Casio Privia PX-310 no audio out

[Alan3666]

Hi everyone, looking for some advice. Just bought a Privia 310 with a number of issues. The seller advised that 8 keys, 5 white and 3 black all grouped together not working. When I first powered the keyboard up all the keys were working fine. The power connector was a bit loose and when I moved the keyboard it powered off. When it came back on the bad keys identified were all dead?
Another issue is there is no audio out left or right. The headphones stereo output is fine. The internal speakers work although the left speaker seems much louder than the right.
The diagnostic routine runs without errors, all leds and buttons working.
I have found basic circuit diagrams for the 310.
Over the weekend I’ll strip it down and clean all contacts.
I’m just a bit concerned that all keys were working then not, and why a group of keys?
Anyone have any insight as to what could be wrong?
Alan3666

 

[Alan3666]

Further update - I connected another keyboard to the midi in port and I can play all keys without issue. I need to have a think about what that tells me.

 

[Alan3666]

reversing the midi connection so that the Casio is the master the eight keys do not sound on the slave.

 

[Alan3666]

Strip down complete. A lot of rust on those hammers. You need to remove the cheeks then the bottom cover and the top cover. That allows you to hinge the keys up and away from the contact strips.
I’ll see if I can attach photos.
One small success! A lower key which had dropped was due to the hammer coming away from pivot. Now fixed.
I removed the rubber contact strip from the affected keys. The etches looked quite dull. I cleaned with spirits. Still no joy. Repositioned rubber strip. Don’t believe the issue is here. I keep going back to the question “why did everything work first time I powered it up?”

 

[Alan3666]

Swapping round the right hand speakers cables I get sound generated on the right channel playing through the left speakers. So looks like all is good when it leaves the amp on both channels. Problem has to be diff treble and bass speakers on right. Not surprised given the amount of rust under here.

 

[happyrat1]

Do a logic trace with a scope.

 

[Alan3666]

Thanks for the input. Yes that’s for next week. I was trying to find better schematics. The PX-110 looks very similar. There’s some circuit diagrams in that service manual. I wanted to see where the audio out signals come from. Is it same source as speakers/headphones? I’m going to strip out the right hand woofer and tweeter and check on bench.
Still thinking about why eight missing notes don’t play?

 

[Alan3666]

I tried (just for something to do) plugging the audio cables into the next pair of ports and I got audio out. That’s when I checked the manual and realized I’d been plugged into audio in. Doh!
RTFM!
So audio out working fine.
I confirmed issue with internal speakers is down to the right side woofer. Found a site that has speakers but doesn’t look like they ship to the UK.
I’m trying to find schematics for the middle keyboard module. My issue starts at C4# and ends at G4#. It’s four white and four black. There’s a chart in the manual where this group of keys show as being related but there’s no explanation of what the chart represents?
I can only see the etch side of the logic board, but it looks like each key goes to a six pin component. On a good key, the top three pins have a square wave. The lower three pins have no signal but when you hit the key a square wave appears on the first two lower pins. Also the third pin with no signal although not effected by hitting that key, shows a square wave when you hit a good key next to it.
The first dead key c4# has a square wave on one set of three and when you hit the key a square wave appears on one of the other set of three pins, but it’s a much higher frequency signal, way higher.
Need a diagram

 

[Alan3666]

Ok so the chart in the manual shows the combination of signals that generate a note. It’s refered to as the key matrix. Each group of eight notes is identified in the horizontal rows. Starting with A0 thru E1. Each row of eight is repeated. First row is FI0, second is SI0. The columns represent location on Keynes. Shown as KC0 thru KC7. So for example FI0 and SI0 along with KC3 plays C1. FI4 and SI4 along with KC4 plays A3. I understand that the FI and SI signals are generated by the rubber pads under the keys. The time between the two determines the velocity of the strike. You can see the black contacts under the rubber are different lengths.

In my case it would suggest that something is wrong with these signals. The rubber pads appear to be ok. The KC signals are common across all the signal groups. The signals that are unique to my group are FI5 and SI5.
Still in the dark without circuit diagrams.

 

[Alan3666]

Taking a different angle. The flat white 30 pin cable that connects the keyboard logic cards to the main logic module carries FI0 thru FI10, SI0 thru SI10 plus KC0 thru KC10.
If I put a scope on pin 30 I can see a fairly flat signal. Same on pin 29. These are FI0 and FI1. If I hit A0 the signal shows a square wave on both pins all the way up to E1. KC0/10 showing a square wave with or without hitting a key.
Pin eleven and twelve relate to my bad keys. Pin 12 (SI5) behaves as the other pairs. Flat signal going to square when you hit C4# thru G4#.
However pin 11 which is FI5 has a square signal which is not changed when you hit the above keys.
I think this is smoking gun. Need to have another think.

 

[Alan3666]

I disconnected the flat cable coming from the keyboard and checked the pins on the MAIN PCB M404-MDA1. That square wave is still showing on one of the pins. It looks like it’s being generated on that module.

 

[Alan3666]

I’ve ordered a replacement board. Could take a while to arrive.

 

[Alan3666]

Replaced logic board all keys now working. Module supplied by Mike Corey, Oregon.

 

[happyrat1]

Congratulations.

Always nice when a learning experience terminates in success