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Applying Power To Your Repaired S-38
When your service work is complete and your radio is ready for power, I strongly suggest using a line isolation transformer to help prevent an accidental shock hazard. See the first picture at the right. The transformer is 120 volts in 120 volts out and can handle about 300 watts, much more than needed here. I also suggest using a voltage variac as shown in the middle picture, if one is available. This variac is rated at 500 watts.
Another neat test fixture is shown in the bottom picture. This is the simple, old reliable fixture that provides a fuse, in this case the light bulb. Keep several light bulb sizes for different loads. A 25 watt, 40 watt and 60 watt bulb would be a good starter collection. If the light bulb lights bright, that means there many be a problem with your radio. It is normal to light bright for a second or so when you first turn your radio on. A soft glow during operation is also normal. The 25 watt bulb would be good for testing any S-38. Bulb size should be about the same or larger than the watts your radio draws.
When powering up your S-38, I suggest attaching a DC voltmeter set on at least 150 volts DC. Connect the positive (red) lead of your meter to the positive end of the 60 MFD filter capacitor and the minus (black) lead of your meter to the minus side of the same cap. As little as about 70 volts DC should make your radio begin to work. (Tune in a broadcast station). Set all controls for the broadcast band, volume at full then as needed. Full normal voltage at this point should be between 100 to 120 volts DC.
If you're using a Variac, I suggest starting at about 50 volts AC then watching for problems. If you're ok after a few minutes, then up the AC maybe 10 volts at a time while observing and listening for audio. If you get to full power with no problems showing and still can't receive, then more troubleshooting is needed. Use standard proceedures for troubleshooting AC/DC radios. BEWARE OF THE HOT CHASSIS.