Sarwan Posted March 21, 2020 Share Posted March 21, 2020 Hey folks, I'm facing an issue with my Casio PX 350. All of sudden today, it decide to no longer power on. Pressing the power-on key results in it only turning on momentarily (its screen goes white) and then it goes down black again in a flicker. I checked AC Adapter's output with a multi-meter, its shows a voltage of 11.94 - 12 V, which I guess should imply it doesn't have any issues. I opened up the Privia (It's out of warranty - I've had the keyboard for two years - and have fixed issues regarding dust over sensor keys, and I'm an electrical engineering undergrad, so I'm comfortable around its insides) and checked it's power supply PCB for a bad solder on the input jack's bracket. Testing over its terminals on the PCB also showed a stable 11.94 - 12 V, so no issue there. Beyond that I couldn't figure stuff out, or more honesty was just to sad/disappointed to work on it. (The piano was very personal to me, idk if that makes sense) Can someone here help me out as to how do I about further debugging this issues? or someone who might have faced this issues. Is there any service manual available for the PX 350 or its power supply PCB that I could maybe study to figure out where the problem might lie? Any help would be appreciated. My country doesn't have an third-party or even the official Casio repair services available, so sending it in for service isn't possible, and I lack the finances to get a new piano anytime soon.. so that's a major bummer. My only hope for now is to somehow resolve the issue with the aid of my few EE skills that maybe applicable. Kind Regards, Sarwan Shah Quote Link to comment Share on other sites More sharing options...
CAVA Posted March 22, 2020 Share Posted March 22, 2020 (edited) I don´t have my PX350 anymore but doing some research I see there is a hard reset or factory reset option that might help if the issue is related to software or an start up issue. They suggest to "Hold down the GMTones button and the Function Button simultaneously while powering up the unit." Check this: https://www.keyboardforums.com/threads/how-do-i-reset-the-factory-settings-casio-privia-px-350m.28570/ I hope this helps. Edited March 22, 2020 by CAVA typo, better wording. 1 Quote Link to comment Share on other sites More sharing options...
Jokeyman123 Posted March 22, 2020 Share Posted March 22, 2020 Haven't circuit-traced the PX350 (I own one-you know I've had mine apart!) a few simple multimeter voltage tests if you haven't done so, and if the hard reset doesn't work-once you can get inside the PX-do some voltage checks at various points-you should be getting 12V or 5V and some cases 3 or so volts in various parts of the circuitry while powered on-start where the power supply input jack is and see ho far your voltage readings go. I'd google for a schematic-I'll check myself, i don't have one to upload here, I will if I find one. when circuit-tracing-I look for continuity across all the circuit-boards-first, try to find where voltage and current is not coming through where you would think-intuitively if you have no schematic-there should be some voltage or current. when troubleshooting at the component level-you have to narrow down an area that might be dead. I'm assuming by your post that it is completely off-no sound coming out anywhere, not just a dead screen. could be a simple as a bad component near where the power jack is mounted-look very carefully for any cracks in solder joints-flex parts around a bit if you can-to see if any solder joints have cracked-it only takes the smallest of cracks on a circuit board to power everything off. i've found several so small, I needed magnifying loupes to see! Good luck, hope its a simple repair. And could be as simple as a data cable not seated fully, maybe.....! 1 Quote Link to comment Share on other sites More sharing options...
Jokeyman123 Posted March 22, 2020 Share Posted March 22, 2020 All I can find so far is the schematic repair manual for a Casio PX700-might be some similarities......... casio_px_700.pdf 2 Quote Link to comment Share on other sites More sharing options...
