Amp build for a first time builder?

[martin manning]

Martin, I'm afraid I'm becoming more confused. So you no longer think using bolts or screws to secure the cap board is a good idea either? I don't really understand what you mean by padding it with weatherstripping. You essentially just want to pack it in but not actualy secure it to the chassis?

Yes, exactly. The black above and below the caps in my sketch is the (neoprene foam) weatherstripping. You can get a roll of this stuff at the hardware store for $5-$6. From Mojo's pictures it looks like the cap board is the same width as the main board, so if you mount it with screws they will come through beneath the main board. There is no reason you can't use self-tapping screws to mount the cap board, since you would be drilling new holes, and elevating the main board anyway. Four 1/4" #6 screws would probably work fine.

On the other hand, a couple of strips of neoprene weatherstripping on the chassis (spaced about an inch apart), and another one centered on the inside top of the dog house would work, and you can always remove it and go with screws later if you want. This is basically what Mojo is suggesting, but they used some felt pads meant for bass guitar pickups ('cause that's what the guy who wrote the instructions had on hand).

[M Fowler]

I let the dogs out and with all that free space between the PT and tone board I put my filter caps there, no dog house needed.

Just saying.

[yoyohomieg5432]

so the plan is essentially the drawing you posted on 1/12? except using a really short bolt and nut to secure the doghouse instead of a self tapping screw

[martin manning]

Yes. The cross section looking the long way would be like this. The dog house mounting screws are not shown, but they'd be just about where the board mounting screws are.

Mark's solution is good too. Modern caps are much smaller for the same capacitance than in the 1950's so it's possible to fit them inside the chassis. There's a little more crowding around the power tube sockets that way.

[yoyohomieg5432]

jus got back from the hardware store, shoudl have everything i need


one thing i noticed when looking at a couple images: the choke seems to be wired to different eyelets?

in this image:
https://tubeamparchive.com/download/file.php?id=25711
and this image:
https://tubeamparchive.com/files/modern ... 31_178.pdf

[yoyohomieg5432]

Wanted to check the ground lugs

[martin manning]

I almost missed the ground lug on the inner side of the left (as seen in the picture above) power tube socket. It would be better if you put the tube sockets on the outside of the chassis so that the ground lugs contact the chassis directly. Will they fit that way?

On the choke wiring, the image with the black board doesn't show one choke wire, and the layout on page two of the .pdf doesn't show the other one. Page one of the layout shows them both, though. I'll fix that and re-post.

This is an example of where you should be checking the layout against the schematic, and at the same time asking yourself if the connections make sense to you. You should be thinking ok, the standby switch connects the B+1 reservoir caps to the choke and to the OT center tap, and then the choke carries the DC from the B+1 node to the B+2 node, and that that is indeed what you are seeing in your amp. This is difference between the people who know what they are doing and the "paint-by-numbers" type.

[martin manning]

I'd rearrange the speaker jacks so they are as shown in the layout, and just leave the extra hole empty.

[yoyohomieg5432]

[quote="martin manning"]I almost missed the ground lug on the inner side of the left (as seen in the picture above) power tube socket. It would be better if you put the tube sockets on the outside of the chassis so that the ground lugs contact the chassis directly. Will they fit that way?

On the choke wiring, the image with the black board doesn't show one choke wire, and the layout on page two of the .pdf doesn't show the other one. Page one of the layout shows them both, though. I'll fix that and re-post.

This is an example of where you should be checking the layout against the schematic, and at the same time asking yourself if the connections make sense to you. You should be thinking ok, the standby switch connects the B+1 reservoir caps to the choke and to the OT center tap, and then the choke carries the DC from the B+1 node to the B+2 node, and that that is indeed what you are seeing in your amp. This is difference between the people who know what they are doing and the "paint-by-numbers" type.[/quote

I. Think I put it on after the picture.. there should be three total on the tubes right?

The board seems to be a bit wide. When I put it down its partially overlapping the hole for the ot wires. Also I'm a little concerned the total height is going to be getting close to the lower output jack. Its already getting in the way when I try to place the board inside.

