Is it okay for capacitors to be close to the main power transformer in S5 K-12 Kit?

[Maxwell Smart]

In putting my amplifier together I have found that my mains power transformer is going to be directly above the 3 large capacitors on the board. There is only about 1/4" clearance. I am wondering (and hoping) that this will be enough to not cause any interference, but I am a tad bit worried about the heat the mains transfomer gives off. Will this be an okay layout?

[Miles Prower]

That's not good. Capacitors don't like heat. What's your ventilation like?

[Soonerorlater]

Looks like you're departing from the photo in your previous thread

Question about potential transformer placement in K-12 Kit

Time for a new photo perhaps to show your new intentions.

[Maxwell Smart]

Yes, an unfortunate byproduct of centering the tubes in the case has now positioned the capacitors much closer to the mains power transformer than I originally anticipated. Here are a couple pictures that show the new layout:

[Maxwell Smart]

Also, to be clear, do I need to ground the base plate of the power transformer or should I only do the output transformers? Thanks

[Soonerorlater]

Your original intention was to hang your trannies from the top plate, is it worth reconsidering this idea, perhaps hanging from a support bar.

Wherever you end up putting your power supplies trannie it's still going to be inside a wooden enclosure which is a good insulator of heat, leaving vents in the bottom would help, drilling holes above the power trannie would also help.

[Maxwell Smart]

Well I am leaving the entirety of the enclosure uncovered on the bottom with 3/4" case feet raising the case to allow for convection cooling, There is unfortunately no room to hang the transformers from the top or otherwise in the case the way I have the current layout.

[Soonerorlater]

I, like you mounted my components on the underside of the pcb. My electrolytic caps are connected to the pcb via short leads and hot glued to one side for ease of upgrading. I didn't notice any bad effect to the sound in doing this. This would solve your issue of overheating the caps.

Mounting the transformer on a floor bar seems another option.

do I need to ground the base plate of the power transformer

Although your power trannie in your kit is supposed to be screwed to a wooden breadboard it was designed to be bolted to a metal chassis. The chassis would have been earthed. If the frame for some reason became live the current would then go to earth. For this reason I would earth the power transformer frame as well as your output transformers.

To avoid hum try not to "daisy chain" your earths together but instead bring your earths together at one point like the "centre of a star"

HTH Bill

[DF96]

To get convection cooling you need holes above as well as below. Think of it like an inverted bucket. Water stays in a bucket unless there is a hole. This is because water is heavier than air. Hot air from hot components will stay in a chassis, however many holes are underneath, because hot air is lighter than cool air. A metal chassis can lose some heat by conducting it to the outer surface, but wood is a poor heat conductor so can't do this.

You should earth all exposed metalwork, including fixing screws, and all major items of internal metal such as transformer frames. With a metal chassis this happens automatically when you earth the chassis, but with a wooden chassis you have to do it individually.