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koh303
24-Feb-2016, 13:26
I have a saunders enlarger which is contentiously on as soon as i plug it in.
The power supply is runnig OK, and inside all looks ok.
The timer circuit in the power supply seems to have no effect on the power to the bulb or fan.
I am guessing the fan should be running as long as the power supply is switched on however in this case the bulb is also on at all times.

Any ideas?

ic-racer
24-Feb-2016, 14:38
What head? What power supply? What timer circuit? What is plugged into what? What does the manual say?

koh303
24-Feb-2016, 16:49
The manual does not say anything about this, because this is not the way the machine should work...

It is a Saunders LPL 4500 VC II connected to an LPL power supply.
As soon as the power supply is switched on, the lamp comes on.
As the lamp comes on right away, it seems there is a short in the power supply's timer circuit, causing it to be on despite the fact there is no timer connected.

howardpan
24-Feb-2016, 16:59
It sounds like your power supply is plugged directly into the wall socket. Instead, the power supply should be plugged into the timer which in turn is plugged into the wall socket. The timer regulates the power supplied to the enlarger.

I know this may sound too simple, but let's first make sure you have all the proper equipment before opening up the power supply.

By timer, I mean a device that looks like this: 147077

There are many kinds with varying capabilities. But in essence, this is a timer-based switch. If you open up the attached brochure, http://www.freestylephoto.biz/pdf/product_pdfs/gralab/Gralab451.pdf you will see there is a power cord which connects the timer to the wall socket. This timer is very simple, so it has only one AC outlet. The enlarger's power supply connects into this AC outlet. When the timer runs, power is supplied to the AC outlet (and hence the enlarger). When the timer stops, power is cut, and the enlarger is dimmed.

This is the basic set up.

Some enlarger power supplies have two different power cords, one to provide power to the fan so that it runs constantly and the other provides power to the light bulb which needs to be connected to the timer. Some timer has two AC outlets, one for the enlarger as described above and the other goes to the safe light. This allows the safe light to be toggled off when the enlarger is powered on.

ic-racer
24-Feb-2016, 17:39
The manual does not say anything about this, because this is not the way the machine should work...

I don't have the manual. How is it supposed to work. How is the lamp supposed to be turned on if not by the switch? Has it always been this way? Is there a schematic of the power supply in the manual? Is there a hook up diagram and is it hooked up per the diagram? What is this "timer circuit" of which you write? I know the Omega power supply does not have any switching mechanism, the timer plugs straight to the 24V transformer (P4), but in a Durst, the timer voltage activates a SCR and Relay to supply voltage to the lamp's transformer.
147076

Duolab123
24-Feb-2016, 19:33
Is this like a Beseler head. Has a power cord for the head/power supply and a Lamp cord for the timer??? Is there something weird with a white light switch?? These enlargers have a lot of praise, looks really cool.
Mike

koh303
24-Feb-2016, 19:44
While i might be mistaken on this, i am fairly certain this power supply goes directly to the wall.
Someone who actually has a 4500 might chime in here??

Because modern halogen lamp enlargers work with higher temps, they have active cooling, usually done by a fan. This fan runs at all times to prevent a bulb and fixture overheating after a long running period.
This particular enlarger (like all LPL machines), has a power supply which doubles as a voltage regulator (82V in this case) - it plugs into the wall, and sends power to the enlarger head. The power to the enlarger runs off a special plug, which feeds both the fan and bulb, though i am not sure if they are on the same line or not (there are 4 leads, so i am assuming not, though they are tied up to tightly for me to follow each one to its end).

The power supply has a 120V outlet socket to power the timer, and in turn, has a second inlet for the timer to plug into to time and work the lamp.

The timer circuit should only run the lamp, while the fan should be running continuously.

Michael Clark
24-Feb-2016, 19:50
My LPL ET 500 timer plugs directly into the Sunders regulated power supply and the power supple has a cord that plugs into the timer. The power supply plugs into the wall socket , and another lead form enlarger plugs into the power supple itself. So the regulated power supply powers both the timer and enlarger. The enlarger is a Saunders/LPL 4550XLG with the VCCE K&IF module.

Michael Clark
24-Feb-2016, 19:57
That took me awhile to figure my last post out, too many lines and plugs but great enlarger.KOK got it right.

Luis-F-S
24-Feb-2016, 20:12
It sounds like your power supply is plugged directly into the wall socket.

The long 3 pronged cord gets plugged into the wall socket. When you turn the power supply on, it turns the fan on and the fan runs all the time. The short cord is used to turn the lamp on and off. This cord (two pronged on Omega stabilized power supplies & 3 pronged in LPL power supplies) gets plugged into the enlarging timer. The power supply also has a plug on the back labeled "timer" shown below. You can plug the enlarging timer into this socket or into the wall socket. If you plug the short from the power supply into the "timer" plug on the power supply, the light will be on all the time.

If you're not doing any of the above and the light is on all the time, the the power supply has a short or other problem and it's time to get it fixed. L

147087

howardpan
24-Feb-2016, 20:26
This may be of use to you: http://www.silveruser.ca/Manuals/LPL7452.pdf

If you look on the figure on page 9, it shows you how the enlarger is wired. My interpretation is 11D is connected to the timer. At least, that is how I have wired my LPL 7452.

koh303
24-Feb-2016, 21:01
This may be of use to you: http://www.silveruser.ca/Manuals/LPL7452.pdf

If you look on the figure on page 9, it shows you how the enlarger is wired. My interpretation is 11D is connected to the timer. At least, that is how I have wired my LPL 7452.

clearly in this diagram, there is a separate lead from the machine to the wall for the exhaust fan, and one for lamp.

This is not the case on the 4500 - there is only one lead, which is controlled form the regulated power supply.

Luis has it right, as i thought. The problem is have no idea where to look for the short. The power supply looks clean and neat inside, and the small printed circuit looks good all around. If one of the rectifiers or transistors is not working, i will not be able to diagnose it without a diagram, which i doubt is available, unless of course someone has one handy?

I will have another look tomorrow, but short of finding anything, i might just wire the fan directly with its own wire and inline switch, and leave the regulated power supply as is, with the timer ahead of it in the line.

koh303
25-Feb-2016, 07:39
:( - Fan runs off 5V power....
There must be a transistor switching component on the little printed board inside which as failed, as i do not see anything that is shorted or wrong.

koh303
25-Feb-2016, 07:50
Found a replacement power supply on Ebay. Will give it a whirl.

Luis-F-S
25-Feb-2016, 08:37
Found a replacement power supply on Ebay. Will give it a whirl.

Probably the easiest fix. Just make sure you get the one for your light source, ie either square (LPL) or round plug (Omega). I have one of each as I bought a spare a while back. I also have an earlier thread that the later 4500-II's can take the 250W bulb as long as the light chamber is vented at the top. L

http://www.largeformatphotography.info/forum/showthread.php?122905-LPL-7452-Power-Supply&p=1250810#post1250810

ic-racer
25-Feb-2016, 14:03
New power supply is a good option. Sometimes having a working unit gives insight to the fault in the non-working unit, allowing one to repair it for a backup.