Just scavenged the power and output xformers from a ST-70 carcass. I have a variac and a DMM, but no 'scope. How can I test them before I commit them to a new build?
Thanks, folks.
Mike
Thanks, folks.
Mike
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Bob Latino wrote:1. For the power transformer ... Connect the two BLACK wires to a 120 volt AC power source ..
Measure the AC voltage across the two RED wires > 700 - 760 VAC
Measure the AC volatge across the two GREEN wires > 6 - 7.5 volts AC
Measure the AC voltage across the two BROWN wires > 6 - 7.5 volts AC
Measure the AC voltage from the RED/BLACK wire to the RED/YELLOW wire > 55 to 60 volts AC
Measure the AC voltage from the BROWN/YELLOW to the RED/YELLOW - 3 to 4 volts AC
Measure the AC voltage from the GREEN/YELLOW to the RED/YELLOW - 3 to 4 volts AC
2. For the OUTPUT transformer ...
The primary side wires BLUE, BLUE/WHITE, RED, GREEN and GREEN/WHITE should have no continuity to ANY OF THE secondary wires YELLOW, ORANGE, BROWN, BLACK
On ethe PRIMARY side wires measuring from the RED wire to each of the other 4 wires should give a resistance of 20 ohms to maybe 150 ohms
On the SECONDARY side measuring
From BLACK to YELLOW - maybe 1 to 2 ohms
From BLACK to ORANGE - maybe 1/2 ohm to 1 ohm
From BLACK to BROWM - maybe .25 ohm to .7 ohm
Bob
tubes4hifi wrote:correction to Bob's voltages - if you measure from RED to RED you are going to get 700-750vac (make sure you have a DMM that can handle 1000vac !!!)
you should have half that much from the RED/YELLOW to each RED lead (350-375vac)