Roland CR8000 buttons repair made easy

Roland Compurhythm drum machine CR8000 with faulty or worn buttons.

Sounds a lot like the TR808, but a design fault makes these buttons useless after a while.

You will have to pull the plastic covers first, to reveal the spring and rubber dome under which we will drop a bit of conductive paint..

To pull the plastic part you need to push the sides using a screwdriver or two like on this video:

Youtuber The Imp Of The Perverse has made a few vids of his restoration-he used my method too, check them

Hohner Basset

When i bought it it looked like this

I opened it up to clean it and realised this wasnt its original colour.

It really was taupe gray before, but the years had the plastic chassis yellowing

I decided to restore it to its original colour (or as close as i could…)

After 5 months of great fun, I had to open it up because the output went silent.

Gutshots of the Hohner Basset!

Lets start with the DIN jack that connects it to the bass amp..

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Keyboard:

Circuit board and caps jungle:

Inside the white enclosure there’s a lamp and a ldr.. this assembly is the actual “percussion” section.

You press a note on the keyboard, the light goes off slowly (sustain) according to the knob position, when not in auto mode.

Video below..

Pcb: 3.1967!!

Ahem this means the caps have been doing their job for 50 long years! Only one of the capacitors has failed, please note- the blue valvo 100uF cap now measures 1uF!

Output DIN and 3 pronged jack, fuse

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Video showing the lamp going off when a note is keyed.

Hohner Cembalet repair

My beloved Hohner Cembalet I has gone silent, all of a sudden.

Here we go with a few pics i took for reference of the main board.

They may help someone else whos trying to fix his Cembalet.. I hope.

Schem and user manual (in kraut):

Hohner Cembalet User Manual with schematic

Update: the Cembalet healed itself and now it works great. I did not have to do anything to it, it just works again, magic, bang.

A friend who’s an electronic repairer said that the most important part to watch out for is the inductor (Spule in german), as it’s custom wound to specs for this instrument.

Yamaha RS7000 keyboard soft touch button repair

I bought some soft touch button replacements for my RS7000, because the keyboard had to be banged on to operate.. 

Here’s how i carried out the button repair.

Disclaimer: please carry out this repair only if you have electronic skills such as soldering, desoldering, handling pcbs and know how to handle electronics. Remove the mains plug on the RS7000 and use care. Do not touch the power supply components. I shall not be held responsible if you hurt yourself or other people or the machine in the process.

First of all, check the new buttons. There are a few tutorials on how to check switches’ functionality using a digital multimeter on the net, google that up. 

Remove all the knobs from the front panel.

Wash them with soapy water using an old toothbrush!

Turn the unit face down, using some soft padding to relieve the knobs from the weight.

Keep this pic as a reference: the position of the midi sockets.

There are 3 types of screws..Put them somewhere safe (i used three fruit jam lids) and remember where each type goes. An additional set of two very thin screws belong to the scsi port. 

As a rule of thumb:

short ones-> they hinge the metal sheet that separates the top from the bottom pcbs. The top left and middle left ones secure the bottom to the metal cover of the power supply as you will realise opening the unit.

Remove the bottom lid. 

Unscrew the midi assembly and the buttons holding the input/ output panel in place and take it off.

Take pictures of the pcbs. 

Pay extra attention to the cables, what goes where. How they are turned, and move them the least you can. They are the right lenght to be assembled, very neatly laid out, Yamaha style😉👌🏻.

The bottom cables are all tied together and they originate from under the shielding metal sheet..right where we want to get! Carefully, gently rock them to pull them out of their sockets.

You will have to remove the card reader assembly, the flat wire (just pull it) and all the screws that link the metal sheet to the case will have to go (pay no mind to my pics cos mistakenly i unscrewed also some of the pcb’s).. 

Below, this is the central layout, the wiring harness pops out from underneath the metal sheet shielding. 

The plastic motherboard shield will have to go. Please note how its left side kind of sits on top of those surface mounted chips. 

Gently lift the shielding metal sheet, get your girlfriend or boyfriend or your best caring and patient relative to hold it up for you.

Remove the cables that hold the keys assembly in place, and carefully slide it out from one side.

Here is the ugly mother.. Turn it around and take a look at how the key covers are snapped in their places. It takes a little inward motion using two fingers from the bottom side, push and they will spring out.

Put them in a sink and wash them with shower soap and water. Brush them with that old beaten toothbrush. Carefully, but with authority. 

Please note that generally there are soft touch and clicking buttons, maybe you want to dust the encoders too, i took a rag and dusted the pcb too, TAKING EXTRA CARE.
If you are feeling tired and the stress of the procedure so far has got you on your knees, put the board in a padded cover and go to sleep.

When you are in the right mood and focused, you may proceed.

Take a look at how the soft buttons are put, their position from all angles. Your new ones will have to be laid out just like that. Maybe even better, if they all look twisted like mine!

Turn the board over, using a hot soldering iron heat up one of the two soldered poles of the switch and using a desoldering pump suck the solder off. Do the same for the other. 

The nice folks at Yamaha have bent the two poles in opposite directions, one upwards – the other downwards, so that to remove the button you must heat up a bit the two points (solder side) while gently applying a circular motion to the button, taking it with two finers, component side..

👁 Like in this video:

RS7000 removing soft touch switches

Using the same procedure, you could also replace a few LEDs if you feel inclined, just be careful with the LEDs height.

Once you are done replacing the faulty keys, put the button masks back on. 

The tap button does not have an LED, but its mask is like all the others (check pic)-it’s all right.

Putting everything back in its place, take special care with the central wire harness: the cables have to reconnect to their original sockets, so beware if they get stuck somewhere they should not-you might not be able to plug them in. Reassemble everything with care in respect to the wires.

It is quite a long procedure, also given how many screws you will have to work with-panic may take over you once you realise there are two pcb levels in this machine, but fear not. It CAN de done!

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