The repair of things like this with a fault as described means that you have to tread carefully - and not simply 'dive in', as is often the temptation, fuelled by enthusiasm.
The one and critical factor that determines the feasibility of a repair of this amp. is to determine if a replacement transformer - and nothing else - will successfully repair it. In my case, I would do the following.
I'd try to find a suitable mains-powered PSU (or two) that will deliver ±45 volts at about 1 amp per output. (I am fortunate enough to have a reasonable stock of test equipment). I'd use that (or those) to by-pass the on-board rectifier in order to test the rest of the PSU + amplifier. If I couldn't find such kit, I know I can lay my hands on a couple of 30 v. 1 amp. (secondary) mains transformers, and by connecting those windings appropriately, make a temporary 'out-of-the-case' lash-up to test the amp. + rectifier + PSU. In other words, a temporary transformer substitute for basic testing.
Either route should enable me to determine if the O/P transistors are O.K. and test for any other major faults: that is all; it's simple a 'go' / 'no - go'; 'do I / don't I' test. I would not be interested in 'performance criteria' at this stage.
At that point, I could then make an informed decision - then talk to the owner of the item.
HTH,
Al. / April 19 //
The one and critical factor that determines the feasibility of a repair of this amp. is to determine if a replacement transformer - and nothing else - will successfully repair it. In my case, I would do the following.
I'd try to find a suitable mains-powered PSU (or two) that will deliver ±45 volts at about 1 amp per output. (I am fortunate enough to have a reasonable stock of test equipment). I'd use that (or those) to by-pass the on-board rectifier in order to test the rest of the PSU + amplifier. If I couldn't find such kit, I know I can lay my hands on a couple of 30 v. 1 amp. (secondary) mains transformers, and by connecting those windings appropriately, make a temporary 'out-of-the-case' lash-up to test the amp. + rectifier + PSU. In other words, a temporary transformer substitute for basic testing.
Either route should enable me to determine if the O/P transistors are O.K. and test for any other major faults: that is all; it's simple a 'go' / 'no - go'; 'do I / don't I' test. I would not be interested in 'performance criteria' at this stage.
At that point, I could then make an informed decision - then talk to the owner of the item.
HTH,
Al. / April 19 //
