Hello.
I am a total novice and I need some help.
I have a hifi turntable with a 9vdc motor and a 15v input. Why it's 15 I do not know.
Without beating around the bush I want to run my turntable on 12vdc. I can explain why but it's somewhat irrelevant.
So how would I go about this? Is it as simple as changing a transformer?
Many thanks in advance for your help.
In case it's important, it's a Pro-Ject Debut Carbon Esprit with speed box (DC motor, auto speed selection)
Oh, please do explain why you want to run your turntable on 12 V DC. Let us be the judge of what is irrelevant.
Also please explain why you think the turntable motor operates on 9vdc when the
manufacturer's literature says the turntable motor is a synchronous AC motor that gets its power from the mains through a transformer and a separate 15 V DC power supply driving "an ultra precision frequency DC-driven AC generator" and provides a two-frequency drive signal to the motor? You may be a total novice, but I am totally confused as to what you want to DO and WHY you want to do it. Is the goal to replace the mains-operated 15 V DC supply with a 12 V battery?
Just FYI,
if a turntable motor operates on DC, i.e., a DC motor whether brushless or not, it would need a sophisticated feedback control system with some sort of tachometer to sense motor rotation speed for comparison with a precision frequency source. Not saying no one has ever built such a beast, but a
synchronous AC motor by design provides a rotation speed that is
exactly proportional to the frequency driving the the motor. This driving frequency is typically the power-line mains frequency (50 Hz where you live), or it is derived from a quartz crystal oscillator if you use something like the Speed Box accessory for AC operated turntable motors.
Every line-operated clock keeps perfect time because they are driven with some form of synchronous motor. The utility providing power ensures that the total
number of AC cycles provided on the mains is corrected to exactly the
right number of cycles once per day, ensuring clocks never gain or lose time over long periods. The super-sensitive ears of audiophiles may be able to detect short-term variations in power-line frequency, so there is a market for quartz crystal oscillator control of the motor driving frequency. A side benefit is the capability to slightly vary the motor rotation speed to accommodate both 33-1/3 rpm and 45 rpm. However, it is too big of a stretch to increase the motor drive frequency high enough to accommodate 78 rpm, so an auxiliary (larger) pulley is required on the motor shaft pulley that belt-drives the turntable pulley.
You
may be able to un-plug the 15 V DC power pack and substitute a 12 V DC power source without modification. I would try this first. If the motor refuses to run on the lower voltage, you will need to replace the 15 V DC mains-operated power supply with another power supply that accepts 12 V DC and produces 15 V DC.
Google is your friend here. There are plenty of DC-to-DC power supplies for sale on the Internet that operate from 12 V DC and provide 15 V DC with at least 0.8 A capability. More amperes capability is okay (the turntable will only use what it needs) but don't go overboard and get one with more than one or two amperes output capability. Perhaps
this one is appropriate to your needs.
