Roland E-20 & L7805C-V overheated voltage regulator

I will share with you the solution of the problem that I encountered with keyboard Roland E-20.
I know that this is not an isolated case. E-20 is rather aged… manufactured in 1988, but because it has a soul, I decided not to give up and attempt resuscitation 🙂


It looked as described below:

Turn on Roland, I play, everything is ok, passes a few minutes and suddenly “POOF…”Volume is MAX even though the potentiometer is in the middle, primer (TONE) changes to 37 BRASS SECT and backlight in the display starts flashing gently, but the values  don’t change, i.e. is still e.g. TONE UP set at 11, but in reality I hear 37.

During this… you can’t turn on the accompaniment, and then after a long moment begins to stutter, next you can not hear all the sounds of the hiting keys.

Once turned off and on again helps for a while and again happens just the same situation….


I advise you to start by checking the power supply and voltage regulator/stabilizer.

In my case it was a perfect hit 🙂 The reason was overheating a voltage regulator L7805C-V

Below you will find solution of this problem step by step:

  1. I unscrewed the cover from the bottom of Roland, łącznie 10 screws (7pcs longer at the edges and in the middle part 3pcs)
  2. After opening the casing I’ve switched it on and started to play, switch on and off various options to find the ovearheating place.

    Roland E-20 look inside after opening the casing

    Roland E-20 after opening the casing

  3. I didn’t have to wait too long, after a few minutes Roland began freaking out as described above.
  4. Around the transformer the temperature was normal.

    Roland E-20 transformer and voltage regulator

    Roland E-20 transformer and voltage regulator

  5. Finally, I came accross on voltage regulator L7805C-V, which was properly overheated.
  6. I looked closer and found that the retaining screw is not fully tightened and the radiator of regulator sticks out of rear wall of casing. In the aperture there was also a remnant of the dried cooling paste.

    Roland E-20 voltage regulator L7805C-V

    Roland E-20 voltage regulator L7805C-V

  7. I unscrewed voltage regulator, I took it out from the socket and cleaned up it and remnants of dry cooling paste. After applying new paste and fix everything back an hour of playing and enable various options NOTHING HAPPENS and everything works as it should :)))


If regulator was properly overheated so the problem could recur, so in this case I would recommend replacement of the regulator on the new one.

The cost is up to 1$ 🙂