Restoring a Hohner Pianet C

Over the years you accumulate stuff. Some good stuff, some bad stuff, and some stuff that just doesn’t make sense at the time.  The good news is that, sometimes that stuff ends up making some sort of sense. With enough time and the right conditions, things that might have been confusing can suddenly become clear, and lead you down a path you hadn’t considered travelling.

And so it is, 20 or so years since my Dad tried to get me interested in electronics, I’ve finally discovered a reason to delve back into that world and expand on my basic knowledge by restoring, renovating and upgrading the electronics (and other parts) of classic keyboards.

The (first) instrument

The first instrument I was going to tackle is my sadly neglected Rhodes 73 Mark II Stage Piano. As luck would have it, just as I started to organise the parts and equipment I’d need to begin work, the opportunity came up to acquire an instrument I’d never really been aware of before – the Hohner Pianet C.

Pianet Model C logo

Unlike the Rhodes, which generates sound when the hammer of a key hits a tine, the Pianet generates sound by ‘plucking’ a metal reed. Each key is a simple rocker mechanism with a sticky pad attached to the end, which pulls the reed up when the key is pressed. Eventually the stickiness of the pad is not enough to hold the reed and it releases, vibrating at the appropriate frequency for the given key. This generates a unique tone that is darker than the more common Rhodes or Wurlitzer.

According to Wikipedia, the Hohner Pianet C is the second of the pianet models manufactured by the Hohner company, somewhere between 1963 and 1966. Considering the age of this instrument, it’s in pretty good condition and is a testament to how well things were made at Hohner.

The case

Cosmetically, the case is made of particle board with a timber veneer, which has generally held up well apart from the normal scuffs and scratches you’d expect after 50 years. The only exception is the left-hand side, where the veneer has been badly damaged and is separating from the particle board. This will have to be replaced, once I identify the type of timber the veneer is meant to be.

Pianet case before restore

The particle board underneath is not veneered and is starting to shed. This will have to be sealed to prevent it deteriorating further. One side of the lid rest is missing, and both screws from the middle panel are gone. The screws should be easy to replace, but the piece of timber for the lid rest will be a challenge.

According to Wikipedia, the model C had a key lock in the middle of the lid, but this one has no sign of a lock ever being installed. I guess they could have made variations for different markets and/or price points. Wikipedia also states that this unit came with four matching legs. These are no longer with the instrument, and it looks like the original mounts have been replaced with alternative mounts, for alternative, missing legs.

This model has a Vibrato switch on the right-hand side of the keyboard and a bar under the base, operated by your knee, which acts as a volume control.

Pianet volume control

Apparently someone thought that would be a good idea.

The sound

In order to make a “here’s what it sounded like before restoration” recording, there has to be …. sound. Unfortunately, in its present state the pianet has 60 keys that generate the sounds of silence. The one key that does make a tone is so quiet  against the ground loop and background noise that it can accurately be described as the key of HUMMMMNBBBBRRSSSSSST. So no recording.

The sound I’m hoping to achieve can be heard in this demo video from Ken Rich Sound Services:

The unit in the video is a model N, which came after the C, but the sound of this unit should be roughly the same.

I’m actually pretty surprised that the electronics are still working at all, given the age. Power goes through the unit, and the lamp in the circuit glows impressively – especially when the Vibrato is activated.

Pianet circuit before restoration

I suspect the two main fixes will be replacing all of the pads on the keys, and the capacitors in the circuit. Time will tell.

Next step

So that’s the current state of this instrument. The next steps will be to disassemble the entire unit for cleaning, inspect the pads, and test the electronics.

One note at a time.