Looking for some obsolete diodes - ISS-220?

[Sean Kerns]

Hi all,

I'm working on fixing a Casio GT-500 MIDI guitar, which let out some magic smoke.
I traced the problem to a melted component which, according to the service manual, is "D1", which it identifies variously as an ISS-220 or an ISS-220L in a couple of different locations.

All I can find about an ISS-220 diode is that it's obsolete. I can't find anything about specs or a substitution for it. It completely smoked, to the extent that I had to pop the remains off the board with some heat, and clean up the pads, one of which had burned off.
Elsewhere in the service manual, it refers to an ISS193TE85L, but I can't find that one, either. Here's what the other one nearby looks like:
This is D2:

 

[Khron]

Try "1SS220".

You can likely use 1N4148 as a replacement though (or whatever SOT23-packaged small-signal diodes you can find).

 

[dmp]

You might find after you replace the diode it fries the new one. Often a diode will fail due to a problem elsewhere, causing too much current.
Do you have a schematic?
Look for capacitors that might be leaking

 

[Sean Kerns]

1SS220 found me some results, thanks! And yes, I expect that it cooked for a reason, so I'm planning to check out what's ahead of that before I sacrifice another one.

 

[JohnRoberts]

Looks like a high speed switching diode... Typical failure modes for diodes are a) forward over-current or b) reverse breakdown voltage. Digikey shows thru hole parts in stock( 1SS220?).

JR

 

[CJ]

Probably a power supply problem , look for a bad filter cap although I haven't even looked at the schematic so ill shut up.

 

[Sean Kerns]

Someone else suggested it might have given its life protecting against batteries installed incorrectly, or some other electrical offense. I haven't even taken a look at the battery pack yet.