ibanez AD-150 delay repair help please!

[onusx]

hi, i have an AD-150 table top delay that got shorted out at a recent practice. opened it up and one trace on the board is visibly burned, one part blew up, other solder connections in the area are scorched but parts not visibly damaged. i cannot find a schematic for this pedal and neither ibanez nor maxon will help me.

in the best case scenario i'm hoping that there are only maybe 4 damaged parts, but i'm not sure what they are and was hoping for some help in ordering the right replacements. i'm new to building and would be stoked if i could fix this myself.

there are 3 components i need clarification on. 1. the one that's definitely damaged is labeled IC 101 on the board-- this should have 3 connecting leads but one exploded off in a blue spark... anyway, it's right by the power transformer and power supply leads and the fuse; this is the effected area. i think the problem was that the person i bought this from had a wrong size fuse and i'm not sure how the short happened. anyway, the IC is labeled "78M15" and also has "TA78015P" printed on it, with "3k" underneath. i found a lot of mouser parts for 78M15, and i'm not sure which i want, or which will work. help on this would be fantastic.

2. there's a cap labeled "47.3" with a Z w/ a line through it and 25v. is this a zener cap? anyone know how to find the replacement i want?

3. the other seems to be a nichicon electrolytic cap-- 16v 100uf-- same question about how to tell which part i specifically want. this one is two shades of blue, and i couldn't read all the writing on it.

it looks like the spark fried the trace from that first IC, through those two caps, and on down one pathway to a ground connection. there is just one trace where it looks like there was copper tape w/ a coating or something and the coating is burned off and the copper tape/trace is coming loose from the board between the contact points mentioned. if i were to remove the effected parts, replace them, take off that damaged copper trace, and rewire the new parts point to point with a small length of wire, would i be on the right track?

i'm aware that there may be damage to more of the parts that i can't see, and that if the transformer's fried i'm probably screwed (i hear they're rare,) but i would like to try the obvious things and just wanted to see if i had the right ideas about how to do that. it can't get any worse than not powering up at the moment.

thanks,

brian

[Impaler]

OK, without the Schematic, the IC is tough to identify without a schematic.

The 78015 is a 15v regulator. I don't see why a 78L15 wouldn't work there.

Zener cap? never heard of one...

The 100µF 16v cap is just that, any brand should do the job.

Wiring p2p shouldn't be an issue as long as you keep your wires short and where they need to be going. If that fuse was too big, toss it and get the right one in there... wouldn't wanna smoke the new parts when you get them in there...

[Mark Hammer]

Obviously, what you have is a power supply problem.  The good news is that power supplies are so bloody generic that a) the parts will *always* be available and reaosnably priced, and b) many people here can talk you through the repair without needing any schematic whatsoever.

First off, a 7815 is pretty much a 7815 is a 7815.  You can use just about anyone's 7815.  You have one choice to make, is it small like a signal transistor or big like a power transistor?  I'm guessing the latter since the standard sizes are for 100ma regulation (small) and 1A regulation (big) and the big ones provide a wide margin of error at very little extra cost.  Just make sure you remember the orientation of the part because obviously pinout matters.

Since you're looking at a 15v supply voltage, I'd replace the 100uf cap with a 25v or even 35v rated cap (indeed, the presence of a 16v supply cap with a 15v may well have been the problem in the first place).  We're talking pennies difference here.  If you want, hike the value of the cap up to 220uf for a little extra power smoothing.

For caps, a 3-digit code is often used with the third digit indicating the number of zeroes after the first two digits.  So, a code of 102 is 1000pf and a code of 473 is 47000pf = .047uf = 47nf.  If you look up the datasheets for the 3-pin regulators, you'll see it is common practice to include a non-polarized cap in the supply circuit.  

I would strongly doubt that the supply circuit for this unit would diverge much from the "textbook" power supplies illustrated in the datasheets/appnotes for the 7815, since there is really very little to be gained by designing it any differently.

Can you use point to point to replace burnt-out traces?  Absolutely.  I would recommend taking a close look at the leads of the components and the connecting wire and tinning both to assure a good joint.  Copper solder pads have the extra features of holding a component stable on the board so if there is any residual part-jiggling, once connected, you may want to secure the part down on the component side with a wee bit of carefully applied hot glue.

Please note that it may also be the case that there are *other* problems with the unit as a result of the PS getting fried that are much harder to see, but you'll need to repair the power supply first to find that out.

In general, the prognosis is good, though.

[onusx]

thank you guys so much for your help. i feel like i can at least get it to power up again now; i really appreciate it. does anyone have any suggestions about where i could go to find a schematic for this in the event that there are other parts damaged and it's still not working after i restore power? any ideas on getting Ibanez or Maxon to help out? it's a maxon 501 board, but when i spoke with their service people they said they couldn't provide any info on non-Maxon products...

i figure this is a lost cause, but what would a repair tech do if he was brought this unit and needed a schem. to fix it?

anyway, thanks again for the help,

brian