bench supply for under $300?

[justanothercanuck]

Hi,  I'm looking to get my hands on a bench supply (or possibly build one), but I'm having some difficulties finding one I like...

Even though the original Korad broke, I've been kindof using it as a yard-stick...  digital screen, load switch, 5A output, etc...  Thing is, I can't seem to find anyone that sells it in Canada.  Maybe I haven't looked hard enough. 

There's a couple of supplies I saw on mouser, but one was only 18V/3A, and didn't have a load switch... and the other one was too expensive for my tastes ($310).  The expensive one would work, but it also has this sliding 100W scale that I'm not really keen about.

I thought about building one from scratch, but I can't find any parts to build my own transformer, and buying a 48V/4.6A AC power brick costs like $150...  there's gotta be an cheaper way to build a bench supply...

Ideally, my specs are something like 30V/5A, that way I can work on laptops without requiring their OEM power brick.  I suppose I could take some ideas from Dave's supply videos, and use some LT3080's and change it to suit my needs, but I'd still need a way to power it.

So, can I stick it to the man and build one of these for pretty cheap, or should bite the bullet and buy a pre-made solution?

Thanks

[david77]

You can get cheap transformers out of old audio power amps. Something like a 2x 100W+ or so amp should contain a nice big transformer. Typically they'll have a split output like 30-0-30V or something similar. In the same amp you'll find at least two huge caps and even heat sinks 

Or have a look around for a ready made PSU. There are lots of them around for very little money from China. Search this forum for teardowns to find out what's good and what's not.
 

[Chalky]

Hi,  I'm looking to get my hands on a bench supply (or possibly build one), but I'm having some difficulties finding one I like...

Even though the original Korad broke, I've been kindof using it as a yard-stick...  digital screen, load switch, 5A output, etc...  Thing is, I can't seem to find anyone that sells it in Canada.  Maybe I haven't looked hard enough. 

There's a couple of supplies I saw on mouser, but one was only 18V/3A, and didn't have a load switch... and the other one was too expensive for my tastes ($310).  The expensive one would work, but it also has this sliding 100W scale that I'm not really keen about.

I thought about building one from scratch, but I can't find any parts to build my own transformer, and buying a 48V/4.6A AC power brick costs like $150...  there's gotta be an cheaper way to build a bench supply...

Ideally, my specs are something like 30V/5A, that way I can work on laptops without requiring their OEM power brick.  I suppose I could take some ideas from Dave's supply videos, and use some LT3080's and change it to suit my needs, but I'd still need a way to power it.

So, can I stick it to the man and build one of these for pretty cheap, or should bite the bullet and buy a pre-made solution?

Thanks

Yes, I bought the 30V / 5A triple output from BK Precision (via Digikey) for just over NZ$300, which is about US$250 I'd guess. 

My alternate plan was similar to your, I was going to build one using a $10 second-hand PC power supply, and then adding a circuit to deliver the variable voltage.  I still might do that.  I have also seen ready made boards that do just that - attach them to a PC power supply and they'll provide you with various voltages, not sure if variable though.  Cheers!

[kripton2035]

this one is available to canada as it is "worldwide free shipping" ...
http://www.ebay.com/itm/New-30V-5A-ALIMENTATI-DC-Power-Supply-Lab-Grade-Digital-Precision-YH-305D-220V-/200822608788?pt=FR_YO_MaisonJardin_Bricolage_ElectroniqueComposants&hash=item2ec1f5d394

[mariush]

I've bought a Tenma  2 x 32v @ 3A  + 5v @ 2A from Farnell:

http://uk.farnell.com/tenma/72-8695/power-supply-2-x-32v-3a-5v-2a/dp/1836057

It's about 180$ in my local currency. 

You can link the two outputs to get a single 64v @ 3A output.

The US version of Farnell's, http://newark.com, has the US versions with 110 V input:

http://www.newark.com/tenma/72-8695/dc-power-supply-32v-32v-5v/dp/59T9189

and they have the 2 x 32v @ 5A version in stock for just a bit over $200:

http://www.newark.com/tenma/72-8700/dc-power-supply-110vac-32v-32v/dp/59T9190

I've posted pictures with it and the insides here on the forum, imho it's a decent linear power supply, good components and construction inside:

https://www.eevblog.com/forum/reviews/tenma-72-8695-2-x-32v-3a-5v-2a-mini-review-teardown/?topicseen

[robrenz]

I have had THIS power supply for about 3 years and it works very well. At $170.00 it is a bargain.
It has the very important 10 turn pots on the voltage controls.  You can parallel the outputs for 30V at 6A.

