Linear Power Supply DIY Weekend Project

[crooner]

Hi fellas!

While not completely convinced about the benefits of a linear power supply for the Squeezebox, the idea of building a dedicated supply seemed like the perfect weekend project.

I headed to Gateway Electronics, one of the few decent places for surplus electronics here in San Diego.

Overwhelmed by the wide variety of chassis power supplies, I was about to settle for a 5 volt 1.5 amp Atari wallwart probably intended for a 1980's computer. It was heavy enough but the case appeared to have been welded shut, no screws. That was a big no-no, so I headed back to the power supply section.

After looking at a few oddly shaped and old Lambda supplies, I came across a nice linear chassis with a fairly hefty transformer and plenty of TO-220 regulators. I noticed it was made by Elpac and rated at 5 volts 2 amps, presto!!! looked like the perfect supply for my project.

The open chassis was not suitable for safe operation without some sort of case. I found a nice aluminum project case that would prove a perfect fit. To round up the supply I bought a fused IEC connector, power cord, fuses and two color coded binding posts.

Total cost was around $40.

Here's a shot of the naked chassis while doing initial power-up checks. Voltage was a rock steady 4.99 volts on my Fluke VOM.

[crooner]

While I was at it, I measured the stock supply's voltage at it read 5.17 volts....

[crooner]

I had to drill holes for the IEC AC connector and binding posts. I am not a pro so they are not perfect, specially the IEC connector :-)

Here's the chassis installed in its case during the final testing...

[crooner]

Here's a frontal shot of the supply.

I decided to add a ferrite core to the AC cables going to the transformer. I had one lying around so why not try it!

Here you can see the nasty hole I punched for the IEC connector. Thankfully it will be hidden from view with the cover on!!!

[crooner]

Here's a pic of chassis with the cover on. I had some Radio Shack banana plugs in my parts box and I thought they would look nice :-)

[crooner]

I am running the squeezebox with the new supply right now. It runs warm on the regulator side, not surprising since it uses five TO-220 pass transistors.

I can't really say if I am hearing a difference or not. The rest of my electronics are still warming up. It would appear the sound is slightly smoother....

I placed the supply in my lower rack, away from the SB itself.

I still have a switching power supply in my laptop. I plugged in on a different outlet to minimize any possible interference. I can always unplug the computer since I usually have it off when listening to music.

I hope you enjoyed my little project. Would love to read some comments!!

[nelamvr6]

Looks like you did a pretty good job! Time for a beer! Now you can relax and listen to some music.

[crooner]

Thanks!
I gotta check if I still have a Heineken left in the fridge :-)

Everything is sounding great right now!

[crooner]

Well...This thing runs really warm. For safety's sake I decided to drill some holes on the bottom of the enclosure for ventilation.

I will also get some 0.25 amp fuses tomorrow. I am guessing this should be the right figure.

This power supply seems to have nice filtering and regulation, I also see an IC in there...

[crooner]

This sucks, I am now hearing some intermittent buzz coming from the box. It's mechanical in nature and caused by the power transformer. I will have to get in there and tighten the tranny bolts or add some damping material.....