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01-07-2019, 02:00 AM
Hi Jmcd
makinrose's point about the mains compatibility stands for most "vintage" gear like old hand-wired Traynors, Tweed / black-face - silver-face Fender amps, etc. inasmuch as those amps have PTs designed for 115Vac or 117Vac mains. Today the mains is more typically 120-125Vac, so we see a bump in the internal voltages by a similar factor.
Traynor uses Hammond PTs which were rated for 11Vac. If we suppose the applied mains is 125V then the voltages will all be higher by a factor of 125 / 115 = 1.087. So an expected 420Vdc becomes 456Vdc.
I spec my dual-range primaries as 120V and 240V, and the universals as 100V, 120V, 240V. I spec the heats to be 6V and 12V and leave off the fraction as all of this combines to keep the heater voltages within their ratings, rarely being higher than spec.
With new caps in place, I don't believe the 457Vdc is an issue on a (non-IC) electrolytic.
Of course, to contradict myself, I did go to 500V caps when a new batch of PTs resulted in 465V. Jmcd's 7V over is just 1.6% and my 15V over is still only 3.3%, but my amp might end up in India or some other place where mains voltages are wildly erratic, ie.e. 260Vac is not uncommon and this represents an over-voltage of 8.3%.
makinrose's point about the mains compatibility stands for most "vintage" gear like old hand-wired Traynors, Tweed / black-face - silver-face Fender amps, etc. inasmuch as those amps have PTs designed for 115Vac or 117Vac mains. Today the mains is more typically 120-125Vac, so we see a bump in the internal voltages by a similar factor.
Traynor uses Hammond PTs which were rated for 11Vac. If we suppose the applied mains is 125V then the voltages will all be higher by a factor of 125 / 115 = 1.087. So an expected 420Vdc becomes 456Vdc.
I spec my dual-range primaries as 120V and 240V, and the universals as 100V, 120V, 240V. I spec the heats to be 6V and 12V and leave off the fraction as all of this combines to keep the heater voltages within their ratings, rarely being higher than spec.
With new caps in place, I don't believe the 457Vdc is an issue on a (non-IC) electrolytic.
Of course, to contradict myself, I did go to 500V caps when a new batch of PTs resulted in 465V. Jmcd's 7V over is just 1.6% and my 15V over is still only 3.3%, but my amp might end up in India or some other place where mains voltages are wildly erratic, ie.e. 260Vac is not uncommon and this represents an over-voltage of 8.3%.
