Helsing
Well-known member
[quote author="NewYorkDave"]Also, a second reverse-biased diode is sometimes seen between the regulated supply and ground for reverse-polarity protection. :green:[/quote]
Ive got a DOA that was latching up if I turned the amplifier on and off at a certain time interval. At power down, the positive rail of the DOA would sink to 0 volts and then go to about -.7 volts. Wait about 20 more seconds and the problem works it self out and the rail goes back to zero. There is a small audio click when it works itself loose. Im using a 7818 here. Confusing I know.
The problem is that if I power the amp back up during this negative period, the amp or the reg(?) latches up, positive sticks at -.700v, the negative rail is at 18v and the opamp output is at -15v. Slight hiss. No audio.
Theres something wrong with the DOA design, since I tested the PSU with several other DOAs and they worked fine.
My real question lies in my psu fix. I did what Dave is talking about about. I added reverse biased 1n4007s from the rails to ground and it solved this problem. The opamp still exhbits the strange behavior but the zeners overcome the latchup and the positive rail pops back to 18volt.
Is a 1n4007 a good choice? Might a germanium stop the negative cyle from happening at all?
Helsing
Ive got a DOA that was latching up if I turned the amplifier on and off at a certain time interval. At power down, the positive rail of the DOA would sink to 0 volts and then go to about -.7 volts. Wait about 20 more seconds and the problem works it self out and the rail goes back to zero. There is a small audio click when it works itself loose. Im using a 7818 here. Confusing I know.
The problem is that if I power the amp back up during this negative period, the amp or the reg(?) latches up, positive sticks at -.700v, the negative rail is at 18v and the opamp output is at -15v. Slight hiss. No audio.
Theres something wrong with the DOA design, since I tested the PSU with several other DOAs and they worked fine.
My real question lies in my psu fix. I did what Dave is talking about about. I added reverse biased 1n4007s from the rails to ground and it solved this problem. The opamp still exhbits the strange behavior but the zeners overcome the latchup and the positive rail pops back to 18volt.
Is a 1n4007 a good choice? Might a germanium stop the negative cyle from happening at all?
Helsing
