Replacing enlarger power supply

Hello,

I recently got a free Vivitar VI enlarger, but the power supply is broke. (Turned it on, got some sparks, then smoke, then nothing...) and I'm trying to replace it. The output is rated at 18.44VAC and 4.5A (ust over 80W).

One idea I had was a laptop power supply. I see a lot of "universal" power supplies that are in the right wattage. My question is that these universal power supplies often give a range of voltage (e.g. 12-20V). Will this work if I just cut the wires and splice them in? Do I need to do something special to get it to the right voltage? Any idea how these things work?

Other suggestions? I'd rather not find another vivitar transformer, only to have it also break in the near future.

Thanks!
Tim

My understanding is the Vivitar power supply is there to provide a STABLE output as well as stepping down A/C to a lower voltage.

The only thing it's powering is a lamp which doesn't care AC or DC. If I cannot repair the power supply, I would go with any power supply capable of supplying the voltage (AC or DC) and able to supply sufficient current. I would first open it up and see what blew though. I *think* there is a large capacitor in there that can go.

If you'd like, I can open mine up and see....

When the large electrolytic capacitor overheated in the Vivitar VI dichroic enlarger owned by a friend, the electrolyte leaked out and the power supply was dead. We bought a replacement motor-run capacitor of the same ratings, installed it and it worked perfectly thereafter. The capacitor cost about $8 at Grainger Industrial Supplies about 1997 when we replaced it. So far as I know it continues to work normally since the capacitor was replaced.

The Vivitar VI dichroic head uses an 80-watt 19-volt EKG lamp. A significantly higher voltage will destroy the bulb.

Yup... as far as I know, it works perfectly too.

Ian has the right idea: first see if you can repair the old supply. Determine where the smoke and sparks came from, and see if you can replace the parts involved. If not, you may have to build a new supply. You generally can't just series the outputs from computer supplies, since most of the outputs will share a common ground (even if there are separate leads). These supplies are rather peculiar to the equipment, so replacement can be tricky. They usually provide some kind of voltage regulation, but not always. They usually have peculiar wiring and switching schemes that you have to figure out properly to make the supply work. Building can be an expensive and complicated option. Try repair.

Another possibility would be to replace the bulb in the Vivatar with a different kind that used 12 or 24 volts (with 80W power). You can find regulated supplies for these voltages easily. That assumes that the enlarger is wired in some simple manner and that you do not have to power a fan. If there is a fan, you may need to replace that, too.

Looks pretty nasty inside. I'm guessing the orange/yellow coating all over the inside (some sort of fluid leaked out all over the place?).




Is the big thing in the middle the capacitor in question, or is that the transformer?

I found a laptop power supply listed at best buy that is 19V, 100W for something like $30. Might be an easier way to go, I'm thinking? If the output is controlled enough to not fry a computer, I imagine it would be ok for enlarging too?

Tim

I just opened mine up. That's much cleaner than mine. An only repairable part is the capacitor which is located at the top of your image behind a shiny metal. To get to it, you'll have to remove the switch, and 3 bolts around it including the ground and it will come out.

Do you see any charred connection/wire?

Modern laptop power supplies are switching type. Regulated and isolated. I'd think you should do fine with that but without seeing (and measuring ) it, I can't tell for absolutely sure. If you give me a couple of days, I can see my junk box and have anything hanging around here. Hate for you to spend $30 for something like that.

Are you in US so I can ship it to you IF I find it?

treddy said:

Looks pretty nasty inside. I'm guessing the orange/yellow coating all over the inside (some sort of fluid leaked out all over the place?).


View attachment 64244

Is the big thing in the middle the capacitor in question, or is that the transformer?

I found a laptop power supply listed at best buy that is 19V, 100W for something like $30. Might be an easier way to go, I'm thinking? If the output is controlled enough to not fry a computer, I imagine it would be ok for enlarging too?

Tim

Click to expand...

Laptop power supply is not a very good choice because it does not regulate voltage well. It is so because it's a charger and not a power supply. The battery acts as a voltage regulator.

By the way, capacitor stores energy. DO NOT handle the connection if your supply was powered in the last few minutes. We are dealing with a failed equipment. Anything is possible. (since you don't seem to be families with electronic circuits)

Plus, the particular capacitor that's in the original power supply is an old PCB type. Do not touch if you see liquid leaking out.

