Boss ME-30 power supply?

[DrNomis_44]

Sounds like it could be either a cracked solder joint around where the DC in socket is soldered to the circuit board, or it could be a bad connection somewhere, or maybe the plugpack adaptor isn't supplying enough current, you can check for cracked solder joints by using a strong magnifier to inspect the solder joints.

Sometimes those circuit board mounted DC in sockets can go bad and develop bad contacts, if the Boss ME-30 is powering up via batteries okay, that suggests to me that the small switch contacts in the DC in socket are okay, the small switch contacts disconnect the batteries when you plug in the plugpack adaptor.

You can check to see if power from the plugpack is getting to the rest of the circuitry of the Boss ME-30 by using a multimeter set to read DC volts, touch the black probe tip to a suitable ground-point on the circuit board and try touching the red probe tip to the solder joints of the DC in socket on the circuit board.


Hope that helps.

[JohnH]

Thanks guys. Yeah the plug pack I have is centre negative, and 1A, so I don't think it should be a problem. Will open it up tonight and have a play around

[JohnH]

Well, the mystery continues. When I checked the voltage at the DC in, I got no response. Two of the solder joins looked poor, so I resoldered those, and now I get a reading at the DC in, but nowhere else in the circuit. I'm assuming it has to be a connection between the DC in and everything else, as it still works fine with batteries, but I can't figure out what's what.

Might try to get pics tomorrow when the light is better and see if the wiring gurus can spot something I'm missing

[dave.king1]

My long distance blind diagnosis is a crack in a PC track between where the power supply connects and the battery connects

[DrNomis_44]

I agree with Dave.king1, have a really close look at the circuit board tracks that connect to the solder-pads on the DC socket's solder terminals, use a X5 or X10 magnifying glass, I bet the crack is right where one circuit board track joins up with the pad for the DC in socket's inner pin.


If it does seem to have a crack in the circuit board track, the way to fix it is to remove all the solder on the pad with some solder wick, then carefully scrape about 5mm of the protective lacquering off the track so that you see some shiny copper, next tin the track where it's shiny, and then get some tinned copper wire and wrap a little bit of it around the DC in socket's terminal protruding from the solder pad, then solder the tinned copper to the terminal, next solder the tinned copper to where you tinned the circuit board track and cut the excess tinned copper wire off, that should fix it.

[HyeProfile]

I have the same issue. I diagnosed the board and in my case, it's not the soldier points for the DC jack, nor the PCB traces. My multimeter was measuring weird voltages, with ~4.5V leaking from positive to negative at the DC jack points when the DC in is suppose to be at 9.6V (for those a little familiar with electronics, this is a clear symptom of one of the PCB components having failed, usually close to the DC-in points). My unit was also powering on properly with batteries, and the batteries and DC-in jack solder points are on the same PCB trace, so that's also a pretty obvious sign that one of the PCB components had failed. I also noticed a black soot mark on top of one of the metal shields soldered to the main PCB, directly opposite to where the jack PCB sits. The main PCB is green and is on "top" [or bottom, when you open up the bottom cover and are troubleshooting with the unit inverted], and the jack PCB is beige and sits on the "bottom" [or top when unit is opened up from the bottom]. I found the soot mark lined up with component D5 on the jack PCB. Upon closer inspection (I needed a magnifying glass), D5 looks like it's a fancy Schottky voltage rectifier diode, and the plastic/ceramic casing looked split. The diode has the marking "S07 037G", so I'm trying to figure out where to get a replacement.

Photo of this baby opened up (unit inverted and bottom cover removed)
Closeup of main PCB (green) and jack PCB (beige)
Closeup of diode D5 on jack PCB (you can see it's cracked)
Closeup of diode D5 from another angle. You can see it's right next to the DC-in jack and power switch

[HyeProfile]

I looked into the ME-30 Service Notes: https://www.synthxl.com/wp-content/u...vice-Notes.pdf

It says that D5 on the jack board is a " Schottky Diode SB07-03N-AA". Gonna try to get a replacement and solder that sucker in, and see if it works. I'll keep y'all in the loop. Wish me luck.

[HyeProfile]

So I found that datasheet on the S07-03N-AA Schottky diodes. It says that it's a Schottky Barrier Diode, 30V, 700mA Rectifier with a Vf max (forward voltage, aka voltage drop) = 0.55V, and that leg #3 is a "no contact", which makes sense since the jack PCB circuit diagram in the ME-30 Service Manual only shows legs #1 and #2 connected. Bot the datasheet and service manual show that #2 is the cathode, so we should be good.

My local electronics shop didn't have the exact same part number diode in stock, but the guy at the counter and I were able to find a suitable alternative diode that should do the job; I got 10× 1N5395 1.5A general-purpose plastic rectifier diodes for CAD $2. They can handle 1.5A vs. the 700mA of the original Schottky diodes, but my biggest worry is that the Vf max on those babies is listed as 1.5V vs. the 0.55V for the original Schottky diodes. For CAD$2 (that's USD$1.5) for 10 of these babies, it's worth a shot. And if they keep on failing every few years, I'll be good until I die with the remaining 9... Wish me luck...

[HyeProfile]

EUREKA. I soldered in the 1N5395 diode and it worked. The unit is powered ON and all the buttons work, no problem. I jammed for a while on various settings and didn't notice anything weird, so I'm considering this a success.

P.S. The original BOSS AC-to-DC power transformer/adapter that came with my ME-30 produces DC out at 9.6V and 200mA, and I looked a bit more carefully at the Vf curve in the datasheet for the 1N5395 general purpose plastic rectifier diode I got as a replacement, and it turns out that at 200mA the Vf max = 0.8V, so it's only 0.25V higher voltage drop than the 0.55V on the original Schottky diodes. Should be fine since most of the electronics downstream should be able to handle 0.25V less voltage without too many issues. I'll post pics of the alternate diodes installed, if anybody is curious...

A big shout-out goes out to BOSS for actually publishing the service notes for their products. Helps us keep these babies running for a long time...