Power supply unknow values Technics SA-GX 470

rodrigostere

New Member
Hello !!! I try to fix a old Technics SA-GX 470, no power up , US model but I cant find a service manual
(120 volts AC) , I am located outside U.S.A , any help will be appreciated !!!
I need voltages of secondary coil (AC). what I get , please look.
Thanks


foto 3.jpg foto 4.jpg
 
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The secondary transformer voltages in your pic looks ok. Please note that the secondary voltages
will be the same, regardless of the primary/mains voltage. The amp may be in protection mode
so it does not respond to power ON.
 
Please ensure the amps voltage setting matches the mains AC voltage.
Heat in standby mode is a bad sign, the amp is doing nothing, simply waiting
for activation via the remote. Please investigate the issue of heat in standby.
 
Thanks for reply , well this receiver is a U.S. model (120 volts , 60 Hz) but somebody re coil (or built a new primary coil) for 220 volts operation , I agree with you Heat in standby mode is a bad sign. I try to measure power consumtion at standby mode.
 
rewinding a transformer from 120V 60Hz to 220V 50Hz, if not done properly and calculated carefully, can result in a transformer heating and humming without any load, what could be your case. So, to me , 1st suspect is the re-winding work. Try the transformer alone, disconnected from the amp, just the primary to the 220V line. If it heats up, the winding is wrong.

I know this because we have 220V here, and I've done those conversions several times, with 2 different techs teaching me about the 50-60Hz issue, and trial-error in some cases, trying different wire diameter and number of turns in a simulation software, until find a transformer that match the Ampere, Watt, Voltage and Physical size of the original.
 
Elnaldo many thanks for the information. Nuevamente muchisimas gracias desde el otro lado de la cordillera de los Andes.
 
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