Sarwan Posted March 22, 2020 Author Share Posted March 22, 2020 Thank you for the advice CAVA and Jokeyman123. I tried the hard reset, that didn't seem to do that job. The issue here is it only powers up momentarily, like the screen goes white for a moment before its dead again. Not even the red-lights power up. The white screen turning on is indicative that the power does indeed reach its essential components, but perhaps only momentarily before it goes back down. Adding to that one thing that I did notice is that, there is a voltage drop across the across terminals at the input jack, when I press the power-on button. Could this be indicative of a short-circuit somewhere in the circuitry? I tried removed all the external components attached i.e. speakers, sub-woofers, pitch wheel, key-sensors, and tried to power the main unit alone, thinking perhaps maybe one of these external components could be malfunctioning/shorting, but no luck there either. I also tried checking the LA5756 (link to its datasheet) switching IC installed on board but couldn't figure out how it was supposed to work. See if you can figure something out on the attached link. (Some debugging results I had on the IC: 12 volts on the pin 1, and there was voltage jump to about 0.6 volts or so, when pressing the power-on button on the pin 2) P.S It's just really difficult to figure out if some voltage is wrong on the PCB, given its complexity, without a schematic 😕 Quote Link to comment Share on other sites More sharing options...
IanB Posted March 22, 2020 Share Posted March 22, 2020 Well hmmm. Is that the only voltage regulator on the board? The LA5756 tries to get its feedback pin to 1.26 volts according to the Datasheet. I presume pin 4 isn't reaching 1.26V? I would suspect though that the regulator won't be the problem and it's shutting itself down due to some problem with what it is feeding into. May be the regulator tho. Let's start where we are; there should be two resistors connected to pin 4, what are their values? Also, if they've used the same circuit as in the datasheet they'll have strapped a diode across the output with it's pointy end on the output and the other to ground. Check that hasn't gone short circuit. 1 Quote Link to comment Share on other sites More sharing options...
CAVA Posted March 22, 2020 Share Posted March 22, 2020 May I suggest to focus your attention on the power adapter? I know you mentioned you measured 12V on the plug but, if damaged, it might not support a load. You might want to try a different one, it is listed as 12V 1.5 Amp so any adapter with a higher amp rating will do it. Issue is I see it has a pin in the center. In any case, I have seen that adapters get damaged with a power surge and they keep showing the voltage expected but are not able to support a load. 2 Quote Link to comment Share on other sites More sharing options...
IanB Posted March 22, 2020 Share Posted March 22, 2020 Good point by CAVA. If you (Sarwan) don't have another PSU to try, it would be worth watching the input voltage on a multimeter or even better oscilloscope when you hit the power on, to see if it sags. 1 Quote Link to comment Share on other sites More sharing options...
Sarwan Posted March 23, 2020 Author Share Posted March 23, 2020 Hey, IanB, when testing the pins for 1.26 V, I did not see that value on any of the pins when pressing the power-on button. I'll check again, could it be that it was very short-impulse that the multi-meter cannot register? Also, I check the potential short-circuit across pin 4. Also, yes, good points guys (I really hope that is the case)... that thought did occur to me, but I wasn't quite sure about it. Plus, getting a new AC Adapter in these quarantine times is a bit difficult, but I'll see what I can do! Thank you folks! I will keep you updated! 1 Quote Link to comment Share on other sites More sharing options...
IanB Posted March 23, 2020 Share Posted March 23, 2020 Hi Sarwan, the 1.26V is the voltage the regulator tries to maintain on that pin, but if it's shut down you're not going to get that. It should be constant all the time it's producing an output. 1 Quote Link to comment Share on other sites More sharing options...
Jokeyman123 Posted March 23, 2020 Share Posted March 23, 2020 The power supply is always the first suspect with problems like this-I learned that as a tech. If you simply check the 12V leads inside connected to whatever circuitboard these are soldered to-the supply should always be supplying its rated voltage to those terminals-even with a short in the keyboard-there should still be live 12v coming from the supply-unless it blows an internal fuse-or there is some kind of short-circuit protection inside the power supply temporarily shutting it down-possibly a thermal protection circuit in the supply but i do not know what is inside these supplies. Before jumping through more hoops-get some other 12v supply as Cava said, and see what happens. any standard 12v wall-wart should work, providing it has correct tip polarity and sufficient amperage. I've stocked up on several portable 9v/12v battery packs for just this purpose. I use these as portable power for my PX350, good for troubleshooting too. Casio does not recommend using anything like this, but is handy to check problems like this one. And a battery is clean DC power, many wall-warts don't have much filtering or protection from voltage spikes or brownouts. Could turn out to be something as simple as an intermittent connection in the barrel plug from the power supply-it is connecting enough to get a little juice to the keyboard, but under load, the connection is failing because it is only partially conducting. I've seen this happen. These barrel plugs fail quite a bit internally. 1 Quote Link to comment Share on other sites More sharing options...
