All Choked Up

[NTBluesGuitar]

I upgraded the choke on my HRDlx-5E5A today to see what affect it would have moving the OT CT to the screens instead of after the choke in the previous version.

Traded JAM a reverb tank (it's on its way soon!), for his spare choke from the Weber 5E7 kit he worked his Bassman-in-Bandmaster build from. Let's all give him a round of applause for his generosity...Many thanks, JAM!

Here's the HRDlx-5E5A as it was:



Here are the chokes side-by-side:







Here's the finished setup:





Initial readings show the plate voltage down to 344V, and a cathode voltage of 120mV to get me to 69% max plate dissipation. I'll play on it some and report back my findings.

B+ is at 361V.

The HRD choke is going into my BFVV project since it's more suited to that build than a tweed anyway.

[JAM]

Everytime I see that choke I'm amazed how big it is. Looks like it's getting good use NT!. What voltage do you have on the screens? It should be higher now than the plates. I bet you can now bias a little colder and still retain a good "Tweed" tone.

[NTBluesGuitar]

Ah...didn't measure the screens. I'll do that soon.

I did play a bit and notice a slightly better feel to the amp. Just a bit more control over the sounds available based on how the guitar is touched. I could also hear more definition between fixed and cathode bias for sure, and it seems that the different Strat pickup combinations are more defined.

Nothing really different sonically, but a slight improvement. At the very least, the iron is configured as a traditional tweed's iron should be.

Again, thanks, Joe. This turned out to be much easier than I thought, given the space I was working with. I'll get some screen voltages up soon.

[JAM]

Hey, your welcome. I'm glad it's getting used the way the 5E5-A was originally configured.

[NTBluesGuitar]

Okay, grabbed some readings, and as you said, the screens are at 351V while the plates are at 345V.

[ziess]

Just got your email.

That's a damn big bit of iron! Either that or the other transformers are tiny.
Funny, the choke that came with my 5F6-A kit was a W022699 general purpose model. All the pictures I've seen of original Bassmen have a similar sized choke to the one I'm using.
The choke listed for the 5E7/5E5/5F4 is the larger one like yours.
I assume the switch is related to the amount of capacitance in the first filter stage which is higher in the later 5F6-A than the earlier Bandmaster/Pro/Super.
JAM, did you try that choke in your 5F6/5E7?

Tommy.

[JAM]

The choke listed for the 5E7/5E5/5F4 is the larger one like yours.
I assume the switch is related to the amount of capacitance in the first filter stage which is higher in the later 5F6-A than the earlier Bandmaster/Pro/Super.

Because it's located before the center tap of the output transformer, it has to have a current rating large enough to handle the plate current too, while the 5F6-A Bassman (and all later Fenders like the AB-763s) have the choke after the CT (and the plates) so it doesn't have to have as large a current rating.

JAM, did you try that choke in your 5F6/5E7?

No, I installed it initially (but not wired in), but since the main reason I went with a Bandmaster Cab (3X10s and Bandmaster OT) was to get some of the weight down, I ordered and used the smaller 22699.

[JAM]

Here's the two chokes side by side for comparison

http://members.canonphotogroup.com/joem/New%20Choke.jpg