Monkeymatic Lassen (Supro 24)

[xtian]

Started building a Supro 6424/1624 style build, using @sluckey 's very nice layout and schematic: http://sluckeyamps.com/supro/supro.htm

I'm using reclaimed iron--a PT from idk where, and OT from '64 Baldwin organ.

Bending my own chassis from 0.090" stock. It's overkill, but I love the thick metal. I have to score part way thru with table saw to be able to bend it with my cheap Harbor Freight metal brake.

I splurged $50 on a proper tool to set the 1/4-20 rivnuts.

Project is going into a salvaged Dean Markley cab'nit: real 80s particle board, this one, not that pretend particle board...

IMG_1520.jpg

[joeboo88]

Good start Aaron. I built one a few months back, using Sluckeys schematic and like it lots.
I have Supro Colored tolex butwill have to wait till spring to build a combo cabinet, and not that pretend particle board either
Joe

[fred.violleau]

Very interesting! What did you use to router the metal sheet? Also, any schematic to share?

Thanks!

Fred.

Fred.

[xtian]

Very interesting! What did you use to router the metal sheet? Also, any schematic to share?

Schematic and layout: http://sluckeyamps.com/supro/supro.htm

I used Greenlee hole punches for the 1.125" and 0.75" holes, and a jig saw for the ugly cutouts for the IEC-with-fuse and the OT (these ugly holes will be hidden from view).

[Synchu]

The chassis looks very nice.
Rectangular holes still bother me as well and I still don’t find enough excuses to buy the IEC punch.

I’d love to hear some tones from this build once is done.

Niki

P.S. Gotta love 80s particle board. Adds a bit of hair to the tone...

[jam-mill]

Nice work Aaron!

I like the start-from-scratch approach to making the chassis.

-jack

[sluckey]

Did you run out of turrets? There's a missing turret and jumper on your board.

[xtian]

Did you run out of turrets? There's a missing turret and jumper on your board.

Shut up.

Uh, I mean, thanks for looking so closely!

[xtian]

Progress.

@sluckey -- I fixed it.

IMG_1528.jpg

[sluckey]

Hey, that works!

[xtian]

Finished and working, but tremolo is not working.

Plate voltage is 360v, cathode 26v across 355R resistor. All other voltages are almost exact matches to Steve's values. My output transformer is small, which is probably the limiting factor in output wattage--I'm getting 12 watts clean into 8 ohms.

I just finished measuring every resistor and double checking each connection in the tremolo circuit. Can't find anything amiss. But no LFO audible, nor visible with scope on V1a cathode.

IMG_1530.jpg

IMG_1531.jpg

[fred.violleau]

Xtian, very clean building as usual, a true wonder for the eyes and hopefully to the ears as well!

A youtube clip maybe?

Fred.

Fred.

[xtian]

Xtian, very clean building as usual, a true wonder for the eyes and hopefully to the ears as well!

A youtube clip maybe?

Sure! Soon as a get the tremolo sorted.

[sluckey]

Might be hard to see the trem signal at V1a cathode because of the 35µF bypass cap. Check it at the footswitch jack instead. Should be ≈ 10VAC RMS @ 3.6Hz – 7.2Hz as read with my Fluke 87V.

If V3-6 is steady the oscillator is not working.

[xtian]

Yeah, it's not working. I have been comparing the Supro values to the Wizard's values: http://www.valvewizard.co.uk/trem1.html

I added a 47uF bypass cap across the 1K cathode resistor, and dropped the anode resistor from 270K to 100K, and now I see a LITTLE wiggle, but not much.

I have also tried three 12AX7s.

Yours worked right off?