I was minding my own business the other day, when I saw that my PSU for my external LaCie HDD had a plug with 4 pins. Turns out it delivers 12V and 5V (2A on each, so that’s enough..)
Anyway, these PSU’s are available online for $20 (see link)
So I was wondering if they could be a good alternative to the original C64 PSU?
I’m probably going to just use 6582’s or 8580’s in the second MB-6582 I’m building, so if anyone could confirm this and help me with the internal PSU for the MB-6582 (Wilba?) to make it work, I’d be happy to try it out!
Might also be a great PSU for future 6582 builders!
The size is like a normal laptop-PSU, so it would be pretty neat!
Will probably last a lot longer then the C64 one too.
The plug could of course be changed to a 7-pin DIN (I could get one at a local store since I allready have the 7-pin PCB mount plug) - or something else.
It should be fairly easy to connect it via the 7-pin DIN socket and make a few changes to the PCB, so that you connect the 12V DC to where the 9V AC would normally go, so it goes through V1 (a 7809)… then depending on whether the 5V DC is regulated or not, it could connect directly to the 5V supply or be routed through an 7805.
You’ll have to check whether the 5V output is regulated or not. I’m assuming it is because it looks like a switch mode power supply, which could be noisy, I don’t know.
I just got the psu from pollin and tested it with my mbSID v2.
About the box:
* boards: modular boards from Mike, revision 2 (the old-school-stuff) upgraded to v2
* sid used to record: 8580R5B
* power: the above mentioned switch-mode psu, 5V directly into the core (w/o 7805), 12V into the sid module (with 7809)
* soundcard: SBLive Player 5.1 *shudder*
Results:
* the first picture is a capture of the noise.
* the second pic is the same part of the wave in spectral view (amplified by 15dB to make it more visible)
* listen to the attached mp3 if you’re not sure if that’s good enough for you
* I added the last screenshot to show what kind of noise I get when the cable is unplugged from the soundcard (before the yellow line sid plugged in, after the yellow line the cable is unplugged) - now you know why I said *shudder* earlier
I just realised that after our long testing session in the chat none of us posted the results - that’s a noisey noisey PSU. See the spikes? they’re bad.
Hihi Yes, it’s spikey (the noise itself is from my PC, the cable etc), but not necessarily noisey (yeah, spikes *are* noise too, I know ;-)). I wouldn’t recommend it for studio use or the likes, but for a cheap and easy to set up (well, there’s nothing to set up really) PSU it’s a good deal @ 3€.
I think both prices are very atractive (i’d never see a price as low as 3€! for a PSU :o), and I’m agree that depending of the setup/application or for tests it would be a good deal…, but unexpensive switching mode PSUs have a lot of negative issues when supplying to digital…especially if the current demand is near to the supply current.
Not only HF and RF noise, or spikes which could (when murphy say it ;D) fry or directly kill any IC, as the normal decoupling capacitors for linear PSU would be not capable of filter them without adding some RF decoupling components. Also, if not properly shielded, problems with electromagnetic interference could happen, by adding noise to near data lines or others…
I would prefer a good classic linear PSU design, its heavier and bigger because the xfmr, but it needs few components, it is durable (correct word?), and today there are very good Low Drop Regulators, that only have 1 or 1,5V voltage drop.
I’ve tried the 3pin regulator LD108X series (pin-to-pin compatible to 78XX), which depending of the current demand, have a drop of only 1V (compared to 3v of 78XX series) and as a result, xfmr can be little smaller, and they don’t get as hot as the 78XX do, as they only “eat” 1V…
As nILS said though, the idea here is a cheap alternative. Sure it puts clicks in the signal, but it’s **cheap**. Perhaps filter caps could reduce the clicking though, if you feel adventurous…
Perhaps filter caps could reduce the clicking though, if you feel adventurous…
Not really a good idea.
Many small switchmode supplies employ regulation feedback loops that are marginally stable these supplies may fail to regulate properly or may not regulate at all if additional filtering capacitors are used at the output.
