The lowest 9 keys on my YPG 235 keyboard stopped working. I cleaned the contact strip. Still no sound everything else works fine. Should I replace the Contact Circuit board or Is there something else I can try first?
Check with Ohm meter B01 and B02 on the left circuit board between the connector and contact. Most probably a corrosion some place (in my experience dust and humidity causing a fungus under the lacquer or some food rests).
Depending on the overall condition of the board - may be easier to just replace it.
In the unlikely event that both check out OK then is on the DMLCD board where these lines connect to
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Thank you for your reply. Can you show me a picture or explain exactly where to place the probes on the circuit board to check between the connector and the contact? I am a novice using an analog voltmeter.
That’ll be a mission for you - OK here we go:
You need to take the key board frame out to start with.
NOTE:
Keep track of various screws as they are not all the same.!!
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Turn the keyboard upside down onto a soft surface and remove all the bottom screws, lift the bottom and detach any cables.
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Now remove all the screws that hold the keyboard frame down.
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Remove the keyboard frame and put on a flat surface with keys up (as you would play it)
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Remove all the screws along the top edge of the keyboard frame that hold down the key sets - the key sets come in packs of three - 2 white and one black
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Remove the keysets left to right until the left board is completely visible - the top black part clips into the frame. Unclip - lift the back all 3 at the same time and move towards you .
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Now you can see the contactor boards - I haven’t got the same set at hand right now but looks similar this.
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Now remove the rubber strips - they are holding down a little as the rubber nipples go though the board. You only need to do the left (or LOW) board …
Now you see this:
- You now have to find the pin number on the connector (red arrow) and follow the track until you get to a first contact (in your case will be one of the black contacts that look like interwoven E’s). Measure with the DMM - should be 0 Ohm. If your DMM has a mode where connecting the two probe pins is getting you a “beep” - that’ll be even easier.
NOTE:
sometime you can actually see the problem on solder joints being corroded and green/brown or tracks being no longer bright green but rather black - this is sort of a fungus growing underneath the lacquer eating away the copper.
If you can see the problem and re-solder it - bingo (hopefully) … if the tracks are “eaten away” by that fungus you will need a new board - in your case not fixable.
Let’s go from here …
(Hope I didn’t scare you too much)
