Hello everybody
I found 3 PSUs in 19" frames in the garbage at our studio. They came from our old interstudio communication system.
http://home.tiscali.ch/screamingrabbit/Pages/PSU/PSU.htm
When you electronic freeks have a look at the pics… is it possible that those are regulated PSUs I could use for my MidiBox LC?
If so, how can I find out how much power I can suck out of them? I think the fuses on the frontpanels are on the primary side of the trafo.
Greets, Roger
Sorry, but the link doesn´t work at my side (there´s coming nothing - even not 404 error).
But: You can test regulated/not regulated with an oscilloscope setted to AC. Put the amplification pretty high, if the 50 hz sinus is just in range of a few millivolts, it should be regulated.
*IF* the fuses are on the primary side: Just take the 220 Volts and the fuses rating to get a power rating (e.g. 20 Watts or whatever) and transform it back to the voltage + current on the secondary side (e.g. 10 Volts and 2 Ampere). To go sure take the half current (e.g. 1 A).
Normally this is OK. I hope… 8)
Hey Roger,
When you electronic freeks have a look at the pics… is it possible that those are regulated PSUs I could use for my MidiBox LC?
They seem to be regulated (The round metal things mounted of the PCB are power transistors in so called TO-3 housings). You can confirm this with an oscilloscope as pay_c mentioned already.
If so, how can I find out how much power I can suck out of them? I think the fuses on the frontpanels are on the primary side of the trafo.
The power should be sufficient to drive 10 MidiBox LCs ;D
These power supplys really look big.
Btw. I see there is something printed on the transformer not readable on the photos. Normally the maximum output current is printed there…
Raphael
Thanks guys!
I updated the pages with the transformer labels (on the PSU1 transformer is no rating readable anymore). I haven’t done this earlier because I thought it’s not only the transformer reliable for the power consumption but also the regulators… is that like this?
These regulators raphael metioned are mounted on a metal plate not on PCB.
I will dismount the supplies to check (trace the PCB tracks) about the fuses are really on the primary side.
Thanks and greets
Roger
PS @ Pay-C :
Is it possible, that your browser blocks the site because of the active content (Hover)?
Hi,
I updated the pages with the transformer labels (on the PSU1 transformer is no rating readable anymore). I haven’t done this earlier because I thought it’s not only the transformer reliable for the power consumption but also the regulators… is that like this?
You’re right. The transformer will give you only an indication of the absolute maximum current.
These regulators raphael metioned are mounted on a metal plate not on PCB.
Ehmm… I’ve written “mounted off the PCB”. [but with one “f”… Sorry for my bad english. :P]
It would help if you could read the markings printed on these babies. I think they are Power-MOS-FETs and with the markings you can get the datasheet via google.
Btw.: Your link does not work here at work, so I will try to look at the lable images in the evening at home…
Raphael
Thanks a lot Raphael
As soon as I have the info from these MOS FETs, I’ll publish it.
BTW: My english isn’t better :
… so we had this so called language barriere ;D
Thanks so far
Greets, Roger
Just curios. At home your link works…perhaps our firewall at work blocks something ???
So I took a look at the transformer labels. They just tell us the maximum apparent power (german: Scheinleistung). But output power schould be a lot lower.
While having another look at your pictures I discovered something interesting:
The +/-12V supply has two fuses which means the are on the secondary side (Two primary fuses would make no sense ;))
Another interesting (but not very helpful) thing:
One of the 5V supplys has a slow-blow fuse (german: träge, the T behind the 0,8A current rating) the other one a fast-acting fuse (german flink, The F behind the 0,5A current rating).
BTW: My english isn’t better … so we had this so called language barriere
I’ve seen you’re from Switzerland.
Are you living in the german speaking part? I’m living just across the lake of Constance in Ravensburg… ;D
Raphael
Hi,
are you sure, that these supplies are switching type ?
They look pretty solid to me. If you look at the pcb’s you can see four diodes for rectifing, a big cap, and a power transistor (I think) . What’s the label of the TO-3 part ?
If I’m right (and thats not sure) you have 3 nice solid parts.
The maximum rating depends on the TO-3 transistor and the transformer. The fuses are really a little bit confusing. I think they are primary. Otherwise they would make no sense on the secondary output. You don’t need such a big transformer for only 1 A output . The 12V unit seems to have two primary fuses. In fact, this only makes sense if this transformer has two primary windings. It would be intresting to measure the voltage on the fuses to identify if they are primary or secondary (just be careful with main power …).
greets
Doc
Thanks a lot guys!
I will deliver the information, as soon as I find time. I’m quite busy right now. I’m building my studio furniture and made a mistake in design. - Now I don’t get the appropriate rack rails and have to build those as well. This means drilling about 400 holes and cut the windings for the screws into those “blank” rails by hand  : ;D 
:-/ 
>:( 
Greets, Roger
Thanks a lot guys!
I will deliver the information, as soon as I find time. I’m quite busy right now. I’m building my studio furniture and made a mistake in design. - Now I don’t get the appropriate rack rails and have to build those as well. This means drilling about 400 holes and cut the windings for the screws into those “blank” rails by hand :
Greets, Roger
Damn I bet you are screaming! :o
Have you considered using a rail/captive nut combo like the blow molded effects racks (skb/gator)? This way you could use aluminum instead of steel (absolutely no fun hand-tapping threads in thick steel, the way my luck runs I would strip out some needed holes…)
Best!
Smash
Have you considered using a rail/captive nut combo like the blow molded effects racks (skb/gator)?
