LPL 4550XL Lamp Issues

NortheastPhotographic · Jan 22, 2020

If you're following my thread on calibrating my RH Analyser Pro you may have seen that I had some lamp flickering issues at the end of a printing session last night. It eventually lead to the lamp occasionally just not turning on, or turning on then immediately turning off again. And sometimes working just fine. But generally it doesn't reliably come on or stay on.

I first took some alcohol and a brillo pad and cleaned the contacts as best I could. I think did multiple rounds of inserting and re-inserting the bulb. This did not seem to work so I installed a fresh bulb, and I'm still getting the same issue.

I would think it's a power issue but the fan doesn't seem to be having a problem, and my timer never flickers, which is also fed by the LPL power regulator, different line of course.

Any thoughts on where I can go from here?

spijker · Jan 22, 2020

The lamp socket might be corroded. I had similar issues as you with my LPL670. Cleaning the socket contacts is next to impossible so I replaced it. That solved it.

NortheastPhotographic · Jan 22, 2020

I spoke to a guy at KHB Photographix and he seemed pretty sure that the older Saunders power supply is the problem. Of course that would mean buying a $600+ dollar part...

Arthurwg · Jan 22, 2020

I believe the power supply can be repaired rather than replaced.

dkonigs · Jan 22, 2020

NortheastPhotographic said:
I spoke to a guy at KHB Photographix and he seemed pretty sure that the older Saunders power supply is the problem. Of course that would mean buying a $600+ dollar part...

Or opening it up and fixing it. It could simply be age-related issues with some of the components. Of course I can't really help with any specific recommendations there, and if you're not equipped to attempt fixing it then $600 might actually be a fair trade for equipment/time/effort/etc.
(If it were me, I'd probably take a peek before replacing it though.)

NortheastPhotographic · Jan 22, 2020

Mine has the 4 prong US power supply going from the regulator. Would a voltage meter show the issue?

NortheastPhotographic · Jan 22, 2020

I checked the 4 prong plug with a multimeter and it was outputting power. I attached the meter to one set of prongs, then the other.

dkonigs · Jan 22, 2020

The fan is probably powered independently from the lamp, as it runs whether or not the fan is on. That's likely why there are 4 prongs in the plug.
That being said, a multimeter alone isn't sufficient to actually test something like this. You'd also need to place a load on there (as a bulb would do), and measure variations in the output. These power supplies are doing some sort of voltage regulation (to keep the output stable when they're working correctly), and such devices do behave differently depending on load.
Of course I don't even know if the output of the lamp supply is AC or DC, and I'm not really an electronics engineer (just someone who's done some hobbyist-level stuff), so its hard to give more specific advice in abstract.
If I had this problem myself, I'd put the supply on the bench and start poking at it a bit more directly. Might even disassemble it and start attempting to test the components.

bdial · Jan 22, 2020

On mine, the fan runs on 120v, only the lamp gets reduced voltage.
When my power supply failed, I made up a substitute using a household dimmer switch, To keep things working until I could buy a new power supply.

wiltw · Jan 22, 2020

NortheastPhotographic said:
Mine has the 4 prong US power supply going from the regulator. Would a voltage meter show the issue?

Not a simple voltage meter, connection to an oscilloscope. And fan does not instantaneously react to brief fluctuations that might be visible via flickering light.
That is why an oscilloscope will disclose what a voltage meter might not be responsive enough to reflect...and the problem might not be a Voltage fluctuation, but an interruption of the Current flow, again the need for an oscilloscope.

George Nova Scotia · Jan 22, 2020

wiltw said:
Not a simple voltage meter, connection to an oscilloscope. And fan does not instantaneously react to brief fluctuations that might be visible via flickering light.
That is why an oscilloscope will disclose what a voltage meter might not be responsive enough to reflect...and the problem might not be a Voltage fluctuation, but an interruption of the Current flow, again the need for an oscilloscope.

Please, please remember Scopes and AC power do not play well together. Know where you grounds go!

wiltw · Jan 22, 2020

George Nova Scotia said:
Please, please remember Scopes and AC power do not play well together. Know where you grounds go!

Identifying the proper point to put the Ground probe isn't hard for the trained technician, and the oscilloscope displays AC waveforms (plus, zero, minus swings of waveform). But a reasonable warning to an amateur sleuthing his own gear!

AgX · Jan 22, 2020

NortheastPhotographic said:
I first took some alcohol and a brillo pad and cleaned the contacts as best I could. I think did multiple rounds of inserting and re-inserting the bulb. This did not seem to work so I installed a fresh bulb, and I'm still getting the same issue.

You can wipe or brush the contacts of the lamp, but not (that easy) those of the socket.

ic-racer · Jan 22, 2020

Lamp socket is a consumable part for high-wattage MR 16 lamps.
https://www.photrio.com/forum/threads/omega-d5500-lamp-socket-replacement.85653/

NortheastPhotographic · Jan 22, 2020

A lot of this is just beyond my knowledge base. The previous owner informed me he did very recently replace the lamp socket with a brand new one so I"m looking at every option right now.

