Grounding areas on chassis plate

[rickdagless]

Hey hey,

I got my mainline chassis plate powder coated -- the guy who helped me out ended up doing both sides (bless him, I think he did it out of generosity), so I've got some scraping to do.  I know this was already mentioned in a thread before ( http://bottlehead.com/smf/index.php?topic=5831.0 ), but I just wanted to be super sure about the details as this is my first build.

Am I to scrape off powder coating at ever soldering tab?  I see, according to the manual, one near the IEC inlet, which I'm certain I'll need to do, but there seem to be others, too (I'm eyeballing 8 others)?  And also, there are the holes where the aluminum standoffs support the 3-lug terminal strip (need each standoff touch bare metal?).  Maybe I ought to go through and do all of the holes, just to be sure.

And finally, how should I go about the removal?  I have some sand paper here, but that seems like it might be a bit difficult to use by hand. <Added>Is there anything simple like a screwdriver I could use, or ought I to just go out and get a dremel?</Added>  What should it look like when I'm done?

Many thanks!

[Paul Birkeland]

The middle 3-lug t-strip on the attenuator is the signal ground connection to the chassis.  I would scrape the powder around all 3 holes where the standoffs mount to the plate there.  To get the powder off, use a tiny knife and just scrape it off.

Any solder tab connected against the chassis should have the powder scraped off under it.  There is one by the IEC inlet, a couple around the tube sockets, and one up on the headphone jacks for shields.

-PB

[rickdagless]

Ah, I see, so the solder tabs at the edges of the output transformers and power transformer are A-okay without scraping.

Many thanks, PB!

[Paul Birkeland]

Yeah, they are, but there is hardware that require a pretty exact hole size to function, so you will want to pass a 1/4" drill bit through the transformer holes (just in your hand is fine), and I think 3/16" through the OPT holes.  I don't really like to trust powder as a long term insulator.

-PB

[rickdagless]

Hey PB,

I understand the part about not trusting powder as a long term insulator -- how does that affect the transformers?

[Paul Birkeland]

You'll see when you get around to mounting the power transformer and output transformers.  We provide fiber shoulder washers that need to sit in the chassis through hole, and if there's powder on the inside of the hole, the washer won't seat properly and insulate the screw shaft from the chassis plate.

[rickdagless]

Ah, I see -- thank you!