Motown Direct Box DIY

[CJ]

taking a stab at the Motown box used in the snake pit ,

used by the guitar and bass players to send a signal to the booth,

this way no amps had to be lugged around and the signal did not bleed as much with everybody coming out of a single monitor speaker driven by a McIntosh amp,

there is no schematic available but some generous people gave some clues to work off of, so it will be trial and error til the ears hear something they like,

gotta start somewhere, that 18 ga. is carpel tunnel city with the hand shears, >

 

[CJ]

about 12 x 8 plus or minus 0.001" strictly eyeball,

corners will get tig welded so no need for spot welding tabs folded over on the corners,

 

[CJ]

ready for the DIY bender,

bar for the long bend,

then the fingers come out for the short side, somebody stole one of my bolts,

 

[CJ]

YES tig welder sits under the bender, bought this for $200, expected it to last about two weeks, but two years later it is still ticking, Argon bottle required, runs on 120/240, dryer outlet uses for 240, easier on the transformer, or whatever circuit they got in there,

30 amps for the light stuff,

 

[CJ]

that's right, certified for nuke plants,

DIY Levis flash dewlap hanging off the helmet, they want about 50 bucks for a leather one,

there is a switch in the torch for on/off, no pedal, so no heat control, use the rod feed rate to regulate heat,

you can put copper bars under the corners to absorb heat but if you burn through, the copper will contaminate your tungsten tip, in fact welders use a penny to make a ball at the end of the tungsten for aluminum welding.

this safe tungsten without the radioactive thorium has to be sharpened more often, i like the old thoriated stuff, too old to care,

this darn 3M Speedglass cost more than the welder but the light activated lens sure is nice,

i tried to beat the 10 second timer on the camera so i could strike an arc but was a little late,

 

[CJ]

sander wheel for finishing the corners,

i did not take a pic of my welds because a dog could crap a better looking bead than mine,

gotta bend a base plate and maybe a lid but the punch is ready for the tube sockets, and the step drill for everything else, expanded medal screening is uber expensive nowadays so i think i will go for a sheet metal lid,

 

[CJ]

Hawk has the best prices on the Hammond transformers, you can also buy them from mouser and digikey,

you can spend as much as you want on the output tube,

i can get either one channel or two channels out of one tube depending on which circuit ends up getting used,

Capacitors are 15 percent off right now at Antique Electronic, enter code "CAP15"

 

[CJ]

roughing out the parts , then draw in the caps and resistors to try to avoid the kludge look,

9 x 12 would have been a bit easier to wire than 8 x 12 but ti should be ok,

keeping the pwr xfmr away from the input circuit,

might add a choke so left room for that,

 

[CJ]

did a reality check drawing and decided to relocate the output transformers, used the chassis punch for the big holes, going to throw some paint on it and wait for the parts,

 

[CJ]

found a couple of Triad OPT's in the back of the sock drawer,

going to run these strapped for 5K : 250 for more headroom ,

the low z cathode follower won't mind, especially with lower plate R of the 6BX7 compared to a 12AU7

the ratio will be about 4.5 : 1, frequency response might even be better with the lower ratio , it does 100 KC with the full primary,

 

[soapfoot]

What’s the part number for that Triad output?

 

[CJ]

HS-52 private label.

i know what your thinkin!

put down some terminals before paint other wise burn through,

learned to put down twice as many as you think you need, that way you only have to add two more,