Technics Piano PX71 No sound fix

Control panel on but no sound coming out of speakers or headphones also with line in. Issue was a switching circuit.

[@johntait5141]

Awesome vid & excellent diligence with the board! Thank you, brother.

[@taddy666]

Thanks man!

[@bepolite22]

For a long time I was trying to fix some Technics sx-pr603, 703, 903 and 1000 with that no sound issue so, your video is like a light at the end of a tunnel to me. Also I had the same issue with some Yamaha digital piano. Now I have to remove the dust from those keyboards and start looking for that signal voltage. If I get some success of course I will post over here to save those keyboards from the landfill.

[@taddy666]

Best of luck with it!

[@bepolite22]

@@taddy666 I got those Technics sxpr603-1000 service manuals and on the MIDI settings it confirm what you said on your video. On the MIDI PART SETTING, LOCAL CONTROL It says: " Use the LOCAL ON and OFF buttons to enable or disable this instrument sound generator. When set to ON, the performance from this instrument is transmitted as MIDI data and also sounds from this instrument. When set to OFF, the performance is transmitted as MIDI data but does not sound from this instrument." Also on the power & tone control/amplifier board, there's is a test point named PMUT, by the side of some transistors as you show in the video. Now I will try to get a working keyboard to see what kind of voltage is there.

[@taddy666]

@@bepolite22 Hi What voltage reading do you get on that PMUT test point?

[@bepolite22]

@@taddy666 I didn't have the chance to go to my friend's storage and check it out. Maybe I can meet him next week.

[@javierrobles4724]

Hello greetings from Mexico, im currently working on a Technics sx 450, with the same situation, due to limited time, i can only invest like an hour or two on the weekends, im going to follow your advice and i will certainly let you know the results.

[@taddy666]

Good luck Javier!

[@DavidStevensMr]

Hello Tom and greetings from the US. Thanks for the video and sharing your solution. I have a similar Technics piano (PX-55) and am experiencing the same problem. I have verified, as you found, that the keyboard generates a fine Midi signal (connected to my iPad w/GarageBand I can play the virtual instruments). I'd like to attempt your solution. I can solder, but I'm not very good at it. Any tips on what kind of wire and how to identify the exact points where I would need to solder the jumper? I'm presuming that both boards were fully removed when you did the repair. Regardless, I'll let you know how it goes one way or the other. Thanks for doing the hard work!

[@taddy666]

Hi David. Have a look at the reply to Max a bit further down on the comments. As I said I cannot remember exactly where I did it and I don't own the instrument and also didn't have the schematic. I thinik I got a similar technics model schematic from ElectroTanya. I just some multistranded flex wire - nothing fancy and yes I took the boards out to solder. Don't use an iron with very high wattage and don't apply heat for too long as you may burn the tracks. Good luck

[@DavidStevensMr]

@@taddy666 Thanks Tom!

[@tandoganpolat7151]

Hi Tom, I need your assistance. I have Kawai CN3, which does not give any sound to the speakers. I have checked the component on sound amplifier. I have also bought Peak Atlas ESR 70 to check the capacitors. Everything looks good. This is my personal piano. When I check the voltage on the both side of the speakers I get the 14 volt from both positive and negative side of the speakers.

[@taddy666]

Do the headphones work? If they do or the line out works then it is prob the power amp or eq amp area. I would have a look at the service manual - especially the block diagram here... www.manualslib.com/manual/1069632/Kawai-Cn3.html?page=17#manual .... and try to isolate exactly where the issue is. On Electrotanya you can download the schematic for free... elektrotanya.com/kawai_cn3_digital_piano.pdf/download.html I'm not really an expert on keyboards as I mainly do electric guitar electronics.

[@the_devils_ivory4838]

This guy has a degree in waffling 😂

[@taddy666]

No its more like a PhD.

[@maxwarfield6699]

Hello from Canada, I believe my synth is “locked” into midi mode as well, and though my synth is a Korg MS2000R, since I’ve tried just about everything I could think of, this might be my last shot at this. So, could you tell me what that chip is [markings, identification] that you are pointing to at 5:30, and also the markings of that transistor, which switches the amplifier on and off. Yeah, it’s a long shot… not even the same brand of synth and all but hey, who knows? Please reply, any insight appreciated. Thank you kindly

[@taddy666]

I can't actually remember and I didn't have the specific schematic for this one. I think the in order not to mute there needed to be 4.5V signal going into the base or gate of whatever transistor I was pointing at there. I took the boards out and traced it back to that chip which I think was some kind of logic chip but that particular logic gate wasn't outputting the 4.5V so I just found a point close by that was continuous with the 4.5V on the input of that gate and jumped it from there basically bypassing the faulty gate. Something like that. A Korg layout/system is likely to be completely different I'm afraid but if you can find a schematic that is well labelled you might find a track that is labelled MUTE or something synonymous.

[@royblake1]

WEll Done Tom i currently have 4- Technics SX-PR702 that seem to have similar problem and have been investigating on and off for a couple of years so any help is always useful and gratefully accepted Where are you Located please as I live in Spalding and would gladly Pay you to come and have a look at my instruments where you would be most welcome Massive help so far I do have Schematics and Circuitry for these. Best Regards Roy Blake

[@taddy666]

Best of luck with it, Roy!

[@taddy666]

I'm actually in Devon so its a bit of a trek!