PX-350 Nasty AC Hum, looking for schematics

[emarsh7]

Hi,
I've had a PX-350M for a number of years. It's started producing an occasional loud AC hum when I'm hitting several keys simultaneously in the lower register and seems to be more likely to do it when the sustain pedal is pressed. I replaced the power supply but that had no effect. I moved to Spain a while back and don't have any repair shops nearby but I do have an oscilloscope and some rudimentary electronics knowledge. Is it possible to obtain a schematic or service manual for this piano?

Thanks,

Eric

[Brad Saucier]

Can you record a short clip of the sound?  I have a feeling it's something which will need a new main board.  

[Jokeyman123]

Don't go by me-I take stuff apart just to see how it works!!! But seriously do repairs and mods alot for a variety of reasons-helps keep me out of the nuthouse-or pushes me close to the door sometimes. This is an odd malfunction in my experience, and if you are lucky-might be as simple as a connection or cable slightly out of its socket-there are quite a few in the 350, I've had mine completely apart and compared to some workstations/keys, it is not all that complex inside. As a tech, i always look for the obvious first-bad connectors, burned or discolored components, pieces running hot that should cool (shorted resistors, caps) pieces running cold that should run warm such as power rectifiers to individual boards for example. Cracked or contaminated IC boards-even a cold solder joint could be causing this kind of symptom. sustain pedal will keep sending audio out, which might mean the problem is in the audio chain somewhere-look at that, see if you detect anything. Does this occur with headphones, speakers or both? If only through speakers-could be audio vibration is rattling something a little loose, especially in the lower register. I say all this as I have not been able to source schematics, although if you can signal trace, you might not need one. post back results if you can fix it, it always helps.

[Jokeyman123]

Sorry to butt in Brad, was working on this post same time as you. I was assuming emarsh that you have no warranty, and are reasonably competent to do this-as further disassembly could cause more damage-just saying, and since you have no tech resources apparently, thought I might help. and you might find a similar schematic for one of the other Casios just to get an idea of th design they use with the Privias. My PX has been faultless for several years, surprised this is happening on yours. Just had to do a major and very costly mainboard replacement myself on another not Casio workstation-since my only tech resource locally closed their doors permanently just a few months ago here in the US, and were one of the few non-Casio competent tech repair facilities for our electronic musical instruments, I had to source the part myself with great difficulty, and installed it myself, with great difficulty, just passing it on. 

[emarsh7]

Hi Guys,

Thanks for the replies. Sorry that I'm slow responding but life got complicated for a while.

Here's a couple recordings of the sounds I'm experiencing. They seem to be getting worse. I moved from the US to Spain a while back so trying to get the piano serviced is a challenge and when you get down to it the PX-350 is not a high end unit and may not justify the expense of repairs.

Since this sounds like an AC hum I replaced the power supply but doing so had no effect. I tried resetting the piano but likewise it had no effect.

I have an oscilloscope but my electronics skills are at the Arduino and basic circuits level.

I've attached videos demonstrating the problem.

At this point I'm trying to decide if this can be fixed or if I should just buy a new keyboard (and if so, what). Perhaps if I do I can use the PX-350 as a Midi device.

Thanks

Eric

[Jokeyman123]

Sounds to me like the piano sample is sticking and you are hearing part of it as a loop-thius is what a short section of a sample sounds like if you were to cut a small portion out and loop it. Is this only happening with the piano sample? I suspect it must be.  What causes this-I am not qualified enough to really know, and I've heard this happening before with other keyboards intermittently. Best guess-it's a software "glitch" not necessarily an electronic one-unless it happens on all the tones. Factory restore isn't helping? Could be as minor as a loose cable, as big as a defect in the mainboard. 

[emarsh7]

It was initially the grand piano sample but it seems to be spreading to others. I tried the reset a few times and it didn't seem to be helping. These things are pretty complex and no doubt beyond my abilities. I guess I'll get as much use out of it as I can.

[Mike Martin]

This is a main board issue, nothing that can be repaired yourself unfortunately.

[emarsh7]

Thanks, that's kind of what I had guessed.

[Wouter]

Hi,

 

My casio px-350 has exactly the same problem after 9 years of working fine. I have been googling for a few days now and there are a lot of people with exactly the same issue (also with other px models). Some have it within two years, so I would say its a design failure. A main board contains a lot of components so I would like to know which component is faulting here. I think Casio should know this by now or do they just replace complete boards without searching for the root cause? 

 

Regards,

Wouter

[mikeskory]

I'm in Michigan and it's 8/9/23. I'm having this same problem with a PX350M. Playing low register with force or hitting several keys at a time will make the speakers crackle. In addition, the headphones jacks do not work although the 2 other outputs works fine...except for the crackle. Did any of you find a solution?

[Brad Saucier]

5 minutes ago, mikeskory said:

Did any of you find a solution?

 

I just marked the solution for this topic.  See Mike Martin's post above marked as solution. 

[mikeskory]

Yes I saw that. I guess I was hoping someone had another plan. I did find the part but it is expensive. Thank you! BTW I really like this forum.

[Brad Saucier]

On 8/9/2023 at 10:53 AM, mikeskory said:

I guess I was hoping someone had another plan.

 

I mentioned this elsewhere, but I'll add it here as well.  All of the non piano tones are usually unaffected, continuing to perform as they should.  That leaves only a need for a piano sound.  Fortunately the keyboard will still work perfectly as a USB MIDI controller.  This means software like Pianoteq can be used as the sound source for piano.  Many people prefer Pianoteq anyways, so that's definitely an option worth looking into.  

[emarsh7]

I was doing a web search and came upon my old post. Here's a followup.

My PX350-M was a fine keyboard for me but when it became evident that there is no fixing this issue, at least not at a reasonable cost, I decided that the time had come to buy a new one. 

I looked at a number of models from different brands in the mid-price range. Because I had been happy with my Privia until it failed I was drawn towards something like a PS-X3100 but ultimately I had to decide if I wanted to spend more money with a company that had already sold me a product that I was unable to get any meaningful support for. My answer was no, I am not willing to do so.

I have a Roland PF-30X on order now. It comes with a five year warranty and for 43 Euro more I was able to extend that to ten years.

As Brad mentioned the Privia still works fine as a midi keyboard or with non-piano sounds. I will keep it around an maybe experiment with it as a keyboard for software synths.