The current capacity of the Champ / VChamp / Princeton / PR / Tweed Deluxe power transformer's HV tap is 70mA.
(IIRC the code for this PT is 125P1B).
Now in the case of a Princeton Reverb w/ 2 6V6s and 4 12AX7s, the max current draw to the HV tap is:
say we have an average 240V on each 12AX7 plate and 380V on each 6V6 plate.
The max plate dissipation is 2.2W for a 12AX7 and 14W for a 6V6.
Therefore we have:
- 2.2W / 250V = 9mA for each 12AX7
Total for 4 12AX7s is 4*9= 36mA
- 14W / 380V = 37mA for each 6V6
Total for 2 6V6s is 2*36= 74mA
Total dissipation for all the tubes is in the 36+74= 110mA ballpark.
Now let's say the circuit is designed to work the tubes at 70% of max plate dissipation.
The total plate dissipation (for all the tubes) would be 110*0.7= 77mA.
Since the PT HV tap feeds 70mA at max, it looks like the PT is undersized (tubes plate dissipation exceeds what the PT can feed).
Now, the questions:
What do you experts think regarding the dimmensionning of that PT?
How comes all those PRs have withstood the test of time w/ such a tiny PT?
Is it safe to run a Princeton Reverb full tilt for hours long gigs w/ the original PT?
Is that tiny PT responsible for the saggy tone (especially when cranking a Tweed Deluxe and hitting a big power chord on the low notes)?
Thanks!!!
Victor
(IIRC the code for this PT is 125P1B).
Now in the case of a Princeton Reverb w/ 2 6V6s and 4 12AX7s, the max current draw to the HV tap is:
say we have an average 240V on each 12AX7 plate and 380V on each 6V6 plate.
The max plate dissipation is 2.2W for a 12AX7 and 14W for a 6V6.
Therefore we have:
- 2.2W / 250V = 9mA for each 12AX7
Total for 4 12AX7s is 4*9= 36mA
- 14W / 380V = 37mA for each 6V6
Total for 2 6V6s is 2*36= 74mA
Total dissipation for all the tubes is in the 36+74= 110mA ballpark.
Now let's say the circuit is designed to work the tubes at 70% of max plate dissipation.
The total plate dissipation (for all the tubes) would be 110*0.7= 77mA.
Since the PT HV tap feeds 70mA at max, it looks like the PT is undersized (tubes plate dissipation exceeds what the PT can feed).
Now, the questions:
What do you experts think regarding the dimmensionning of that PT?
How comes all those PRs have withstood the test of time w/ such a tiny PT?
Is it safe to run a Princeton Reverb full tilt for hours long gigs w/ the original PT?
Is that tiny PT responsible for the saggy tone (especially when cranking a Tweed Deluxe and hitting a big power chord on the low notes)?
Thanks!!!
Victor
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