12VDC - Have I blown my KIT?!

Why should the store take it back? It's your mistake and you have blown it up!

I did'nt mean return it for a replacement. I was thinking perhaps it was repairable? Does anyone know? based on the above, do you think I have blown it up?!!

If the power supply that you've bought is genuinely AC output, then the piece of kit is not going to have liked it much, for sure. There are two simple possibilities. First is that there is an internal fuse of some description. May be a wire ended or surface mount type, or may be a fusible resistor. Second possibility is that there is a polarity protection diode across the power input. If you put AC directly across a diode, it will fail short-circuit in fairly short order. However, in either case, it's not to say that the circuitry beyond didn't suffer damage before the diode failed, or fuse blew. I would take a look inside first, provided that you're reasonably sure what you're looking for, and have a meter to check said components if you find them.

Arfa

Thanks Arfa, thats very helpful. I dont think I have the knowledge to mess around inside this device, so I will send it back to the manufacturer to see if it is repairable. Damm, that was an expensive mistake ($400). I'm off to cry now ;(

Cheers mate....

The power supply you connected, probably did not match to the required specifications. You will have to send the unit back for service, unless you are proficient to do the service work on it.

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Jerry G. ======

I have a piece of audio equipment (M-Audio 410 firewire audio interface) that requires 12V DC (1000mA) I bought it in the states with a US adapter and step down convertor (240->110). Everything was working fine until I thought I should go out and buy a UK voltage adapter to replace the cumbersome setup of AC adapter -> step down transformer -> US/UK plug.

I bought a '1000mA Variable Voltage AC/AC Adapter' with a 12V setting. After plugging it in, the lights came on and then went out on the device, andthen nothing! Is it because I bought an AC/AC adapter and not AC/DC adapter?? Could this cause the kit to stop working?? Its gonna be such a pain to try and return this to the store I bought it from in the US (Im in London), any help would be seriously appreciated.

Regards, Nick.

You may be lucky and just shorted a protection diode on the power input, it's worth checking. You can't legitimately return it to the store, you broke it.

snipped-for-privacy@yahoo.com ha escrito:

have you tried it again with your original setup of stepdown transformers? if still dead you'll have to do as the others suggest and check the diodes across the input. it'd probably be cheaper to just pay someone locally to fix it than ship it to USA. look for a repair shop

-B

Nice little piece of equipment... A shame you have buggered it up though.

I dare say even some of us "experienced" techs have made a similar error in our haste to get something up and running, particularly in our learning phase. There is no doubt that once having made such a stupid error of judgement we sure didn't ever make the same mistake again.

As to fixing it... I'd say you will have to return it to the manufacturer. It is uP controlled and almost certainly will use lots of smd.

The device *should* have reverse polarity protection, which could be either (1) a reverse-biased diode across the input, or (2) a diode in series with the + rail after the power jack.

What will happen if you connect an AC adaptor? Well, in the first instance the diode will short out the negative component of the AC supply, and allow the positive component to pass. The shorted negative component will quickly either damage the power supply or blow a fuse in the appliance itself, provided the manufacturer has been thoughtful enough to add one to the design. At that price, they damn well should. Hopefully all this will happen before any other damage can be done.

In the second instance, the series diode will rectify the AC to rough, half wave DC. This could explode electrolytic caps and cause the internal regulator to malfuction, with possibly catastrophic results. The fuse may well not fail until it is too late, if at all as there may be no overcurrent situation until a semiconductor fries.

The only way to know for sure what the damage is, is for a tech to look inside. You may get very lucky and it could just be an internal (probably miniature surface mount) fuse. OTOH, it could be a write off, there's no way to tell from the outside. If specialist SMD ICs are blown, forget about a local tech repairing it, it will be a manufacturer/dealer repair only, and they might consider it uneconomical to service.

Dave