I have a V1 as well, and its a very good enlarger (or I think so anyway). I have thought about what I would do if the power supply packed up, and I think if I couldn't fix the original PSU, I'd look at replacing the original bulb for a 12V one of similar shape. The original is classed as a "dichroic projector bulb", and there are lots of other dichroic projector bulbs of similar size. The "dichroic" bit means the heat can escape through the reflector of the bulb. When these units were made, halogen lighting was not so popular, now its easy to get 12V power supplies designed for lighting (I agree, a laptop PSU is not the way to go - I doubt it will work well).

here's a typical 12V PSU for lighting

http://www.lightbulbs2u.com/105va-dimmable-12v-transformer-p-638.html

You probably won't find an 80W bulb to match the original, so perhaps go up a bit to 100W or down a bit to 50W. You might have to change the bulb holder, but you can easily get these.

Here's a 100W 12V bulb that would work with the power supply above

http://www.lightbulbs2u.com/a1231-efp-12v-100w-gz635-p-520.html?gclid=COnY-Nuyu7UCFUnMtAodU2AAUw

OK, these are UK, but you must have similar on your side of the pond.

Just to add, I usually print 8x10, and my print times are in the range 10-20 seconds with the standard 80W bulb. I think I would be tempted to go down to 50W to begin with. All that will happen is print times will be marginally extended. I suspect not by as much as the difference in rating suggests.

I got at the capacitor (which I deliberately left off overnight and also discharged just in case). No signs of charring either there or on any of the wires. Without actually charging it up and testing it, I'd say it looks fine. My (limited) familiarity with electronics is all in computer circuits and low voltages, not with high voltages and power supplies. For that reason, I think I'm not going to go any further in testing the components.

Chan, thanks for the bit about the voltage regulation coming from the battery -- I hadn't thought that through all the way.

Tkamiya -- if you come up with anything that might work, I'd be happy to hear. Might cruise some craigslist too and see if I cant find something that might suffice.

Tim

I was thinking about this route too -- just switching out the light source whole-sale with something more modern. Sunk cost of the bulb I just bought would be annoying, but a big deal. Thanks for the links. I'll check them out.

Tim

Thanks for the links. I'll check them out.

Click to expand...

I didn't do too much research for them....... There are probably many alternatives out there. Still don't know where you are UK or US??

I'm in the US (Filling out profile now...)

Philips makes a 75W 12V bulb with the same base. That might be a nice solution.

Most bulbs seem to be "multi-reflective," having what looks like a faceted inner surface. It seems to me that would be a huge problem with printing, but maybe I'm wrong. Anyone know if by the time the light gets down to the negative it won't matter?

Tim

On the V1 with its "light pipe" I doubt it will make any difference if the bulb refelector is faceted or not. The end of the "pipe" is diffuse.

Have you got the manual? It tells you how to take the condenser apart to clean it. I think it may be online somewhere, but if not say, and I'll scan mine.

Thanks for the offer. I got the manual from Ollinger's Guide to Enlargers.

Please don't set about modifying mains-powered electronics unless you know exactly what you're doing, which clearly is not the case here. A darkroom fire and/or electrocution is not worth it.

If it's a 19V bulb, the cheapest and safest option is to use a laptop power supply of sufficient power rating. It will even have better regulation than the old magnetic supply!

If it's a 24V bulb, you can buy 24V switching power supplies off eBay for peanuts, well under $100 for 300W+.

The faceted reflectors on some bulbs will be irrelevant for an enlarger; they're just a slightly different approximation of the parabola behind the filament. If you're replacing the bulb with a new/different kind, what matters with a condenser enlarger is that you get the filament in the exact same spot or the condensers won't be focused right and you will get uneven lighting of your negative. If you're building a replacement bulb mount, include some fine sliding adjustments to get it all aligned. Don't put a higher-powered bulb in the enlarger unless you upgrade its cooling.

treddy said:

Looks pretty nasty inside. I'm guessing the orange/yellow coating all over the inside (some sort of fluid leaked out all over the place?).


View attachment 64244

Is the big thing in the middle the capacitor in question, or is that the transformer?

I found a laptop power supply listed at best buy that is 19V, 100W for something like $30. Might be an easier way to go, I'm thinking? If the output is controlled enough to not fry a computer, I imagine it would be ok for enlarging too?

Tim

Click to expand...

Is that dry? It does not look different from the usual lacquer that most transformers are dipped in. I don't see a regulated supply, just a transformer. Is there any more to it. Can you check the resistance on the primary and secondaries of the transformer. This sparked and smoked? Is there a fuse?
What do the two white wires go to? What is the structure the red and yellow wires go to?

Here is a replacement transformer but it only has one set of secondaries.
http://www.alliedelec.com/search/productdetail.aspx?SKU=70181275

Actually, the transformer visible in that picture of the internals looks like a ferro-resonant constant voltage transformer. Note that there appears to be core between the two winding sections. This was pretty typical for CV stuff - Sola is one brand name I remember. I'm not sure what the gizmos on the plate on the left are but looking again, they are probably terminals of a capacitor clamped down and sticking out the underside of that plate/chassis.

