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TI-99/4A rolling white bars and a low pitch humming on power up

EPOHouston

Experienced Member
Joined
Jan 10, 2020
Messages
59
Location
Houston, Texas
I know the external power supply is good, and I know the RF modulator is in good shape. The unit was in bad shape, so I wouldn't be shocked if there's multiple faults here... I don't know much about fixing the TI 99, so I was wondering if someone could help me diagnose it. Thanks!!
 

Ksarul

Experienced Member
Joined
Apr 30, 2007
Messages
450
Note: the external power supply just steps the AC voltage down to something the console's internal power supply can handle to create the DC voltages the console needs (+5, -5, and +12 volts). The internal supply is under the cartridge slot.
 
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