I secured the dog house. Pics ill post later

[yoyohomieg5432]

I cant do multiple attachments from phone for some reason

[martin manning]

I only see four wires going through the chassis? Also, you need to install a rubber grommet in the chassis hole to protect the insulation on the wires.

[yoyohomieg5432]

I almost missed the ground lug on the inner side of the left (as seen in the picture above) power tube socket. It would be better if you put the tube sockets on the outside of the chassis so that the ground lugs contact the chassis directly. Will they fit that way?

On the choke wiring, the image with the black board doesn't show one choke wire, and the layout on page two of the .pdf doesn't show the other one. Page one of the layout shows them both, though. I'll fix that and re-post.

This is an example of where you should be checking the layout against the schematic, and at the same time asking yourself if the connections make sense to you. You should be thinking ok, the standby switch connects the B+1 reservoir caps to the choke and to the OT center tap, and then the choke carries the DC from the B+1 node to the B+2 nuhode, and that that is indeed what you are seeing in your amp. This is difference between the people who know what they are doing and the "paint-by-numbers" type.

What do you mean put the tube socket on the outside? I thought the whole piece was called the tube socket so my terminology must be wrong.

Also there is 5 wires voing through the chassis I just drille a hole for the top right one to preserve some length

What's wrong with my speaker jacks? I have two on top and one on bottom like the layout. I just filles the empty with one of the rca jacks so I didn't have a big open hole

[yoyohomieg5432]

Also heres what I was talking about when I said the board kind of overlaps the hole for the ot. Opinions on how the board is placed before I begin to drill holes for it? I realize the whole board isnt shown I can take a better picture tomorrow but it's shown to start like half an inch to the left of the input jacks. (Half an inch towards the edge of the chassis)

[martin manning]

What do you mean put the tube socket on the outside? I thought the whole piece was called the tube socket so my terminology must be wrong.

Maybe I should have said put the socket's mounting flange on the outside. That means inserting the socket through the mounting hole from the outside of the chassis rather than from the inside. It should fit through the hole going in from the outside. My thought is that the ground connection will be more reliable if the ground lug contacts the chassis directly. How about the retainer clips? They should go on when you attach the sockets to the chassis,

Also there is 5 wires voing through the chassis I just drille a hole for the top right one to preserve some length.

They all go through the same large hole in the chassis, right? If so, it must be hidden in the picture. You do need to put a grommet in that hole, though.

What's wrong with my speaker jacks? I have two on top and one on bottom like the layout. I just filles the empty with one of the rca jacks so I didn't have a big open hole.

You can fill the hole with an RCA jack later if you want, but it might be in the way now. I was thinking use the two holes closest to the open side of the chassis and the hole closest to the power tubes for the third jack to get the best access for wiring them in. That way the OT wires will be comming from the direction of the empty hole.

Also heres what I was talking about when I said the board kind of overlaps the hole for the ot. Opinions on how the board is placed before I begin to drill holes for it? I realize the whole board isnt shown I can take a better picture tomorrow but it's shown to start like half an inch to the left of the input jacks. (Half an inch towards the edge of the chassis)

The wires from the OT will have to make a sharp bend to clear the board as soon as they come through the chassis. Take a look at Mark's picture above, the Mojo pics, and the original. The board is pretty well centered top to bottom in the original, but more toward the bottom (tube socket side) in the others. I would think centering it would give you the best access to all of the mounting screws. Placing the right edge of the board about 1/2 inch or so from the right edge of the chassis sounds good.

It's very tight in there, so get as much of the chassis wiring done as you can before mounting the board. The sequence I wrote in the build guide reflects that. I'd mount the transformers and wire them in at this point.

[martin manning]

Here's another nice 5F6-A build by forum member snuffy to look over... https://tubeamparchive.com/viewtopic.ph ... ht=bassman