damage the diode was trying to stop.

Unfortunately this is getting more common - most old pedal power supplies were in the 200-500mA range and so would shut down before the diode (usually 1A-rated) burned out, but a lot of modern pedals use such high currents that supplies capable of well over 1A are now often found, and if you don't spot the problem quickly enough they will destroy the diode… and then the pedal. I've seen a few recently where something like a 1300mA Line6 power supply has been connected to the wrong pedal, and cooked it completely. The 'One Spot' type of high-current power supply are also a problem for this.

So really makers should be switching to using series protection diodes - which are better anyway since they 'block' rather than 'short' the wrong supply, but have the disadvantage of lowering the voltage slightly.

ah ok good to know, cheers