I Bought a Roland SC-155 today went to power it on and got zero power. no standby. nothing. I was looking for troubleshooting videos when i found this one. Though its not a desktop synth. the 9V power delivery is identical. Thank you so much for outlining the common issue of people using the wrong polarity power supply. AND that it blows out the diode. Also thank you for talking about a good sub for the diode. I wound up using a slightly more robust one because i had it on hand but it fixed my SC-155. So thanks again. you rock. I knew the issue was in the first few components, and figured someone used the wrong psu.. but did not know about rolands "fail safe" diode. thanks a ton.
Thanks for the video, it is well explained. I can only speak for Australian issued Boss and Roland PSUs, some of which do not have the conventional symbol showing the polarity of the barrel jack. In fact there is no indication. I can imagine a musician who has collected a number of synth and FX units could easily assume if the voltage matches and it is says Roland or Boss and the product brand matches the PSU brand it is easy to assume the polarity will be correct. The only safe way is to do what you did and that is find the schematic and use a multimeter to find the polarity of the PSU. Then label the cord or write on the PSU the polarity and what it is used to power.
You can usually fix plastic with sandpaper and water and going finer and finer and finishing off like you would polish a car with cutting compound and polish. That is how I fix the edges of acrylic that has been sawn.
Nice easy fix, but as you mention, a fuse certainly could have provided better protection. I find that many modern, low powered devices don't have fuses but at least this one had polarity protection which is also sometimes sadly lacking. With regards to the keys, I'd try sanding them before paying out for any parts as plastics can often be resurfaced to great effect. Thanks for the video.
How will a fuse protect it, since it only deals with the amount of current flow? A sacrificial diode expressly used for the purpose of reverse input voltage makes the best cents. I say 'cents' because that diode only cost a few cents and it will protect the rest of the electronics that will cost many bucks to repair if it should ever get reversed voltage applied. It may be a huge inconvenience to get into the instrument to repair; but leaves an indelible memory point to always be careful to use the EXACT properly phased power supply for the keyboard . . . Keep 'em coming - Artie!!!
If the reverse voltage protection diode shorts the device is a dead short to the wall adapter. In extreme cases the wall adapter could overheat and cause havoc, since most adapters are not fuse protected. I think it is bad practice to leave an electrical device device completely unfused.
Hi Art, great video and really good to see the circuit diagram for the D5 power section. I have JV-30 which has a similar main board power supply section, the synth powers up with lcd showing backlight but no text in the display, no sounds or leds, the unit is dead apart from the backlight. It has 9v rail up and 5v rail up. The +12v and -12v are not up (one is floating around 6v), they are controlled by a pulse and nand logic gates, and one of the lines from the cpu, which is down. I checked the 5v voltage regulator (L78MR05R, same as Juno D5), and it is giving a nice 5v output, but i can't see any pulse generated on the xreset line at power on. Do you think the 5v regulator could be causing the problem, and stopping the CPU from booting? I can see pulses on the address bus and data bus, and a nice sine wave from the xtal clock, so looks like the cpu is alive at least! Have you ever come across a fault like this? It would be great to get this synth back up and running again!
First check why you're missing voltages from the power supply. Next check the reset line on the cpu for proper activity. If that's good see if you're getting any activity on the data and address lines at the cpu. Good luck.
That sounds like your power supply is working, but the main circuit board is not because the LCD is not getting initialized. You'll need to troubleshoot the board.
Thank you. This diode was exactly what my D5 needed and now it works great. It's people like you that make the internet great.
I Bought a Roland SC-155 today went to power it on and got zero power. no standby. nothing. I was looking for troubleshooting videos when i found this one. Though its not a desktop synth. the 9V power delivery is identical. Thank you so much for outlining the common issue of people using the wrong polarity power supply. AND that it blows out the diode. Also thank you for talking about a good sub for the diode. I wound up using a slightly more robust one because i had it on hand but it fixed my SC-155. So thanks again. you rock. I knew the issue was in the first few components, and figured someone used the wrong psu.. but did not know about rolands "fail safe" diode. thanks a ton.
