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bossarea
Forum Admin

United Kingdom
3652 Posts
Posted - 01/27/2006 :  20:45:34  Show Profile  Visit bossarea's Homepage  Reply with Quote
The protection diode on my PS-2 has shorted. I don't have a schematic but I think it's a S5500G as this part of the circuit is pretty much identical to other pedals.

My electronics pusher don't have this type so I'm wondering what to replace it with. I suspect it has a fairly low reverse breakdown voltage to protect the rest of the circuit from high input voltages but I'm still tempted to replace it with a standard 1N4148.

Anyone know of a good replacement?

phostenix
Gold Member

USA
754 Posts
Posted - 01/28/2006 :  18:46:18  Show Profile  Reply with Quote
This just in:

Just got my PS-2 service manual from Boss. It's the big original, not a copy.

If it's D1 on the digital board, I'd say you're correct with the S5500G. For some reason, on this SM they don't identify parts by the schematic labels. There's just a list of diode part numbers. There are 4 listed, the S5500G is at the top of the list.

I got a pedal recently that had been over voltaged and the reverse polarity diode had burned. Burned through, charred PCB, burned trace, the whole deal. That's got me to thinking that the voltage & current ratings on that diode could be higher. If it shorts, that's OK, because it still protects the circuitry. But, if it opens, then the pedal could be damaged. In my case, the pedal was O.K. He must have pulled the power just in time as the smoke poured out of it.

Grace and peace,

Steve
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bossarea
Forum Admin

United Kingdom
3652 Posts
Posted - 01/30/2006 :  20:35:58  Show Profile  Visit bossarea's Homepage  Reply with Quote
Thanks, I had a closer look at it today and found that the diode wasn't the only thing that had gone wrong. There's also a blown capacitor so I'll be ordering my copy of the schematic tomorrow. A blown capacitor should be easily seen but these surface mounted components are so tiny I almost overlooked it.
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