What is under that plate presumably holds the key. There are indeed usually capacitors in ferro-resonant supplies and caps do not age gracefully.

(Of course, it could be good now that you've let the smoke out. )

IC-Racer,

It's a ferro resonant transformer. Behind the steel plate on upper half of the box, there is a large oil filled capacitor. That and the extra winding on the transformer act as a regulating mechanism. (I have the same unit right here)

OP:

I'm afraid to give you any instructions because you appear to be not familiar with this type of circuits. There are only few things that can fail. One of the windings can blow or short, capacitor can leak, overheat, or in rare cases, short, or the switch can go. Testing require a live circuit and I definitely won't recommend you'd try it. You said "spark" "smoke", etc. Since I don't see any liquid leaks or burn marks, I'm GUESSING power switch may be the issue. If you have a multi-meter, you can check the switch. Beyond that will be a risk worth not taking.

Are you going to print color or B&W? If B&W, voltage regulation isn't important. Any transformer that is capable of producing the proper voltage and current will do. If you were closer to me (I'm in Central Florida) I'd take you to one of the surplus shops around here and hook you up with a proper switching power supply.

Despite what has been said, most of current Laptop power supply does not use battery as a regulator. If that were the case, you can't operate the laptop without a power supply. (and I can). I also did a load test with what I have. It is certainly regulated. I have a 15 volts 5 amp supply for Toshiba, so I tried it with my Vivitar VI. There WAS a problem. It appears it has some kind of a protection circuit. It won't reliably produce output when lamp was connected. It works if I let it come up to voltage first, then connect. If I keep it connected and power up, it won't. So in enlarger application, it won't work. At least the type I have won't.

If you're building a replacement bulb mount, include some fine sliding adjustments to get it all aligned. Don't put a higher-powered bulb in the enlarger unless you upgrade its cooling

Click to expand...

If you do go down the replacement bulb route, this isn't necessary. The V1 uses a standard size dichroic projector bulb, albeit an unsual rating. Suggestion is use a same size but different rated bulb to use standard lighting transformer. The bulbs front face is the positioning mechanism. You might have to change the mount to suit a different rated bulb. The V1 has passive cooling. I doubt 80W to 100W will cause a problem.

Thanks for all the help everyone -- this has been extremely helpful!

I've thrown in the towel on repairing the power supply. I just don't know enough about what I'm doing, as is clear. While the sparks and smoke were fun and all with the case on, not so much with the case off

My current plan is to get a new linear regulated power supply such as this guy:
http://www.ebay.com/itm/Samlex-RPS1...ly-used-great-working-condition-/370724961156

And to use a 80-100W bulb that uses the same mount (there are many) and is matched to the voltage of whatever power supply I find. In some cases, I'm even seeing power supplies where I can adjust the voltage so maybe if I find one of those cheaply enough I won't even have to change the bulb, and could switch to a 12V later without getting a new supply.

It seems that most voltage regulated supplies are switched nowadays, so it has been trickier than I expected to find a linear regulated supply. I have a few options I'm working on, but they all are of the hobby type. While I'm fine with that, any other suggestions on a good source for a new linear regulated supply?

treddy said:

Looks pretty nasty inside. I'm guessing the orange/yellow coating all over the inside (some sort of fluid leaked out all over the place?).


View attachment 64244

Is the big thing in the middle the capacitor in question, or is that the transformer?

I found a laptop power supply listed at best buy that is 19V, 100W for something like $30. Might be an easier way to go, I'm thinking? If the output is controlled enough to not fry a computer, I imagine it would be ok for enlarging too?

Tim

Click to expand...

Actually, it looks very simple for an enlarger power supply. That is a ferro-resonant transformer (the big thing with brown coil windings), which works with the capacitor (the other thing) to regulate the voltage. These capacitors frequently fail, and my guess is that was what happened. You can probably replace it easily, but the value (microfarads and voltage) is critical, and you need to replace it with something with the same ratings. As for the computer power supply, it looks like that would work fine. Your enlarger does not seem to have any strange circuitry, just a regulated power supply and a lamp. Before you buy the supply though, check to be sure the power wiring goes righ to the lamp and that there are no additional electronics in the enlarger. If there are, you may need the regulated ac supply, not the dc you get out of the computer supply. You may be able to find a local electronics hobbyist of ham radio operator who can help you.

nworth said:

Before you buy the supply though, check to be sure the power wiring goes righ to the lamp and that there are no additional electronics in the enlarger.

Click to expand...

Yup, the power supply is directly connected to the light with a couple twist on wire connectors.