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Hello! I'm in the process of getting a Hohner Electra-Piano T to work properly for a customer. I thought I'd share some info on it here, also to get some suggestions perhaps; mainly on what materials to use for the dampers! Originally it looks like the reeds were dampened by some kind of clay pieces - or at least it has turned to clay.

Has anyone found a good replacement material for these dampers in terms of sound and durability?

The other thing that seems to need replacement is the little foam cushions that the hammer assemblies land on; these have become brittle.

Here are some pictures:









A lot of the damper blocks had already fallen off; I took all of them off except the lowest



The light brown foam piece that's brittle and squashed

I see, thanks... I was thinking that perhaps someone had already made a list of specific components like the low-noise transistors that he mentions, which I couldn't find in the text. Perhaps I could make one down the line.

Do you personally prefer a method like this over swapping the entire unit for a remake from VV, EPS or Retrolinear for instance?

Hi all,

A discerning customer just pointed me to this page detailing some interesting low noise mods for a Wurli 200A:

https://illdigger.wordpress.com/2016/07/03/wurlitzer-200a-piano-repair-and-low-noise-mod/

Have these been discussed here before? I couldn't find anything about it through searching. Also, has anyone tried these? Any opinions? Is there any more information available on which parts are required exactly, like the low-noise transistors?

Or perhaps the maker Johnny Illdigger would be available to offer some more info? Looking forward!

Good news! The Pianet N is working now. A couple of observations:

- turns out the volume pedal is necessary for proper output! this may have been completely evident to most already... I wasn't aware of this. My friend who repaired it in the end made a DIN plug with a 50k potentiometer on it, which works too

- it looks like the resistors are worth replacing - they were quite brittle and out of spec, and seemed not very high-quality to begin with

- it looks like it would be well worth placing the transformer in an external enclosure, seen as the hum it causes being right next to the pickup is quite substantial.

Ah I see, thanks.

I just got word back from EP Service: they're working on developing the new Pianet N preamp further; they're not completely satisfied with it yet so currently it's not for sale.

Another route I'm considering, seen as the germanium transistors apparently are relatively noisy by nature, is to convert the pre to silicon transistors. That would entail altering some other parts as well, but it seems with a little research it would be doable:

http://audiokarma.org/forums/index.php?threads/replacement-for-ac125-germanium-transistor.250005/

Ah I see, thanks for that info. I'll contact EP Service to ask about that newly developed preamp, they don't seem to have it listed in their store at the moment.

The AC125 transistor is available here: http://markhindes.easywebstore.co.uk/AC125_AKHNR.aspx
and the AC107 here: http://markhindes.easywebstore.co.uk/AC107_AKKHN.aspx

I'm also still curious whether my measured voltage of 325 Volts instead of 400 could be the culprit, and if so how... and could it be the mic transformer that's broken?

I'm not really sure what you mean by "earthing" the hammers... the Pianet has a fresh set of Ken Rich sticky pads, but I don't see how these could be earthed...

In any case the noise is on a much higher level than any shielding could reduce... it's like 99% full-blast noise with a tiiiiny little amount of tone somewhere in the background. So currently my guess is that it's one of the transistors that's given out.

Hi all,

I'm restoring a Pianet N for a customer, and I could use some help on how to tackle the issue of it producing mainly a *lot* of noise and little tone - although there is some, faintly in the background.

The preamp is the version with the AC125 & AC107 germanium transistors, which I suspect might be the culprits... I've replaced all the capacitors already, to no avail.

The +400 volts indicated in the schematic is only 325 volts measured, perhaps this is an indication of a defective power transformer or bridge rectifier, and the reason for the low signal-to-noise ratio further down the line?

Can anyone tell me what the AC voltage at the transformer should be?

Any tips greatly appreciated!

Alright never mind... turns out I forgot that one of the two amp channels I was using to test had its Treble turned down all the way.

DUH

my bad. As you were.

Hi guys,

I'm optimizing a D6 for a friend and have hit a challenge with its overall frequency response; I usually work on Rhodes pianos so I could use some help with this.

The thing is that this clav has a significantly reduced high end, which has become apparent to me now that I have a second D6 next to it that sounds way brighter in comparison. They also differ in that the brighter one has the preamp board directly attached to the rocker switch panel; the darker one has the separate board screwed to the case floor.

Some time ago I did the upgrade mods to the darker one found here: http://clavinet.com/d6upgrade.htm - this was before I had noticed the overall darkness; I did test the sound difference after each individual mod and only heard (some) noise reduction, no drastic EQ changes.

Also I compared individual EQ bands between the dark & bright D6's I have here - it really does sound like there's an overall EQ difference, not related to the individual bands.

So before I launch into a more involved investigation of this particular preamp, does this issue ring a bell to anyone? Perhaps something typical like a transformer at the end of its life or something?

Thanks!

I was fitting an extra pair of line inputs to a 4-pin suitcase (using this really simple passive mixer schematic based on 10k resistors), which worked - but then disaster struck: during testing there was a short circuit on the power switch, which made the circuit breaker of my home wiring kick in.

The piece of foam that normally prevents the power switch contacts to touch the metal plate above it turned out to be missing... I hadn't noticed that. At the moment the amp isn't working, so I thought maybe someone here could give me some info before I take it to my buddy who is a proper electronics engineer but doesn't have special expertise on this amp.

Some observations:
- the pilot light still comes on;
- apart from some charring on the power switch contacts (on the inside the unit) there is no visible damage to any of the parts or wires;
- when I measure the voltage on the power module connectors, I get 24V and +/- 44V, the latter of which seems a bit high;
- the pre-amp outputs are still working, so the pre-amp is OK it seems.

Has anyone been in the same situation? Any pointers on how to approach/what to test would be greatly appreciated, thanks.