Hello Guys, I hope you are fine. I upload this diagram concerning to an Class H American Audio amplifier which does not activate the high rail (+/-125V) to the output stage. This amplifier is supplied with +/-63V for low voltage and +/- 125V for high voltage but the man who is checking it out, said that when the volume is turned all way up, five volts are only given to the final stage for both rail. The amplifier sounds good but the output power is lesser than it can deliver. What test do you suggest for this amplifier? Thanks beforehand.
If you ask these questions , you might NOT want to attempt repair of this amp.
I don't mean this in a bad way , but would feel bad if somebody got hurt.
OS
I don't mean this in a bad way , but would feel bad if somebody got hurt.
OS
With all due respect, this design of amplifier, has a complicated class H drive. As mentioned, if you need to ask these questions, get it serviced by a qualified electronics engineer.
Excuse me for this thread. It is not my amplifier, it is not my repair. But you are right because I posted a thread to help someone whom I don't even know and I wanted to search about this circuit that drew my atenttion and get your opinions. And the same time I wanted to help him but no problem, thank for replying.
We only said this because 65V rails have really hurt. 125V - I would even be scared(slightly).
If the amp "sounds nice" without "overdrive". Lower rails must be OK.
At 5 V , the amp would not work at all. Upper rails (125v) , and that cool class H current mirror follower/or upper rail diodes ... must be defective.
OS
If the amp "sounds nice" without "overdrive". Lower rails must be OK.
At 5 V , the amp would not work at all. Upper rails (125v) , and that cool class H current mirror follower/or upper rail diodes ... must be defective.
OS
Hi Ostripper, I think I wrote something wrong in my first message. I meant the low voltage (+/-LV) goes up to +/-70V maximum when turning the volume pot all way up. The high voltage (+/-HV) is not being switched to the overdrive. Thank you for your answer and opinion. I will send a message to the guy is repairing this amplifier. Any opinion is also of great help to me because I want to study this amplifier. Thanks.
The rails aren’t switched by the volume pot. they’re switched by the audio signal. You need an audio signal of >65Vpk to switch on the 125V rail.
I’ll echo what everyone else has said. If your level of understanding is such that this isn’t obvious, you shouldn’t be messing with this amp.
I’ll echo what everyone else has said. If your level of understanding is such that this isn’t obvious, you shouldn’t be messing with this amp.
The reason may be simple, but difficult to find. The amplifier is complex. Has a dangerous voltage. We need a qualified repairman.