Wooden Circuit Boards?

[Matt J]

Hey everyone.
New member and poster here, and I've got a question I was hoping some of you might be able to help me out with.
I've heard that HAD built a few amps using wood as the circuit board material. (I can't recall right off where I first read this from) Has anyone here tried doing this? Where there any drawbacks such as grounding problems or issues with heat buildup? I have a nice sheet of rosewood I'm considering doing this with for an 18w amp I'm building.

Thanks for any feedback!
- Matt J.

[crbowman]

Don't know about REAL wood. I know HAD used wood grained formica extensively. Real wood might be a little moisture sensitive.

[BobW]

Matt, I used wooden boards on this novel 50W ODS. I was trying to see how "cheap" I could make this. No problems encountered after over a year and a 1/2 of gigging w/ this beast. If you keep your amps indoors and, in addition to the internal heat generated inside the chassis, you should have any problem with a wooden board. the biggest issue is overheating the board with power resistors, soldering irons, etc.

https://tubeamparchive.com/viewtopic.php?t=2399

FWIW, the eyelets were way too big in the pics, the boards were re-built using smaller eyelets.

[Structo]

I haven't ever heard that HAD used real wood for his boards.
I think you are referring to the formica boards such as Two Rock still uses.

[BobW]

I haven't ever heard that HAD used real wood for his boards.
I think you are referring to the formica boards such as Two Rock still uses.

Agree, but believe that Matt could still use his rosewood board w/o any problems for his 18W amp build.

[Structo]

Yes it should work fine as it is a hard wood.
The only problem I foresee is making the rosewood thin enough to work with available eyelets or turrets.
I would also be tempted to spray a clear lacquer over the wood to seal it before installing the eyelets to guard against moisture absorption.
But of course that may cause unhealthy fumes when heating the eyelet when soldering.

I use 1/8" eyelets for 1/8" G10 board. Of course this is overboard as 1/16" board is perfectly fine.

I get the board and eyelets from Hoffman and he only sells the 1/8" G10.
I made my own staking tools out of a center punch I chuck into my drill press.
I use tape on the top side to hold the eyelets in place then flare the back of each eyelet with the punch.
Works pretty darn slick.

[briane]

in addition to the internal heat generated inside the chassis, you should have any problem with a wooden board.

While it will work, assuming you use hardwood (cuts it down to the one problem, see below), there is one major reason NOT to do this....

Big power resistors, especially in larger amps, can actually flame up when the burn up, for quite a little while (less than a minute, more than 20 seconds). If that resistor was tight on a piece of very dry 3/16" rosewood or oak (lets say for example)....There is an extremely small chance the board could catch on fire...And likely destroy the board before the lack of oxygen in the chassy put the flame out.

Basically theres a very, very small chance someday it could get really, really messy.

[Structo]

That is true as everything has a flash point at which it will catch fire with flames.

They do have those flame proof resistors (metal oxide) that I believe are designed not to actually flame up if they get real hot.
But they probably can get hot enough to cause something else that is flammable to catch fire.

Unlike the old carbon composition resistors that would actually catch fire if they overheated.

Another good method is when using the square sandbox type resistor is to mount it so there is an air gap underneath it, that allows more air circulation and will allow the resistor to run cooler.

I have a small printed circuit board that is from a solid state effects loop.
It has two 5 watt power resistors on it.
Where those two resistors are, the circuit board has several 1/8" holes drilled through the board to allow air to circulate around the resistor.
I thought that was a pretty good idea as I hadn't seen that before on any other pcb.

[Structo]

Matt, I used wooden boards on this novel 50W ODS. I was trying to see how "cheap" I could make this. No problems encountered after over a year and a 1/2 of gigging w/ this beast. If you keep your amps indoors and, in addition to the internal heat generated inside the chassis, you should have any problem with a wooden board. the biggest issue is overheating the board with power resistors, soldering irons, etc.

https://tubeamparchive.com/viewtopic.php?t=2399

FWIW, the eyelets were way too big in the pics, the boards were re-built using smaller eyelets.

