Yamaha E-5 Humming mystery

[FranciscoD]

Hello, I'm currently in the midst of repairing an old Yamaha E-5 that was out of use inside an old colonial church. I am no electrician but been inmersing myself in literature for the past 5 days and asking electricians friends several questions. I'm in the process of taking all the dust that has been hoarding this beast, last oiled on the year 1984.

The organ turns on, the keys are fine and most of the stops work without issue, except a few lower horns that produce a high pitched noise. The speakers produce a very loud hum which by reading some of the posts here and there have concluded that it could be a faulty cap either on the pre-amp or amp. Pedal is non working at the moment I suppose its not correctly placed but that's another issue.

Here's some videos of the sound and high pitches stops.

Thank you.

[Larason2]

Welcome to the forum! I have a Yamaha E5R, very similar to yours. However, I ended up removing all the circuits and turning it into a MIDI controller. The humming seems to me to be a short causing current from the power supply or amplifier/pre-amp to feed into the speakers. I wonder if it could also be coming from the tremolo motor however. Does it change at all by adjusting the tremolo speed? (Small knob on the right hand side). Another possibility is degradation of the polystyrene used to make the speaker cones, but I think this is less likely.

The high pitched noise when you press the lower keys is probably a short somewhere in the tone circuits. When you open up the top of the organ, you will see a rack with a lot of circuit boards in it. From those come wires that go to every key. Make sure all of the wires are intact, and none of them have insulation chewed off by mice. Replace any wires that look like they have been chewed through.

If the noise is a short in the power supply or amplifier, it could be tricky to fix. There are a number of large capacitors that can be dangerous. You may want to enlist the help of one of your electrician friends to help there. It might be easier and safer to replace both with newer equipment, but it would be more expensive.

As you said, replacing capacitors in an analog organ is always a safe bet. To save you time, it is helpful to have a copy of the schematic to help isolate which are the most likely capacitors to replace.

For the pedal, the most common cause of problems is a burned out bulb. Check to make sure it is lit when the organ is on. If not, take the bulb out and take it to an automotive parts supplier. I have read that type of bulb is common in automotive use.

I have a schematic of the E5R in case that is useful to you. I also speak Spanish, so if you don't understand anything I can translate. For either of those, feel free to send me a personal message.

[FranciscoD]

Hey, thank you so much for the detailed response. I will be checking around the wires, the sound does change when adjusting the speed and when turning on the rotary.

I do have a copy of the E-5 schematics and will be using them to sort out the capacitors. Will look into the bulb of the pedalboard and see if need to be changed.

Gracias también por la opción de traducir, no creo que la necesite.

[Larason2]

Ok, sounds good. If the noise continues when the tremolo motor is not spinning, then it is likely not the motor. If you don't see disintegration of the foam cones at the edges of the drivers, it's likely not that too. The frequency of the sound is around 60 Hz, so that does point to electrical contamination of the signal. It could also be helpful to carefully examine the power supply and amplifier (on the same board), and make sure all the components look in good condition. To find shorts you may have to remove the board from its mounting, but be careful, as that is where the business end of the capacitors is.