Amp build for a first time builder?

[yoyohomieg5432]

1) i'll post a pic of the push button things when i can

2) i'm assuming i can just put in the three guitar cable jacks in place of the RCA ones right? Since i'm never going to be using RCA.

3) there is one problem with the chassis. the pre drilled holes for the OT are too wide for the pre drilled locations on the chassis. Two holes fit but the other 2 won't. I have two options the way I see it: drill two wider holes on the chassis (the OT runs off the chassis a tiny bit) or drill holes on the OT a little closer.

I'm not going to lie, I already drilled two new holes on the chassis. I will be able to fit a nut to secure the screws but you just mentioned using washers and the holes are currently too close to the chassis wall that a washer is not going to work unless i instead drill holes narrower on the OT.

[martin manning]

I like your set-up Mark, but we have 2, 4, and 8-ohm outputs here.

Homie, see if you can figure out all of the mechanical assembly. Just fit things up hand-tight, and then post some pics. You want to find out if something isn't going to work before you get started with the wiring.

[martin manning]

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[martin manning]

2) i'm assuming i can just put in the three guitar cable jacks in place of the RCA ones right? Since i'm never going to be using RCA.

Yes, replace the 4 RCA's with three 1/4" Switchcrafts like I show in the layout.

3) there is one problem with the chassis. the pre drilled holes for the OT are too wide for the pre drilled locations on the chassis. Two holes fit but the other 2 won't. I have two options the way I see it: drill two wider holes on the chassis (the OT runs off the chassis a tiny bit) or drill holes on the OT a little closer.

This is why I suggested filing notches in the transformer "feet" so you could use the existing chassis holes. Lock washers are pretty close to the size of the nut. Are you sure you can't get one on? Another option would be to use thread locking compound (Loctite e.g.) on those nuts, or if they are so close to the chassis wall that they can't turn, then they won't be able to loosen up.

[yoyohomieg5432]

2) i'm assuming i can just put in the three guitar cable jacks in place of the RCA ones right? Since i'm never going to be using RCA.

Yes, replace the 4 RCA's with three 1/4" Switchcrafts like I show in the layout.

3) there is one problem with the chassis. the pre drilled holes for the OT are too wide for the pre drilled locations on the chassis. Two holes fit but the other 2 won't. I have two options the way I see it: drill two wider holes on the chassis (the OT runs off the chassis a tiny bit) or drill holes on the OT a little closer.

This is why I suggested filing notches in the transformer "feet" so you could use the existing chassis holes. Lock washers are pretty close to the size of the nut. Are you sure you can't get one on? Another option would be to use thread locking compound (Loctite e.g.) on those nuts, or if they are so close to the chassis wall that they can't turn, then they won't be able to loosen up.

as is i have to reposition point the screw towards the center of the amp so that i can get the screw on and start to tighten it, but it's touching the wall as i screw it on so unless the washer is identical in size i don't think it will work.. i think i may just drill 2 holes in the OT so that i can use the predrilled holes like you said

[yoyohomieg5432]

installing pots now.


the bag gives a number like 1MA potentiometer. does the A refer to audio taper? Others have 25KL meaning linear taper?

-using 1MA for both volumes and bass.

-the schematic says 250k Lin. for treble, but from the mojo supply i have 250KA potentiometer. is this wrong? for the moment i'm using the 250KA here for treble.

-25KL for mid

-from mojo i have 5KA i'm putting in for presence. I'm confused again though because the schematic is using 5K linear.

[martin manning]

You are correct re A indicates audio and L indicates linear taper. The tapers on the layout are better for spreading the effect over the rotation of the pot, but what you have will work of course. Maybe if you complain they'll send you some new ones...

[yoyohomieg5432]

i attached 3 pictures. the first is that weird thing I have no idea what it's for. The second is of the turret board. A 3rd is what i have of the chassis so far. I'm assuming the turret board needs to be mounted to the chassis, right? Where does this happen though? The turret board has 4 holes in it currently that are all on the bottom of the board and only 1 on the top corner. are these holes used for mounting? It doesn't really make sense to me that they're all on one side. Also, the chassis has no holes at all for this so I would need to drill holes in that too, right?

[yoyohomieg5432]

also. can i get some advice for when i begin to solder onto the turret boards? do you just lay the component on top of the eyelet,

or do you thread it through the hole and then fill the hole with solder once everything has been placed onto that eyelet? if this method, should i bend excess wiring from the caps/resistors underneath or cut them off?

does everything need to be soldered to the eyelet at once or can i add one piece at a time? it seems like i could as long as i get all of the solder hot

[martin manning]

Huh... The blue thing is a stomp switch like you would use for a pedal. Bonus!

