First tube amp build: Fender Deluxe AB763 style amp (no reverb).

[Justin Thomas]

I found F&T's for about 5.00. Still overpriced, but they fit the board I have and are relatively easy to get.

The 22uF/500V are about $2 less from where I get most of my parts from... just for next time! And there will be a next time.

Justin

[Enzo]

I haven't bought caps in like four years, and I didn't recall 475v. Cool they have them.

16 is a tiny value they used back when caps were expensive, today a 22uf is about the same thing and cheaper and easier to get. Chances are the old 16 measured a lot higher anyway.

Sprague Atoms are specially made to look like old caps for the restoration market. Don't waste your money.

[bob p]

Sprague caps have that Mojo thing that some people like to pay for when they're building an amp to take pictures of it.

Just kidding of course, but there are lots of people who demand radial caps because they're following a layout diagram. And they like them to be blue...

Unfortunately axial caps are expensive today. CDE are tremendously high, Spragues to a lesser extent. F&T is the best deal out there right now if you have to have that packaging. There are cheaper options, like IL and the China brands. I don't like those, they don't last. I think that F&T is a good choice for people who want a drop-in part for old Fenders. The JJ cans are a decent/inexpensive option. I've used the 40/20/20/20 in Deluxe type builds but they won't fit under a doghouse.

Now that we're in the 21st Century it doesn't make sense to design a layout around axial caps. They're just too hard to find and too expensive when you have to buy them at a specialty house. Radials aren't always the answer either. I decided a long time ago that I was going to adapt my designs to use snap-in caps for power supplies. They're easier to get because that's what the world has gone to. I don't have any reservations about putting snap-ins in an amp, either by drilling 10mm spaced holes for snapping them onto a G-10 board, or by laying them down on their sides, holding them with zip ties and running jumper wires to the board.

[mikepukmel]

Sprague caps have that Mojo thing that some people like to pay for when they're building an amp to take pictures of it.

Just kidding of course, but there are lots of people who demand radial caps because they're following a layout diagram. And they like them to be blue...

Unfortunately axial caps are expensive today. CDE are tremendously high, Spragues to a lesser extent. F&T is the best deal out there right now if you have to have that packaging. There are cheaper options, like IL and the China brands. I don't like those, they don't last. I think that F&T is a good choice for people who want a drop-in part for old Fenders. The JJ cans are a decent/inexpensive option. I've used the 40/20/20/20 in Deluxe type builds but they won't fit under a doghouse.

Now that we're in the 21st Century it doesn't make sense to design a layout around axial caps. They're just too hard to find and too expensive when you have to buy them at a specialty house. Radials aren't always the answer either. I decided a long time ago that I was going to adapt my designs to use snap-in caps for power supplies. They're easier to get because that's what the world has gone to. I don't have any reservations about putting snap-ins in an amp, either by drilling 10mm spaced holes for snapping them onto a G-10 board, or by laying them down on their sides, holding them with zip ties and running jumper wires to the board.

I think the next build, Im going to figure out how to make a really small board that fits under the amp, and uses radials.

[mikepukmel]

Progress is going slowly, mostly due to mechanical stuff

I got a cap board from the same vendor who sells the chassis. The mounting holes lined up fine, but the flange on the cap board sat right on top of about 1/3rd of the wire hole grommet. So, had to re-drill and move one grommet hole. Not such a big deal, but now the grommet hole doesn't sit right under the corner of the cap board so the wiring doesn't drop down 90 degrees into the grommet hole, its offset a bit. I don't think this will be a horrible thing, but its not going to be pleasant to remove the wiring if need be.



The bigger issue was that the board offsets I bought, hex threaded rod coupling nuts, 3/4" put the cap board up too high so that the caps hit the bottom of the can. <frown> I tried a bunch of stuff, ended up grabbing the coupling nuts with a vice grip and a piece of cardboard, and cut them about in half with a hack saw, then filed off the bottom of the cut so they fit the chassis ok. The goal was to have the piece of the coupling nut bolted to the chassis so it would be easy to get the board on and off with out a lot of effort, if need be.

Finally! Board dry fit is OK.



I think. The screws look far enough away from the H.V. connections, the cap can fits with good clearance from the top of the caps, and the wiring all fits.

With all of the drilling and hole moving done, I think I can finally start putting the actual electronics in. FINALLY!

The next build, Im going to get boards, chassis and cap can that all fit without this much extra work.

[mikepukmel]

... I've used the 40/20/20/20 in Deluxe type builds but they won't fit under a doghouse. ... .

Bob, were you able to move he bigger caps inside the chassis someplace?

[bob p]

Bob, were you able to move he bigger caps inside the chassis someplace?

Once you get past the idea of using Spragues the caps get smaller.

You'd think that space would be a problem for amps that didn't plan room for caps within the chassis, but that's not really the case because today's caps are so volumetrically efficient (small in terms of volume per uF) that it's pretty easy to shoehorn them into the amp if that's what it takes.