Did you finish this amp Bob?
How thick was the wood you used for the boards?

Cool looking cab on that.

[Sonny ReVerb]

We discussed wood boards in this thread a bit.

[BobW]

Tom, the amp was finished over 2 years ago, was a novelity, and out of the realm of what I normally build. The boards were 3/16" from what I recall, and required longer eyelets, but found some locally available at a now, closed down, Mom and Pop electronic parts store. It required 6 standoffs for the main board support.

FWIW, as a novelity, the wood does work, but prefer garolite for better reliability, re-workability and appearance. In reality, since it takes a considerable cost to build a 100W or 50W HRM / ODS, etc, it's really pennywise and pound foolish to build boards using wood.

[Structo]

We discussed wood boards in this thread a bit.

I remember that thread.
Isn't there a slang word associated with the old fibrous Fender boards?
Like Fenderitis or something?

I believe that old board material was a thicker version of fish paper.
So being fibrous it is more prone to absorbing moisture from the air.
Especially if the amp is stored without use in a damp location like a basement.

The reason they used the backer board on the old Fenders was because they didn't really use any type of standoffs for mounting the boards.
They were screwed down tight to the chassis floor therefore requiring the backer board to insulate the circuit board from shorting out to the chassis.

There are so many choices for good circuit board material these days with the various types of Garolite or other epoxy/ glass sheet materials, that I think the only reason to use the wood grained Formica is for looks only.
Perhaps when HAD used it there was not the availability of the fiberglass boards there is now. I don't know. Maybe he thought it looked cool.
I know that Two Rock uses the Formica and most likely for looks only.
They also mount most of the first stage components on the back side of the board most likely for keeping them from prying eyes.

I think when we go beyond what is good for functionability we are simply geeking out for aesthetic reasons only because how many guitar players actually take a chassis out and ogle the cool circuit board insides?

You could always build the amp on Plexiglas boards and put them into a head cab made from clear Lucite if you want all the guts to show in all their glory!

[mlp-mx6]

"Tweed disease" is the term I've heard.

[Structo]

"Tweed disease" is the term I've heard.

Ah, maybe that was it or Tweeditis.

[Matt J]

Thanks for all the great responses!

I'm currently sanding down the board to 1/8 thickness, it's a nice sheet of rosewood with a good grain pattern to it, originally for a fretboard. I have all the eyelets and a template for drilling. I just picked up the eyelet staker and a rubber mallet to press them in, I will be using the tape on one side method too. Everything came from Watts Tube Audio.

Good info on raising the resistors up on the board to prevent heat damage. I'm making some strips, 3-4mm in height I will lay under them when I populating the board to keep them raised when soldering them in. I think it would be a good idea to spray the board with some type of sealant, would a silicon based water proof substance work well?

The build is not for anyone else, it's my own and something I've wanted to do for a long while, so I decided to add some extra touches to it. It's my first build, but I have taken a very long time reading up as much as I can on amp design, safety, and construction before I start anything serious. Patience is a real necessity in these sort of things! Kit is a GDS 18w TMB version. I've switched out the caps for Sozo yellow mustard, resistors are 1w carbon comp. Pots have been changed to PEC. Cabinet is from Swanson, all mahogany with silver grille cloth, that I am going to finish in a red stain color. I'm turning a sheet of ebony into the faceplate as well. I may add a boost footswitch to cascade the normal channel into the TMB channel.

I'd like to build a JTM-45 next, then move up to a Dumble. I'm especially interested in a ODS #40 clone.

Ha, you know I've actually considered putting the clear plexiglass cover on the back to show off the wiring? I'm still debating over it, but if I can find a piece that close in size I may see how it looks.

Thanks again! It's been very fascinating reading up on everything on the forum here.
- Matt J.