View Full Version : Saunders 4550 w/ Kearsarge 301?

17-Apr-2008, 13:45
I recently upgraded my enlarger to a Saunders 4550 (VCCE) which I assumed would work with my Kearsarge 301 timer as my previous enlarger did (Omega DII with a Super Chromega). I received the enlarger yesterday and upon plugging hooking it up to the timer I found that the enlarger light will not switch off in the "time" position, basically its always on. I swapped out the timer for an old Time-O-Light all-manual timer and everything works as it should. I've read that this is a possible problem with electronic timers and certain enlargers but haven't been able to figure out whether there is something I can do about it in order to be able to use my Kearsarge timer or if I'm destined to have to use something else.

Any help would be greatly appreciated.



Ted Felton
17-Apr-2008, 14:35
I have a Saunders 4550 XLG with which I used to use the Kearsarge 301. I now use a Kearsarge 403 and a Stop Clock; however I keep the 301 as a back up. I went into the darkroom and hooked up the 301 and it works fine. Do you have the enlarger plugged into the enlarger outlet on the timer, not the safelight outlet?

Kearsarege timers are excellent but he is out of business. A casualty of the digital age.


17-Apr-2008, 19:41
Yep, everything is in the correct places (same setup that works with the time-o-lite), timer plugged into the Saunders power supply timer socket, power supply plugged into the wall with the short timer plug going to the plug outlet on the timer...comes on, just won't go out for the "time" function.

I can't seem to find the post now but read somewhere that it had to do with solid state(?) relays vs. electronic ones which hold some sort of a charge once a current goes through them and am guessing there isn't anything I can really do about it other than find a timer without the same circuitry, any one have a stop clock lying around they aren't using.....doubtful. Any other ideas?

Ted Felton
17-Apr-2008, 19:52
The 4550 will work with the 301.

Make sure the plug from the power supply is plugged into the enlarger socket: when looking at the 301, face toward you and the plugs on top, the enlarger socket is the one in the middle, the foot switch is to the left, the safe light outlet is to the right. If the enlarger is in the safe light socket (far right) it will be on when the timer is off (not timing).


17-Apr-2008, 20:49
Alright, there are two plugs coming out of the enlarger power supply, one short one that says to enlarger, one long one that I'm assuming goes to the wall. I'm putting the short one in the enlarger socket (they're labeled) on the timer, the long one into the wall and the timer plugged into the socket on the power supply that says timer. I've also tried the timer plugged into the wall with no luck. I'll give it another go but I'm pretty sure I've got it all where it needs to be, particularly since it works fine with the other timer. We'll see...thanks for the help.

17-Apr-2008, 21:33
I tried it again and it definitely doesn't work. I can actually turn off the timer and the enlarger stays on. If I replace the enlarger with any other electrical appliance (including the old enlarger), everything works as it should. If I use the exact same configuration with the time-o-light, the Saunders words perfectly. I can only guess that there is some conflict between the two..

Mark Woods
17-Apr-2008, 22:51
Could there be an issue with the ground? Get a volt meter and see if the ground works on the timer. Just a thought. Gotta love electronics.

Ted Felton
18-Apr-2008, 05:01
The owner of Kearsarge told me that it was best to plug the timer directly into the wall outlet, not the enlarger's power supply/regulator because there might be a conflict. You may try that.


18-Apr-2008, 11:41
Thanks, I think I tried that already but will give it one last try. As far as the ground, I'll see what I can do about getting one of my friends who knows something about electronics to take a look, thanks for the idea.

Strangely, I looked through my pile of random ebay darkroom junk last night and found another somewhat simpler Kearsarge timer and tried it out...same exact thing, works with anything I plug into it other than the enlarger. Who knows, looks to me like it must be something specific to them with the Saunders. Thanks again for all of the help, looks like I may be stuck with the time-o-light until I can find a deal on something better.

