boss dd-3 won´t turn on

[bagudan]

Hi.
I just recieved an old dd-3 blue label made in japan. The problem is that it won´t turn on. Neither the led or the effect. There´s a signal in the bypassed mode. There is 5 volts coming from the regulator. The D6 diode is not blown. The momentary switch is working. Can´t find any broken wires. Would absolutely love to audioprobe this thing to see if the longchip is dead, but I can´t turn it on?

My question is. What chip, or IC am I looking for, when it comes to the switching parts of this cirquit? i´m guessing it´s IC9 (BA634) Never heard of this chip, and it´s kinda funny looking?

Here´s a link to a schematic

http://www.hobby-hour.com/electronics/s/dd2-delay.php

Thanks

[Processaurus]

it won´t turn on.

Be more specific, do you mean there is no sound when the effect is on?  Or that there is no delay sound mixed with the dry?  What do you mean, there is signal in bypass mode?  It is switching modes when you press the switch?

Is there signal coming out of the direct out?

Is the BA634 (it is a custom Roland chip, a flip flop IC, like the cd4013 but single) changing state (push once, pin 2 is 9v, push again, pin 2 is 0v) when you push the footswitch?  What are the voltages for that chip and q13 and q12?

[bagudan]

Hi
Thanks for the reply
I´ll try to be more specific.

There is no switching the effect on. Only dry signal whatever you do. The led remains dark! There is signal from the direct out jack

Voltages on the IC
1: 9 volts (reads zero when holding down the switch)
2: 320 mv (nothing happens when switching)
3: 0 v
4: 9v
5: 1,6 v

q12 (can´t tell what kind of tranny it is, but it has thre legs!:))

0v
middle 1,7v
0v

And q13 is missing. Well it´s not missing I guess, but I cant´ find it in this mess of a board. So many wires, so many small components

[geertjacobs]

Have you checked the mute circuit before the BA634?

[bagudan]

No I haven´t. I don´t quite understand that part of the schematic. How do I check it?

[geertjacobs]

The sound of the effect is muted for 5 seconds as shown in the little graph in the left bottom corner of the DD-2 schematic (junction R65 and R60)
After power-up of the pedal, capacitor C50 charges slowly. After a while it turns off Q13, which turns off Q12 and then pin 5 of the BA634 should be pulled up to 9V.
I can't find a datasheet for the BA634, but my guess is that pin 5 should be 9V for the BA634 to be active.

My guess: probably C50 is bad.

edit:
pin 5 of the BA 634 is the reset pin, doesn't say if it's high active or low active though.
http://www.synfo.nl/servicemanuals/Boss/DD-2_DD-3_SERVICE_NOTES.pdf

[thetragichero]

probably a blessing in disguise... i can't stand the dd-3

[Processaurus]

Oh.

Interesting analysis geertjacobs,  yes, definitely suspect C50 if that 5 second hi pulse isn't happening when the pedal's power is connected.  Also Q13.

5: 1,6 v

I bet the the pin 5 reset is active low, and q12 is a switch to pull it low for the first 5 seconds after the pedal is plugged in.   something is pulling that pin low continually though.

q12 (can´t tell what kind of tranny it is, but it has thre legs!:))

0v
middle 1,7v
0v

If those voltages are right, then q12 is suspicious.  The middle is the same voltage as pin 5 on the flip flop, so that's probably the collector.  The other two are the same voltage, so both the emitter and base are at 0v.  The emmitter will always be 0v, it is connected to ground.  That means the base isn't held high (9v), and the transistor isn't being turned on, so it should look like an open circuit between the collector and emitter.  But for some reason the collector isn't 9v even though it should be (R59 should hold pin 5 high whenever q12 isn't turned on).  That makes me think either Q12 is fried, R59 isn't connected on one end, or D7 possibly might be bad, or possibly the BA chip is fried and that pin is shorted internally.  Or we don't have the right schematic!
Some things to check:

Check R59 has 9v on the side tied to +9, and beep continuity to pin 5.

Pull Q12, or pull out the middle pin, whichever is easier, to disconnect Q12 from the flip flop reset pin 5.  Power it up.  Does pin 5 get close to 9v?  Does the pedal work then?

And q13 is missing. Well it´s not missing I guess, but I cant´ find it in this mess of a board. So many wires, so many small components

Mine had a little funny daughter board back by the DC input, perhaps it's on there, and not on the main pcb?

[geertjacobs]

I have a DD-2 that had a similar problem:
it would start just fine but within a minute the led would fade out and the sound was gone.
I also suspected the BA634 and even managed to find a replacement, but it didn't solve the issue.

Since I was stuck, I sent the DD-2 to forum member Dirk-Hendrik for repair and he found that C50 was dead.
He was so kind to explain what had happened.

This problem seems really similar.

