Tech21 SansAmp Geddy Lee YYZ Protection Diode Replacement

[Wolfeman Bass]

My Geddy pedal recently stopped working and I took the PCB out and the protection diode has shorted. Which diode should I use to replace it?

 

[johnh89]

Need to try and get hold of schematic ideally . Not sure how it is intended to work . The form factor looks like it is a zener diode but voltage rating is unknown . I'll do a bit of research and post back here if I find anything relevent .

 

[Wolfeman Bass]

Need to try and get hold of schematic ideally . Not sure how it is intended to work . The form factor looks like it is a zener diode but voltage rating is unknown . I'll do a bit of research and post back here if I find anything relevent .

Thank you so much! I've been stressing over this as I have very little knowledge on electronics and I want to repair my pedal. I looked online and I find all kinds of suggestions but most people lean towards the 1N5817 schottky. Maybe I'll just grab that one.

 

[johnh89]

This is the only SMD diode I can find that looks similar enough . It is a zener diode in an SOD-80 package but without the schematic , it is hard to work out the voltage rating .

 

[Wolfeman Bass]

View attachment 7537899
This is the only SMD diode I can find that looks similar enough . It is a zener diode but without the schematic , it is hard to work out the voltage rating .

I know. Tech21 doesn't give out the schematic. But the Schottky should work fine, right? The one in the pedal looks like a 1N4148 from all the digging I've done.

 

[johnh89]

It depends on whether it is used in a series or parallel configuration . If parallel then will be a zener diode , if series then would be a conventional rectifier .

 

[johnh89]

Based on the above , if you look at the bottom left hand corner of the schematic , it has 2 diodes for protection . D5 is a silicon rectifier in series and D1 is a 10V zener in parallel . As this is also made by Sansamp , I'm am guessing that they would use a similar setup . Any idea what caused the failure ?

 

[Wolfeman Bass]

D7 is the only diode used for protection on my YYZ by the power supply.

 

[SharpCat]

Any idea what made it fail? That could give a clue on what the diode died trying to prevent. Do you have high voltage or reverse polarity pedals on your board that could have accidentally had their power plugged in to this?

 

[cataract]

I would get in touch w/ Tech 21 and have them quote me the cost for repair. Probably not expensive

 

[Wolfeman Bass]

Any idea what made it fail? That could give a clue on what the diode died trying to prevent. Do you have high voltage or reverse polarity pedals on your board that could have accidentally had their power plugged in to this?

This is the only pedal I use. Try to keep it simple.

 

[ardgedee]

Any idea what made it fail? That could give a clue on what the diode died trying to prevent. Do you have high voltage or reverse polarity pedals on your board that could have accidentally had their power plugged in to this?

That was the first thing to cross my mind. The diode is unlikely to have spontaneously failed. Something made it fail, in which case a replacement diode would also fail when that something happens again.

 

[GregT]

Tech21 took care of one of their pedals for me a while back. He was honest and told me it it failed because the soldering was faulty and I had it back fast.

 

[babsobass]

Have you tried asking Tech 21 what the diode is? They should know.

 

[agedhorse]

There is no way to know what the diode is by looks. The same diode can look a little different depending on the manufacturer, and it can be any of a number of protection circuit designs using different parts. Most of there types of diodes are unmarked.

Either trace the circuit out, or send it to the manufacturer for a proper repair.

 

[johnh89]

I agree with agedhorse above . But if you are determined to have a go yourself , be prepared for failure if mistakes are made . You could try to remove the diode and power up the pedal , paying strict attention to polarity and voltage . If pedal will not power on at all with diode removed , then it is likely a series protection and can be replaced with a rectifier . If pedal powers on then it is likely a zener diode in parallel . Also bear in mind that there will be a reason that the diode failed originally and may have caused , or been caused by , damage elsewhere on the board .
Its your choice , but be prepared for a purchase of a new pedal , or at least a board if it doesn't work out .

 

[crguti]

If you remove the diode then your pedal will work again, but it won't have over-voltage protection.

 

[johnh89]

If you remove the diode then your pedal will work again, but it won't have over-voltage protection.

Maybe . See above....

 

[agedhorse]

If you remove the diode then your pedal will work again, but it won't have over-voltage protection.

Maybe, maybe not. Like others, you are guessing rather than understanding how the various protection circuits work.

 

[agedhorse]

I agree with agedhorse above . But if you are determined to have a go yourself , be prepared for failure if mistakes are made . You could try to remove the diode and power up the pedal , paying strict attention to polarity and voltage . If pedal will not power on at all with diode removed , then it is likely a series protection and can be replaced with a rectifier . If pedal powers on then it is likely a zener diode in parallel . Also bear in mind that there will be a reason that the diode failed originally and may have caused , or been caused by , damage elsewhere on the board .
Its your choice , but be prepared for a purchase of a new pedal , or at least a board if it doesn't work out .

Correct, and there are also a variety of different circuits that use transistors, MOSFETs etc. as switching and crowbar elements.