29-Apr-2008, 21:15
So the problem continues: I was lucky enough to find a used Stop Clock Pro on the forum and since the Kearsarge wasn't working I used it as an excuse to upgrade to the timer I really wanted. I wrote to RH Designs to make sure it was compatible with the Saunders and they said that it was. In addition the person I purchased it from used it with a Saunders and said it worked fine. Long story short, I hook it all up tonight and I get the same thing. In the process I've got a few more clues: first off, the enlarger goes on, even if the timer is off (off as in switched off), second, every couple of times I flipped everything on my circuit breaker was flipped off and lastly, holding on to the short plug (the one that is supposed to trigger the light via the timer) I got shocked, nice little bonus. So Ted, you and Mark are probably both correct. From all of this I'm gathering that there's a leak somewhere in the power supply as somebody above suggested but I'm not exactly sure where to go from here. It'd be nice to avoid sending it away to Saunders if it could be something simple to track down...any suggestions? I know pretty close to nothing about electronics so I'm wondering if I can just take it to somebody who works on electronics or is the power supply something too specific that I should only send to the manufacturer? Any help would be greatly appreciated.

Thanks, Mike

Donald Miller
29-Apr-2008, 22:27
OK since it is impossible to get the lamphouse plug and socket reversed, let's begin with the other connections. The power supply 120 volt cord and plug need to be plugged into a constant supply (read wall outlet).

At that point with the power supply switch off, you should have no voltage to either the 120 volt outlet on the rear of the power supply, the timer cord and plug, or the cord to the lamp house...as indicated by the lamp not lighting.

Next with the power supply cord to the power supply plugged into a wall outlet turn on the power supply...you should have no power to the enlarger lamp. However you should have 120 volts nominal to the 120 volt timer plug on the rear of the power supply. You also should have 82 VAC to the timer cord plug. This the one that probably shocked you since it is a male plug with exposed terminals.

When you plug the timer power supply into the rear of the power supply and the power supply plugged in and the power supply turned on you should have an indication that the timer is energized...but you will not have any power to the enlarger lamp or fan.

Next with the timer plugged into the 120VAC socket at the rear of the power supply, the power supply plugged in and the power supply turned on you should next plug the timer plug from the power supply into the enlarger socket on your timer and your enlarger should now power up for focusing...turn off when the timer is turned off...turn off when the power supply is turned off and you should have the timer controlling the exposure when you call for the timed function on the timer.

These enlargers operate with 82 volts to the enlarger lamp...therefore the 82 volt power must originate from the power supply (step down transformer) feed through the timer relay and then back to the enlarger lamp. The 120 volt is there simply to supply voltage to the step down transformer in the power supply and to supply the control voltage for the timer that you use. I would seriously doubt, barring someone playing electrician before you got it, that you have a problem...the only problem that I could see is a stripped wire going to chassis ground (would trip the control fuse on the rear of the power supply) or a relay with frozen contacts (unlikely since you have tried a number of different timers.

I seriously doubt that you have a ground problem since the ground circuit is only involved in the event of a voltage leak to chassis ground. It is a safety on the unit. The ground is not involved with either of the two voltages involved or any of the control functions. This is AC and not DC voltage.

Hope that this helps.

Best regards,

Ted Felton
30-Apr-2008, 08:52
I would like to repeat one thing. In my discussions with Kearsarge he has constantly said it is best to plug the timer into a wall outlet, not into the enlarger power supply.


30-Apr-2008, 09:30
Thanks Donald and Ted. Early this morning I went back out to the darkroom and gave it one more try, taking care to do exactly as described. I plugged the enlarger power supply into the wall outlet (actually tried two different outlets and a power strip just to be sure). At this point if the power supply is off, there is no power to the enlarger or outlet on the back of the supply. Power supply on, enlarger fan on and power to the rear outlet. I then plugged the timer into the power supply outlet (also tried it directly into the wall). Turn on power supply, timer can be turned on and off and the fan comes on for the enlarger. So far, so good. Finally I take the short plug (male, and yes, its the shocker) from the power supply and plug it into the enlarger outlet on the timer, WHAMO, on comes the enlarger light whether the timer is on or off...same thing as before. I also on a whim tried the same arrangement with an old Gralab timer I use for developing film, everything works fine with the enlarger. Gralab and Time-O-Lite work fine, two Kearsarges and a Stop Clock don't work. Needless to say I'm about ready to have this thing operational.

As I am slowly becoming obsessed with this, on my ride into work I'm going over the 3000 different sequences I've tried and I remember that with both the Time-O-Lite and the Gralab there was at least one time where I plugged in the short cord from the power supply to the timer and the light came on whether I flipped the time/focus switch or not. Eventually I realized that the lamp would in fact go off, it was just that it had to run through its timed countdown in order to flip the relay back over to the focus/time switch. What I'm now wondering is if this could be the case with all (what are the odds?) of the electronic timers....maybe they are "stuck" in the middle of a countdown and just need to run out to flip things back over to the focus/time switch. Seems to me that this would be reset when the timer was turned on and off but maybe not if they are truly analog relays.

