Fender 5E8-A choke mod

[Tweedguy]

First, I want to thank everyone who replied to this post, your comments and insight have been very valuable.

My first question is what are the specs on your choke? Most chokes sold for Fender amps have too much resistance to be used before the OT connection.

I got the specs on the choke used to build my 5E8-A Twin. It's made by Mercury Magnetics, this is what they sent me:

"The FC-TTWIN is approximately 60 ohms, 150 ma, and 3.5 H. These are approximate. Also, the originals in Fenders varied. We chose this one from an original for its tone."

The interesting thing is, they offer this choke for the High-power 5F8-A and the Low-power 5E8-A which have the choke placed in two diferent locations. Could this choke be ideal in both amps? They clone these from an original but I don't know which amp this choke came out of. Can anyone tell by the specs?

[Ears]

Could this choke be ideal in both amps?

It depends on how you define ideal.
Where it can go is limited by its ratings. 150mA means it can be easily used in both amp designs as a ripple-filter when placed post the centre tap node (i.e. for screen and preamp supply). But looking at GEC specs two 6l6s in push pull at full power might be estimated to pull at least that amount at about 400v plate and screen, depending on the chosen load. So it is unlikely that 4 tubes of 5f8 will allow this choke to be safely used BEFORE the OT in the 5f8.
When the choke doesn't carry the plate current its current rating can be far lower. Look at the current specs for 5881 or 6l6 in Class AB p-p. IMO, from a book read point of view, this choke is probably overrated for current for placement just as a screen/preamp supply filter. Ideally one with higher inductance and lower current ratings will do a better job in regulating and smoothing the screen and preamp supply and keeping things quiet. That doesn't mean this is neccessary inadequate for smoothing the screen supply. But you don't need a 150 mA choke when screens and preamp are probably pulling less than 50mA, otoh you certainly won't melt the choke. You WILL need the 150mA rating to use this choke for output tube anode supply as in the 5e8 design.
But don't forget that the plate supply will reject/cancel a great deal of power supply noise. Due to three factors: 1) amplifier topology - balanced tubes and transformer inherently cancel supply noise; 2) the plate current of tetrodes and pentodes is largely independent of plate voltage; 3) inductance of primary winding in OT will also help a little to buck the hum.
I'm replying purely from an engineering point of view, members with vastly more practical experience in tone matters may have more to say, such as Loudthud in his observation that some players actually miss the supply noise if it is absent.

They clone these from an original but I don't know which amp this choke came out of. Can anyone tell by the specs?

As it appears overated for the 5f8 I'd pick the 5e8. But to hazard a guess Fender may have used them in both simply because they had them in stock.