[madires]

I have had THIS power supply for about 3 years and it works very well. At $170.00 it is a bargain.
It has the very important 10 turn pots on the voltage controls.  You can parallel the outputs for 30V at 6A.

You can't go wrong with a Mastech PSU. Inexpensive, mostly solid and easy to fix (no fancy stuff or parts).

[justanothercanuck]

The supplies I mentioned earlier were the BK 9110 and the Extech 382202...  I'm sure they're okay supplies, but who knows, maybe my standards are too high. 

If triosmartcal was in Canada, and the original Korad didn't blow up, I'd probably buy one in a heartbeat.  But I didn't know newark delivers to Canada, I'll have to flip through their stuff... 

Thanks

[PaulAm]

If you're looking for cheap; find a dead UPS that uses 2 12V batteries; that will have a nice transformer good for around 28V, then add this:
http://www.electronics-lab.com/projects/power/001/index.html 

There are lots of circuites, that's just one I had handy.  And, if you want a digital meter, add this:
http://www.electronics-lab.com/projects/test/007/index.html

[Thor-Arne]

If you're looking for cheap; find a dead UPS that uses 2 12V batteries; that will have a nice transformer good for around 28V, then add this:
http://www.electronics-lab.com/projects/power/001/index.html 

There's a update to that schematic here.

[justanothercanuck]

If your looking for the korad supply you can get it off Amazon.ca. I would check delivery charges and that it is the new version. For even if it cost $20-30 for delivery its not bad for the price. The seller seems to have good feedback.

http://www.amazon.ca/KORAD-KA3005P-Programmable-Precision-Adjustable/dp/B0085QLNFM

$125...  wow, that's cheap...  Even cheaper than triosmartcal.   For that price, I might just buy it for giggles to see if it blows up when I plug it in. 

I noticed the pictures are for the old revision, and the 240v version, but I asked them and they said it's the 120v version.  Looking through the comments seems they don't sell the old revision either, so it's looking very promising...   

[robrenz]

$125...  wow, that's cheap...  Even cheaper than triosmartcal.   For that price, I might just buy it for giggles to see if it blows up when I plug it in. 

Not cheap when you consider that it is only one output and you are getting three on the $170.00 Mastech.  But you are getting more features on the Korad.

[PaulAm]

If you're looking for cheap; find a dead UPS that uses 2 12V batteries; that will have a nice transformer good for around 28V, then add this:
http://www.electronics-lab.com/projects/power/001/index.html 

There's a update to that schematic here.

Thanks for that update.  I had just tagged the circuit for future reference without closely examining it.  Now I've added the update to the bookmark.  Add the LCD display to that and it looks like a fairly nice PS.

[nixxon]

If your looking for the korad supply you can get it off Amazon.ca. I would check delivery charges and that it is the new version. For even if it cost $20-30 for delivery its not bad for the price. The seller seems to have good feedback.

http://www.amazon.ca/KORAD-KA3005P-Programmable-Precision-Adjustable/dp/B0085QLNFM

$125...  wow, that's cheap...  Even cheaper than triosmartcal.   For that price, I might just buy it for giggles to see if it blows up when I plug it in. 

I noticed the pictures are for the old revision, and the 240v version, but I asked them and they said it's the 120v version.  Looking through the comments seems they don't sell the old revision either, so it's looking very promising...   

US$ 105 incl. shipping here:

http://www.amazon.com/KORAD-KA3005P-Programmable-Precision-Adjustable/dp/B0085QLNFM/ref=sr_1_1?ie=UTF8&qid=1359400572&sr=8-1&keywords=KA3005P

Reviews for the particular item aren't only positive, but the unit seems to hold up.

[grenert]

How about $135 for a triple output?  The model number suggests it is a Mastech, but who knows?  Disclaimer: I do not have this PS and have no idea if it's any good.
http://www.elexp.com/tst_0033.htm#3002

[justanothercanuck]

How about $135 for a triple output?  The model number suggests it is a Mastech, but who knows?  Disclaimer: I do not have this PS and have no idea if it's any good.
http://www.elexp.com/tst_0033.htm#3002

Looks ugly.