i bought a second hand cheapy yamaha keyboard, PSS580, (The home type with built in speakers) it works ok in one speaker, and i thought the wires must have come disconnected in the other speaker. But on plugging in the headphone jack, the sound was mute there as well.
i know its a component failiure of some kind, but was wanting some ideas what it could maybe be, i'm thinking an opamp problem, or dac failiure?
wiggling some IC,s and opamps on the board, does not cut in or out.
Any ideas please?
i know its a component failiure of some kind, but was wanting some ideas what it could maybe be, i'm thinking an opamp problem, or dac failiure?
wiggling some IC,s and opamps on the board, does not cut in or out.
Any ideas please?
Trace the speaker feed back to the power amp... determine what the power is (chip amp, Class D, discrete etc) and then scope the input to said amplifier to get an idea of where the fault lies i.e. before or after the audio power amp.
If the channel is 'dead' then check continuity of the speaker feeds back to the power amp.
If the channel is 'dead' then check continuity of the speaker feeds back to the power amp.
WHy do you know it is a component? COnnections are just as important as components.
My first suspect will be the volume control itself. Especially if it is a slider. In the spirit of divide and conquer, I check the signal there to see if the amplifier part is bad or the signal is not being generated. Even moreso if it is a stereo slider.
Looking, I see the amp is a stereo chip AN7148. The master volume is indeed a dual 10k control and the wipers feed directly to the power amp IC through a pair of 10k resistors. The amp is on the power supply board, and the signal enters that board on the last two pins of the ribbon, and go directly to the ends of the control. The headphones run off the speaker line anyway, so whatever happens at the speaker will also happen at the phones.
On the digital board, the sound comes out of one of the 64 pin ICs, through a dual op amp IC and on to the ribbon. That is a 4558, IC12.
My first suspect will be the volume control itself. Especially if it is a slider. In the spirit of divide and conquer, I check the signal there to see if the amplifier part is bad or the signal is not being generated. Even moreso if it is a stereo slider.
Looking, I see the amp is a stereo chip AN7148. The master volume is indeed a dual 10k control and the wipers feed directly to the power amp IC through a pair of 10k resistors. The amp is on the power supply board, and the signal enters that board on the last two pins of the ribbon, and go directly to the ends of the control. The headphones run off the speaker line anyway, so whatever happens at the speaker will also happen at the phones.
On the digital board, the sound comes out of one of the 64 pin ICs, through a dual op amp IC and on to the ribbon. That is a 4558, IC12.
Mooly thankyou for your logical solution, and Enzo, brilliant work, i did spray contact fluid on the volume slider, but to no avail, and for some reason, i felt that the headphone and speaker were working off the same signal. all the ribbon wires to the power/amp board are sound, i cant read schematics, but i can see the general flow of the audio layout. i have a multimeter, and i can set it to continuity, where would i start to test the board? once again thanks for your help , its much appreciated.
You may have cleaned the slider but that doesn;t mean it works.
Can you identify the ribbon cable that connects the digital board to the power amp board? Can it be disconnected? If so pull the ribbon off and measure from the hot end of the slider to ground on each side, do they measure the same? Now measure the wiper resistance to ground at all the way up, at mid point and at zero. Do you get about 10k, about 5k and about zero ohms?
With the ribbon off, powered up, the power amp and speakers should still work, so with the volume at max, tough the two end pins of the ribbon, and see if they make hum out a speaker.
With everything connected, set your meter to AC volts, and probe the two end pins of the ribbon. Strike some keys, do you see the volt meter jump with the sound? Do both pins do that or just one? That is a crude way to test if the digital board is making an output.
Can you identify the ribbon cable that connects the digital board to the power amp board? Can it be disconnected? If so pull the ribbon off and measure from the hot end of the slider to ground on each side, do they measure the same? Now measure the wiper resistance to ground at all the way up, at mid point and at zero. Do you get about 10k, about 5k and about zero ohms?
With the ribbon off, powered up, the power amp and speakers should still work, so with the volume at max, tough the two end pins of the ribbon, and see if they make hum out a speaker.
With everything connected, set your meter to AC volts, and probe the two end pins of the ribbon. Strike some keys, do you see the volt meter jump with the sound? Do both pins do that or just one? That is a crude way to test if the digital board is making an output.
thanks Enzo
been hellishly busy, but am back home at weekend and will give you updates, thanks again for your reply, , i think the ribbons are non removable, the only one i think on the whole board which can be removed is the main board to keyboard panel.
been hellishly busy, but am back home at weekend and will give you updates, thanks again for your reply, , i think the ribbons are non removable, the only one i think on the whole board which can be removed is the main board to keyboard panel.
Connect the two sliders of the vol pot together briefly, that will check the signal feed as if sound is now there, the pot or feed from the pre amp chip is faulty. If no signal and you confirm the amplifier has signal on both pins 2+5, then likely the amplifier has an issue. It is unlikely for only one side to fail but not impossible.
All Fixed !!
😀 it was a bridged solder on the board where the volume slider was, cleaned it up and resoldered it, and both channels are perfect.
i want to thank you all for your precious time and help, and Enzo, the schematics will help me no end as im going to add a resonant filter into the signal path and circuit bend a few features.
😉
😀 it was a bridged solder on the board where the volume slider was, cleaned it up and resoldered it, and both channels are perfect.
i want to thank you all for your precious time and help, and Enzo, the schematics will help me no end as im going to add a resonant filter into the signal path and circuit bend a few features.
😉
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