Maker Pro
Maker Pro

Yamaha PS-35

Dirty Contact

Nov 24, 2012
22
Joined
Nov 24, 2012
Messages
22
Volume Controls

Pics of Master Vol Control Slider front and back views.

I have 3 readings 10.0K.....8.1K........7.0K.......There are two more slider pots which are Arpeggio and Bass Chord their readings are identical.
1.0 1.15 1.18

The connections I measured are the top and bottom of the sliders the other don't give me any readings all zero.

Do not blame me for the scrapings around the solder connections on the board! Someone has had a go at this before!!
 

(*steve*)

¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd
Moderator
Jan 21, 2010
25,510
Joined
Jan 21, 2010
Messages
25,510
I can't see where this is in your photos. Can you point it out to me?

Slider pots often have more than three connections, and in this case often some of them are connected together.

It looks to me that you've not measured across the correct pins (or that there is a problem with the pot).
 

Dirty Contact

Nov 24, 2012
22
Joined
Nov 24, 2012
Messages
22
Pot position

Go back to Page 1 and look up Pic P1030580 very center is the rotary pot for the transposer and above that is the master slider volume pot.

New readings from the two top connections on the master slider 10.2 top
2.1 middle
0.0 bottom.
 

(*steve*)

¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd
Moderator
Jan 21, 2010
25,510
Joined
Jan 21, 2010
Messages
25,510
OK, the last measurements are close to what I'd expect from a log pot.

What you have is the wiper and the ground connection to the pot.

Another pair should read 0, 8, and 10 - this will be the wiper and the hot end of the pot. (relax if they're not exact; 0 should be :)

From this, you can determine the wiper, the ground end, and the hot end. I need you to mark those points on an image so I can think about them :)
 

KJ6EAD

Aug 13, 2011
1,114
Joined
Aug 13, 2011
Messages
1,114
Regarding the three wires to each speaker; they may have a second driver such as a tweeter in each speaker enclosure.
 

Dirty Contact

Nov 24, 2012
22
Joined
Nov 24, 2012
Messages
22
Hi Steve,
I have bought an identical keyboard for my grand daughter so the pressures off! I think we have gone far enough with this dysfunctional board don't you? It seems to be something expensive like one of the major chips. I am quite prepared to change one if it can be identified as the cause but I feel any more expenditure of time on it will be wasted.
Thanks so much for your efforts it is very much appreciated. If you think we are getting somewhere them we'll carry on. I don't like being defeated by a mere keyboard!!
 

Dirty Contact

Nov 24, 2012
22
Joined
Nov 24, 2012
Messages
22
I think we are giving up on this keyboard! Two of the wires to the speakers are common earth so there are only two feed wires.
Thanks for your interest.
 

(*steve*)

¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd
Moderator
Jan 21, 2010
25,510
Joined
Jan 21, 2010
Messages
25,510
It certainly doesn't look like something obvious.

Still, it's always worth poking around to find out.
 

(*steve*)

¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd
Moderator
Jan 21, 2010
25,510
Joined
Jan 21, 2010
Messages
25,510
Where else would you expect me to be? :D
 

Dirty Contact

Nov 24, 2012
22
Joined
Nov 24, 2012
Messages
22
Hi Steve,
You never know you might have been with those LEDs in the sky!
I came back on the PS35 because, having delivered the new one to grand daughter I thought to persist with the duff one. I have obtained the service book from Canada with the parts lists and full circuit diagrams. Having those, I explored the Master Volume control circuit. The capacitor on that looked a bit cooked so I changed it.... .Went for lunch in the kitchen forgetting I had left the power supply on. Suddenly there was a clapping coming from my den!! The thing had sprung to life very loudly! However when I went to turn the volume down I found it was at the lowest setting and moving it towards full volume it went quiet again at the half way point. I can regain the volume by moving the slider towards low but it does not control the volume at all. All the keys work and other functions but I don't claim to have tried them all. I then suspected the diode was allowing reverse current on the Master Vol. so I changed that but it did not make any difference. Over to you!
 

