Turntable DC Supply 24V Very Complex/Strange

[ridikas]

Need help to double check this schematic so no boo boos happen. It's rather complex and somewhat strange. It will be powering a turntable's motor. Thanks guys.

The unmarked capacitor is 4.7uF electrolytic.

 

[natad123]

half wave doubler + current amp? just a guess.

 

[Lojzek]

Wouldn't it be better to build a simple series pass regulator
with a zener diode as a voltage reference to a bjt? How many
amps does your motor need to get started ?

 

[phaselag]

It is a simple pass regulator. The driver emitter current is added to the output, which slightly adds to efficiency.

paul

 

[xrk971]

Wouldn't a shunt regulator have better performance noise wise?

An externally hosted image should be here but it was not working when we last tested it.

 

[Mooly]

You'll struggle to get a clean and regulated 24 volt rail from an input of around 25 volts DC (18vac * 1.414) using a linear regulator.

This looks more like an active ripple filter with zener limiter that stops the output going above 24 volts or should the input happen to be a bit higher.

 

[Ketje]

Need help to double check this schematic so no boo boos happen. It's rather complex and somewhat strange. It will be powering a turntable's motor. Thanks guys.

The unmarked capacitor is 4.7uF electrolytic.

And if you draw it like this ?
Just a compementary Darlington !
Mona

 

[Mark Johnson]

It's the zener + emitter follower "voltage regulator" shown on Wikipedia

with a Sziklai-pair implementing the emitter follower

_

 

[Mooly]

Except the input voltage isn't high enough to get it to regulate well......

Just calculate the zener current and available base current to the NPN device. Ultimately though, I suspect non of this matters for its intended application as a motor PSU.

 

[llwhtt]

Since there is only polarity needed what about removing the center tap ground. That would give you 18VAC instead of 9VAC. Is the 24VDC output grounded?

Craig

 

[Lojzek]

The transformer secondary should be wired for voltage doubling
and then drop 24 V on Zener and the rest (24V) on a resistor that
defines the Zener holding current with the load (motor) attached.

 

[llwhtt]

My post should said since only "one" polarity is needed.........oops.

Craig