Sharp VZ-3500 turntable voltage?

[ms660]

Originally Posted by knorxou

Now this is the part where my basic electronic knowledge reaches a point of some (hopefully small) confusion.
Normally I'd figure I could just supply the voltages needed to the specific pins and just have them all share the same grounds leading back through pins 1 and 4.
Pins 5 and 6 however mention different directions for the same voltage. Does that mean I'd have to supply two separate sources for 15v going into different "directions" in regards to the common ground?
Sorry I am lacking the exact terms in English. I have experience with curcuits mostly from working with microcontrollers but rarely ever had to work in environments using multiple different voltages in the same curcuit.

Yes, two separate 15 volt supplies, the -ve of one connected to the +ve of the other, that connection being connected to ground, that then leaves a 15 volts +ve supply and a 15 volts -ve supply both with respect to ground.

If you follow the schematic to the power board you can see that those two supplies are obtained via their respective regulators from two bi-phase full wave rectifiers (D451) and with respect to the turntable control board those two supplies supply the phono equalizer IC (IC507) and the cartridge signal selector IC (IC506)

The 15.8 volt supply supplies the 9 volt regulator for the motor supplies, the 5 volt regulator which supplies IC501, IC504, IC509 etc etc and also supplies the run voltage for the tonearm solenoids (SOL 501 & SOL 502)

The 24 volt supply supplies the voltage for the door solenoid (SOL 503) and the start voltage for the tonearm solenoids mentioned above.

So far as I can make out.

If that's any help.

Lawrence.

[knorxou]

Yes a lot of help thanks!
So just to make sure I got that right: I have two different 15v power supplies but one is connected to GND with its - and one with its + ?
and the two GND on the connector lead

I thought the easiest would probably be to get a 24v power supply and use some step down circuits for the other voltages.
Do you think I can use just any old step down circuit or do I have to watch some criteria? I know some step down the voltage by pulsing it. Would that possibly affect functionality?

Also do you have any idea regarding my phono question from before?b

[ms660]

Originally Posted by knorxou

Yes a lot of help thanks!
So just to make sure I got that right: I have two different 15v power supplies but one is connected to GND with its - and one with its + ?
and the two GND on the connector lead

I thought the easiest would probably be to get a 24v power supply and use some step down circuits for the other voltages.
Do you think I can use just any old step down circuit or do I have to watch some criteria? I know some step down the voltage by pulsing it. Would that possibly affect functionality?

Also do you have any idea regarding my phono question from before?b

In the link below is a circuit which is essentially the same function as the one in the Sharp, you will notice the center tap on the transformer secondary, that point is the -ve of the +ve supply and the +ve of the -ve supply, in other words it's common to both.

https://www.petervis.com/electronics...er-supply.html

The phono signal out from the turntable board, connector CNS102, the screen of the screened cable is the common ground for the Left and Right channels, the other two wires in that cable are the Left and Right channel signal outputs from the phono equalizer amplifiers, those outputs along with the ground are the ones to use if you wanted to connect it to an external amplifier (Line/Aux. input) The other wire (Brown) is, so far as I can make out, normally connected to ground when the Phono function is selected by the function switch (SW101-A) on the tuner board.

Remember that the power supply just referred to above is not the 15.8 volt supply, that supply will need to be separate, there's also the 24 volt supply for the solenoids to consider, why not use the existing supplies?

Lawrence.

[knorxou]

Originally Posted by ms660

In the link below is a circuit which is essentially the same function as the one in the Sharp, you will notice the center tap on the transformer secondary, that point is the -ve of the +ve supply and the +ve of the -ve supply, in other words it's common to both.

Thanks for the detailed explanation I think I understand that part now

Originally Posted by ms660

The phono signal out from the turntable board, connector CNS102, the screen of the screened cable is the common ground for the Left and Right channels, the other two wires in that cable are the Left and Right channel signal outputs from the phono equalizer amplifiers, those outputs along with the ground are the ones to use if you wanted to connect it to an external amplifier (Line/Aux. input) The other wire (Brown) is, so far as I can make out, normally connected to ground when the Phono function is selected by the function switch (SW101-A) on the tuner board.

