suitability for a pedal power supply

[njkmonty]

i was looking at making a power supply spyder, and i came across quite a few of these:

could these be suitable for isolated pedal use if i regulate each one?

[njkmonty]

i quickly gave it a shot,  made an over regulated rectifying circuit, and noticed that the voltage cycles from 7.8v throught  to 9v
i put some big caps after it, not much change
any thing that can be done to get it to stay closer to 9v?

[GibsonGM]

Well, they're not made to give quality power...different application and all.
You could try a bridge rectifier with filter cap, into a 7809 voltage regulator, see if that does it?

Don't know what you tried ("over regulated rectifying circuit"?), but if anything will do it, it should be the addition of a real regulator.   You should 'have enough voltage left over' to power the regulator if this is actually 11.6VAC  RMS.   After rect., you should get 14V +   

[njkmonty]

You could try a bridge rectifier with filter cap, into a 7809 voltage regulator, see if that does it?

thats what i did!

[duck_arse]

"soft start" might be a clue. (I rekon RG will be onto this soon.)

are you in AU, njk?

[merlinb]

i quickly gave it a shot,  made an over regulated rectifying circuit, and noticed that the voltage cycles from 7.8v throught  to 9v
i put some big caps after it, not much change
any thing that can be done to get it to stay closer to 9v?

Not quite sure what you did, but some of these off-line switchers will only give a stable output voltage when a decent load current is drawn.

[drea]

You might be interested in this analysis and teardown video of a similar power supply https://www.youtube.com/watch?v=O6_fa7ylXWA

I'm not sure I'd choose it to get a nice clean DC.

[njkmonty]

yeah qld, Duck-arse

i was looking into one of those spyder 9 isolated transformers from weber
https://taweber.powweb.com/store/wpdlxfmr2sch.jpg
but small bear and weber charge 50 - 60 just for delivery to australia.
the 2 options im looking at as far as i am aware are transformer and switch mode.
i was under the assumption that switchmode was inferior but ive come across gig rigs etc and unsure which way to go.
ive got a lot of pedal etc so i need a lot of isolated regulated any ideas
http://www.thegigrig.com/usa/acatalog/Power.html

[davent]

I went with 5 small dual 12v secondary transformers from Digikey, was much less then getting the Weber into Canada.

[AdamM]

Are these things isolated from mains? I'd concentrate on answering that question before doing anything else.

[merlinb]

Are these things isolated from mains? I'd concentrate on answering that question before doing anything else.

Yes, they have a little transformer running at high frequency. At least, most do... maybe some don't? Easy enough to measure the resistance between input and output wires.

[GibsonGM]

Not quite sure what you did, but some of these off-line switchers will only give a stable output voltage when a decent load current is drawn.

Best idea I've heard re. this thing - try loading it.   470 ohm resistor or something.  See what happens.

If you attached it properly to a known-working regulator, you should have been fine, so "it's probably not that kind of power supply" is my guess.  Yeah, some ripple could occur, requiring more/bigger filter caps, but I don't think THAT kind of swing should have happened...

[Jdansti]

It might better to take a used wall wart or laptop supply 12-20VAC or DC and regulate it down to 9VDC with several cheap regulators and caps.

[duck_arse]

+1 on the bust-out wall warts.

maybe you could sacrifice one to see what's inside usable. I was surprised by the queensland specific approval, woulda thort all the larger internationals would have covered it. I found this, but it only explains some of the marks, doesn't specify whether converter or plain transformer:

www.tridonic.com/com/en/download/Approval_marks_and_symbols.pdf

[merlinb]

I was surprised by the queensland specific approval,

Australia has some curiously rigorous electrical standards, considering how much more likely the average Aussie is to be killed by, oh, everything outside the house.

(or indeed, inside it... )

[duck_arse]

we're easily surprised, too.

[njkmonty]

its the giant bunyips you need to be careful of in the top end

[duck_arse]

I've only just turned on images, merlin, to see your pic. except for the 6 foot carpet snake in your photo, that could be my workspace in the shed. it's too cold at the moment to go out and check how those spiders are doing.