itsJoel Posted January 26, 2023 Share Posted January 26, 2023 So I came across an MT-65 that I pretty much got for free. It is in seemingly good condition both internally and externally. However it won't turn on. My immediate suspicion is the use of a wrong power cord by previous owners. However I cannot see anything particularly bad on the circuit boards. I however do not have any particular experience in repairing faulty circuit boards such as soldering, only cleaning them. So far I have only used fresh batteries to power it, since I do not yet have the appropriate power cord. I am also looking into getting a soldering station and a multimeter if it comes to that. Any insight is appreciated DEEPLY. Joel Quote Link to comment Share on other sites More sharing options...
itsJoel Posted January 26, 2023 Author Share Posted January 26, 2023 Quote Link to comment Share on other sites More sharing options...
itsJoel Posted January 26, 2023 Author Share Posted January 26, 2023 might as well add this Quote Link to comment Share on other sites More sharing options...
pianokeyjoe Posted January 26, 2023 Share Posted January 26, 2023 You tried it with batteries and it turns on? Or you tried with batteries and it did NOT turn on either? From the looks of it the unit looks very clean for the age and it requires 7.5VDC at 600mA NEGATIVE CENTER PIN Polarity for the AC to DC power adapter. Quote Link to comment Share on other sites More sharing options...
pianokeyjoe Posted January 26, 2023 Share Posted January 26, 2023 1 hour ago, itsJoel said: So far I have only used fresh batteries to power it, since I do not yet have the appropriate power cord. I assume from this statement it works on batteries. If that is so, then the issue is the power adapter HOLE. It looks like the metal contact inside is bent or broken. That contact is responsible for switching between Wall power and batteries when no plug is inserted into the hole. I forget which way it does it, but essentially, if you do not have a power plug inserted, the contact switches to batter power only, while switching OFF AC power input. But if a plug is inserted into the hole, that contact switches in the other direction allowing power to be fed from the AC adapter but cuts power to the battery compartment to avoid back feeding power to the batteries and thus exploding them in the keyboard. From the look of the hole, seems some one shaved some of the plastic to make the hole bigger and bent or broke the metal contact at the bottom of the hole so that now the thing is stuck on battery power mode only. You say in the title DOES NOT POWER ON. But you say you used it with fresh batteries. Sooo.. did you try a Center Negative 7.5VDC adapter and it did not power on but with batteries it does power on? Quote Link to comment Share on other sites More sharing options...
itsJoel Posted January 27, 2023 Author Share Posted January 27, 2023 22 hours ago, pianokeyjoe said: I assume from this statement it works on batteries. If that is so, then the issue is the power adapter HOLE. It looks like the metal contact inside is bent or broken. That contact is responsible for switching between Wall power and batteries when no plug is inserted into the hole. I forget which way it does it, but essentially, if you do not have a power plug inserted, the contact switches to batter power only, while switching OFF AC power input. But if a plug is inserted into the hole, that contact switches in the other direction allowing power to be fed from the AC adapter but cuts power to the battery compartment to avoid back feeding power to the batteries and thus exploding them in the keyboard. From the look of the hole, seems some one shaved some of the plastic to make the hole bigger and bent or broke the metal contact at the bottom of the hole so that now the thing is stuck on battery power mode only. You say in the title DOES NOT POWER ON. But you say you used it with fresh batteries. Sooo.. did you try a Center Negative 7.5VDC adapter and it did not power on but with batteries it does power on? Poor wording by me. The unit does NOT turn on with batteries either. What I meant to say was that batteries is all I have tried so far, since I do not have the appropriate DC adapter. Now the previous owner has claimed that it doesnt turn on with an adapter either, but I need to confirm it by buying my own adapter and trying it out... 1 Quote Link to comment Share on other sites More sharing options...
pianokeyjoe Posted January 27, 2023 Share Posted January 27, 2023 Ahh, ok thankyou for clearing it up. Ok. For the Casio MT series that uses 7.5VDC you can buy a NEGATIVE CENTER 7.5VDC(not AC)at 600mA or higher amps, powersupply. The barrel plug size I do not know by heart, but when you search Ebay for power supply for Casiotone MT65 you should find the one you need. Just make sure the polarity is correct. Now, as for battery operation not working, the metal inside the hole that is bend is a switch to switch between the wall power and batteries so it must be broken and not making contact to make complete the circuit to batteries power. Lets hope that is all it is. Looking at your pictures, your boards are all very clean which is amazing! So battery corrosion inside or water damage is not evident. Let us know what happens when you get the correct PSU for it. Quote Link to comment Share on other sites More sharing options...
itsJoel Posted January 27, 2023 Author Share Posted January 27, 2023 YES!!! The new PSU did the trick. Thank the gods. Thank you for replying, and fast as well. Might have to do something about that switch if I ever want to use batteries. Got any advice on how to go about fixing that? Quote Link to comment Share on other sites More sharing options...
pianokeyjoe Posted January 28, 2023 Share Posted January 28, 2023 Not worth fixing, just use the wall power and thank God lol! The power input is molded to the white plastic so no real elegant fix. Just enjoy it. If you want you can always make a external battery pack with 5 AA batteries plugged in the power input hole making sure the center pin is NEGATIVE.. Ebay is your friend Quote Link to comment Share on other sites More sharing options...
itsJoel Posted January 28, 2023 Author Share Posted January 28, 2023 Thank you for your tips. Have a good day sir! Joel 1 Quote Link to comment Share on other sites More sharing options...
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