Boss DD-3 Not Working, help troubleshooting please

[pfapin05]

If I use the DC input jack to power it, it passes signal through and I can hear my guitar signal going through it but the led dosent light up and the delay doesnt work. If I put a battery in it, no led comes on, no sound at all from my guitar. I am handy with a multimeter, but am new to troubleshooting this kind of stuff. Would someone mind helping me get on the right track to troubleshoot this please?

I read this in another thread that had a similar problem...

"Check if the zener diode (D6 in the schematic) hasn't been fried. It serves as a safety if someone uses a wrong power supply."

So I went ahead and hooked my multimeter up to the only diode I saw that was labeled D9 and it registered at .480. I think that someone told me that a diode is bad if that value is under .500 is that correct? They told me that I would be able to remove the diode all together and check to see if the pedal is working correctly just as long as I never connect anything but 9VDC center negative to the pedal.

What would you guys suggest I do? I really want to get into doing this sort of thing, I like this kind of stuff! Any help is greatly appreciated and thank you in advance!

[drummer4gc]

Which version of the DD3 is it? Made in Japan or Taiwan? Long chip, square chip, or smd components? Check out this link with some info about the different versions and let us know.

http://www.bossarea.com/boss-dd-3-digital-delay/

[pfapin05]

Its a DD-3A (says on the pcb board) and the serial number on the back is RO 89176 and it is made in Taiwan. It looks like it has a square chip.

[drummer4gc]

Cool. So, some things to check -

Here's a service manual and schematic: http://www.synfo.nl/servicemanuals/Boss/DD-3A_SERVICE_NOTES.pdf

Not sure what D9 should read in circuit, but you can check for correct voltages at D9 cathode (+9v) and junction of R63 and R59 (+4.5v). My guess is they will be fine if you've got signal when the pedal is off. If you aren't getting voltage here, you can remove D9 as you mentioned in your first post and see if that gets the pedal up and running (with a correct power supply, of course).

It seems like you have two problems - you get bypass signal with a power supply, but no bypass signal with a battery? Check the battery snap connections and the power jack for proper connection to figure this out. You should have bypass signal with both if there isn't a connection issue here.

Your second issue is that the pedal doesn't turn on when switched. This could be a hardware issue with the switch, a problem with the switching circuitry, or a power issue. Wouldn't hurt to spray some contact cleaner in the switch, or disconnect the wires going to the switch and then try tapping them together.

If you've gotten to here with no luck, it's time to follow the debugging instructions in the sticky thread at the top of this forum. Voltages for all IC pins, diodes, transistors, etc. Last thought is that many of these pedals suffer from dried out electrolytic caps - you could replace all of them if you want to go brute force on it, but you may not have to if you debug a little bit.

[pfapin05]

With the switch disconnected I put the two wires together from the switch and hooked up the battery cable and I got signal to pass through so maybe the switch is bad, but it still didnt power up so should it have powered up when I touched those two wires together? Should I have soldered them together, or is touching them together adequate enough? I was able to look up how to properly test a diode and that was fairly easy. Now I have to figure out how to check for correct voltages at D9 cathode (+9v) and junction of R63 and R59 (+4.5v). Can you tell me what settings I need to use on my multimeter to do this and how to properly measure those spots? Im sorry that I dont know, and really appreciate your patience.

[pfapin05]

HAHA. After doing all this stuff I had the idea to try another battery and low and behold the pedal works. The other battery I was using worked on another pedal but not this one for some reason. Thanks for all your help.

[drummer4gc]

Delays like this are often battery hogs and need batteries to be nearly new to work properly, where a fuzz circuit might run on a battery that's half dead. I'd run it on a power supply to save yourself from running through 9 volts all the time. Glad it's working for you though!

[pfapin05]

Thank you, I would still like to get some non working pedals to see if I can repair them in the future. Seems like an audio probe could help me out if I make one.