The Sprague caps that most people are used to buying don't need to be anywhere near as big as they are. They make them that big to look "proper" in old-gear retrofit situations. Once you get past the mojo of using Spragues, it's not at all hard to find physically small caps to replace them. Locating modern high density caps inside of the doghouse is not difficult. Just pay attention to the dimensions when you're reading the spec sheets.

[g1]

Bob, were you able to move he bigger caps inside the chassis someplace?

I believe he was speaking of the multi-cap in single can not fitting in the doghouse.

The JJ cans are a decent/inexpensive option. I've used the 40/20/20/20 in Deluxe type builds but they won't fit under a doghouse.

[mikepukmel]

I believe he was speaking of the multi-cap in single can not fitting in the doghouse.

Oh yeah, ok, thanks. I forgot about those things. The first time I saw them for sale, I though it was a screwed up photo. Great big huge thing, two leads come out one end, one lead comes out the other.

https://www.tubesandmore.com/product...f-electrolytic

[Justin Thomas]

I think bob was referring to THIS guy:
https://tubedepot.com/products/jj-ca...uf-x-20uf-500v

The dual cap you posted MIGHT fit in a doghouse, but most of those style that I've seen are low-voltage types for cathode bypass duty. Old Fenders sometimes used dual-section Mallorys to save space for an extra wire lead in a tiny eyelet. Personally, I prefer to use single caps for anything except filter cans that are already on a chassis...

F&T is trying to do some limited customer bases a big favor - some of their offerings are direct replacements for vintage parts that are difficult or impossible to find. Those three-lead caps are some. I do appreciate the effort, even if I don't necessarily use them, because their prices are better than anybody else for a specualty item... and I think F&T just look cool...

Justin

[bob p]

Yes, I was referring to that JJ can-type cap that clamps onto the chassis, the one in Justin's link.

With those, you mount it like a tube -- connectors inside of the chassis, bulky part sticking out on top (marhsall) or underneath (fender). the only "fit" criterion is whether there is room for the mounting hole/bracket.

I'm like Justin, I prefer discreet single-element caps, but I've had a chassis that was already prepared for a can and I've used the JJ with good results.

[Justin Thomas]

I usually end up using the CE cans, because I'm largely using hollowed-out chassis from the wayback days, which are already cut with the four-tab mounts. I've used CE, JJ, F&T cans, all with no trouble, other than occasionally having to re-engineer the mounting. I'll use the CE cans for customers, but my builds don't need the expense!

I also use Illinois, F&T, Sprague (cathode bypass only), Suntan (Chinese Cheapies) for single section caps. I haven't ever had a problem with any of them that weren't stupidity-induced on my end...

Bob, have you seen the builds where they clamp the TOP of the can to the inside of the chassis, then run wires to/from the terminals? Kind of a neat idea, if you budget for space... Chuck H. has also put up a picture of how he mounts cans to a board with zipties, probably similar to what you do. I have yet to try that. One day I MAY try to mount a snap-fit on a turret board; I have found that many PC-mount pins fit in the turrets I use.

Anyway, so many options and so many ways to get the job done well, if you understand the principles behind the technique...

One way to do it:


Justin

[bob p]

Bob, have you seen the builds where they clamp the TOP of the can to the inside of the chassis, then run wires to/from the terminals? Kind of a neat idea, if you budget for space... Chuck H. has also put up a picture of how he mounts cans to a board with zipties, probably similar to what you do. I have yet to try that. One day I MAY try to mount a snap-fit on a turret board; I have found that many PC-mount pins fit in the turrets I use.

Ive seen that but never done it. It's a great way to take advantage of that space under the transformer if you're using an above-chassis X-type transformer mount.

[mikepukmel]

My recollection is that the DR uses 32/16/16/16 as the 4 nodes, so he's going to need five 16uF caps to get there, tying two 16 together for the first node.

*** To do that he'll need to move the resistors one position to the left in his mockup before he solders them in, putting a jumper in the rightmost position. ***
Those F&T are rated at 475V so I wouldn't worry too much about working voltage on them. that's a nice board. Where did you get it?

Just heated up the soldering iron after all the drilling and stuff done, and re-read your post. The two resistors were reversed. THANKS!!!

[mikepukmel]

A question about the black band on signal capacitors (e.g. like Mallory 150's or orange drops). I read:

"Although non-polar, old paper capacitors had black bands at one end. The black band indicated which end of the paper capacitor had some metal foil (which acted as a shield). The end with the metal foil was connected to the ground (or lowest voltage). The purpose of the foil shield was to make the paper capacitor last longer. When replacing these old paper caps with new film capacitors, you do not need to worry about which end goes to the lowest voltage side."

on justradios.com. is this actually true? The banded side is the case side, right? So, doesn't it matter whether when you have a really small signal like right around V1, if you put the signal into the case end or into the other end, wouldn't one be more likely to pick up noise?

Thanks!
Slow Learner.