Who would be able to repair power supply units?

George Nova Scotia · Jan 23, 2020

Any chance any has ever come across a schematic for this power supply? It would be handy to have.

wiltw · Jan 23, 2020

NortheastPhotographic said:
A lot of this is just beyond my knowledge base. The previous owner informed me he did very recently replace the lamp socket with a brand new one so I"m looking at every option right now.

Who would be able to repair power supply units?

Any competant electronic technician could figure things out, particularly if he had a schematic for item under repair. The issue might be, however, that things that have Printed Circuit Boards could be constructed in such a manner that it is very difficult from the standpoint of the mechanical removal of the failed part...it can be challenging particularly with what are called multilayered circuit boards...but those are rather unlikely within a power supply which is rather simple electronically.

The power suppy within your enlarger is likely to consist of a subassembly... a box of completed circuit which was purchased from another (power supply) company and incorporated into the head of your Brand Y enlarger, and it can be very hard to get anything for. A technician can figure out what is wrong, and then get luck to find a part which is electronically the right value and it FITS!

adelorenzo · Jan 24, 2020

I have been thinking about this for a while as I have a second unit without a power supply that I'd like to get operational. Plus I want to be prepared for the day when my power supply might die.

** disclaimer: I am not an electrical engineer. Feel free to correct me on any of this. **

The XL units use an 82V/250W halogen bulb whereas the non-XL units used a 24V/250W halogen bulb with the same socket connector. The thing is 82V AC power supplies are not easy to come by. However, 24V DC power supplies are super easy to get in whatever configuration that you need. A light bulb should run as well on DC as it does on AC. I'm assuming that you will have less light to work with but should still be doable.

So what I'm thinking is to get a 2-channel 24V DC power supply with sufficient wattage/amperage and wire it in to power a 24V bulb using the existing socket. Replace the 120V AC fan in the head with a DC-powered computer fan that runs off a second channel of the power supply.

Another option is just to get an inexpensive adjustable DC bench power supply to run the lamp. One of those will give you 82V. Then just wire the fan straight into the mains power.

Either of those options is well under $100 but will require some DIY work.

There are places that make custom power supplies but I don't think that you'd be able to get that done any cheaper than you would just buying a unit from KHB.

bdial · Jan 24, 2020

^^^ What he said
That's pretty much my plan for whenever/if the 82v power supply dies on mine. The power supplies seem to be a bit of a weak point to these, the original on my enlarger died, and I was lucky enough to find a replacement in the used market for not much money, though it took quite a while. 24 v power supplies are much more common and used on a few color enlargers from Omega and probably Beseler.

dkonigs · Jan 24, 2020

As I also have a similar enlarger ( LPL 7452L, which is also sold as the Omega/LPL 4550XLG), this thread is making me want to run over to mine with a multimeter and figure out exactly what its actually putting on that plug. Far too many unknowns in this conversation thread. That being said, when mine does start to have issues, I'm far more apt to simply open it up and try to figure out what's wrong. However, mine is fairly new, so we'll probably go through a second death-of-film before that happens. (And I really don't want to dismantle/reverse-engineer mine given that its currently working perfectly fine.)

voceumana · Jan 24, 2020

Beware of replacing the fan unit--a mis-balanced fan can induce vibration; I imagine LPL selected the fan used based on solid technical specs.

KHB Photografix, I believe, can repair the power supply. Note that if you haven't tried a new bulb, I would start there. It doesn't matter how recently it was changed out, it may be failing.

adelorenzo · Jan 24, 2020

I've opened my power supply up. It is one small integrated PCB-type power supply unit that does all the work, a simple thing to find in other voltages but not in 82V. I tried googling the part number on it but nothing came up.

NortheastPhotographic · Jan 24, 2020

voceumana said:
Beware of replacing the fan unit--a mis-balanced fan can induce vibration; I imagine LPL selected the fan used based on solid technical specs.

KHB Photografix, I believe, can repair the power supply. Note that if you haven't tried a new bulb, I would start there. It doesn't matter how recently it was changed out, it may be failing.

I have tried a new bulb as well as cleaning the unit. I'm trying trying to go through everything I can before I have to order a new power supply.

George Nova Scotia · Jan 24, 2020

A couple comments. Power supplies can be simple or complicated. I believe 82v usage comes from the use of half wave rectifiers. A single diode will result in just under 82v from 120vac. The complication comes with trying to requlate it to a constant voltage for the lamp. Fans are often 120vac using separate wiring and either on all the time like the LPL or switched with a relay.
Power supply design might be a good subject for another thread.

NortheastPhotographic · Jan 27, 2020

I ended up going another way and ordered a Heiland LED set for both color and B&W. No spitgrade, I'll stick with the Analyser Pro.

IF anyone needs a VCCE and sorta junker but working DIchro module let me know! hah.

LPL 4550XL Lamp Issues

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