Gigaworks regulated PS

[dahlberg]

Is there anyone here that has tried this Gigawork PS. Any comments would be greatly appreciated. First project would be to replace the switchmode PS in my "LEM-dx24" digital filter.

Low noise High Current dual power supply LT1083CP kit | eBay

[!]

^ It would be easier to judge if they included a BOM, a schematic, and shots of the bare PCB to see how it's routed, and some basic info about your input and output voltages and currents needed, but from what is present it looks like a pretty standard/basic LDO linear design, assuming no faults it should work fine. I don't recognize the Nichicon capacitors (lmaking me wonder if they are fakes) but I am most familiar with their low ESR types (which would've been a better choice, but everything has its price).

Personally I would prefer one that used 35V or higher rated electrolytic capacitors so it could take 24VAC input too, but if the transformer(s) you'll use supply 18VAC or less (they spec even less, 15VAC), it should meet the basic need.

The potentiometers on it make setting the voltage convenient, but for long term use I would replace the POTS with fixed resistors so there is no mechanical aspect or voltage drift over time (set POT to get the right voltage then measure the resistance and use two suitable fixed resistors as a replacement, or consult the LT1083 datasheet for the equation to calculate resistor values.

It is still left up to you to determine if your input voltage, minus output voltage, multiplied by current needed, is within the capability of the heatsinks provided in the environment (case) it'll be put in. The page states usage up to 3A but that highly depends on input-output voltage difference too. I would "guess" those heatsinks are good for about 4-5W (at most) dissipation in a vented chassis, but that the capacitors nearby won't like the heat level at 5W.

[CharlieLaub]

This is what you want:
Power Supply Board Kit, PCB, Based on LM317 & LM337 IC

dual regulated supply, done right. They show the schematic, so you know what you are getting. Very reasonable priced, too.

-Charlie

[dahlberg]

Hello.
Thanks to both of you.
For the first project I would need +/-12v and +/-5v and if I'm going for the gigawork PS it will also be dual regulated, how the pcb is routed is for now a mystery though (tried mailing for answers but the mail bounced, I will try again later). For the gigaworks it seems that I'm getting a lot of components for 26$ though. I'm quite satisfied with the "Lars Dac1 mk2" from gigawork as well so......

The other PS looks nice as well but 1,5amp seems a bit on the edge,
the crossover is labeled with "power consumtion 40w"

I'm still looking for a decent transformer, 50va 230v 2x9v + 2x12v but I have'nt found one yet.

Ps. Are there any significant differences betwen the actual regulators.

[!]

The gigaworks regulators are LDO, low drop-out type which means you can run an input (rectified DC voltage from the transformer) much closer to the output voltage, which is useful if your design doesn't have a lot of voltage margin and/or to reduce heat. However if you find the transformer(s) you mentioned, with those output voltages, either board should do the job sufficiently, the regulator choice isn't very significant. One may be slightly better regulated than the other but for practical purposes doubt it will make a difference, other factors like board layout, wiring, the powered device design will make more of a difference.

It would be easier to know if there are any issues with either if you specify the following two things or at least consider whether they cause too low a voltage or too high a heat level with the transformer and PSU board you consider using:

1) What transformer, once you find one, the voltage rating you settle for if you can't find the ideal one.

2) What current for the +-12V and for the +-5V. For example, suppose you needed 200mA on +-12V and bought the transformer you mentioned. With it having 2 x 12V, rectified you have +-15.6V peak going into the regulator. Subtracting +-12V output it's a 3.6V difference. That is enough of a difference you could use the non-LDO regulator design that Charlie linked, in this case the amount of heat either product produces is the same. 3.6V x 200mA = 0.7W heat, a low enough heat that either PSU could handle it.

However, if your current was high enough to cause 3W or more heat, the gigaworks you linked seems more suited because it "looks" like it has larger heatsinks. The same applies to the 2 x 9VAC transformer winding(s) and +-5VDC outputs, multiplying voltage drop x current to get power loss will tell you if the heatsink looks sufficient or not.

[dahlberg]

Just measured currentdraw, 12v x 200mA 5v x 1000mA.

I found some transformers, sec 2x12 and 2x6v

[!]

With those transformers (assuming rated for that much current) either regulator board would work for 12V, but on the 2 x 6VAC winding(s) you'd only have roughly 7.1VDC going to the regulator so the Gigaworks would work because it uses the LDO regulator but the other board wouldn't work as a 2.1V drop from 7.1V to 5V is too little for the regulator ICs it uses.

Both boards have sufficient heatsinks with that load and 2x12VAC and 2x6VAC transformer.