24-12-2024, 10:13 AM
As far as tant bead capacitors go, it is all to do with headroom. Back in the day, when I was designing equipment, I used lots of tantalum bead caps on the power rails. The data book said to use 6V parts on 5V rails and 16V parts on +/-15V rails. They made those voltage ratings at common rails +1V for that reason.
If any of my designs is still in use (and this was mil-spec gear) I can absolutely guarantee those caps will be failing short circuit now, after 40-odd years.
Provided that you use capacitors with enough headroom >>1V I suspect they will be reliable enough. So 10V rating on 5V rails and 20-25V on 15V rails. I do not know what voltage rating was used on the £25k phono stage.
I think it is telling that Tektronix went from using immolating tants to electrolytics in later production. As an example I have several 7A26 dual trace vertical amps, some with tants and others with aluminium electrolytics, fitted from new. But they followed the rail +1V for their tants. And astonishingly a 50V tant bead on the 50V rail. No prize for what happens to that part.
Craig
If any of my designs is still in use (and this was mil-spec gear) I can absolutely guarantee those caps will be failing short circuit now, after 40-odd years.
Provided that you use capacitors with enough headroom >>1V I suspect they will be reliable enough. So 10V rating on 5V rails and 20-25V on 15V rails. I do not know what voltage rating was used on the £25k phono stage.
I think it is telling that Tektronix went from using immolating tants to electrolytics in later production. As an example I have several 7A26 dual trace vertical amps, some with tants and others with aluminium electrolytics, fitted from new. But they followed the rail +1V for their tants. And astonishingly a 50V tant bead on the 50V rail. No prize for what happens to that part.
Craig
