It’s an SL1200 Power Struggle

…So since the “export” power transformer has just recently dried up in Japan, I wanted to figure the most economical and electrically sound and safe way to convert 120V AC Technics SL1200 turntables to 240V AC with the least fuss whilst still leaving them double insulated as per the original specification and Government regulations.

TestingI set one up and monitored its current draw under various conditions and the results were interesting. The original transformer provided 32VAC on its secondary at idle BUT as the current demand increased to the maximum the secondary voltage dropped to 27VAC..

Here’s the results for interest’s sake…
Primary Volts = 242VAC – Secondary 32VAC
AC current demand Idling – 350mA
Idling with lamp on – 430mA
Rotating at a constant speed with lamp on – 450mA
Stalling platter with lamp on – 955mA
Spinning backwards with lamp on – 1030mA
At full peak current demand AC drops to 27VAC

Not really an issue as the DC voltage required is 20V DC BUT I considered the peak current demands the motor circuit required during spin backs and stalling and observed a slight loss of recovery torque due to the poor regulation of the standard power supply compared to my test bench power supply.

Transformer detailI have found a modern toroidal power transformer that not only has a minimal electric field so as not to interfere with the close proximity of the motor circuit’s feedback windings but gave a slightly quicker recovery time as a power supply.

Ultimately I can convert export SL1200 to 240VAC and make them have better recovery from stalled at a very reasonable price and they look good.

Word!

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