Mooer Red Truck

[stevenrb718]

Customer brought in a Mooer Red Truck pedal that is confusing the hell out of me. Mooer hasn't been very helpful and has not provided a schematic. The pedal uses a WRA1209CS-1W voltage converter. When plugged in, the pedal doesn't power up and the converter gets pretty warm. The output voltages all test low, and the main 9V line all the way to the plug tests at 2.6V. When pulling the regulator, pin 2 (Vin) up to the plug is a nice 9V. But of circuit, the regulator seems to test fine. The problem in circuit seems to be pin 3 (ctrl) which goes nowhere. The required 500mv at pin 3 seems to be created by the regulator itself. In circuit, there is no 500mv at pin 3. If I inject the 500mv into pin 3, the whole pedal jump-starts and functions properly. I've swapped the converter and they all have the same symptoms. I'm so lost at what could be pulling down the ctrl voltage since it seems like a NC, unless something in the output line is messing it up. I doubt there's a schematic floating around somewhere...?

[g1]

There are no application examples that do not use pin 3, so I think that is where you must look. (datasheet attached)
Is it perhaps a multi-layer board?

[stevenrb718]

There are no application examples that do not use pin 3, so I think that is where you must look. (datasheet attached)
Is it perhaps a multi-layer board?

Very well could be, but I can't tell for sure. I checked continuity to the pin all over the unit and never found a point. The datasheet is very specific on the ctrl pin and the voltage required to kick the regulator on. I'm very confused why I the regulator seemed to produce the voltage to pin 3 on it's own out of circuit. I need to pull it and try that again.

[stevenrb718]

There are no application examples that do not use pin 3, so I think that is where you must look. (datasheet attached)
Is it perhaps a multi-layer board?

With the regulator pulled, pin 1 GND, pin 2 injecting 9V, I get 0.63V on pin 3. Pin 6, 7, 8 produce nothing. The 9v is pulling at 0.03A. When connecting pin 7 to ground also, as that is grounded at the pad of the pedal, I get 9V and -9V at pins 6 and 8. When the regulator is in the unit, I seem to lose the 0.63V on pin 3 unless I jump-start it. I can't for the life of me find continuity where pin 3 goes.

[g1]

Looking again at the 'application note', it seems pin3 can float (I think).
"CTRL terminal: When open or high impedance, the converter work well; When this pin is 'high'; the converter shut down".

There is mention of start-up current. Have you tried other supplies, or checked ripple at start-up attempts?
(edit: 1Amp minimum supply required)

[stevenrb718]

Looking again at the 'application note', it seems pin3 can float (I think).
"CTRL terminal: When open or high impedance, the converter work well; When this pin is 'high'; the converter shut down".

There is mention of start-up current. Have you tried other supplies, or checked ripple at start-up attempts?
(edit: 1Amp minimum supply required)

I've tried a couple different power supplies plus my bench, all with the same issue. Without the regulator in, the 9V rail through the early stages of the pedal is solid. When the regulator is fully installed, the 9V line crashes to 2.6V until injecting pin 3. Pins 6, 8, 7, & 1 shouldn't be pulling anything down as that's V+, V-, and ground. Pin 3 seems like a NC and that leaves pin 2, Vin. Having the regulator removed, I ran jumpers for only pin 1 and 2 to the pedal. When plugged in to power supply, pin 3 is still the 0.6V, but nothing happened with the pedal, and the regulator gets super hot. With the bench? The voltage cycles up and down between 5V and about 9V, with the pedal flashing LEDs. I'm assuming that's due to not being able to run a full boot-up procedure. Why would the regulator act differently on the bench vs a couple other power supplies?

[g1]

Having the regulator removed, I ran jumpers for only pin 1 and 2 to the pedal. When plugged in to power supply, pin 3 is still the 0.6V, but nothing happened with the pedal, and the regulator gets super hot. With the bench? The voltage cycles up and down between 5V and about 9V, with the pedal flashing LEDs. I'm assuming that's due to not being able to run a full boot-up procedure. Why would the regulator act differently on the bench vs a couple other power supplies?

Sorry but I'm not understanding this part. And you have not addressed the current capability of your supplies (1amp minimum required).

[stevenrb718]

Sorry but I'm not understanding this part. And you have not addressed the current capability of your supplies (1amp minimum required).

Sorry, bench is 30V/6A.

I ran the removed regulator to the input side of the pedal with jumpers. Only connected GND and Vin. When using my bench to power the pedal, the pedal starts to boot up, but obviously doesn't make it past initial stages since the regulator isn't connected for the output (9V and -9V). However, when using the power supply that came with the pedal or several of my own power supplies, the pedal doesn't show any signs of life and the regulator gets very hot. The regulator that was in the pedal to begin with and the replacement regulator have both functioned the same way, so I don't believe it to be a fault of the regulators.

[g1]

Sorry if I missed it, but just to be sure, have you tried it with the regulator fully installed but using your bench supply as the power source?

[stevenrb718]

Sorry if I missed it, but just to be sure, have you tried it with the regulator fully installed but using your bench supply as the power source?

Yes, same outcome. Bench is pulling only 2.6V at 0.16A, obviously that's the reason the regulator is getting warm, but I can't find what's pulling it down. I don't have a second benchy, but I'd imagine if I injected the 0.6V to pin 3 the pedal would then take 9V and power up properly, like it does on a PSU.

[g1]

Yes, same outcome. Bench is pulling only 2.6V at 0.16A,

I don't understand this statement. Isn't the bench supply regulated? Why isn't it holding 9V ?

[stevenrb718]

I don't understand this statement. Isn't the bench supply regulated? Why isn't it holding 9V ?

I really have no idea. That's why this thing has been confusing me. A partial short maybe? The regulator gets crazy hot. My new set of regulators should be in today, so I'm going to just swap that. Mooer never gave a schematic so I'm flying kinda blind. If they don't work then I'm giving it back as a no-fix.

[g1]

Ok, but what do you mean about your bench supply? It is telling you it is only putting out 0.16A, but can't hold up the 9V and drops to 2.6V at it's output terminals?
Is something wrong with it? You said it was a 6A capable supply.
The regulator needs a supply that will hold rock solid at 9V during start up. If it doesn't get that, it can do all kinds of weird things, probably including over-heating.

[stevenrb718]

I really don't know what the issue was with the power supply pulling down. I've never had a problem with my bench. I took it apart, got some deoxit into the encoders, and did a quick blow-out. Everything seems to work fine as it always has. I did get the new voltage regulator for the pedal. I popped it in and ran off the bench and it worked perfectly. I then tested it with the PSUs I tried before, and it worked with every one. I guess I'll rule it to the original replacement was a dud. Oh well, several power cycles and 20 minutes of playing through it to test, and back to the customer it goes.

[GardenShedGuitars]

Hi there stevenrb718,

I have a mooer preamp live on the bench with similar symptoms. Where did you manage to find the wra1209cs-1w regulator? Ive also pulled the regulator and trying to test by connecting 12v at pin2 and read nothing at pin 4 or 6.
did you manage to find out what to do with pin3 to test the regulator?