boss dd-3 won´t turn on

[ilcaccillo]

check that you have 9 volts on the other end of  R59

Thank you so much for your replies.

Yes I have 9v on the other side of R39, it actually connects directly to the 9v rail
Sorry forgot to mark that on the diagram

I will test as you both suggested. Thanks

[drummer4gc]

I just got done repairing a couple of these long chip dad-3s. One thing I noticed is that the solder pads and traces are very fragile and do not tolerate much repair work, as they'll begin lifting and making poor connections really easily. Check over your boards real carefully to look for any poor connections or lifting traces.

[ilcaccillo]

yes that's true.

I have a really small tip soldering iron, which I can regulate the temperature. I have to be really careful while unsoldering the components so I don't lift any pad or track.

Specially this part of the circuit,  when D6 burns , common in this circuit, it makes a hole in the PCB.
I have 3x DD2 on the workshop, and all of them have holes in place of the original D6.
When D6 burns it can take or not with him some other components. The first to look for is C49, replace that cap when you fix the D6 issue.
R59 can also suffer so that needs to be checked. In my case I replaced R59 also and then had to fix the tracks.

As far as I can see I don't see any other damaged tracks or pads.

Also another classic is broken wires, basically before trying to fix the unit you should re-solder all the wiring in the pedal, if you do this then while you are fixing the pedal you will just break 2 wires instead of breaking 20 if you don't resolder them beforehand.

[ilcaccillo]

Hi,
I'm checking the pedal.

So without D5, D7 and Q12 voltage at pin 5 was still not 9V. Today was 3.8V

I took the flip flop BA634 out and all the voltages in the circuit at the empty pads are:
Pin 1 -8.96V
Pin 2 - 0V
Pin 3 - 0V
Pin 4 - 9V
Pin 5 - 9V

I injected 9v at Pin 2 empty pad and the effect and Led turned on.

So it seems I have a shot BA634, it's bad news since they are not made anymore.

I measured the DC resistance between the Shot BA634 pins and it measures like this:

[ilcaccillo]

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.

Sorry, I didn't understand how can I test the BA634 on a breadboard.
Could you please explain with more detail?

I also checked the 634 datasheet, there's a test circuit diagram but no description so I don't know what should I be seeing when testing it.

Thank you so much

[duck_arse]

the datasheet located here:
http://shop.strato.com/WebRoot/StoreES2/Shops/62070367/MediaGallery/Datasheets/BA634.pdf

if you connect on the BB pins 3 and 5 to ground and pin 4 to (+) supply, and the switch, resistor and cap to pin 1 as in your circuit, you should be able to observe pin 2 toggle on each press - if the IC is still good OK.