Boss DD-3 schematic needed for repair

[FatMike]

Hi,

I bought a broken Boss DD-3 Digital Delay on E-Bay in order to repair it and use it. However, repairing it seems to be much harder  than I thought as I supposed the switch to be broken, a missing connection, broken cable or something like that...

First of all, does anyone have the schematic and could send it to me? I only have one of the DD-2. By the way, the pedal was built in Japan, not  in Taiwan (don't know if this makes a difference anyway).

Now here's what's wrong with the pedal: When I step on it the LED turns on, but there is no effect at all. Like a permanent bypass.
I already checked the board for missing connections / bad soldering points, but everything looks pretty correct. No parts that look like broken either.

Does anybody have an idea what could be wrong with the pedal (maybe someone had already similar problems with his DD-3 and knows how to fix this)? Could the main IC be broken (are these ICs easy to destroy?)?

It would be nice if someone could help me, otherwise I guess I  have to sell the pedal on E-Bay again.



Thanks,

Fat Mike

[FatMike]

Sorry, but I have to put this topic on top again... :wink:

Does anyone have this schematic? I really need it.  



Thanks,

Fat Mike

[MartyMart]

http://www.pbase.com/image/36708510

Here you go, DD2 and DD3 schem !!

Marty.

[FatMike]

Are there no differences between the Boss DD-2 and DD-3 delay? Seems like this schematic is for both Effects. So why are there 2 different pedals?



Fat Mike

[Peter Snowberg]

That looks fairly easy to follow the schematic (thanks Marty! ). The next tool you'll need is an audio probe (see the FAQ section).

(1) Check for audio at pin 1 of IC4 (a 4066 CMOS switch).

(2) If you hear something there.... look next at pin 1 of IC3. (a 5218 opamp)

If you don't hear anything at the first test point, your problem is before the microcontroller (IC7, which is a Z80 derivative microcontroller) and should be easy to fix. If you hear audio at the second point, chances are very good that IC7 is fine and the fix will also be fairly easy.

Let me know what you find and we'll take it from there. As long as IC7 is OK, you should be able to repair it.

[Zero the hero]

I had a similar problem with a DD-5 and it was a broken 7805 regulator.
The first thing you should check is the correct supply at the end of this regulator.
Then follow the signal path and see where the signal is lost.

[TheBigMan]

Are there no differences between the Boss DD-2 and DD-3 delay? Seems like this schematic is for both Effects. So why are there 2 different pedals?

Fat Mike

The price of DRAM dropped hugely in 1986, so Boss reissued the DD-2 as the DD-3 and the DSD-2 as the DSD-3 rather than slashing prices on the existing pedals.  There is now a newer version of the DD-3 with a DD-3(A) PCB, but I don't know when the change occurred.

[Peter Snowberg]

I had a similar problem with a DD-5 and it was a broken 7805 regulator.
The first thing you should check is the correct supply at the end of this regulator.
Then follow the signal path and see where the signal is lost.

There is nothing like the voice of experience.

Do check the voltages first, then check for audio along the numbered test points in the schematic. Just be sure to hit "original" size when viewing the schematic, then follow the numbered squares 1 to 5. Once you see how far the signal goes, tracing it to the bad component may be really easy.

I fixed an Ibanez Modulation Delay for somebody a couple months ago that had lost all of the effect. The problem turned out to be a bad 1uF cap that coupled two parts of the signal chain. Looking at the DD-2/3 schematic, it was the equiv. of C28.

It's always a great feel to bring gear back from the dead. Especially if you pick it up for a bargain in the first place and repair it for 10 cents.

[Zero the hero]

It's always a great feel to bring gear back from the dead. Especially if you pick it up for a bargain in the first place and repair it for 10 cents.

And more expecially when other repairers say that "there's nothing else to do"!!! It happens with that DD-5. It had been tested by two other people that said that all the chips were fried, so the best thing to do was to buy a new one...
Not today, babe...

[cd]

FatMike, does the DD-3 use surface mount or regular through hole components?  I'm thinking of picking one up to mod, but SMD components would seriously discourage that.

[FatMike]

Hi,

thanks a lot for all of your replies! I haven't had much time this week to check out any of your advices. And anyway, I don't even own a multimeter  :oops:  so I have to repair the pedal together with a friend (actually I don't even know enough about electronics to repair this pedal on my own  :cry: ). But I'll probably have a look at the pedal again this weekend. I'll keep you up to date...

@cd
I don't know exactly what you mean by "surface mount" components, but there aren't any SMD components inside of this effects, only "normal size" components mounted through hole (at least in this japan-built one).
However, none of the ICs is mounted on a socket.

[cd]

surface mount = SMD

Thanks FM, that was exactly the answer I was looking for.  Time to find one of these guys cheap to mod!

[FatMike]

Hi,

I checked the points that Peter mentioned for audio (Pin 1 of IC 3 and 4). I could hear audio at both points, not quite clean, a little bit distorted, but it guess that's normal  :roll: .
I also checked some "waveform check point" mentioned in the schematic (those boxed numbers) for audio. I checked point 1, 3 and 5 (as those were easily to find), could hear audio at all of them. So the microcontroller (IC7) seems to be OK, right?

So what else can I do now? I haven't checked the 78L05 regulator yet (as I didn't know how  :oops: ).

Zero the hero, what exactly do you mean by

The first thing you should check is the correct supply at the end of this regulator

Measuring the voltage at the output of that 78L05 regulator? If yes, which value is normal?


Thanks again,

Fat Mike

[puretube]

5V