Hoffman style Xpress board

[joebob]

Here is a different version of the Hoffman layout for an Xpress. There are differences; the input is on the right and power switch on the left. I believe this to be accurate. I know there are die hard wreck fans that consider this blasphemous but if J Marshall said I can't do anything with this fender amp. He'd be selling shoes in London. Or if HAD said I'm not going to waste my time with this 5F6A, I'm going to San Francisco and sell Incense. Where would we be? I was just thinking out of the box, playing around trying something different. The placement of some parts is not written in stone, the OT & PT obviously could be moved around some as well as the finals. Yes, there is no filament wiring in the layout. I would think a DIYer or builder wouldn't need his hand held for everything.
Hey, I have 2 weeks off and it's too cold outside to do anything else, and i've finished my Christmas shopping already.
Dave

[gahult]

None except the first thing that hits me is you're trying to stuff 17 1/2 in.
of board into a 17 in. chassis.

Gary

[Jana]

shoehorn?

[gahult]

And Vaseline, that 17" outside.

Gary

[Ron Worley]

My guess is that the proximity of the PS / filtering to the Preamp and the ensuing changes in lead dress will make this amp sound different than an Express. It certainly could be noisier and less stable.

Uncle Kenny had a reason for how he did a lot of things..... YMMV....

Ron

[bnwitt]

Wow, everyone and their dog is using my visio templates

I would suggest canning the 25 watt cement resistor for a 5 watt. The 25 watt is tremendous overkill and you can condense your board with the smaller one.

[drhulsey]

Wow, everyone and their dog is using my visio templates...

That's what you get for being so generous

[FYL]

From my files. The 47pF crossline cap is missing, some component values aren't canonical, grounding is Hoffman-style.

[Jana]

This is just a suggestion.

One thing that strikes me is the long runs from the filter caps to the points on the board. The high voltage line is laid out nicely and is kept very clean and short but then the filter caps have the long runs. If it was me, I would
1. do away with the cap board
2. move the main board a tiny bit to the right, this would line up things even more on the tube side with the board
3. put cap cans under the board, maybe half under, half exposed on the control side. They would be very close to the resistors in the B+ string. The leads would then be very short for both the grounds and +.

I know this would be a significant deviation from the TW "grail" as far as the type and brand of filter caps used so maybe this isn't an option for you.

If you're set on using these caps, maybe a dog house, fender style, on the top side of the amp? Leads would be longer than cans but still shorter than it is now.

Or, if the chassis is deep enough, mount the caps right on the board, either topside or underneath?

Just some thoughts.

[Zippy]

If you are going to go "Hoffman style", look 'round his website to see how he distributes the power supply caps along the length of the chassis. I recall a Fender rebuild that looked especially clean with the supply caps tucked between the board and front panel.

[bnwitt]

I've built many a Hoffman style amp and many of them in old fender chassis with the cap can on the back of the chassis. This of course makes some of the wires from caps to the point on the board long. This causes absolutely no problem at all and no noise. So, I wouldn't worry about the long wires, just don't run them near any signal wires. I would run them in a bundle under the board down close to the chassis and peal each one off as it arrives at it's tie in point. Use a different color for each wire and don't connect them to the end of the board like you have them shown.

[joebob]

He does the string of filter caps on the bassman 5f6a, i believe. I am going to make the changes people have suggested and re-post sometime. Thanks for all the input. I tried to keep the flavor of the express as much as possible with this layout.

D

[bnwitt]

He does the string of filter caps on the bassman 5f6a,
D

He does it on a lot of amps but you don't have to.

[joebob]

I changed the layout and posted a complete amp.

[Jana]

joebob,

I like the way you have put the caps on the board, this certainly makes a short run for the + side. But why run the grounds for the B+4 and 5 caps over to the ground lug? I would ground them to the ground wire that runs right underneath them. The B+3 cap, I would ground that to the buss/ground on the back of the presence pot. just my thoughts.

(everybody's an expert, especially when someone else is doing the work, lol)