Found another issue with this driver board I’m working on. The Marantz 2330b drivers (Q709,Q710 and Q739,Q740) are faulty. In one channel the 2SA913 is measuring with a gain of 2 and the 2SC1913 is measuring with a gain of 0. One option is to go with MJE15032 and MJE15033 and roll with it. Though some are not big fans of this option due to the fact that the MJE devices are much slower at 30 MHz vs the originals which were quite fast at 120 MHz.
There is a thread here https://audiokarma.org/forums/index.php?threads/is-there-a-sa-7800-recap-list.795519/#post-11010875
where markthefixer discusses where he wish he had stocked up on some faster parts when they were available, since they are no longer available he was toying with the idea of swapping in some KSA1220/KSC2690. They’re much closer at 175 MHz.
I was curious if you got anywhere with that Mark and what your conclusion was. Anyone else that wants to give their thoughts please do. Specs look to be fairly close with some being better for the KSA/KSC devices and some being better for the 2SA/2SC.
For the PNP it seems the specs for the TO126 seem to be better in all cases except Vcb and Vce which won’t matter in this case. Well and the fact that it’s in a smaller case and can’t dissipate heat as quickly.
For the NPN it looks like the only issue is Ic, the original being rated for an additional 300 mA.
As Mark mentioned there must be adequate heat sinking and in this case there is.
I’m guessing that in the case of the 2230b that I’d be asking way too much of the smaller devices, but if someone thinks I’m wrong please say so. Basically I’d like to see if maybe Mark had any luck with these swaps in anything or if he gave up on the idea as it didn’t work well and also to get the thoughts of others on this idea. If I should just use the MJE devices then I guess a 2330 with slower drivers is better than a 2330 that doesn’t work at all.
Dan
There is a thread here https://audiokarma.org/forums/index.php?threads/is-there-a-sa-7800-recap-list.795519/#post-11010875
where markthefixer discusses where he wish he had stocked up on some faster parts when they were available, since they are no longer available he was toying with the idea of swapping in some KSA1220/KSC2690. They’re much closer at 175 MHz.
I was curious if you got anywhere with that Mark and what your conclusion was. Anyone else that wants to give their thoughts please do. Specs look to be fairly close with some being better for the KSA/KSC devices and some being better for the 2SA/2SC.
For the PNP it seems the specs for the TO126 seem to be better in all cases except Vcb and Vce which won’t matter in this case. Well and the fact that it’s in a smaller case and can’t dissipate heat as quickly.
For the NPN it looks like the only issue is Ic, the original being rated for an additional 300 mA.
As Mark mentioned there must be adequate heat sinking and in this case there is.
I’m guessing that in the case of the 2230b that I’d be asking way too much of the smaller devices, but if someone thinks I’m wrong please say so. Basically I’d like to see if maybe Mark had any luck with these swaps in anything or if he gave up on the idea as it didn’t work well and also to get the thoughts of others on this idea. If I should just use the MJE devices then I guess a 2330 with slower drivers is better than a 2330 that doesn’t work at all.
Dan
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