Brad Saucier Posted March 23, 2020 Share Posted March 23, 2020 Try another power supply. Quote Link to comment Share on other sites More sharing options...
Sarwan Posted March 23, 2020 Author Share Posted March 23, 2020 I have a question. Getting a new AC Adapter could take up-to a month for now, given the lock-down/quarantine requirements where I live. I have 12V AC/DC Adapter, except that its rated at 12V - 1A, whereas the Casio Adapter is rated at 12V - 1.5 A, and neither the pin sizes, nor I'm assuming the polarity matches Do you think it is wise that I cut off the pin plus a small section of wire off the Casio adapter, and couple it with the 12V - 1A AC/DC Adapter? Would that work for the sake of testing? What are some of the considerations I'll need to take in terms of polarity? I was reading that the Casio Adapter has an internal third pin as-well, is that correct? Quote Link to comment Share on other sites More sharing options...
CAVA Posted March 23, 2020 Share Posted March 23, 2020 That could work for testing. Please notice the standard power supply is rated as 1.5 Amp so you can use the one offering 1A but avoid high loads or it will damage the power supply. To avoid high loads, just plug the piano, turn it on and press a few keys at low volume, it should confirm everything is correct on the piano side and you will confirm you need to buy a new power supply. About the connector with the 3rd pin, I am not sure about the pin out, I found it is called "barrel 5.0/3.0 with central pin" but I couldn´t find information about the function of the central pin, I see some laptops use something similar for a signal between the charger and the laptop and, without it, the power is not delivered, but Casio probably did something specific with it. You mentioned you feel comfortable doing electronic reparations so you might test the power supply with a simple circuit and even be able to measure the current it delivers. You already know it works at 12V, 1.5 Amp, so, by using a simple Ohms law, you could use a load of 8 ohms or above. Review those calculations and see what makes sense in your testing, probably using a simple circuit. Be careful, there is a risk of damaging the power supply, your piano or hurting yourself in the process. 1 Quote Link to comment Share on other sites More sharing options...
Jokeyman123 Posted March 23, 2020 Share Posted March 23, 2020 My Casio supplies only have 2 power points-tip and sleeve. DO NOT put the wrong polarity into the keyboard. It may do alot of damage if you reverse the polarity of your power supply-it MUST MATCH the keyboard's power jack polarity. I would not power the PX350 for very long with a supply that is under-rated for current (amperage). It will overload the power supply, can overheat it-isn't great for the PX350 either, but it won't do damage to it-but I wouldn't use an "undercurrent" power supply for very long. as CAVA said, I don't think you will damage anything for testing-just to see if the keyboard works-to see if the power supply is the cause. but like Brad said, get a good Casio supply if this turns out to be the problem. All my Casio power supplies are pretty "beefy" well-made solid supplies. Even with the covid-19 pandemic, you may still be able to get shipping if you order a supply from an online source-at least in the US all the major carriers are trying to maintain supply lines-as of today 3/23/2020 although they are cutting back service-walk-in delivery depots are no longer available at least here in PA. and Amazon i understand has also cot back on delivery services/vendors and shipping partners. Might still be worth it to order online. Quote Link to comment Share on other sites More sharing options...
IanB Posted March 23, 2020 Share Posted March 23, 2020 Does plugging in a headphone jack on this keyboard disable the built in speakers? If so, that will reduce the power demand. 1 Quote Link to comment Share on other sites More sharing options...
