Pearl PH-44: Have I killed it?

[SyntheticBiscuits]

*NOOB ALERT*

Hi guys,

So I got an old Pearl PH-44 phaser (the big six-knob one) and managed to make a mess of it pretty much straight away. I put the tip on the power adaptor on the wrong way (positive rather than negative polarity) and so when I flicked the switch I got a popping sound and The Ominous Blue Smoke. I've opened it up (now several months later) and taken a look at the boards but there's no obvious sign of damage. No severed connections; no fried components; nothing, but it no longer switches on either powered from batteries or an adaptor. I'm a complete electronics novice so I need some help. How likely is it that it's irreparably screwed? If it's repairable then where should I start? What's the issue most likely to be? Any help/advice would be appreciated.

Thanks,

SB

[armdnrdy]

Without seeing a schematic (see if you can find one to link) my guess it you at least fried the protection diode. (if there is one)

This is a pretty good place to start.
http://www.diystompboxes.com/smfforum/index.php?topic=29816.0

The more information the better.

[SyntheticBiscuits]

Thanks,

There's a (very grainy) schem of the power supply etc at http://s853.photobucket.com/user/bernardduur/media/Schematics/PearlPH44-Power.jpg.html if that helps.

SB

[armdnrdy]

Yes...I saw the drawings in several parts.

Since you are armed with the power supply drawing...best to check if the unit is getting the proper power.

Do you have...or have access to a meter?

[SyntheticBiscuits]

I might have one knocking about somewhere. I'll have a look this evening.

Looking at the schem my first thought would be that C60 & C61 are to blame, so once I'll check those first.

[Mark Hammer]

As a proud owner of one of those, that's not exactly the sort of pedal you want to damage! 

[armdnrdy]

Check L12 the voltage regulator.

You should have around 18 volts on the input and around 12 volts at the output.

If you can see the actual markings on the regulator...check the internet for the data sheet so you will have the correct pin out. I'm not sure if it's a 7812 or a L78L12. Different pin out for each.

[SyntheticBiscuits]

I got it cheap because it's not in great cosmetic shape (almost no paint left on it) but when I ran it off batteries when I very first used it it worked great. Also I can just about read on the schem that it's a 7812. I'll have a check of the input & output voltages when I can get my hands on a meter.

[armdnrdy]

Don't trust the schematic!

I don't see a 7812 by the power input jack in images that Mark Hammer posted. It does look like there is a T0-92 device in that location.

Check and visually verify type.

[SyntheticBiscuits]

Just checked on the board and it's definitely a 7812 (marked L78M12CV). It's the TO-220 type if that helps at all.

[armdnrdy]

Okay...
Looking from the printed side, from left to right:
Input, Ground, Output

Check the voltages when you get your hands on a meter.

[SyntheticBiscuits]

Ok thanks. I'll report back when I've got some readings.