Amp build for a first time builder?

[M Fowler]

There are some youtube videos by Gabi showing how wire things up if your interested.

Below is the filament wiring.

http://www.youtube.com/watch?v=7O0_dlKkzSE

[yoyohomieg5432]

There are some youtube videos by Gabi showing how wire things up if your interested.

Below is the filament wiring.

http://www.youtube.com/watch?v=7O0_dlKkzSE

thanks, i'll check it out.

i also have the picture of the board martin was requesting. i attached pictures of the soldered filter cap board from the front and back as well so you guys can check it out.

[martin manning]

Looking good so far. You don't need quite so much length of component lead under the board. Not a problem here as there is lots of room and if you ever have to replace those caps its easy to lift the board and get under it. On the main board there will be other eyelets nearby, and you will want to be able to remove and replace a component without having access to the bottom. That full bend will make that difficult.

What are the dimensions of the main board?

[yoyohomieg5432]

i've attached another pic of the modifications for the adjustable bias (where i was planning on placing the holes). how does it look? also, i circled two eyelets in orange that are on my board but don't seem to be on the diagram. Is it common to have eyelets that aren't being used?

Also, I'm wondering how i modify the board? do i just drill with 1/8" and then pop in an eyelet?

board dimensions are rougly 11.5"x3"

[rp]

BTW not everyone knows this but the original Fender layouts were drawn to show the techs (lovely lasses with soldering irons) exactly where to run the wires when soldering up. So if you follow that you amp should be trouble free for noise and oscillations. Good luck.

[martin manning]

Here's how I'd do the mods to the board. You can use the extra eyelets as shown (the ones where the B+1 ground and the B+2 ground wires are attached), or you could remove them and just run the wires under the board through the holes. The new eyelets (shown in red) will fit in a 1/8" hole, then you need to flare the eyelet on the back side. A couple of light taps with a center punch or other conical-point tool will do it.

[martin manning]

BTW not everyone knows this but the original Fender layouts were drawn to show the techs (lovely lasses with soldering irons) exactly where to run the wires when soldering up. So if you follow that you amp should be trouble free for noise and oscillations. Good luck.

They were mostly Latinas, as I recall from one of the Fender histories. One called Lupe was known as the go-to gal for wiring up new prototypes. Another case where women were thought to have the right kind of manual dexterity needed for such work.

[martin manning]

Here's a little better view of the power supply section on the main board. I scaled the components to the correct dimensions to make sure everything will fit, and added the other choke lead and the filament CT (which I left out above). You might want to add another eyelet for that choke lead, which I show in pink. There is a lot going on in this area, and it has high voltages, so it's critical to get it right.

[yoyohomieg5432]

you mentioned #4 and #6 screws for the tubes. any recommendations for fastening the circuit boards? and the PT/choke?

also, i have a question with the eyelet pattern you gave for the bourns trimmer. the dimensions of the eyelets are much larger than the separations of the pins themselves. why these dimensions? The only way I could see this working is if i flatten the pin out for maximum length. but even then the pins aren't long enough to fit into the eyelet, they'd probably be laying on top

[yoyohomieg5432]

another question with the area involving the heater elevation circuitry. i'm adding another eyelet for the 27k and 10u cap in parallel. as shown here: https://tubeamparchive.com/download/file.php?id=25711 there is a black wire connected to another eyelet under the amp and then from there to ground. however, here: https://tubeamparchive.com/files/modern ... 25_158.pdf it just shows B+2 ground feeding from that new eyelet through a hole to the top of the board. i'm assuming since i don't have a hole there on my actual board you are substituting that with this eyelet? in this case why should i solder the black connection and then create another blue wire out for B+2 ground? Why not just use one piece of wire and feed it through the eyelet?

[xtian]

you mentioned #4 and #6 screws for the tubes. any recommendations for fastening the circuit boards? and the PT/choke?

I like stainless steel hardware, and order from mcmaster.com. I use machine thread #6 for most chassis fixtures, #8 for heavy PTs, and more recently, #4 for tube sockets. Items that don't need a lot of torque like circuit board, cap cans, tag strips, wire stays, etc, get a #6 threaded into the chassis itself. That is, I use a #6 drill+tap (cheap from Harbor Freight) to drill and thread a matching hole for the #6 screws.

For items that are more critical or need better support (PT, OT, choke, ground connections, IEC power socket) I use a nut and lock washer (nuts with attached lock washers are nice!).

[martin manning]

The pattern for the Bourns trimmer is one I have used. You have to bend the pins straight out and then bend a bit straight down with needle nose pliers. On the use of the eyelets note above I suggested that you could use them or remove them and just feed the wire through the hole.

[yoyohomieg5432]

are we sure that the capacitor on the far right of the board is 220uF? That seems pretty big. i've also looked twice through my stuff and dont see anything of that size

[martin manning]

are we sure that the capacitor on the far right of the board is 220uF? That seems pretty big. i've also looked twice through my stuff and dont see anything of that size

The original used that value, but it is really about five times larger than necessary to fully bypass the 820 ohm cathode resistor. In the Mojo stuff you should have a couple of 10uF 150V or so for the original bias supply, and then one other electrolytic rated at ~25V for V1's cathode. Maybe a 47 or 22uF?

I agree #6 hardware for the octal sockets and circuit boards, #4 for the 9-pin sockets. You should have hardware in the Mojo kit to mount the tube sockets, transformers (OT at least), and choke. They didn't plan on your attaching the circuit board to the chassis, so you'll have to make a run to the hardware store.

Here's a pic of a Bourns trimmer on eyelets.

[guitardude57]

are we sure that the capacitor on the far right of the board is 220uF? That seems pretty big. i've also looked twice through my stuff and dont see anything of that size

All my schemos show 320uF