DIY JTM 45/100 Style Guitar Amp

[thousandshirts]

I just finished a DIY kind of job on a JTM 45/100. I put a build page up at:

http://www3.telus.net/public/wbrooke/45-100.htm

Lots of pictures, so beware if you're on dialup. The website isn't finished. I hope to add more pictures, more data, and sound clips.


A few pics:

[MrTransistorm]

Nice job!

All that braiding must have taken a while.

[thousandshirts]

Originally posted by MrTransistorm
Nice job!

All that braiding must have taken a while.

Thanks, Dave.

The braiding took a bit of doing to get the hang of. Some practice made it enjoyable. The key was learning to keep a fairly strong but equal tension on each of the wires as I went along. After I got a triple braid, I attempted the quadruple braid. After making some test braids, I did a pull test, and I must say, they are very strong!

[thousandshirts]

While we're here, I'm wondering what the advantages/disadvantages of putting the two center taps of the power transformer (both HT and heaters) on the same fuse to ground. In the last photo, on the transformer, you can see I've used a green wire with a yellow stripe on it to connect two of the PT lugs together, and then to ground via the flush mount fuse mounted just below the PT in the picture. The top side is the 375-CT-375 side (blue with white stripe is the common lug), the bottom side is 3.15-CT-3.15 (heaters), and the two CT's are green w/yellow stripe. It works beautifully as is, and works beautifully with the two separated (and running the heater center tap directly to ground without fuse, but fusing the HT CT). Having the heaters fused is nice. Maybe I'd use more fuses over the years, by a small amount? I know my *** is covered so far as protecting the transformers are concerned. I can deal with the odd tube replacement. But technically speaking -- is there a best way to do this? Put that fuse someplace else entirely (there is a separate Mains fuse, the layout is near the bottom of my website)? Hmm. Thanks in advance.

[kevinkr]

I think you want to separate the filament and high voltage center taps - if that fuse blows the filament to cathode insulation in your tubes could be the next thing to fail - and that could be very bad.
Just put the fuse in the line to the high voltage center tap and ground the filament center tap directly.

Looks great otherwise.