100v - 120v volt tranny outputs

[crunchman]

What is the difference in using the 100v or 120 v tranny outs, does this all depend on the bulb being used or does it effect the secondary output ?

[Bruce / Mission Amps]

What is the difference in using the 100v or 120 v tranny outs, does this all depend on the bulb being used or does it effect the secondary output ?

20v?
That is a +-20% change of primary voltages the PT is expecting.
If you ran the 100v tranny on 120v then all the secondary voltages would be 20% higher.
If you ran a 120v tranny at 100v then all the secondary voltages would be about 20% less.
It is a ratio.... primary in .... secondary out.

[Chuck H]

Well... The OP did say 100V or 120V "tranny outs" ??? I didn't know how to interpret this so I passed this up earlier. But...

As Bruce notes, if it's the primary we're talking about ("outs" would typically be the secondary) then 120V on a 100V primary is 20% higher and 100V on a 120V primary is 20% lower (actually 16.667% for the latter). This could probably be worked out for anode and cathode supply voltages but if this is a tube amp it can be a real problem for filament voltages that need to be within 10% of spec.

[Bruce / Mission Amps]

Yeah I think the OP meant the outs being the secondaries.
Off subject a bit:
During my extremely cheap and broke days, I ran a ton of NOS 5V6GT power tubes I found here in Denver on a 6.3vac filament line with a couple back to back 1n5308 diodes in the legs with nearly zero effect, other then the tubes sounded fabulous and were 1/4 the cost of NOS 6V6s, so when they wore out faster the 6V6s.... they just got tossed out.

[jmaf]

Yeah I think the OP meant the outs being the secondaries.
Off subject a bit:
During my extremely cheap and broke days, I ran a ton of NOS 5V6GT power tubes I found here in Denver on a 6.3vac filament line with a couple back to back 1n5308 diodes in the legs with nearly zero effect, other then the tubes sounded fabulous and were 1/4 the cost of NOS 6V6s, so when they wore out faster the 6V6s.... they just got tossed out.

I read somewhere that vintage 6v6 amps made by Fender have a big issue with the 110 to 120 V standardization in the USA? They supposedly ran on the limit of the 6V6 plate voltage and capacitor ratings and the 9% increase would break them, I don't recall exactly which. Don't know if relevant to the OP's question, and I don't remember specifics, but I thought I'd mention.

[Chuck H]

From what I've read the amp in question would be the Deluxe Reverb. It's common practice to either heat the bias until plate volts drop OR cool the bias to reduce dissapation. These two avenues depend on the specific tube and it's proclivities toward failure. Due to differences in construction some tubes will tollerate the higher current and others will tollerate the higher voltage. Of late most 6V6 tubes are better with the higher voltage. I can also tell you from first hand experience that SF models are prone to even higher plate volts than their BF counterparts. I worked on a SF Vibro Champ that had 428Vp... For a class A 6V6 amp?!? It's still working fine but I know this is one amp I'll get to see again as some point. Other Fenders are also too high with modern wall voltages (mine reads between 123VAC and 127VAC most of the time).

[crunchman]

Thanks guys, I was just trying to figure out if my NE51 was usable with the 120V primary, I'm told it will be fine, its rated at 90-105V. The PT has 100 and 110 also so I thought maybe I should use the lesser ones.Just an over-reaction on my part..........Thanks

[Diablo]

Yeah I think the OP meant the outs being the secondaries.
Off subject a bit:
During my extremely cheap and broke days, I ran a ton of NOS 5V6GT power tubes I found here in Denver on a 6.3vac filament line with a couple back to back 1n5308 diodes in the legs with nearly zero effect, other then the tubes sounded fabulous and were 1/4 the cost of NOS 6V6s, so when they wore out faster the 6V6s.... they just got tossed out.

So why did the 5V6GTs wear out faster than 6V6s? Were you burning up the heater filaments from too much voltage? How about running those 5V filaments from the heater supply for the tube rectifier? Of course then you couldn't run a tube rectifier - but you could use one of the Weber copper cap rectifiers. I've got a pile of those 5V6GTs too, and am thinking how best to use them.

[Chuck H]

I've got a pile of those 5V6GTs too, and am thinking how best to use them.

I think you answered your own question... For your next project build an amp for them with the power tube filaments fed from the 5V PT supply. You could even use a tube rectifier since there are PT's available with ample 5V capacity for an indirectly heated rectifier AND a pair of power tubes. Make the filament supply internally switchable so that when you run out of 5V6's you can flip the internal switch and power the tubes from the 6.3V supply and use 6V6's.