Chassis Layout Tutorial/Tips

[w9bea]

Hi All:

I just finished the Power Supply for my Heathkit VF1 VFO.  Works great, just need a socket, a fuse holder and a few other touches and it is done.  Makes plenty of B+ and darn near zero ripple.

I am interested in building a medium power tube AM transmitter and perhaps an amplifier down the road.  I am poring over my old handbooks thinking about designs....

Is there a tutorial, a paper or a website that shows one how to properly lay out a chassis?  I did okay on my layout; in that I placed the filter choke under the chassis away from the power transformer....  but I suspect I could have been smarter on where I placed my terminal strips, the placement of the rectifier socket, routing or wires, choice or wire colors, etc.  When I go to build a more complex project with multiple stages like a transmitter, I think I need some schooling on where to mount components to eliminate heat, hum, flashover and feedback problems.

Any such thing on the internet or a book I can go off and buy?

Appreciate the info.

73--Wally W9BEA

[W3GMS]

Wally,

Well first off congrats on finishing up your small power supply. 

A lot of what your asking comes from understanding the circuits that your building.  You can take a great design and lay it out wrong and it just will have a multitude of problems.  Things like power supplies are not generally very critical.  When you get into RF stages and even audio amplifiers it gets more critical.   I usually look at the circuits "loop currents" and that helps a lot in assisting with a good layout.  Things like bypass capacitor placement and there ground returns are also important. 

I do not know of any cookbook on this subject and again, start with understanding the circuit and understand the purpose of each component in the design.  After that, get some construction articles out of the handbooks and articles from magazines and look at the schematic and then notice the placement of the various components.  That should give you a basic feel for it. 

Nothing beats experience and start with something simple, maybe a 1 or 2 stage something and learn from that as you then build things with more complexity. 

As you begin, if any question come up raise them here on the technical section and I am sure you will get loads of guidance.  You can then go through them and pick the ones that seem appropriate to what your doing.   

Building is loads of fun and I think you will find it very rewarding.

73,
Joe, W3GMS

[Pete, WA2CWA]

QST, December 1951, page 25, How to Build a Transmitter
QST. July 1951, page 38, How to Layout a Transmitter

[N2DTS]

Depending on what you are building, and what parts you have, you have to play chassis chess.

Power supplies and modulators are not critical, but you still have to plan a lot, as some things should not be close to other things, room is needed for inputs and outputs, high voltage needs to have plenty of clearance, and for something to look nice, things should be symetrical and laid out is a sensible order.

I like my front panels having everything lined up and in the right places, and that can be hard with parts sizes and so on.

I get all my parts and lay things out many different ways before the building starts.
I might even have to use different parts then planned for.

For RF circuits, more planning is needed, grid circuits have to stay away from the plate stuff, parts not having high voltage on them should be close together with the shortest wires.
Anything with high voltage on it needs plenty of space between it and anything else.

I find the chassis chess the most fun part of building.
Using what is around to build something good looking that works.

[K1JJ]

Hi Wally,

Generally, if you lay things out the way they are logically presented/positioned in the schematic, this is a good start.


The power supply stays together, the VFO stays together, the tube RF input circuitry stays together, the pi-network components get grouped together, the low level audio is isolated, the high level modulator stays together -all isolated, etc.  

With audio and RF circuits, we don't want the inputs to "see" the outputs.  The higher the frequency and higher the gain of a stage(s), the more shielding and thought we need so this does not occur - or unwanted oscillations and stabilities may occur.

Spend some time looking over commercial and well designed homebrew rig pictures and you will learn a lot.

Good luck.

T