Hi guys,
I am currently stumped on a couple of things I have here that are faulty.
One of them is this Bang & Olufsen amplifier.
I am getting DC on the outputs. The output transistors read OK and are not shorted - and there is a schematic included inside the unit (great idea!)
I have attached a scan of the final output stage and also the headphone socket which leads on to the speaker sockets.
I've circled the points in question in red. I was hoping someone could tell me why this is...? As you can see there is a 3000uF capacitor in series with the output to the 'phones/speakers and the circuit shows that there is 18.6volts DC on the 'other' side of it. What I am getting is that same 18.6volts on the side going to all the sockets...! On both channels.
At first I assumed both caps were shorted in some strange manner (even though my meter told me they weren't)... so I replaced them anyway. It was the same... in fact no matter what capacitor I put in there I get that 18.6 DC voltage where I shouldn't.
I even thought maybe this is how it should be (...?!?) and momentarily connected a speaker to check how it behaved... needless to say it didn't like it..!
Does anyone have any idea please, why no electrolytic capacitor seems to block DC in this particular instance...?
Cheers,
Tom
I am currently stumped on a couple of things I have here that are faulty.
One of them is this Bang & Olufsen amplifier.
I am getting DC on the outputs. The output transistors read OK and are not shorted - and there is a schematic included inside the unit (great idea!)
I have attached a scan of the final output stage and also the headphone socket which leads on to the speaker sockets.
I've circled the points in question in red. I was hoping someone could tell me why this is...? As you can see there is a 3000uF capacitor in series with the output to the 'phones/speakers and the circuit shows that there is 18.6volts DC on the 'other' side of it. What I am getting is that same 18.6volts on the side going to all the sockets...! On both channels.
At first I assumed both caps were shorted in some strange manner (even though my meter told me they weren't)... so I replaced them anyway. It was the same... in fact no matter what capacitor I put in there I get that 18.6 DC voltage where I shouldn't.
I even thought maybe this is how it should be (...?!?) and momentarily connected a speaker to check how it behaved... needless to say it didn't like it..!
Does anyone have any idea please, why no electrolytic capacitor seems to block DC in this particular instance...?
Cheers,
Tom