custom chassis: does material matter?

[denti alligator]

I have a custom Crack chassis that I got from Jim R. that looks to be some kind of plastic. Hard to tell, but doesn't look like metal. Maybe Jim can chime in on what it is, but I wanted to double-check that using such a plate would not pose a grounding problem.

 

[Leland Hankins]

If I remember correctly you will not have to isolate a component from the plate, i.e. transformer etc, but the component will still have to be grounded to the common ground tab.  I have built several Bottlehead and other products with non metal top plates without any problems, but heat can become a problem depending on the material used.

Lee Hankins

 

[denti alligator]

I think it's acrylic. Jim says PB was consulted on this when he ordered the plate, so maybe he can chime in on how best to ground it.

 

[Paul Birkeland]

I can't imagine that I would've recommended acrylic as a top plate choice for a Crack, unless there's a metal plate underneath it to hold at least the octal socket, otherwise you'll just melt the plate.

 

[Leland Hankins]

Plexiglass has a melting point of 320 degrees F (160 degrees C).

 

[denti alligator]

Honestly, I can't tell what the material is. I'm hoping Jim can clear it up. It's a nice looking plate, and I'd like to use it, but I want to be sure first.

 

[Kris]

Post a picture.

 

[denti alligator]

Jim thinks it might be polycarbonite (lexan). He had it made by Font Panel Express. That's all he can tell me.

Here's a pic.

P.S. I held it an inch from the surface of my electric stove, set on high, for about 10 seconds. No drooping. I expect this is lexan, though maybe I should hold it for 30 seconds to be sure.

 

[Deluk]

You can hot mould Lexan with a heat gun so not ideal in this application. Google it. It's very tough, but that's partly due to its flexibility.

 

[denti alligator]

Sure, but compare the heat the Crack generates to what a heat gun generates. Huge difference.

 

[Paul Birkeland]

To me that looks like an aluminum chassis milled by Front Panel Express that has been powder coated white, then engraved and infilled.  Notice how the edges of the cut holes are shiny metal?

 

[denti alligator]

The edges of the holes are actually transparent or milky white. I'll post a closeup later today.

 

[Paul Birkeland]

Take a utility knife and scrape away some of the material on the inside edge of the power transformer hole.

I recognize the work as being from FPE.  The white finish is slightly pooled on the edges, indicating that the piece has been powder coated.

 

[denti alligator]

Yeah, I think you're right. I was deceived by two things: 1) the way the light plays off the white top coat is really amazing and tricks the eye. At almost all angles it looks transparent on the inside. 2) it doesn't feel as dense or heavy as the usual BH metal plate.

 

[denti alligator]

Unrelated matter, but instead of starting another thread I'll post it here.

I appear to have applied too much heat to the power switch. One of the tabs is no longer rigid and moves with the switch (see linked video). Does this need replacing? If so, what is the part no. I'm looking for one on amazon, so I can use Prime to get it by Saturday, and it's hard to find one with the right dimensions.

https://www.dropbox.com/s/bkeabg9uxz825vs/IMG_0190.MOV?dl=0