Ditto X2 Looper repair

[clarisso11]

Hi everyone,

my Ditto X2 looper recently gave up on me (bought used, no warranty). Would it be completely hopeless to try a repair?

Symptoms: No power at all, no LEDs, doesn't respond.

I have fixed a bunch of pedals in the past, but not much smd. I have checked the power supply, the DC jack seems to receive the proper voltage, but haven't tested beyond that. I have used a separate 9V 200mA power supply and fresh batteries, no success. The foot switches seem to be working fine, with a nice audible click. All tested with guitar and amp connected to Mono jacks. Sprayed down with contact cleaner, no change.

I'm hoping this is just a failed component in the power supply circuit, where would I begin to do some troubleshooting?

Here is the PCB:

[Digital Larry]

Unless you are able to find and supply a schematic, or possibly draw one yourself from the board, I think it's going to be very hard for anyone to help you.  I look at the PCB and I see some components missing.  It's probably normal but how am I to know?

PS.  Since you supplied some REALLY nice in focus photos I looked at them anyway.  As you may have guessed, the power supply is in the upper left of the second photo.  One of those components is about as big as a grain of sand.  Let's hope it's not that one!  I don't see anything obviously wrong.  Could be:

a) mechanical failure - broken wire, cracked solder joint, broken SMT component.
b) Electrical failure, e.g. shorted electrolytic.  Can't see anything wrong visually.  No burns or distorted (swollen) components.  You can probably measure right across any of the large electrolytics with an ohm meter - they should NOT be shorted.

Also, since it's just sitting there, resolder the connections on that green jumper wire connected to the power input jack.

[garcho]

Not to discourage you but these are notorious for "bricking" themselves.

[clarisso11]

Not to discourage you but these are notorious for "bricking" themselves.

I had a feeling that might be the case..

[clarisso11]

Unless you are able to find and supply a schematic, or possibly draw one yourself from the board, I think it's going to be very hard for anyone to help you.  I look at the PCB and I see some components missing.  It's probably normal but how am I to know?

PS.  Since you supplied some REALLY nice in focus photos I looked at them anyway.  As you may have guessed, the power supply is in the upper left of the second photo.  One of those components is about as big as a grain of sand.  Let's hope it's not that one!  I don't see anything obviously wrong.  Could be:

a) mechanical failure - broken wire, cracked solder joint, broken SMT component.
b) Electrical failure, e.g. shorted electrolytic.  Can't see anything wrong visually.  No burns or distorted (swollen) components.  You can probably measure right across any of the large electrolytics with an ohm meter - they should NOT be shorted.

Also, since it's just sitting there, resolder the connections on that green jumper wire connected to the power input jack.

Thanks for having a look! Sounds like it might be a gonner.

One thing that doesn't get mentioned much when people talk about SMD vs through-hole is repairability -  real shame that the trend seems to be going towards smaller parts, harder to repair yourself!

[ElectricDruid]

+1 for the excellent photos. It's not easy to take such a good shot of a board, but it makes a hell of a difference for those of us having a look!

I wonder if you could find a part number on one of the larger SOIC chips. There's probably something pretty obvious like an op-amp somewhere. Then get the datasheet for that chip, find out where the power pins are and you can test whether there's any power to the board. It does sound like not, but you never know.

[garcho]

What an odd board, something like 1/4 of the SMD pads are unpopulated. ICs, transistors, a bunch of caps and resistors.

[clarisso11]

+1 for the excellent photos. It's not easy to take such a good shot of a board, but it makes a hell of a difference for those of us having a look!

I wonder if you could find a part number on one of the larger SOIC chips. There's probably something pretty obvious like an op-amp somewhere. Then get the datasheet for that chip, find out where the power pins are and you can test whether there's any power to the board. It does sound like not, but you never know.

Thanks! Good idea, might give that a go.

[clarisso11]

What an odd board, something like 1/4 of the SMD pads are unpopulated. ICs, transistors, a bunch of caps and resistors.

I agree, it's quite strange!

[free electron]

It's a common technique to design one board that can accommodate different hardware revisions or different models. They can then just mark not required components as DNP (DoNotPopulate) and the fab house will not install them.

For troubleshooting i'd start with checking the power rails, measure the current consumption. Is it more or less normal for this pedal? Too high or completely zero?
I marked a few things on the schematic which i could recognize:



The interesting points to measure the voltage against GND are marked with arrows. The values will tell more what's going on. The fact that the pedal does not respond at all indicates there might be something wrong with the DC-DC converter, which generates the supply voltage for the brain, the mcu. Can you read the markings on the chip above the L4? I see 88 something...

C256 might be one of the MCUs supply rail decopupling caps. If it reads 0V across the cap - the MCU is not getting power. Hence the pedal appears dead.

Thanks for the great pics, saved in case i will have to fix one of these in the future.

[garcho]

It's a common technique to design one board that can accommodate different hardware revisions or different models.

Right, this one just seems a little excessive. They have other Ditto loopers but each one is in a different enclosure. It looks like at one point at least, they made another pedal in the same enclosure, Spectra Drive. That might be it, eh? That would explain the extra ICs that are maybe more op amps or something similar and more passives, where as Ditto revisions are probably more code than components.

[Sweetalk]

Start from the begining, did you check the diode D6?, seems to be the reverse polarity diode. Then like said earlier, check the power rails, the linear regulator an DC-DC blocks