lab psu with negative and positive output (symmetrical?)

[neslekkim]

what is recomended as cheap ones here?, I have found some small that uses 7809/7909, but is there anything just a little bit better?
need it adjustable, for various testprojects, some use 12v, some 10v, some 20v etc..

I guess an Rigol dp831 could do, but maybe a bit overkill, something along the lines of this would have been ok I think: http://www.ebay.com/itm/371706127105

[bitseeker]

What you're looking for is a dual- or triple-channel power supply. Alternatively, you can use two separate single-channel supplies wired in series to provide positive and negative outputs. Multi-channel supplies usually save cost and space, and provide tracking of the positive and negative rails.

There are a variety of brands and models out there, but something like the HP E3630A (0 - 20V @ 0.5A, -20 - 0V @ 0.5A, 0 - 6V @ 2.5A) or HP E3631A  (0 - 25V @ 1A, -25 - 0V @ 1A, 0 - 6V @ 5A) are examples.

[CJay]

Depends how much money you want to spend and how sophisticated you want to be.

I've just picked up a Farnell TOPS3D which is an old, dual tracking PSU (+/-7-18V I think) with a lower voltage variable (4-6V) supply at some amps.

Ideal for a cheap bench supply for analogue things, think it cost £32

[neslekkim]

What you're looking for is a dual- or triple-channel power supply. Alternatively, you can use two separate single-channel supplies wired in series to provide positive and negative outputs. Multi-channel supplies usually save cost and space, and provide tracking of the positive and negative rails.

There are a variety of brands and models out there, but something like the HP E3630A (0 - 20V @ 0.5A, -20 - 0V @ 0.5A, 0 - 6V @ 2.5A) or HP E3631A  (0 - 25V @ 1A, -25 - 0V @ 1A, 0 - 6V @ 5A) are examples.

ah, those looks nice, not bad priced either if one get them used.
Do you know if the input voltage on these are adjustable?, can't find any in norway, but lots of them on ebay, but I guess they have fixed input voltage?

Buy the looks of it, it looks like E3630A and E3631A are totally different series also?, does not look alike at all? similarly with price?

[bitseeker]

ah, those looks nice, not bad priced either if one get them used.

Yes, you can get them used at good prices with a little patience. It's worth it for the quality. They're both linear power supplies and the lower-power E3630A is fanless, too.

Do you know if the input voltage on these are adjustable?, can't find any in norway, but lots of them on ebay, but I guess they have fixed input voltage?

I believe the 3630 is fixed input voltage. So, you have to get it with the proper rating. The 3631 has multiple taps on the primary. You select the voltage on the main PCB and change the fuse to fit the current rating for the selected voltage.

Buy the looks of it, it looks like E3630A and E3631A are totally different series also?, does not look alike at all? similarly with price?

Yes, they have different output limits, displays, cooling, etc. I included them as a couple of examples of good-quality triple-channel supplies with bi-polar output at a reasonable price on the used market. They also have good resale value if you decide to upgrade to something else later.

However, these aren't the only such supplies available, just something for you to get familiar with this type and know what to search for.