Boss DD3 SMT version mode selector issues

[filmdiary]

Hi.

I've been converting tube radios and projector amps into guitar friendly instruments and am very comfortable with point to point wiring and tube circuits. I have very little experience with SMT tech and microchips so here I am trying to learn something new! 

My Boss DD3 started acting up lately so I've opened it up to see if there is a fix for a mode selector switch that seems to be malfunctioning. The LED lights up only in the shortest delay setting - S / 50ms. It will come on in the other mode settings when the foot switch is held but doesn't stay on once its released. I've searched the internet and have found a couple of threads where the rotary switch is replaced but it seems like the part is very difficult to find and I'm not convinced that the switch is the problem.

Has anyone had this issue? I'm wondering if there might be a way to mod the circuit using a different switch or if there's another component causing the problem? I've removed the existing switch from the board and it looks like there is a logic circuit that remembers the last switch position.

I've downloaded the DD3(T) schematic which appears to be the correct version.

Thanks in advance!

[PRR]

Welcome!

> I've downloaded the DD3(T) schematic which appears to be the correct version.

Pointer? Link? "DD3(T) schematic" comes up with a lot of crappy spam, everything $80.88.


If http://thermionic-studios.com/wiki/images/3/39/Boss_DD-3Schematic.png is the thing, the Mode switch *appears* to be simple 2P4T which can be replaced with a $2 3P4T rotary. I have no idea if it will fit or where the wires go.

[PRR]

Switch on DIP era DD3:

[r080]

Welcome to the forum! I believe I may have seen your post on the gearpage.

Is the pedal working normally with the exception of the LED being off when not expected?

If you really do have the schematic for the recent version, that could prove useful. I am not looking too closely, but it seems the version PRR posted has the switch involved with the LED. It seems likely a newer version would have the switch as an input to the microcontroller, and just a single output pin on the microcontroller handling all the LED on and off needs. I think that was how the DD5 was set up.

I am going to look at the schematic a bit more carefully.

[r080]

Okay, well I was very wrong. I see what you mean about the logic circuit - BA634 chip in the DIP version. It looks like that is controlling the output to the LED.

A trick with this forum is a google search like this - "site:diystompboxes.com BA634"

There were a few old posts about that chip, including some relating to that potentially failing because of a bad regulator. Thad didn't make sense to me, as it is running from the 9V supply.

You might be able to manually short out the different pins for the switch to see if the behavior is the same. If it is, then changing the switch may not help, and you might want to start checking voltages.