Sarwan Posted March 23, 2020 Author Share Posted March 23, 2020 Alright, I will keep these things in mind. That's the plan Jokeyman123, once I have it tested, if the supply is the issue then I'll get a new once. Since its not easy to get it shipped where I live and the original one is a bit expensive too, so no point in spending on it if I'm not sure. IanB, I'll unplug the internal speakers from the main PCB when testing. I'll try all these things after my mid-term tomorrow. Thanks folks, will keep you updated. 1 Quote Link to comment Share on other sites More sharing options...
Joe Muscara Posted March 24, 2020 Share Posted March 24, 2020 FYI, the power adapter for this model is the same for many other Casio models, such as many of the Privia and CDP series and some CTK and WK models. It should be easy to find or borrow (at least during normal times). Also, it can be worthwhile having a spare, unless you never take the keyboard out. 1 Quote Link to comment Share on other sites More sharing options...
Sarwan Posted March 24, 2020 Author Share Posted March 24, 2020 Hey folks.. So the good news: its powering up. The bad news: I can't hear anything. Checked using Midi, getting input from keybed. So I'm assuming something isn't right with the speakers? Could it be this brick doesn't have enough juice to power the speakers? Its rated 12 V - 1 A .. I can expect some sound? no? Quote Link to comment Share on other sites More sharing options...
Sarwan Posted March 24, 2020 Author Share Posted March 24, 2020 Nvm, I had missed one connection!! It's all good now. I'll order a new brick! Thank you so much everyone for your input! Bless u all! I can't tell you all how relieved I am 3 Quote Link to comment Share on other sites More sharing options...
CAVA Posted March 24, 2020 Share Posted March 24, 2020 1 minute ago, Sarwan said: Nvm, I had missed one connection!! It's all good now. I'll order a new brick! Thank you so much everyone for your input! Bless u all! I can't tell you all how relieved I am Excellent news! Be careful, do not operate the piano with the 1Amp power supply, you could damage both. 1 1 Quote Link to comment Share on other sites More sharing options...
IanB Posted March 24, 2020 Share Posted March 24, 2020 Great news, glad to hear it! 1 Quote Link to comment Share on other sites More sharing options...
Sarwan Posted March 24, 2020 Author Share Posted March 24, 2020 I'm using the keyboard in LocalCtrl: Off Mode, with the internal speakers disconnected. I'm essentially using it only as a MIDI controller. Do you think that'll keep me in safe bounds for a 1 A brick? The new brick will take at-least a month to arrive and I would really like to play via my laptop in the mean time if you guys think that would be safe? Quote Link to comment Share on other sites More sharing options...
IanB Posted March 24, 2020 Share Posted March 24, 2020 Well, it may well be okay, keep an eye (or hand, rather) on the PSU to check if it's overheating. We already know the keyboard's regulator shuts itself down if the input voltage is too low. 1.5A is going to be the maximum power draw with some headroom. Since you have a multimeter, you could measure the input current to see what it's actually drawing. I don't think you're at all likely to damage the keyboard, though it's possible you could damage the power brick if it doesn't have overcurrent protection. 2 Quote Link to comment Share on other sites More sharing options...
Jokeyman123 Posted March 24, 2020 Share Posted March 24, 2020 Very good-like I said (not to be a smarty-pants) first rule I learned in troubleshooting-always suspect the power supply first. The other rule-the one hand rule-always keep one hand working and the other hand away from your circuits-even some of these low voltage devices can give you a nasty shock-if you become one of the components! a strong enough current/voltage can go from one hand to your other to complete a circuit-and will run through your heart-your body becomes a big conductor. actually-this was the first rule my instructors taught me-the power supply was the 2nd! You are in no danger with what you are doing, but just in case for future repairs. Even a desktop computer motherboard can be fatal if you touch the wrong parts with 2 hands. Not kidding. 2 Quote Link to comment Share on other sites More sharing options...
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