Yamaha Pss 460, no sound! Amp La4500 replaced, but nothing!

Stereokromatik · Joined: Feb 21, 2012 Posts: 5 Location: Brazil

Hi, everyone... I got a pss 460 from a friend, in immaculate condition, without any brand of use, however, it doesn't have any kind of sound...
It was kept for a long time... the speakers are perfect, and potentiometers too... all the commands where the leds light up, correspond normally, as if the keyboard were working normally. I suspected it was the La4500 chip, bought the new chip, installed it and even so it doesn't come out any kind of sound... The motherboard is in immaculate condition, smelling like new! To check if there was any kind of cold soldering, I reheated ALL solders from ALL installed chips, and no success again. I would like suggestions!
Next suspects would be the ym3014 (DAC) and ym3812 (OPL2)... what do you guys think?

DES · Posted: Sun Oct 10, 2021 11:32 am Post subject:

Check the headphone jack…most interrupt the speaker signal so if it was broken or had something jammed in it the speakers might not work. Also, if you plug headphones in and can hear it, you’ve narrowed down your search. Check wiring too.

Riva Lima · Joined: Mar 30, 2022 Posts: 5 Location: Brazil

Good Morning! Sorry for the delay in getting back to you... but still no success, the headphone plug is working fine, no fault but no sound either, no short on that component... is it the DAC YM3014 or the OPL YM3812?

DES · Posted: Thu Dec 08, 2022 10:53 am Post subject:

I suppose it could be one of those, but you might want to do a little more investigating first. So if I understand you correctly, you can plug headphones in but still no sound in the headphones? I would look at all of the surrounding solder connections and see if there are any bad connections. Wouldn’t be a bad idea to reheat/reflow the solder. Check all wire connections. You want to check the volume control solder and/or wire connections. There may be some FETs just before the output audio chips that are used to mute the outputs during power-on to prevent loud pops from getting thru. These do have a tendency to go bad when around static electricity prone areas.

The chips you mentioned could be bad however in my experience it’s usually something much simpler…

Good luck! And Happy Holidays!

Dave

Riva Lima · Joined: Mar 30, 2022 Posts: 5 Location: Brazil

DES · Posted: Sat Dec 10, 2022 1:00 pm Post subject:

Ok, so you checked the headphone jack...make sure you do a continuity check THRU the headphone jack, just to be safe and absolutely rule it out. You said you checked all solder connections on the ICs - that's good. You need to check all the plugs and make sure their solder joints are good. And, make sure all the cables inside are plugged in correctly - Usually the only way you can do this is because each connector is a different pin count. However there may be similar connectors nearby. Do you know if the keyboard is actually sending data? Might be a ribbon connector not sitting well. Something else to try - a lot of keyboards have internal Demo songs... see if there are any and try that. You could probably also try the built in rhythms and see if they are working. If you can't hear them but they appear to be working, start tracing the path. See if you have any Data going into the DAC and then look at it's output. Do you have an oscilloscope? If not, see if you can borrow one from a friend or there are fairly inexpensive ones on Amazon, etc... You could just start swapping out ICs - a practice we used to call 'Easter Egg Hunting', hoping to find the bad part. However, that can get pricey - especially if the swaps don't fix the problem. Plus, you could introduce more problems...

Riva Lima · Joined: Mar 30, 2022 Posts: 5 Location: Brazil

Dear friend, the only thing that is lighting up on the keyboard, is only the power led, no other function works... you only know that the keyboard is on, with the red light... and nothing else... none button turns on no panel led, nothing... not even pressing them... only the led light indicating that the keyboard is turned on, all internal and ribbon cables are connected perfectly...
Thanks for replying again... I'll post a short video showing how he's doing.

https://youtube.com/shorts/Lu6LF4WTJf0?feature=share

DES · Posted: Sun Dec 18, 2022 10:20 am Post subject:

Ah, that’s significant info…. You need to check the internal power supply and distribution. Besides a main input fuse (I’m assuming this runs off a 12vdc wall wart power supply), there may be more. There could be a 5v supply, etc. So you need to check all of that to what should be there and whats not, if anything. Always verify symptoms, then power supply. Were you ever able to get a schematic? Yamaha used to be good about that, but it’s been years since I worked on their gear.