DD-2/3 repair notes

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laurie
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DD-2/3 repair notes

Post by laurie » Fri Aug 24, 2018 12:30 am

BEFORE DOING ANYTHING ELSE... what are you powering the pedal with? If you are using an external supply and you are experiencing strange symptoms (pedal stuck in hold, weird repeats, etc.) check the pedal operation with a known fresh alkaline battery.

These pedals, plus the DSD-2 and DSD-3 are known to have weird problems if not used with a high quality regulated power supply. Worse than that - operating from an unregulated supply for extended periods will kill the pedal - this is the most common cause of D6 burning out, and a burned out D6 is probably the most common fault.


Also... don't forget that there is a 5 second delay between when the pedal is powered on and anything working.


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There are more and more dead and sick DD-2 and long-chip DD-3 pedals turning up as they get older and older.

The following list is in the order that I have found to be most common for the DD-2 and long-chip DD-3.

Here is one source for the schematic: http://www.hobby-hour.com/electronics/s/dd2-delay.php


1) Failed capacitors.

SYMPTOM: echoes go up in volume with each repeat and eventually turn into a distorted mess.

CAUSE: C31 (10µF) fails causing the compressor half of the compander to stop working. This allows the expander half to continually expand the signal, raising the volume and turning it into a distorted mess.

SOLUTION: Replace all electrolytic capacitors around the compander – C31, C30, C34. Use tantalum if normal can electros don’t fit.

2) Failed D6.

SYMPTOM: pedal is completely dead. Visible burning around the legs of D6 and nearby tracks. UPDATE: a recent fault indicates that sometimes the pedal can work with a failed D6, but have no repeats.

CAUSE: incorrect AC adapter - specifically an unregulated adapter. MORAL: always use a Boss PSA adapter!

SOLUTION: Replace D6 with an 11V (or 12V) 1W Zener. There will almost always be a need to carefully repair the tracks around D6 – the tracks are quite thin and will burn out when D6 burns out.

POSSIBLE COLLATERAL DAMAGE: If D6 has failed short circuit on an external supply and then the pedal is checked using a battery, the current delivered by the battery into the short circuit can sometimes burn out the contacts in the DC input jack and this jack will need to be replaced. One symptom of this is that, once repaired, the pedal works on the PSA power supply but does not work on battery.

Repaired DD-2. A couple of braided copper strands were run along each burned trace to replace the burned copper:
D6 fix.jpg

3) Failed “mode” switch.

POSSIBLE SYMPTOMS: pedal fails to turn on, pedal only works in “hold” mode, pedal LED comes on but no sound. The only way to know for sure is to use a meter and test the switch in all positions.

CAUSE: age/abuse.

SOLUTION: Order a new switch from Roland and replace.

4) Broken wires.

POSSIBLE SYMPTOMS: no sound, failure to turn on.

CAUSE: Almost always caused by someone swinging the board out too many times.

SOLUTION: Visual inspection, plus GENTLY pull each wire to see if it is still firmly connected. Re-solder those that are broken.

5) Q9 leads broken.

SYMPTOM: No delayed sound. Signal is present at the emitter of Q10, but not at C34.

CAUSE: some pedals have Q9 bent over in the factory to make it fit in the case. This stresses the legs and over time one breaks off.

SOLUTION: Replace Q9. Almost any small signal NPN transistor will do (take care with the pin-outs).

6) Master clock fails.

SYMPTOM: No sound. Use a scope to check the clock is running (pin 63 of the long-chip). The waveform is NOT meant to be “clean” – as long as it is there.

CAUSE: Unknown.

SOLUTION: Replace U8. Note that this must be a “HC” spec TTL chip.

fuzzbuzzfuzz
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Re: DD-2/3 repair notes

Post by fuzzbuzzfuzz » Mon Aug 27, 2018 12:05 pm

Thanks Laurie, important stuff!

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Goran
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Re: DD-2/3 repair notes

Post by Goran » Thu Oct 25, 2018 7:02 am

Great work Laurie! Vet useful to know!

spunko
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Re: DD-2/3 repair notes

Post by spunko » Mon Aug 05, 2019 11:44 am

Hello Laurie, I have an old boss dd-3 japan, long chip version.

The problem is, when you plug the PSU or bateries, the led will ligth at full and the pedal is always on, if you try to switch it off, it will only dim the led, but as soon as you lift you foot, the pedal is on again. It never turns off, and it will only make a whistle sound. Like when you put your mic pushed to the speakers. All modes do the same, execpt for HOLD mode.

All modes: led always on and gives the whistle sound. When you push the swicth to turn it off, the led will dim and the whistle sound rises in pitch. As soon as you lift your foot, the pedal will behabe like said above, it will never turn off.

HOLD mode is the opposite. Also, the whistle sound can vary with the time knob.

Does anyone have encountered this problem?

Video here: https://streamable.com/z1rbq

spunko
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Re: DD-2/3 repair notes

Post by spunko » Fri Aug 09, 2019 2:51 pm

bump

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laurie
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Re: DD-2/3 repair notes

Post by laurie » Tue Aug 13, 2019 1:06 pm

I've never seen anything like this before. It *feels* like it would be something around the main controller (the long-chip).

Unfortunately, the only way to track down something new like this is to get the pedal disassembled on a bench and trace what's going on with a 'scope.

spunko
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Re: DD-2/3 repair notes

Post by spunko » Tue Aug 13, 2019 6:08 pm

Thank you for the reply.
I guess I'm stuck then, I don't have an scope. Just a fluke multimeter :)

I was thinking in changing all the electrolytic capacitors and try again, but I don't know if it's worth it.

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Pepe
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Re: DD-2/3 repair notes

Post by Pepe » Tue Aug 13, 2019 7:08 pm

Well, it couldn't make things worse. The amount of electrolytic capacitors inside of the DD-2 or the early DD-3 is manageable.

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laurie
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Re: DD-2/3 repair notes

Post by laurie » Wed Aug 14, 2019 12:25 pm

Where are you located? If you are in Canada you could send it over to Calgary and I'd take a look at it.

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