I think I still don't 100% understand its purpose then. So what would be the better practice since I just want to connect an external preamp: leave the brown cable out or connect it to the common GND?

Originally Posted by ms660

Remember that the power supply just referred to above is not the 15.8 volt supply, that supply will need to be separate, there's also the 24 volt supply for the solenoids to consider

I thought just the supplying circuits need to be separated. wouldn't use multiple parallel step downs after one 24v power supply do that job?

Originally Posted by ms660

why not use the existing supplies?

two reasons:
1: I broke it
2: It's ginormous

[ms660]

Connect the brown that's connected to CNS102 to ground.

You need 15 volts +ve and 15 volts -ve with respect to ground.

You also need approx. 15.8 volts +ve with respect to ground (16 volts would be ok)

You also need 24 volts +ve with respect to ground.

Those supplies will have to deliver the current that's required, whatever that may be.

Lawrence.

[knorxou]

Originally Posted by ms660

Connect the brown that's connected to CNS102 to ground.

You need 15 volts +ve and 15 volts -ve with respect to ground.

You also need approx. 15.8 volts +ve with respect to ground (16 volts would be ok)

You also need 24 volts +ve with respect to ground.

Those supplies will have to deliver the current that's required, whatever that may be.

Lawrence.

thanks for being so thorough.
Just to make sure I'm not doing anything stupid. Couldn't I just use a 24v power brick plus three of these to get the other voltages?

Also I thought I had to be exact with the 15.8v as it leads to the power supply for the servos. Or will that always give them a stable voltage?

[ms660]

I think the best way would be to repair the existing power supply.

Lawrence.

[knorxou]

Originally Posted by ms660

I think the best way would be to repair the existing power supply.

Lawrence.

That's not a very helpful response.
How would it be better for me with incomplete understanding of electronics to tinker with some broken high voltage equipment instead of using out of the box working solutions?
It also goes completely against the premise of my question. I don't want to run the record player in its original configuration. The original power block is a huge transformer connected to an even bigger board that is also hardwired to the amplifier and all kind of stuff. I don't need all that dangling next to it.

Look if you don't feel like going into all these details I understand I've been asking a lot of very basic questions and you're here on your free time I get it.

[ms660]

Originally Posted by knorxou

That's not a very helpful response.
How would it be better for me with incomplete understanding of electronics to tinker with some broken high voltage equipment instead of using out of the box working solutions?
It also goes completely against the premise of my question. I don't want to run the record player in its original configuration. The original power block is a huge transformer connected to an even bigger board that is also hardwired to the amplifier and all kind of stuff. I don't need all that dangling next to it.

Look if you don't feel like going into all these details I understand I've been asking a lot of very basic questions and you're here on your free time I get it.

I've already said what supply voltages are needed, it's up to you where you get them from but be aware that you will need a separate winding for the 15 volt split rail supply.

The link I posted shows the set up for a split rail supply, it's important to note that the transformer secondary is center tapped just like the one in the Sharp power supply, you can either use a transformer with a center tapped secondary or a transformer that has two identical secondary specifications, with the latter the two windings should be connected in series, that connection point will be, in effect, the center tap.

Regarding the 15.8 volt supply, 15.8 volts is the voltage quoted in the schematic but in the circuit description it's quoted as 16 volts, if you follow that on the schematic you will see that it's regulated down to a lower voltage (approx. 9 volts) for the motor supply.

The 15.8/16 volts and the 24 volts needs to come from a separate winding or transformer than that used for the split rail supply.

Lawrence.

[Lloyd 1985]

Just a thought, the original mains transformer would be worth testing out of circuit, if you can disconnect it’s secondaries, then connect the primary to mains via a lamp limiter, you could see if it’s ok, if the lamp in the limiter glows dimly or not at all, then the transformer is probably ok, if it lights up brightly the transformer is probably toast! If it looks ok, you could then measure the outputs of the secondaries to find which one is which, and that’s then one part you don’t have to try and source, and we already know will be up to the job. Then all it would need is some rectifiers, and some suitable voltage regulators, some of those little Chinese adjustable ones would probably do it.

Regards
Lloyd