I want to build a power supply

[Agent 48]

I would like to build a 13.8 volt DC regulated power supply that can deliver at least 7 amps 10 amps would be more ideal.

I have most parts already such as a couple of decent mains transformers - output 15 volts AC. I have high current diodes suitable metal boxes to house stuff in to and I have spare toggle switches rated for 240 volts plus a few good heat sinks and terminal posts. I have a lot of parts to build a power supply.

I've already made the bridge rectifier part... mounted the transformer into the box...

Now there are a lot of videos and schematics online which is all very well but the thing I'm lacking is something that will give me the current I require, this power supply will need to give me between 7 & 10 amps?

[ch25]

15V from transformer is not enough.

[Agent 48]

OK I can put that transformer aside for something else.

I have another transformer but its on the large side so a bit too big for the original box I had in mind to use. I have another box I can use for it and that can deliver 30 volts AC or 50 volts DC when its connected to another AC to DC rectifier I made for it years ago. That one came out of a broken 200 watt audio amp maybe that one is better to work with?

I also have a microwave transformer.

[Agent 48]

I will do this with the 15 volt transformer just to make use of it.

[Buick Mackane]

If you want a power supply with more current than you'll ever need take a look at server power supplies. There's a ton of information about them on the forum and they are very cheap. A few simple modifications are needed to bring them up to 13.8 volts.

[Agent 48]

There not those switch mode power supplies?

I wanted to make use of my parts I've got. I found a ready made board 13.8 volt regulator DC to DC and can deliver up to 8 amps so that will save on some hunting about for circuits and components. All I have to do is build the bridge rectifier and the rest is ready made.

[Buick Mackane]

There not those switch mode power supplies?

.

Yes they are. But the one i'm using that can deliver around 70 amps is an HP Model. And has a very clean output. No strange noises heard on the bands

[14CS06]

Hello

6 x TIP 2955 = 30A

@+
Claude

[Agent 48]

Interesting... They seem cheap enough on ebay I've been reading up on them.

I know with the ATX PC power supplies they worked as well but were only ever a temporary solution. Maybe the server power supplies are different and better. They sound like they could be.

I have my old trusty 20 amp linear power supply to use. My main interest was building one from the parts I have and making use of my old mains transformers. I'm more of an old skool man when it comes to ham gear. I may buy one of those HP server power supplies to play around with and maybe mount one into a more vintage style enclosure with a toggle switch & power LED with some terminal posts, definitely another possible power supply project worth thinking more about...

[Agent 48]

Hello

6 x TIP 2955 = 30A

@+
Claude

Excellent... thanks for the schematic

[ch25]

Hello

6 x TIP 2955 = 30A

@+
Claude

Best way to fry your radio.

[Buick Mackane]

Take a look at the link below from our resident power supply guru sureshot. Sadly no longer an active member. Dave really knew his stuff.


viewtopic.php?t=49694&hilit=strictly+linear

[ch25]

PS mentioned up is also a bad choice.
In case of failure full voltage and maximum current after rectifier goes to the radio.
There is no protection at all.
Chris

[Agent 48]

Crowbar circuit... that will protect the transceiver.

I'll also be adding a couple of extra fuses just before the output of the power supply. I'll probably aim for between 10 amps and 20 amps keep it simple. Lots of good info on that other thread I've been learning a lot about power supplies.

[Agent 48]

I also have quite a few of those old 3 amp CB power supplies I think they do about 2 amps MAX they were the type that got banned in the 80s because they were deemed unsafe and I can see why with the fuse being on the wrong side and the fact that there is no protection between the metal case and the transformer pins so if you happen to put slight pressure on the top of the power supply, the metal casing touches the transformer pins.

I plan on improving these and they need re-capping anyway. As they need work I may as well see if I can squeeze another amp or two out of them by changing some components. There were better transistors made since these power supplies were made. If I can make them 4 - 5 amps then its all good. They go for about 30 to 40 quid now on the bay but I'll be hanging on to mine.

First is to tackle the safety issues.

There was a video done on them somewhere on YouTube

These are the ones I have. I got lots of them.