That's where things stand now, I'll try it out tonight and see if that makes any difference, if not, I'm about out of ideas. Thanks again for all of the help and suggestions.

30-Apr-2008, 19:55
Latest update: I tried running it through a couple of countdowns with both the Stop Clock and the Kearsarge w/ no luck, lamp will not go off for focus, doesn't even matter if the timer is on or off, somehow it is getting power. Also tried it with both the timer plugged into the wall and into the power supply. I'm sort of at a dead end for ideas, not really sure at this point what to do, here's a picture of what I've got going for connections, any help is once again greatly appreciated.

30-Apr-2008, 20:58
One more piece of information, hopefully one that leads to a solution. I did some more reading and finally found a thread I had seen awhile back:


I tried what several people describe by hooking up both the enlarger and a light to the timer...with this setup the enlarger works perfectly. Reading the description of why means almost nothing to me so any deciphering would be nice. At this point I'm wondering if I really have to plug two things into my timer to make it work? In the above URL there is a description of a more permanent solution ("A 1 watt 22K resistor wired accross the enlarger's relay coil/SSR LED would be a more permanent fix"), is this something I want to mess with or should I just be looking for something that sucks some current and preferable doesn't put off light?

Kirk Keyes
30-Apr-2008, 21:23
I'm in Portland and I have a Saunders 4x5 enlarger. Would you like to come over and try your timer on my enlarger? I've used me enlarger with the Saunders powersupply hooked to an Omega CT-40, a Gralab 505, and Gralab 900 - works just fine with those.

Donald Miller
1-May-2008, 02:32
What was stated in the thread that you referenced makes perfect sense to me. I kind of wondered after your earlier post whether that was not happening. Basically what this amounts to is that the timer snubber circuit (to keep the relay contacts from arcing) is passing enough current to energize the relay or triac in the power supply. Since putting more load (the light bulb) into the circuit solves the problem, it more or less proves that is what is happening. So far as repair, you could open the power supply with the voltage removed of course and see if you can identify the componant (relay or triac). If you can, then you can probably get the resister (very low cost componant) at an electronics supply firm...even Radio Shack may have it.

Should you decide to do this yourself, you will need to connect one of the leads of the resister on one of the relays coil connections and the other lead of the resister on the other coil connection. I will leave it for you to decide if this is something you want to attempt. In lieu of that you might see if you know someone who has a better knowledge of electrical circuitry and/or electronics to do this for you.

Kirk Keyes
1-May-2008, 08:19
Instead of a big resistor, why not get a red LED lightbulb and stick it in a readinglamp and then plug that in. At least you get a little light and it's safe.

1-May-2008, 09:20
I think for now, since I'm no electronics guy I'm going to just be happy that I can use the timer and the enlarger together and figure out some sort of "safe" light (thanks for the idea Kirk) that I can plug into the timer with the enlarger. I'm assuming this won't in any way damage the enlarger's power source/timer or risk burning down the darkroom, if this isn't the case somebody please let me know. At some point maybe I'll see if I can have the power source modified with an additional resister, we'll see. Kirk, thanks for the offer to test out the timer with your enlarger, I may take you up on that at some point if any new problems arise, for now I'm satisfied to be able to have everything operational.

Thanks once again everybody for the help and the input.


Donald Miller
1-May-2008, 10:03
The addition of a low wattage auxillary lamp should not exceed the current design parameters of the power supply. A question along these lines is do you have the XLG model? if so you have less powersupply headroom as the enlarger lamp is already higher wattage than the lower powered enlarger.

The XLG model power supply is fused for 350 watts. The lamp consumes 250 watts and the fan and timer require some additional wattage so I would not get too carried away with the lamp that you add to this load. Worst case scenario is that you will take out the 3AGC fuse...if that should occur do not add a larger fuse since that will place the step down transformer at potential for failure.

1-May-2008, 11:18
Thanks Donald, I have the shorter model (4550xl?) and am going to add something small onto the timer so it shouldn't be a problem. I also got an email from Richard at RH designs about something else to check inside the timer, with any luck that'll end up being the problem and I can alleviate the extra light all together, we'll see.