Dead keys Roland HP 700

[Nick Albright]

Hello. This is my first post here on this forum so bear with me.

This Roland HP 700 that I have has some dead keys. The keyboard is pretty old and out of warranty. I took it apart and cleaned the contacts and what not, but that did not fix the problem. I also disconnected and reconnected all the wires that connect to the keyboard.

I noticed that the dead keys are grouped in pairs in every other octave except for the last few. The picture I attached shows the groups. The dead keys are the inside pair of the black and white keys I have marked.

If anyone knows the problem or has any idea on how to fix it, that would be great.

 

[happyrat1]

Only thing I can think of is trying some contact cleaner on the ribbon cable connectors and looking for broken traces on the PCBs.

You could at least power it up and carefully check to see if you're getting voltages on the positive rails of the key contacts.

Otherwise it could be a failure of the keyboard scan multiplexing chips.

More likely though a broken or missing contact on a PCB.

Gary

 

[happyrat1]

Or an even more likely possibility. A faulty ribbon cable connector.

You might have to replace a ribbon.

Check for voltages and see.

Gary

 

[happyrat1]

It might help if you pick up one of these and learn how to use it as well...

http://www.amazon.com/Elenco-LP900-625-Logic-Pulser/dp/B0002E7X5O

Gary

 

[PascalMarie]

Hi Dear Nick, I am working on the same problem on Roland U-20.
All dead keys have been repeared with Graphit 33, the same as
KEYPAD FIX REPAIR REMOTE CONTROL TV DVD SKY ALARM KEYFOB & MUSIC KEYBOARD. (Ebay)

Your problem seem different, cause there is exactly 8 between your dead keys.
A#1 to F3, F#3 to C#4, D4 to A4, A#4 to F5
Please look for a short circuit between signals on flat cables going to mother board.

I am looking for Service manual For Roland HP-700, and
for U-20 factory load card.
Best regards

 

[PascalMarie]

I am fixing a Roland HP-700 now, changing the potentiometers, re-soldering the voltage regulators, cleaning the contacts of keys G#3 and A3.
This piano sounds very good, for a forty old one !
If you can phone with your PC , I am in French country, so please take care of the time zone. (+33)614 919 xxxx. Change xxx with 476.
PascalMarie