Crawls Backward (When Alarmed)

IconProjects, musings about guitar builds, guitar repairs, vintage tube amplifiers, old radios, travel, home renovation, and other stuff.

Transformers, Sockets n' More on the '42 Amp

When I originally was envisioning this amplifier, I looked at a lot of pictures on the internet of other homebrew amps that folks had built.  One thing I really liked was the look of a polished metal chassis surrounded by a wood frame.  It looks really...well, finished and perfesshinul-like. 

So I set about trying to polish my Budd aluminum chassis.  This is the short version of a long story, btw. 

First I just took Mother's Mag and Aluminum polish to it.  The polish is great - I use it a lot.  It gets a nice high gloss shine.  The problem was there were a fair amount of fine scratches in the aluminum from...well, I think aluminum just attracts scratches magically, like ants to an ice cream cone dropped on the ground.  So then I started reading (on the internet, so it all must be true) about using fine sand paper on the aluminum.  This I did, from 400 to 2000 grit.  The scratches were then super fine.  I tried the polish.  I even used a machine polisher.  It looked great from 2 feet away.  But up close it was not meeting the Yr Fthfl Blggr Quality Assurance Test (tm). 

So I gave up, shot the thing with primer and then copper hammertone paint.  I suppose there is a secret to getting a seriously perfect shine on aluminum, but I ran out of patience this time.  The paint turned out pretty well as a Plan B anyway.

Now, back to the fun stuff!

With the chassis freshly painted, I can finally start bolting on the hardware.  This is straightforward.  You can see where I use rubber grommets on the chassis holes where wires pass through - e.g. the transformer wiring.  Gives a neat finished look and prevents 300 volts DC from shorting to ground if wire insulation were to chafe.

In the process of assembly, I found that one needs to be careful putting fasteners onto a painted chassis.  Should your screwdriver slip, you might make a scratch in your paint.  Not, mind you that I did this...okay I admit it.   After the first slip, I put blue painters tape around all the holes to prevent scratches.

Here's the final chassis with the power (on the end) and output transformers, tube sockets, input socket, speaker connectors, volume pot, and power switch all mounted.

The big rivets down the middle hold a couple of terminal strips on the underside of the chassis that we'll use for wiring.  True point-to-point, baby, no PC boards here!

I also made another mini-advancement in my building on this project.  I started to use nuts and bolts for the tube sockets, but they looked really garish, cheap and too homemade-like.  So I invested in a pop rivet gun and used rivets for the tube sockets and terminal strips.  Then I took metal polish to 'em - look pretty neat I think.


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