[Ferdi]

Hi guys, I plan to build a new power supply for my (RWA modded) SB3.

I've ordered a PSU from Welbourne Labs:
http://www.welbornelabs.com/psreghc.htm

I've ordered a transformer from Amplimo in NL:
http://www.amplimo.nl/download/80va.pdf

I've ordered a noise filter from Conrad:
http://www1.nl2.conrad.com/scripts/wgate/zcop_nl2/~flN0YXRlPTI2MDAyNTYxNTk=

This should allow me to make a nice kit-based powersupply. I am quite certain I can solder up the circuits according to the instructions and make the PSU work.

I am struggling with mounting of the boards in the case I bought. The case consists of steel top- and bottom halves that have no obvious way of mounting anything. So far I've thought that I might just drill holes in the steel plate and connect the boards using small nuts, bolts and seperators.

Am I missing anything obvious? how do you guys mount circuit boards?

Thanks!

Ferdi

[ohenry]

I like to use 4-40 or 6-32 threaded standoffs made of either nylon or aluminum.  They come in different lengths.  Double female threaded standoffs are nicer to use, IMO, because they allow you to secure the standoff to the chassis and board via a small screw from each end. Also, there are male/female configurations where one end (the board end) is secured with a nut.  Those work well too, but the hex nut can take up more space on the board and can be an issue on some very small and crowded boards (e.g., amp3 t-amp kits).

Unthreaded spacers are a little more cumbersome to use because a long screw must traverse the spacer and board from the bottom and be secured with a nut.  It sounds easy enough, but in a crowded chassis, that can be a challenge.

Check out Digi-Key or Mouser or your local Rat Shack for standoffs.  Rat Shack typically stocks the 1/2 in. long, 4-40 threaded double female aluminum style in packs of four.

[Ferdi]

Hi Ohenry, standoff is the word I was looking for. Separator was the best I could come up with. 

Comes from not having English as a first language, I guess.

Any other good tips and suggestions, anyone?

[Wayner]

Don't forget grounding the chassis as it is made of aluminum. A 3-prong grounded cord is advised.

W

[Ferdi]

HI guys, thanks for the good suggestions. I'll keep you updated on my progress.

Werner, the case is actually steel but I'll make sure there a good grounding connection.

Have a nice Sunday!

[andyr]

Hi Ferdi,

Mmmm, sorry, I have some problems with using "standoffs" - either nylon or aluminium - as they are solid!

I believe in isolating the PCB from the case as much as possible ... so that vibrations set up in the case from either external (air-borne) or internal (power transformer buzzing) vibrations have a difficult time getting to PCBs.

So I stand off PCBs from the case bottom using 3/8" Sorbothane pads, using nylon bolts (not steel bolts, which are "solid").

And, yes, make sure you have an earth wire from the chassis IEC socket ground pin to a bolt through one of the case sides (or base plate).

Regards,

Andy

[ctviggen]

And also use "star grounding" if you have multiple grounds.  Star grounding is essentially grounding every ground to a certain point (i.e., chassis ground), and this system will look like a star in the sense that all wires will be spaced radially around the ground screw. 

[Ferdi]

Hi guys, thanks for your comments. 

I have since received all the parts and put together the powersupply. I have some more considerations but will start a seperate thread for that.

Ferdi