Behringer DR400 Tap Tempo repair

[marcelomd]

Hi,

This week I got a second hand Behringer DR400 Delay/reverb to play around. The tone is good enough for me. The problem is that when I engage the tap tempo, after about 10s the pedal goes into some kind of invalid state. In this state the pedal passes only the unaffected signal. I can engage and disengage the tap tempo (the led blinks red in time) but the sound is still unaffected. Turning the mode knob makes the blue led blink and some modes loses volume as "normal". Still no effect. Turning the unit off and on restores function until I engage the tap tempo.

The pedal is relatively cheap, but not a trivial amount of money here, so the seller offered some cash back instead of a return. I did not respond to him yet. Is it worth the hassle to debug and repair it? It is my first delay/reverb pedal, and I'm not sure if I will ever use the tap tempo function.

Thanks!

[stallik]

I have the DD version so not sure if this is a valid comment but on mine, the tap tempo is simply a momentary switch. I can imagine that a failed switch may cause  these symptoms. If it's not the switch but on the main pcb, you'll have to deal with smd components
I've not been too impressed with the reliability of mine, in fact it stopped generating any kind of delay and is in the 'for repair' pile. I doubt I'll ever get to it as I have much better DIY alternatives

[marcelomd]

If I engage the tap tempo and do nothing else, after a few seconds the sound just reverts to the dry signal. Mid note. The blue led (bypass) is lit and the red led blinks (tap function) as if operating normally.

The switch looks ok. It registers every press and tap. The tap tempo led blinks in time with the tapping as expected even in the failed state.

If it was a Boss analog pedal I would say the bypass latch circuit is busted.

[marcelomd]

I opened the pedal to see if there is anything obviously wrong. Nothing =\

I recorded the problem happening, if anyone is interested.

https://www.dropbox.com/s/nqxsrfo4kic0wol/VID_20180531_185829.mp4?dl=0

https://www.dropbox.com/s/qj0kn1yqlmf2qfw/VID_20180531_194350.mp4?dl=0

I think I'll return it.

[marcelomd]

I opened it up and saw nothing obviously wrong, so maybe it was a defective unit. Anyway. Mailed it back today. The guy was furious and said he did not knew the pedal was digital or had tap tempo (despite he announcing it as digital). He probably was lying.

Thanks!

[ElectricDruid]

Perhaps the poor chap has something wrong with his eyesight? I can't see how you'd miss that it's digital otherwise...

[siro78]

Hi guys.
I had a similar problem.

When I power up my DR400 the effect works fine but if I move any potentiometer the output become dry and the effect disappears.
Then, shutting down and power up the pedal again, it restart working with new parameter updated!

Very strange.
It's seem that at startup it read the potentiometer correctly and write the DSP well.
On run time the parameter updated corrupt or the DSP firmware or internal switching components engaged between dry and effected signal.

As soon as I have time I try to sniff the comunication between uC and DSP at startup and on runtime parameters update.
Stay tuned

[marcelomd]

Some modes have a noticeable volume drop. When in failure mode, the pedal I had (I returned it) also presented this volume drop in certain modes, even if the output was 100% dry. Those volume changes tells me that the components were operating and more or less communicating, but the current effect wasn't being excited correctly. Maybe there is a timing, or modulation signal that is getting lost.

I don't have an oscilloscope or protocol analyser at home, but the board appeared to be ok, except for a few cold solder spots.

If it was a firmware bug I suspect this issue would be reported more often.

Keep us posted =)