The holes you see in the eyelet board are for wires. Look closely at the layout and you'll see. Perhaps they did not provide any mounting holes in the chassis or the board. Look at the '59 Bassman pics and you'll see (I think) three mounting screws. There are probably no holes for mounting the cap board either. Get all of the chassis mounted parts attached and then determine where the board mounting holes can go and not interfere with transformers, etc. Don't forget that you are going to modify the board for the adjustable bias supply and filament elevation network, so you'll have to plan for that too.

Read over the build guide re soldering components on the eyelet board. Eyelets, not turrets! Yes bend leads over slightly then cut off excess lead length leaving maybe a mm sticking out below the eyelet.

[yoyohomieg5432]

Huh... The blue thing is a stomp switch like you would use for a pedal. Bonus!

The holes you see in the eyelet board are for wires. Look closely at the layout and you'll see. Perhaps they did not provide any mounting holes in the chassis or the board. Look at the '59 Bassman pics and you'll see (I think) three mounting screws. There are probably no holes for mounting the cap board either. Get all of the chassis mounted parts attached and then determine where the board mounting holes can go and not interfere with transformers, etc. Don't forget that you are going to modify the board for the adjustable bias supply and filament elevation network, so you'll have to plan for that too.

Read over the build guide re soldering components on the eyelet board. Eyelets, not turrets! Yes bend leads over slightly then cut off excess lead length leaving maybe a mm sticking out below the eyelet.

Ok I'm looking back at the schematic for the board. THere's an image for the under board wiring as seen from the top. Are those wires, such as v5 g1 and v4g1 feeding from the bottom back up to the top through those holes?

could you also explain some of the naming? The under the board diagram has wires labeled 'V5 g1' and 'v2a g'. I'm not really sure what these are referring to. I can't find anything with those labels on the schematic on the first page.

[yoyohomieg5432]

also... was just looking at the wire included. there's one package of yellow wire that's 22 gauge and one package of green wire that's 18 gauge. Why different gauges? Is there certain places I should be using the green wire over the yellow?

additionally, your schematic shows 22uF 450V caps? The ones I have are 22uF but 500V.. does this matter?

[martin manning]

The tubes are V1 through V6 beginning at the input and g is grid, g1 is grid 1.

The green wire is evidently for the filament wiring and the yellow is for most everything else. Are there any other colors?

Higher voltage rating on the caps is fine.

[yoyohomieg5432]

The tubes are V1 through V6 beginning at the input and g is grid, g1 is grid 1.

The green wire is evidently for the filament wiring and the yellow is for most everything else. Are there any other colors?

Higher voltage rating on the caps is fine.

nope, that's the only 2 colors. can you explain what you mean by filament wiring?

can you answer my other question two posts above i beleive: " Are those wires, such as v5 g1 and v4g1 feeding from the bottom back up to the top through those holes? "

the filter cap board also has the holes for wires but i don't really think those are necessary are they?

I just soldered the filter cap board. i didn't solder the wires coming off of the board, but did everything else. I ran continuity tests on the interconnections to check my soldering/wires and it checked out. i can take a pic tomorrow.

[martin manning]

Filament is another name for the tube heaters. The current is pretty high in that circuit (~3A), so I guess they thought that heavier gauge wire is needed there. It's not, and it will be a little harder to work with. Having only two wire colors is a pain- it'll make it harder to keep track of the wire runs from the cap board and leads from under the main board. I'm even less impressed with Mojo now than I was previously.

Additional to the labeling on my drawing, the preamp tubes have two triodes each, so V1 has a V1a and a V1b triode. V1ag is V1a's grid, V1ak would be its cathode. It's best to understand the function of each connecting wire and component is as you go along, and locate it on the schematic. You are much less likely to make a mistake.

"Are those wires, such as v5 g1 and v4g1 feeding from the bottom back up to the top through those holes?"

Yes, exactly.

"the filter cap board also has the holes for wires but i don't really think those are necessary are they?"

You can run the leads on top or from underneath and bring them up through the holes. When you attach the leads to the cap board you'll have to gauge the required length. I guess you could actually attach either end first, and it might even be easier to solder them inside the chassis first and at the cap board end last.

Here's where I'd place the mounting screws for the main board. Post a straight-on (squared up with the camera) photo of your eyelet board and its dimensions. I'll mark it up with the required modifications.