Cash in hand

[Andy Le Blanc]

close tolerance with the test fit... 1/4 inch

combos are tricky to scratch build as a one off, if it didn't fit I'd be screwed.

I'll plan the next one much looser, it'll make for an extra inch, maybe just
plan the speaker board differently, one board width can make the difference

[Phil_S]

Hey Andy, I think this one qualifies as amp humor. Gosh, did you ever get lucky. Even luckier if there is no unwanted magnetic coupling. Good luck!

[Andy Le Blanc]

we'll see...

[Andy Le Blanc]

happy find at micheal's crafts... they have over to the crafts a selection of birch plywood

that gets incredibly thin... 32nd's and 16th's... great for amp dashboards

easy to work, glue on or attach with the pot nuts... easy to apply art to, kind of nice.

[Regan]

Double stick tape works good with control panels too
Nice amp!!!
Regan

[Andy Le Blanc]

pictures and progress

[Andy Le Blanc]

a couple more of the dash

I couldn't find a finishing washer for the pilot, so I made one out of a mic stand nut

[Colossal]

Very nice Andy, thanks for sharing those. Is the preamp board material masonite?

[Andy Le Blanc]

the issues that have come up so far have been standby pop, presence pot scratch and heater hum.

standby pop is a one cap fix

the client wanted a old fashioned presence control, but boy oh boy...
I'd forgotten just how apparent the scratch could be, voltage one the pot...
I'll be fixing that..

I'll put in a hum pot too, I'm on the fence whether to reference it to ground or -/+

the only real mod from circuit is how I have the screens, a 470r series resistor
and a bleeder to ground before the screen grid resistors , keeping the screens 5-10 v negative relative to the plates,
zero signal at the selected bias point for the power supply... Tube type doesn't matter (with exception of ideal loading) if you bias the PS to a consistent point and maintain the
screens relative to the plate at that chosen operating condition


The PCB is hard board (turd board), actually has an electrical rating that improves with age. a vintage character thing.. too funny

[rp]

Does that thin veneer drill ok, cutting edge of bit doesn't catch and tear or break it? How'd you do the graphics? Looks nice BTW.

[Andy Le Blanc]

getting there still some clean up to do and some value substitutions

[Colossal]

Andy, thanks for identifying the board material. That looks slick. I like the Faraday coil around the tone stack leads!

[Andy Le Blanc]

It's plywood... and it was fine to machine, surprisingly.

I cut it to size, clamped it the chassis and drilled it in place using the chassis as a guide, using a stepped bit.

The lettering is just pencil and a stencil, under a quick coat of poly...

keep it stupid,.. simple

Most issues are resolving, hum pot helps... still have to chop stick for hum
may replace a few grid leads with shielded cable.

Still on the fence about the bass response, cap values post of, and the input cap of the phase invertor.

already been trying out 12ay7 in the pre and 820 vrs 1.5k at follower driver.
been liking a 12ay7 in the first stage, its from a twin 5e8-a, and a 12ax7 follower.

most else is coming together. I be back onto finishing the cabinet

the tight coil around the tone stack leads does seem to help, more for shielding,
but I know it effects tone a smidge,

oh ya turd board.. theres such huge variety in vintage amps, and none of it is any good, the capacitive effects of the crap materials that end up inside of amps does effect tone, its stupid... but it does, you don't necessarily want quality, for the tone...

[Andy Le Blanc]

a few changes very near the completion.

[Andy Le Blanc]

It seemed to settle out on .047uf caps on the power side, and a .0047 input cap to the invertor.

Theres a good deal of variation thru out fender and marshal...

Installed shielded cable on the grid lead of the follower, from the tone stack to the input of the invertor,
and the grid lead of the input side of the invertor.

between this and a 250r hum pot, got the rig down to nearly hum free.