Hello,
I'm trying to replace the wall-wart transformer of my Moog Rogue synthesizer with a built-in transformer.
The original transformer specs according to the schematics are 24V AC, which is then rectified by an 7812 and 7912 to provide +12 and -12V.
The Moog's power is rated at 6W in the service notes and needs, according to the same notes, 200 mA. The actual wall wart original Moog transformer is rated 20V, 500 mA, so it supplies 10VA and since the Moog is rated at 6W, it wil draw some 300 mA max (20V*300mA = 6W), correct?
Anyway, my main question is this: I happen to have a 12VAC, 1A transformer; would this be enough?
My reasoning: 12VAC RMS = 16.97 VAC peak. 0.7V drops over the 1N4004 diode (in positive halve of the cyle), so 16.27Vpeak is fed into the 7812. The 7812 has according to the datasheet a typical dropout voltage of 2.5V, so it needs at least 14.5V (peak, I suppose?) to deliver a stable 12V at the output. If I feed it with 16.27V, that should be ok, no?
Same for the negative half of the cycle; 0.7V drops over the other 1N4004 diode, so I'm feeding -16.27V in the 7912.
As for the amperage, my transformer would be able to supply 1A and since the Moog only needs 300 (or, by a safer margin, 500), that should also suffice? 12V*500mA = 6W?
Is this correct or am I confusing things or overlooking something?
I'm trying to replace the wall-wart transformer of my Moog Rogue synthesizer with a built-in transformer.
The original transformer specs according to the schematics are 24V AC, which is then rectified by an 7812 and 7912 to provide +12 and -12V.
The Moog's power is rated at 6W in the service notes and needs, according to the same notes, 200 mA. The actual wall wart original Moog transformer is rated 20V, 500 mA, so it supplies 10VA and since the Moog is rated at 6W, it wil draw some 300 mA max (20V*300mA = 6W), correct?
Anyway, my main question is this: I happen to have a 12VAC, 1A transformer; would this be enough?
My reasoning: 12VAC RMS = 16.97 VAC peak. 0.7V drops over the 1N4004 diode (in positive halve of the cyle), so 16.27Vpeak is fed into the 7812. The 7812 has according to the datasheet a typical dropout voltage of 2.5V, so it needs at least 14.5V (peak, I suppose?) to deliver a stable 12V at the output. If I feed it with 16.27V, that should be ok, no?
Same for the negative half of the cycle; 0.7V drops over the other 1N4004 diode, so I'm feeding -16.27V in the 7912.
As for the amperage, my transformer would be able to supply 1A and since the Moog only needs 300 (or, by a safer margin, 500), that should also suffice? 12V*500mA = 6W?
Is this correct or am I confusing things or overlooking something?
Attachments
-
81.1 KB Views: 60