Hello again,
I started restoring a marantz 1122dc with a blown output stage and someone's attempts to repair it. The outputs had been replaced by BD911 and BD912 which didn't seem a good idea as they are way slower than the original nec transistors. I have been advised to replaced the 2 pairs per channel with one single more powerful pair which I did (2sa1943+2sc5200). But now I think I might have bitten of more than I can chew.
I can't afford getting back to the original devices and would like to try and make it work with the ones I have now but I heard that I need to redesign the VI limiter in order to protect the outputs without the protection kicking in to soon. This is the schematics for the main amp with in red the emitter resistors I removed with the second pair of outputs. Is there a simple way to recalculate the values of the different resistors in the limiter or should the existing circuit actually work fine here ? I will get some new emitter resistors of 6 or more W for the remaining pairs.
Any help would be welcome
I started restoring a marantz 1122dc with a blown output stage and someone's attempts to repair it. The outputs had been replaced by BD911 and BD912 which didn't seem a good idea as they are way slower than the original nec transistors. I have been advised to replaced the 2 pairs per channel with one single more powerful pair which I did (2sa1943+2sc5200). But now I think I might have bitten of more than I can chew.
I can't afford getting back to the original devices and would like to try and make it work with the ones I have now but I heard that I need to redesign the VI limiter in order to protect the outputs without the protection kicking in to soon. This is the schematics for the main amp with in red the emitter resistors I removed with the second pair of outputs. Is there a simple way to recalculate the values of the different resistors in the limiter or should the existing circuit actually work fine here ? I will get some new emitter resistors of 6 or more W for the remaining pairs.
Any help would be welcome