Morning everyone.
With your help I’ve succeeded in getting the Marantz 1060 running but with an issue !
Background: I received the amp with a dead right hand side power amp channel. Looks like a power transistor had shorted to base and took every transistor except H702. The 2 x 1N60p diodes also bit the dust. So to this end, the boards been re-capped and every transistor carefully replaced with suitable equivalents carefully chosen with the help of some very decent and knowledgeable members on here. New pots have also been added.
However, now I’m tuning the thing up. Bias can be set without issue, but when attempting to set the symmetrical clipping there is a problem. I read that a good starting point is 50% of the main cap voltage across the big coupling capacitors then go in with the scope to tweak. I’ve got 71v at the big cap and when I go anywhere near 35.5v , i.e. over say 33v, when I increase then decrease the volume the voltage at thie coupling cap runs off to around 50v + causing crossover distortion at lower levels. Im using 1khz sine wave and an 8 ohm dummy load.
I can get it to stabilise with the bottom waveform clipping 1st at around 32.5v.
any ideas, anything I'm doing wrong?
Cheers, Jools
With your help I’ve succeeded in getting the Marantz 1060 running but with an issue !
Background: I received the amp with a dead right hand side power amp channel. Looks like a power transistor had shorted to base and took every transistor except H702. The 2 x 1N60p diodes also bit the dust. So to this end, the boards been re-capped and every transistor carefully replaced with suitable equivalents carefully chosen with the help of some very decent and knowledgeable members on here. New pots have also been added.
However, now I’m tuning the thing up. Bias can be set without issue, but when attempting to set the symmetrical clipping there is a problem. I read that a good starting point is 50% of the main cap voltage across the big coupling capacitors then go in with the scope to tweak. I’ve got 71v at the big cap and when I go anywhere near 35.5v , i.e. over say 33v, when I increase then decrease the volume the voltage at thie coupling cap runs off to around 50v + causing crossover distortion at lower levels. Im using 1khz sine wave and an 8 ohm dummy load.
I can get it to stabilise with the bottom waveform clipping 1st at around 32.5v.
any ideas, anything I'm doing wrong?
Cheers, Jools
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Got to the bottom of this. The 2 clipping diodes 1N60 diodes I originally replaced with eBay cheapo specials. Turned out these where causing the symmetrical clipping problem. Now replaced with some original and genuine Toshiba 1N60. Amps set up and sounds amazing