No I didn’t… too late  :( I’m done. -  Now I propably own the most expensive rack rails in  the world  :-* (calculated approx. 6 hours)
Here the printing on the power regulators:
the 5V units use Sanken SI-3554M
the 12V units Sanken SI-3120M
http://www.sanken-ele.co.jp/en/index.html
I can’t find any datasheets. Not on the Sanken site (they just write: discontinued) nor by google.
Can anybody help? Does anybody have one of those electronic bibles in which you can find all the data of transistors?
Greets, Roger
BTW: The fuses you can see on the frontpanel are on the secondary side. The main also has fuses built into the socket: T315mA/250V
The fuses are really a little bit confusing. I think they are primary. Otherwise they would make no sense on the secondary output. You don’t need such a big transformer for only 1 A output .
… is it possible, that they are chosen that low to protect the powered equipment they have to supply?
Greets, Roger
The SI-3554M crosses to an NTE931.
The SI-3120M does not cross reference to any known part, but chances are it’s a standard low-dropout 12v regulator…
… is it possible, that they are chosen that low to protect the powered equipment they have to supply?
Yes. Most decent broadcast gear has external fuses for each rail of the power supply.
Best!
Smash
Wow,
so those TO3 parts are 3A regulators. Fine!
Just change the fuses and have a go !
greets
Doc
Thanks guys!
I read in the datasheet for the ALPS faders, that max. used Motor current is 800mA.
I’m planning a 24 Fader Box and it’s possible, that as a snapshot all faders have to move together… where do I get a 19,2A 12V Powersupply (no switching type) from?
I see on Thorsten’s LC-PSU-pdf, that he uses a 1,5A fuse for one MF-Board (8 faders = 6.4A)… can somebody explain me that? Is that because there are only pulses driving the motor?
… and another question:
Is it possible to connect PSUs in parallel like batteries to raise the possible current? If yes, any type?
Greets, Roger
… and another question:
Is it possible to connect PSUs in parallel like batteries to raise the possible current? If yes, any type?
NO, don’t do this!
And don’t do this with batteries too!
If the output voltages are not precisely(!) the same, one PSU(Battery) (The one with the higher output voltage) will “supply” the other PSU(Battery). This can kill your PSU. :(
But you can use different supplies for each MF module. ;)
I’m planning a 24 Fader Box and it’s possible, that as a snapshot all faders have to move together… where do I get a 19,2A 12V Powersupply (no switching type) from?
I see on Thorsten’s LC-PSU-pdf, that he uses a 1,5A fuse for one MF-Board (8 faders = 6.4A)… can somebody explain me that? Is that because there are only pulses driving the motor?
i don’t have a MidiBox with motorfaders.
But in this ‘MidiBox of the week’ posting you can read that 3A are enough for moving 16 MFs simultaneously:
'>http://www.midibox.org/cgi-bin/yabb/YaBB.cgi?board=gallery;action=display;num=1083500709;start=0#0
Or just email some of the guys who have already built a MB with 24 faders… (Look at all those MB LCs in the gallery or in the “MB of the week” section)
Raphael
i don’t have a MidiBox with motorfaders.
But in this ‘MidiBox of the week’ posting you can read that 3A are enough for moving 16 MFs simultaneously:
http://www.midibox.org/cgi-bin/yabb/YaBB.cgi?board=gallery;action=displa y;num=1083500709;start=0#0
Or just email some of the guys who have already built a MB with 24 faders… (Look at all those MB LCs in the gallery or in the “MB of the week” section)
… well I thought it will work 
… but I would like to know why. - Why does the datasheet say: 800mA?
http://www3.alps.co.jp/pdf/2004pdf/pdf_e/Potentiometer/Mixers/mortor.pdf
Greets, Roger
@Raphael: Sorry, I never answered you the question about Switzerland: Yes I’m from the German speaking part.
The 800mA is max rating and could happen under certain conditions. I’d take it serious and calculate with the 6.4A @ 8 faders – and look for strong cables between the PSU and the faders and a very clean ground wiring. Typical current could range at 300-400mA only per fader, but you never know…
In my current evaluation for a LC24 I’m calculating with a 20A @ 12V PSU – which withstands all “electronic earthquakes”… Don’t take it as a joke, it’s serious power calculation resulting out of some bad experience with “cost saving” PSU ideas in the past for other electronic equipment.
A good idea is also a power distribution as POL (point of load) – means first PSU stage down to 15V for the full amp range, and then smaller 12V regulators per 8 fader strip. But this is a professional PSU application which needs good calculation of all parameters.
Cheers,
Skunk
… assumed, the faders will draw 800mA each: Will the track on the PCB to J3 -J10 be able to handle this amount of current?
Maybe a question to SmashTV (I’m using his MF-Boards)
Greets, Roger
… assumed, the faders will draw 800mA each: Will the track on the PCB to J3 -J10 be able to handle this amount of current?
Maybe a question to SmashTV (I’m using his MF-Boards)
Greets, Roger
The answer is yes it will. On a bad day this trace can handle around 5A of constant current at this voltage without thermal issues.
My definition of a bad day is:
Thinner copper layer than the laminate I use (.75oz vs. the 1.5oz laminate I used for those, crucial to make it home-etch friendly),
Constant loading (not the intermittent load as it’s used in real life),
Much higher than normal operating temp. (the best way to cope with thermal issues).
PCB fab variations can kill a design, so I test assuming the worst case to find the needed trace width vs. pcb real estate ratios.
Best!
Smash