Good prints, followed by darker ones, and back to good ones...

[tezzasmall]

Over the last couple of printing sessions, I have a problem that has appeared out of no where and is not going away!

For no reason, I initially got a couple of good prints, which then were followed by one or two darker prints, looking about 1/2 f-stop darker, and then back to correctly exposed prints again.

Initially I tried changing the developer (as this has solved unknown problems in the past), from Ilford Multigrade to home mixed D72, but the problem continued.

Today, I did a lot more test strips and prints, changing my RH designs analyser, with probe, to a more basic one without the probe. The problem continued. I then changed the bulb in my 2/14" Omega enlarger, which has no transformer and plugs straight into the main, with a different 100 watt bulb. The problem continued...

I know very little about electronics, but have read in the past about 'voltage spikes' and 'fluctuations'. Could something to even out the mains voltage help?

ANY suggestions would be gratefully received.

Terry S

 

[Dali]

Without negaitve on, if you turn on the enlarger, do you see any light fluctuation? I ask you that because I had by the past some exposure issue ( I could see the light intensity changing while exposing...) and I had to re-wire part of my enlarger to get the light stable again.

 

[koraks]

Could something to even out the mains voltage help?

Highly unlikely.

It is however possible that there are bad contacts in the bulb socket; I'd check the socket and replace if necessary.
Also I assume you have verified the timer of the RH clock for correctness using a stop watch. Sometimes relays can become 'sticky', although it's not very likely to be the cause of your issue (still more likely than mains voltage fluctuations).

 

[petrk]

As koraks said. I had similar problems. In my case, the RH Analyzer Pro turned out to be defective. It needs to be fixed. Try to disconnect RH Design for exposure and measure the exposure manually or using other timer. Will it be the same or will it improve?

 

[ajmiller]

What paper are you using Terry?

 

[Bill Burk]

"Omega enlarger, which has no transformer and plugs straight into the main, with a different 100 watt bulb. The problem continued..."

Voltage Stabilizer - YES.

I got one but then immediately went over to cold light for my Omega DII. So I never got the full benefit of it.

But they're great and will do what you need for an incandescent bulb.

 

[Vaughn]

Anything else major on the same circuit -- fridge, etc.?

I had a bank of eight Beseler 23Cs that were blowing bulbs right and left. I called the Plant Operations electricians in, they could not figure it out. I got the volt meter out and eventually found that one of the trusty old Time-O-Lites was sending out a spike of voltage when it shut off. If someone down the line had their enlarger on at the same time, it would blow their bulb. It was frustrating as heck for awhile.

 

[gone]

Wouldn't you want to stick a multi meter probe into the wall socket and confirm that there actually is a voltage fluctuation/spike issue? That's where I'd start. First, I'd look at all the connections from the plug to the bulb though.

As mentioned, once your eyes get accustomed to the dark, turn the enlarger on w/o a neg in it and see if you visually see any changes in the light intensity. It sounds like something else to me, but I wouldn't ck anything else until I saw that there were no spikes on a meter. Truthfully, I'm not sure 1/2 stop between prints would be a concern w/ my negs though.

 

[Pieter12]

1. Same negative?

2. Take the analyzer out of the loop, make manual test strips.

 

[koraks]

Multi meters will virtually never pick up spikes. They may or may not accurately monitor fluctuations. If you're serious about the hypothesis that the line voltage is the problem, call an electrician.

 

[Nicholas Lindan]

It's odd that you are getting darker than normal prints. Normally I would suspect the wiring at the enlarger's lamp socket, but that would result in the odd lighter print. Unless, of course, the normal run of things is a bad connection that occasionally makes good.

I would tighten the connections at the lamp socket - it's like chicken soup: it can't hurt.

I doubt it is a dip in the electrical supply from the fridge or air conditioner cycling as again it would lead to lighter prints.

Are you using the 'Analyzer' part of the RH designs unit to determine print exposure - it could be the probe on the analyzer that is acting wonky. Is there any dust or fluff in the probe's sensing hole? But, as you say the problem persists even when you swap out the timer this is a very unlikely cause. But cleaning the probe just adds more chicken soup.

Then, it could be something mechanical - like the f-stop adjustment on the lens. Do you open and close the aperture between prints? If so then the problem maybe that the diaphragm doesn't always close to the same spot.

 

[tezzasmall]

Thanks for all the suggestions peeps. Something came to me last night, that I need to check first before anything else.

I will report back if it doesn't work.

Terry S

 

[Kilgallb]

I had a similar issue, drove me crazy. Turns out my old lens iris leaf was not working properly. One leaf would stick then suddenly snap in place. I threw out the lens.