No sound when hitting some keys

EP-50's are notorious for problems with either the 4.65 voltage feed to the velocity sensitive keys or failure of the small zenner diaodes. Each key has a pair fo split circles on the circuit board under it. When you hit the key you connect each side of the circles and the harder you hit the keys the quicker the circuits close the louder the sound. Problem is if the voltage to either circle fails, due to bad solder, scratch on circuit board, failed diaode then the sound disappears. The fix is simple if you are knowledgeable on solder on circuit boards, can use a multimeter and can dissassemble and reassemble the keyboard. If you have to take it to a repair shop it is probably not worth fixing as this is not one of the better Roland products

Likely a problem with the power connector or the power adapter. Make sure you are using the original power adapter as often replacements don't work and universal adapters seldom work.

Two things come to mind: 1. These synths have mute and output control settings. Verify they are correct as even a factory reset might not set them to default. 2. The next thing is that the volume control itself is damaged which requires internal investigation. Was this working and was there an accident with it... dropping manhandling, or accident with power or cables? There could be a cable that has fallen off between the main board and where the audio outs and jacks are. Be very careful if you open this of ribbon cables from the halves of the shell.

no sound well it has to be used w something from garageband reason, etc u cant just plug it in and play it . so for instance garage band , you wanted the grand piano u open the grand piano and start hitting the keys. should be no problem I have the same one

The key contacts are dirty. These contacts are conductive rubber "pills" (black) in silicone rubber domes. There are TWO per key and when you press a key, one hits first then the second. The time between this is measured by the processor and generates a "velocity" number which controls the loudness as would a real piano being sensitive to the rate/speed which you hit a key.

Unit has to be dis-assembled and the keys taken off and the contacts AND the CIRCUIT BOARD TRACES they press onto using ONLY 99% isoprophyl alcohol and Q TIps. Do ALL the contacts while you have it apart. Be VERY careful to not damage the ribbon cables tying the top of the case to the bottom AND document which screws go where as there are usually several different threads and lengths..

This probably is not a DIY repair... The audio comes out of the CODEC and is buffered by Op Amp used as filters and then goes through the volume controls, After that it goes to the jack board with buffer OP amps. First thoughts might be a damaged volume control, however, the "B" outputs don't go through volume controls...

About the only thing I would think you could do is to CAREFULLY open the unit and look for a loose cable involved with sending the audio to the volume control panel and then the cable that takes the audio to the jack board...

More than that you would probably need to take it to a shop equiped to troubleshoot.

Check that the front of the keys is not hitting the lower plastic case front. If they hit it, then you need to disassemble the case partly and see what has shifted. It is ALSO possible that something has caaaused the aftertouch sensor to move out of position and it is hitting the keys early. ANY of these conditions needs to be addressed before damage is done.

USUALLY the keys are matrixed in groups of 8 starting at a "C".

Each key USUALLY has two contacts. The differential time between the contacts closing is measured as "velocity" which is used to control the amplitude of the sound. The matrixing of the keys may be done in any of several ways but usually the bank busses are driven and the keys outputs are merged with diodes. You really need a schematic and Yamaha will usually supply the service manuals on CD for about $15.

If conductive rubber contactss are used, those should be cleaned with 99% isoprophyl alcohol. DO NOT USE CONTACT CLEANER !!!!!

Also clean the traces the contacts contact.

When a bank of the 8 keys are dead, you MAY have a broken trace on the coircuit board or a broken cable wire. Be careful inremoving ribbon cables as the end wires are pulled from the contacts unless the pull is distributed across the cable.

Is it a dynamics sensing keyboard (does it sound soft when you play softly and loud when you hit the keys hard)?

If so, you need to clean the double contact under those keys that sound too loud (if contacts are dirty, the key might either not work at all or it may loose the ability to sense how hard you hit it and will work at full volume).

You'l probably need to disassemble the unit and remove the keyboard to be able to remove the keys that don't work well, after you've done so, you need to clean the lower (under) side of the double rubber button which is struck by the key when you hit it, also be sure to clean the contact tabs on the circuit board undereath the rubber pad (you can use ethyl or isopropyl alcohol and "cotton sticks").

This should do the trick if the contacts are dirty, but it may have no effect if they are damaged or worn out (in such case you would have to replace the rubber pad for that particular key).

regards

3rq8 (Triarcuate)

Do you cover the keyboard when not in use as small particles of dust can make their way in between the keys?

You can try blowing any obstruction out with a can of compressed air, may solve your problem.

As I'm not familiar with this Model, does the keyboard have 'touch response' on board? If so there will probably be a 'Contact' strip made out of tubular rubber under the keys and this can sometimes 'burst' especially on a certain key that is played most of the time. For example if you play mostly in the key of 'G' or keys that use that note....

Hope you find this helpful......