- High Voltage OP amp - 1 Update
| Trevor Wilson <trevor@rageaudio.com.au>: Sep 05 06:10AM +1000 On 4/09/2022 10:28 am, Phil Allison wrote: >> I am servicing a power amplifier which uses a dual, 8 pin DIP OP amp. >> Unfortunately, the rail Volts on the OP amp (LF353) is +/- 22 Volts. > ** That is a mistake, all versions of the Sumo 9 used nominal +/-20V rails fed from series regs with 20V zeners. **Oops. You are correct. The negative rail is fed from a 20 Volt zener and the positive rail is fed from a series transistor, with the base tied to a 20 Volt zener, in series with a forward biased diode. >> I need a suggested replacement. > ** Which MUST be a FET input op-amp. **Yes. There is that. > **Course it is, they are meant to be 19.5V each anyway. >> They must remain at +/-22 Volts. > ** Humbug. **True enough. I had neglected to examine the schematic before I posted. According to the schem, it is +/- 20 Volts. -- This email has been checked for viruses by Avast antivirus software. www.avast.com |
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