I'm glad that the video was more than just entertainment for you.
This is an AMAZING VIDEO! THANK YOU!
The player must have sweated pure acetone.
Maybe it was used by aliens.
Thanks for the video, it is well explained. I can only speak for Australian issued Boss and Roland PSUs, some of which do not have the conventional symbol showing the polarity of the barrel jack. In fact there is no indication. I can imagine a musician who has collected a number of synth and FX units could easily assume if the voltage matches and it is says Roland or Boss and the product brand matches the PSU brand it is easy to assume the polarity will be correct. The only safe way is to do what you did and that is find the schematic and use a multimeter to find the polarity of the PSU. Then label the cord or write on the PSU the polarity and what it is used to power.
You can usually fix plastic with sandpaper and water and going finer and finer and finishing off like you would polish a car with cutting compound and polish. That is how I fix the edges of acrylic that has been sawn.
A nice easy fix. Surprised that there was no fuse. Thanks for the keyboard video.
Thanks for the info ….
Peace be with you, brother!
Nice easy fix, but as you mention, a fuse certainly could have provided better protection. I find that many modern, low powered devices don't have fuses but at least this one had polarity protection which is also sometimes sadly lacking. With regards to the keys, I'd try sanding them before paying out for any parts as plastics can often be resurfaced to great effect. Thanks for the video.
Can I some questions about the Roland repair?
How will a fuse protect it, since it only deals with the amount of current flow? A sacrificial diode expressly used for the purpose of reverse input voltage makes the best cents. I say 'cents' because that diode only cost a few cents and it will protect the rest of the electronics that will cost many bucks to repair if it should ever get reversed voltage applied. It may be a huge inconvenience to get into the instrument to repair; but leaves an indelible memory point to always be careful to use the EXACT properly phased power supply for the keyboard . . .
Keep 'em coming - Artie!!!
If the reverse voltage protection diode shorts the device is a dead short to the wall adapter. In extreme cases the wall adapter could overheat and cause havoc, since most adapters are not fuse protected. I think it is bad practice to leave an electrical device device completely unfused.
Hi Art, great video and really good to see the circuit diagram for the D5 power section. I have JV-30 which has a similar main board power supply section, the synth powers up with lcd showing backlight but no text in the display, no sounds or leds, the unit is dead apart from the backlight. It has 9v rail up and 5v rail up. The +12v and -12v are not up (one is floating around 6v), they are controlled by a pulse and nand logic gates, and one of the lines from the cpu, which is down. I checked the 5v voltage regulator (L78MR05R, same as Juno D5), and it is giving a nice 5v output, but i can't see any pulse generated on the xreset line at power on. Do you think the 5v regulator could be causing the problem, and stopping the CPU from booting? I can see pulses on the address bus and data bus, and a nice sine wave from the xtal clock, so looks like the cpu is alive at least! Have you ever come across a fault like this? It would be great to get this synth back up and running again!
First check why you're missing voltages from the power supply. Next check the reset line on the cpu for proper activity. If that's good see if you're getting any activity on the data and address lines at the cpu. Good luck.
Hi sir I have Roland xp-10 but display is yellow and black blocks so please help me
That sounds like your power supply is working, but the main circuit board is not because the LCD is not getting initialized. You'll need to troubleshoot the board.
hey i dont get it! mine has an internal power supply with a normal 220v cord
My display is not working
maybe you can give me any clue's?
(I am not a technical wonder :-)
I kay get the d 10 soon will be able to run 12 volts?
I believe that the D-10 already has an integral power cord, no need for a power adapter.
@@artifactelectronics ok
J'ai le roland D-5 qui ne s'allume pas
First check the output from the power supply and then check the protection diode.
That guy liked A minor only?