This definitely looks like a switching power supply. Modifying the circuit into a lab supply which goes down to (somewhere close to) 0 V and with adjustable voltage and current limits will be non-trivial. At best you may be able to use one of its output voltages as input for a power supply, similar to an external power brick or battery used in Dave's and Richard (amspire)'s designs.
If 18 W is from the external label, than that's probably the peak power it can draw, not the amount of DC power it can supply continuously. The efficiency is below 100%, for starters. It will also be divided across the various output voltages, although the majority of the power will probably be on one of the rails (15 V for the motors?).
They work great as power supplies. I have about 4 bench supplies I've built from power supplies salvaged from dvd players, vcr's, directv receivers.
All the ones I've salvaged have been a separate board, so what I'm about to say might be of no use for you but could be of use to someone else.
Usually there will be a bunch of outputs 3.3,-5, 5v, 12v, 9v, 6v, etc.. but they will be off. This is because there is an enable line that needs to be pulled high to turn the power supply on. Usually there is a 3v3 or a 5v output that is on all the time, this is what you use to pull the enable line high and turn the rest of the power-supply on. This is because normaly there is a power latch and when you hit the power button on your equipment it is turned on by pulling the enable high.
This is not universal, some are always on, some need to be pulled low, so it will just take some fiddling usually before you can use them.
Oh, and flatscreen monitor back-light drivers are a nice source of 600v @ a few ma. I want to make an adjustable high voltage power-supply with one of them one day. Pretty dangerous if you don't know how to handle high voltage though. So I don't suggest you mess with this unless you know whats up.
That must've been a really cheap VCR if the PSU is part of the main PCB and the input lead is just soldered in... but looks like they were nice enough to silkscreen where you should cut if you want only the PSU
The outputs will be the traces that cross the line, there will be output rails and ground. Possibly an enable input as well.
The PSU circuit itself looks very simple and reminds me of a laptop AC adapter. It's all low-density through-hole construction so tracing the schematic won't be hard. I don't see any controller ICs, so the oscillator is probably made from discretes. Keep in mind this also means there is likely no protections either.
2501: 4 legs, couldn't find anything that makes sense from the web.
switching power supply can't be without some sort of oscillator or IC controller, correct? and what does "protection" mean then, if you don't mind explaining that a little?
They work great as power supplies. I have about 4 bench supplies I've built from power supplies salvaged from dvd players, vcr's, directv receivers.
All the ones I've salvaged have been a separate board, so what I'm about to say might be of no use for you but could be of use to someone else.
Usually there will be a bunch of outputs 3.3,-5, 5v, 12v, 9v, 6v, etc.. but they will be off. This is because there is an enable line that needs to be pulled high to turn the power supply on. Usually there is a 3v3 or a 5v output that is on all the time, this is what you use to pull the enable line high and turn the rest of the power-supply on. This is because normaly there is a power latch and when you hit the power button on your equipment it is turned on by pulling the enable high.
This is not universal, some are always on, some need to be pulled low, so it will just take some fiddling usually before you can use them.
Oh, and flatscreen monitor back-light drivers are a nice source of 600v @ a few ma. I want to make an adjustable high voltage power-supply with one of them one day. Pretty dangerous if you don't know how to handle high voltage though. So I don't suggest you mess with this unless you know whats up.
no, touchh, this is very helpful and useful to me, thank you very much, really appreciate all that info!
when measuring, i just plugged it in without pushing the power button, and got that bunch of voltages. guess this means the power is always on? advantage of cheap VCR's
you have 4? could i have one?
do you have the circuit design, physical design, the building of them, and maybe some notes, warnings, etc., documented somewhere on the web?
thank you for the high voltage warning too, that's what scares me away form vaccum tubes for now, but they do look cool.
From the photo it looks like an optocoupler / optoisolator -- "NEC 2501 optocoupler" turns up hits on the web that might be worth investigating. You can see the fat white line nearby that separates the two sides of the power supply (control and grunt, basically), and a slot in the board under the component; a four-legged component that straddles such a split is a reasonably good bet to be an isolation component in the supply's feedback loop. Basically it allows the control side of the supply to see what's happening in the power side without having a direct connection that would break the isolation.
Or at least, that would be my understanding, but I could be mistaken since I'm pretty much a newbie at this sort of thing too
Yeah I guess the cheap VCR's have all power enabled all the time.
Sadly I don't document most of the stuff I do, something I should start doing more often... Next time I find a power-supply I'll and mess with it I'll try to document it.
You can use the 5V for micros , 15V for opamps ( Sadly no negative voltage so you have to use a virtual ground )
+/-30 i don't really know what they are useful for , 37(or rather 35) neither do i know what they are useful for .
High voltage opamps maybe ?
You would have to rewind the transformer to do that.
You can be okay with a http://www.bristolwatch.com/ele/lm317.htm and a small heatsink , i don't think there's much power anyway .
But a decently sized 6C/W should be okay .