Re-animating the dead

[hoffy]

Hi, what are the general tips around reviving dead gear?

I've heard people say "discharge the capacitors" but what exactly is that?

Also... What simple tests can be done to ascertain where the problem is? Like checking if a circuit is getting power? (I'd assume that would involve a multimeter, and i have one, but wouldn't have a clue how to do anything with it except find out the value of a resistor).

Any general tips, or links, i'm sure would help a lot of people.

Ta.

[Ciderfeks]

Hi - I'm new to this too but i have found the "discharging capacitors" trick to be useful in reviving what appears to be a fried project. First, remove the batteries, then look for the capacitors on your pcb - the larger ones near the battery input wires are often likely candidates - then just short the legs of said capacitor with your bend-finding probe. ie join the capacitor legs together momentarily with a bit of wire! Capacitors will discharge slowly by themselves if left alone which sometimes results in seemingly dead gear coming back to life after a couple of days but the shorting out method speeds the process up. I've found the replys to this post useful too <http://www.circuitbenders.co.uk/forum/index.php/topic,440.0.html> especially the tip about using a resistor of >100 Ohms in line with whatever probe wire you're using to look for bends, it gives you that extra bit of protection when using the "poke it and see" technique which my lack of attention in physics lessons has reduced me to!

[hoffy]

I use an electronics "station" thing that has potentiometers, LED's, a breadboard, speakers, and lots of other things which i use for my probing. It's really easy to hook up IC's and other things on the breadboard which can open up experiments a lot, and as you've pointed out, can help the "point it and see" technique which we all use too

Thanks for the reply. I'll have to try discharging capacitors next time i break something.

But what i was really looking for was... There must be some sort of standard routine that electronics repair people go through to find simple problems when general consumers return their TV's, DVD players, those sorts of things. Obviously you'd look for any places where the wires/connections have broken, but then what? How would you check if power is getting sent to all the components? And if it is, then what would you check next..? If everything is grounded as it should be?

I opened up a Yamaha DX 27 I bought (in bad condition). It was working fine, and then i opened it to secure a power connection that was falling out. The power connection thing (where'd you plug in your adapter) had already been replaced/changed at least once, so I assume that is the problem again. But anyway, i resoldered a joint, put it back together... and it's never turned on since. I couldn't have fucked it up too bad- it's not like I was paticularly careless when opening it or probed *anything*... so....

I would guess that the problem would be easy to fix, as with lots of broken things. But i just don't know how to find that problem.

[Circuitbenders]

The first thing to check if you think theres a power problem is if the power socket itself is actually working. The best way to do this is to plug the power in and use a multimeter to check the voltage at the socket solder joints. You might also want to try checking the voltage at the next solder joint into the circuit from the power input just to make sure everything is actually connected.

Next thing to look at would be the voltage regulator if there is one. This is usually a three legged squareish component that sometimes has a small heatsink attached to it. Basically this takes an input voltage over a certain range and outputs a steady voltage at a set value that can be used by the rest of the circuit. Typically you might measure something like 9-12v or more at the input pin, 0v at the ground pin and 5v at the output. You should check the datasheet of your particular component but if the regulator is getting very hot or you're getting some very unlikely measurements then it probably needs replaceing.

[hoffy]

Thanks heaps, looks like i'll have to figure out how to use my multimeter and go from there. I didn't play with the circuit at all, So I'm assuming everything works as it should. I hate it when I break something simply by opening and closing it again.

[ne7]

another important life saver i've found is "contact cleaner" - isopropyl alchohol or similar is great if u get an old toy or jeyboard with loads of dirt or leaky battery gunk all over contacts just use some cotton swabs to clean it down with this stuff and it'll work like new - once the alchohol has evaporated (which is very quick) - i've revived loads of kit like this - including stuff like gamegears that were bought as "faulty" off of ebay

[hoffy]

Thanks everyone

My DX-27 got opened again last night, It wasn't being responsive at all, then i plugged in a power adaptor- which was turned on, as was the keyboard- and sparks flew out of the fuckin' thing like crazy...

I think i might have plugged a -ve centered power supply when it needs +ve centered.

... but it wasn't doing anything at power up before then anyway. So does anyone know a decent site where I can get scans of the Yamaha DX 27/DX 100 Service notes or manual? Or a site that can tell someone how to use a multimeter (yes, I've got one, but i can't get any numbers of it that mean anything).

Either way, I fucked it good. Not sure if I'm ready to throw it away just yet, but i paid about US$25 for it, so hopefully I can make that back on e-bay selling it "as is"

[Gordonjcp]

Plugging in the wrong polarity of power supply shouldn't cause a problem.  It won't work, but that's all that will (or won't) happen.

[hoffy]

That's what I figure, because I've done it hundreds of times Oh well. On this particular occasion It looked the 4th of July, or at least what 4th of July looks like on TV; I'm not american, afterall...

I'll think i'll just pay to have it fixed, but thanks for all the help all the same guys =). I'll be sure to check this thread the next time I destroy something