[Processaurus]

I thought so too, until I thought about the voltages.  I don't think it is C50, if these voltages are correct...  The base of Q12 would be stuck at 9v if it were shorted out, but here it is 0v, normal operation of the Q13/C50 part of the mute circuit.

[cjlectronics]

A common problem with the DD-2/3 is leaky 10uf capacitors.  Look at each 10uf electrolytic cap... if you see crusty white stuff underneath one or more of them, replace them all.
This will cause no sound.  This is a tech note Roland sent to all authorized service centers and I have repaired a few with leaky caps.

CJ

[bagudan]

Whoa! Thanks a lot for all the replies. Unfortunately I wont get my hands on the pedal until this weekend, but I appreciate all the suggestions and will let you know how it goes.

[geertjacobs]

Any luck?

[bagudan]

Tried replacing some of the mentioned caps, with no luck, and then i had to go to Berlin for a week. So I need time. Never enough time for this hobby:(
Will get into it later though

[valdiotube]

Hello,

I have a DD-2 that works fine BUT never tun on on first pedal pressing after inserting the guitar cable to input jack, to be more specific:
if i insert cable on input jack and press once the pedal, it wont turn on until the second of third pressing but after that, as long as the cable remains inserted to the input jack, pedal will switch as it should, one press for turn on and one press for turning it off
if I simply remove cable from input jack and reinserted, have to press the pedal 2 or 3 times to turn it on (1st time) after that 1st time on, it will switch great for hours

what could it be the issue with mine, I did replace a diode back in time, D6 I think, not sure, its a diode in the corner but not sure if I installed the correct one, whats the value of this diode or part number???

is there something else I should try to fix this 1st turn on after inserting cable...

thanks in advance for your help

Jose

[ilcaccillo]

Hello,

I have a DD-2 that works fine BUT never tun on on first pedal pressing after inserting the guitar cable to input jack, to be more specific:
if i insert cable on input jack and press once the pedal, it wont turn on until the second of third pressing but after that, as long as the cable remains inserted to the input jack, pedal will switch as it should, one press for turn on and one press for turning it off
if I simply remove cable from input jack and reinserted, have to press the pedal 2 or 3 times to turn it on (1st time) after that 1st time on, it will switch great for hours

what could it be the issue with mine, I did replace a diode back in time, D6 I think, not sure, its a diode in the corner but not sure if I installed the correct one, whats the value of this diode or part number???

is there something else I should try to fix this 1st turn on after inserting cable...

thanks in advance for your help

Jose

I know this is an old thread, but I'm fixing some DD2 pedals with the same problem.

Jose, the pedal takes 5 seconds to turn on.
So power the pedal, insert the input jack cable (this will provide voltage to the circuit),
wait 5-7 seconds.
Press the pedal, doesn't turn on?

[ilcaccillo]

Been trying to repair a DD3 unit that won't turn on.
I can get it working in the "Hold" Mode but not in any of the other 3 Delay positions.
I have the Dry sound, but nothing happens when I press the pedal, no led on, no effect.

This pedal had failed due to the D6 common problem.
D6 replaced and tracks were fixed.

Replaced all the Electrolytic caps in that area just to be safe (no signs of electrolyte leakage anywhere on the pcb)

I have a working unit that I'm using to compare voltages.
At the BA634 Pin 5 I have 4.2 volts instead of 8.6v like in the working unit.
here are the voltages:



Mode Switch - measured continuity between different positions, all is good with the switch.
R59 - measured good 10K
R60 - measured good
R61 - measured good
C50 - was replaced for new one
Q12- tested fine in the Peak Atlas

What could be the cause of having half the voltage (4.2V or 4.3v) instead of 8.6V at the BA634's Pin 5?

I guess I'm left with the BA634 and D5 and D7.

Did anyone in this thread was able to fix their unit?

thanks

[ilcaccillo]

How can I test the BA634 flip flop?

[duck_arse]

if you take the BA634 out of circuit, does the Q12 collector voltage go high/stay high? if so, it points to a bad BA, which you can stick  into the breadboard, pull pin 5 high, and then toggle pin 1. if the output doesn't change, is dead.

oddly, the Rohm datasheet shows this IC working with positive ground test circuits.

[slacker]

I would remove D5, D7 and Q12, so that the only thing connected to pin 5 of the BA5634 is the 10k resistor to 9 volts. Then see if you get 9 volts on pin 5, if you do then, see if it's working as a flipflop by pressing the stomp switch, the voltage should alternate between 0 and 9 volts each time you press the switch, if it does then it's working and the problem is related to one of the components you removed or something else attached to one of them.
If you don't get 9 volts on pin 5 then check that you have 9 volts on the other end of  R59, if you then do what Duck suggested.

If you remove the BA634 and connect 9 volts to where pin 2 went that should turn the effect on, ruling out problems elsewhere but as hold mode works the rest of the circuit is probably ok.