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Hi,

I'm a new member at the forum and hope this thread may be of interest to some of you. Inspired by the "DPs Exposed!" thread , I decided to undress my 14 year old Digital Piano, an Orla Concerto C9 and do some much needed fixes.
This is probably very old, low grade tech to most of you, but I was wondering how'd its internals compare to the more recent DPs. This thread aims to document the result of the dissection. To keep the size of the posts manageable (and since I can't write it all at once) I'll split it into several posts, so bear with me.

Best regards to all and a happy new year!

Tiago

Great, let's see 'em!

The Pedals

The pedals are enclosed in a metal box, stuffed inside a hollow MDF base. The pedals were making some "squeeks" each time they were pressed and were bottoming out quite hard, so this was a good candidate to start the operation.

Lets get on with the pics:

The undressing:



Detail of the mechanism:



As you can see, the mechanism is quite simple. The pedal resistance is managed by a spring and when pressed brings the two metal sheets into contact. The next photo shows the mechanism when pressed:



The problem with the "squeeking" was readily identified as the pedal was slightly rubbing the adjacent platic. This was promply corrected with some lubrication with lithium grease:



As to the sound of the bottoming of the pedal and when it was released, it was due to the rubber stops being out of place and the felt cloth being worn. These rubber stops were again put to their places with contact glue and the felt reinforced with some quick patches.

Rubber stops while being glued:



Placing new felt (you may see the wear on the original felt):



All fixed up with rubber stops in action:



For completeness sake, the pedal is connected to the DP main body through a MIDI connector, even though it only signals a continuity test (when pressed) on these pins:

Pins 3, 5: Left Pedal
Pins 2, 4: Middle Pedal
Pins 1, 4: Right Pedal

Here's a photo of the connector:



The pedals are now working again, this time a lot more silently, as they should.

On the next thread, we'll start dealing with the internals.

I can't see any of those pics.

I think it's your connection or computer, Ando. I see them fine.

Power input

Lets move on with the undressing of the DP. I'll start with the internals and will leave the keyboard for last.
Here is the frame with the keyboard already removed:



At least everything seems to be properly grounded. The major components are spaced apart so their identification was rather easy:

• Power supply (fused AC filter)
  
• Power supply (transformer)
  
• Power amplifier
  
• Headphone inputs
  
• Loudspeakers
  
• Main controller (brains)
  
• Key Scanner

The power chord goes from below the DP, straight to the on/off switch, and into the AC filter which precedes the transformer:



The layout of the AC filter:



The transformer outputs 3 different voltages which are plumbed into the power amplifier board and redistributed to other components. Here are the output voltages:

• +13.8V
  
• -13.8V
  
• 7.5V

Next post: Amplifier stage, headphone outputs and speakers[/u]

Amplipifier board, speakers and headphone inputs



The speakers are mounted face downwards, much as I've seen in any other DP. They are 4 ohm, 4.5" full range drivers. They are unbranded so their maker is unknown to me. As it seems to be usual, there is no enclosure whatsoever, so T/S parameters are somewhat irrelevant anyway.

The left speaker is next to the AC filter and in the upper left corner of the image you can see the headphone inputs. The black rubber hose beside it houses the power chord I mentioned on the previous post and ends at the power switch. Likewise you may see the two grey wires that return from the switch into the filter.



Here's a detail of the right speaker, unmounted from its position. I wonder how all that metal affects the sound. Certainly there are better ways to protect the speaker from unintended contact.



The headphone inputs seem to be a major problem with this DP because there's always a faint hum at both inputs. I suspect the cause is related to the big distance the audio signal must travel from the amplifier board to the connectors. The ribbon cable that brings the signal also seems quite an odd choice (quality wise) as I suspect it doesn't provide any shielding from all those power cables nearby. I soon intend to provide a better routing and carrier to the signal and see if I can improve the signal quality. As a last resort, a replacement of the position of the audio inputs and possibly the connector themselves is also an option on the table.

Here's a close-up of the cheap connectors:




Moving on to the amplifying board, I assume the 4 big diodes at the left form a full wave rectifying bridge with the big capacitors stabilizing the voltage from the transformer. At the left of the rather large heatsink is a 1A low voltage dropout regulator.



There are 2 TL072 opamps that may provide the amplification to the headphone outputs, but this is only wild guess at the time and I may be completely wrong about it. I couldn't identify the power transistor attached at the heatsink because it has an aluminum plate covering it at the front. I may unmount it a later time when I have thermal paste around if necessary to mount it again.
Finaly, the connectors at the top of the photo provide (left to right) 2 AUX inputs, and 2 line level outputs.

Next stop... the key scanner board.