(*steve*)

¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd
Moderator
Jan 21, 2010
25,510
Joined
Jan 21, 2010
Messages
25,510
That really sounds like a fault in the volume control. I'll have to read back and see if we've been through that.
 

(*steve*)

¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd
Moderator
Jan 21, 2010
25,510
Joined
Jan 21, 2010
Messages
25,510
You never know you might have been with those LEDs in the sky!

With my posting history I may still be posting for years after I'm pushing up daisies! :D

I see we've looked at the volume control before.

Does wiggling the volume control do anything?

Does the headphone output work now? What does the volume control do to it?

Perhaps you can scan and post the part of the circuit diagram that contains the volume control.
 

Dirty Contact

Nov 24, 2012
22
Joined
Nov 24, 2012
Messages
22
Master Volume Control

View attachment 6982I am doubtful of it being the vol.control, I have checked it out and it does exactly what it should do. A component is blocking the normal input and the output line is being overwhelmed somehow by an input which fails beyond the 1/2 way point of the slider when the normal input takes over. Very peculiar but these happen with electronics don't they and I am not experienced enough to follow this through without.
Ah I posted that before I discovered you had added some more....hang about and I'll see what I can do!
The vol.cont. is not affected by wiggling.The phones work in the same way as the speakers but I notice that I was over estimating the position of the Master Vol. It reduces the sound to almost nothing as it is moved up towards the max.position by 1/3rd from the bottom. The same happens with the phones.
I think I have got the block diagram in but the circuit diag. said it was too many bites to upload so I compressed it and I hope it worked. I will try to attach the circuit for the destination of MV1/2/3 from Master Vol. to PC Driver.
Had a go but not sure its worked.
 
Last edited:

Dirty Contact

Nov 24, 2012
22
Joined
Nov 24, 2012
Messages
22
Master Volume Control

I am doubtful of it being the vol.control as I have checked it out and it does exactly what it should do. A component is blocking the normal input and the output line is being overwhelmed somehow by an input which fails beyond the 1/2 way point of the slider when the normal input takes over. Very peculiar but these happen with electronics don't they and I am not experienced enough to follow this through without.
 

(*steve*)

¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd
Moderator
Jan 21, 2010
25,510
Joined
Jan 21, 2010
Messages
25,510
I'm afraid that image is totally unreadable.
 

(*steve*)

¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd
Moderator
Jan 21, 2010
25,510
Joined
Jan 21, 2010
Messages
25,510
Here is the image...

attachment.php


It's a little fuzzy, but I'm pretty sure I can make out most of it.
 

Attachments

  • Yamaha_Circuit.jpg
    Yamaha_Circuit.jpg
    22 KB · Views: 212

(*steve*)

¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd
Moderator
Jan 21, 2010
25,510
Joined
Jan 21, 2010
Messages
25,510
OK, it looks like the pot is used to alter the current through a LED and that LED is used to illuminate some LDRs which control the levels from the mixers.

Is it possible to check that the LED changes in brightness as you expect as the volume control is swept from one end to the other?

Is there any possibility of there being a light leak or another LED which lights up?
 

Dirty Contact

Nov 24, 2012
22
Joined
Nov 24, 2012
Messages
22
I understand the circuit better from your last diagnosis but I am getting even more peculiar results now I have been trying it with various control buttons in use. I cannot see any LEDS lighting up at all except P.Supply and the upper & lower range LEDs.I have identified the amplifiers NJM4558 (3 of them) and the 2SA733 but they do not feed into any LED that I can make out. The Master Vol. slider is giving varying results...now it only results in sound when at its lowest position. Testing voltage across it with the meter it behaves exactly as it should, varying the voltage steadily across the whole range. Where a voltage is given on the circuit diag. I am working through and testing them all as I find them.
 

(*steve*)

¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd
Moderator
Jan 21, 2010
25,510
Joined
Jan 21, 2010
Messages
25,510
I'm not very happy with the circuit diagram. Several things appear wrong.

However, check the voltage across the resistor connected to the emitter of the transistor which drives the LED. As you vary the volume control it should also go up and down.
 
Top