Hi.
I have this multieffect (korg ax5G) for guitar. I'm attempting repair following the service manual for the ax3g, wich is almost the same.
Thread:http://www.diyaudio.com/forums/instruments-amps/170013-korg-ax-3g-modification.html
The symptoms: The unit keeps rebooting after a few seconds.
First thing on the list: The power supply adaptor is not regulated, so I insert a protoboard with a 7809 regulator and proper circuitry to keep 9V as the unit requires. No change.
I opened the unit and find that the regulator (a ur3325), keeps overheating, creating the 3,3V line to drop and the reset circuit to make its job.
I suspect the near electrolytics, so I replace the electrolytics on the 3,3V. Keeps resetting.
The central chip, (MB87R1420PMC), the brain of this unit, also seems to give heat, but not as much as the regulator.
I try to find this regulator, no such luck, so I get a pair of LM1117 3,3v and 2,5v, wiring properly and desoldering the original regulator I solder these replacements.
These LM1117 support 9v on IN pin, so I do not put them in cascade 9->3,3->2,5 ; a 1,5v difference Vin-Vout is needed acording to datasheets, a maximum of 12 is allowed.
Now the 3,3v line seems to works ok, measuring in ohms with multimeter around 1K (before soldering the regulators), this reading goes up beyond 2k becouse of the capacitors.
In the 2.5v line I read 60 ohms, I change all electrolytics on this line, I keep reading 60 ohms.
I take my chances, 5/60=83mA, ok, I finish soldering and power up the unit, the 3,3v line is ok, so no reset but the leds start making some strange pattern.
I measure the 2,5v line... 1,07V, and that lm1117 creates heat.
I'm thinking right now in changing the decoupling smd capacitors in that line (100nF 0805package), but I'm starting to suspect that the main chip must me shorted inside on that line.
The only way (I think) to be sure about this is removing all caps on the line and measure DC resistance, or removing one by one and keep cheking in case is one of the caps, but the heat was pretty high on the main chip at first.
Replacing it is not an option. It's a korg chip.
Ok... any thoughts before starting to remove the smd capacitors?
Anyone had this kind of problem with this multieffects or any similar? I'm putting a lot of time on this and I thought It was the regulator, now I really don't know.
I have this multieffect (korg ax5G) for guitar. I'm attempting repair following the service manual for the ax3g, wich is almost the same.
Thread:http://www.diyaudio.com/forums/instruments-amps/170013-korg-ax-3g-modification.html
The symptoms: The unit keeps rebooting after a few seconds.
First thing on the list: The power supply adaptor is not regulated, so I insert a protoboard with a 7809 regulator and proper circuitry to keep 9V as the unit requires. No change.
I opened the unit and find that the regulator (a ur3325), keeps overheating, creating the 3,3V line to drop and the reset circuit to make its job.
I suspect the near electrolytics, so I replace the electrolytics on the 3,3V. Keeps resetting.
The central chip, (MB87R1420PMC), the brain of this unit, also seems to give heat, but not as much as the regulator.
I try to find this regulator, no such luck, so I get a pair of LM1117 3,3v and 2,5v, wiring properly and desoldering the original regulator I solder these replacements.
These LM1117 support 9v on IN pin, so I do not put them in cascade 9->3,3->2,5 ; a 1,5v difference Vin-Vout is needed acording to datasheets, a maximum of 12 is allowed.
Now the 3,3v line seems to works ok, measuring in ohms with multimeter around 1K (before soldering the regulators), this reading goes up beyond 2k becouse of the capacitors.
In the 2.5v line I read 60 ohms, I change all electrolytics on this line, I keep reading 60 ohms.
I take my chances, 5/60=83mA, ok, I finish soldering and power up the unit, the 3,3v line is ok, so no reset but the leds start making some strange pattern.
I measure the 2,5v line... 1,07V, and that lm1117 creates heat.
I'm thinking right now in changing the decoupling smd capacitors in that line (100nF 0805package), but I'm starting to suspect that the main chip must me shorted inside on that line.
The only way (I think) to be sure about this is removing all caps on the line and measure DC resistance, or removing one by one and keep cheking in case is one of the caps, but the heat was pretty high on the main chip at first.
Replacing it is not an option. It's a korg chip.
Ok... any thoughts before starting to remove the smd capacitors?
Anyone had this kind of problem with this multieffects or any similar? I'm putting a lot of time on this and I thought It was the regulator, now I really don't know.
A replacement chip or you mean a complete unit?
Also I suspect you did not mean "flea bay", this is as calling it "evil-bay", isn't it?
I emailed korg requesting a service manual, but I doubt they could supply the chip, I don't know. I will contact korg global and let's see what they say.
Thanks!
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