Ilford 500 contrast control problem: 2 Part Question.

My ilford enlarger has started to malfunction. I have the 500h head and the cpm controller. I am getting inconsistent contrast/light intensities .....for example, grade 5 will intermittently be much brighter (possibly a grade 2 or who know what). I changed bulbs, and I'm still experiencing the same problem. Anyone have similar problems in the past? I imagine it's the cpm controller. Any advice on how to check the controller? I have no experience and can't do this myself. I do have the parts manual.

Part 2. I have a spare 500c controller I am going to hopefully be able to use. My question is the manual for the 500c says that the bulbs are 150 watt. I was using the 300 watt bulbs. Can I continue using the 300 watt bulbs, or do I need to switch to 150 watt bulbs ?

Thanks for any help with this! I'm hoping I won't have to switch to another system !!!

Gary P

Hi Gary. One of the first things I'd suspect is the lamp sockets & lamp contacts. It doesn't take much to cause problems. I had a problem a while ago where one lamp didn't lite, changed bulbs ok, put the originals back in ok. Likely some corrison on the contacts.

As far as I know the controllers are interchangeable. Re the 150w vs 300w the main change was some added heat shields in the head. Later versions of the power supply added some extra isolation but they are basically the same.

My first suspect would be the contacts and various cables, then the parts in the power supply, lastly the controller. Trouble is these things are getting old, so lots of points of failure.

Thanks George....I changed bulbs and I am still experiencing the same inconsistency problem. I will try cables , then the power supply. I have two complete systems, so hopefully I will be able to get it working again. If not, I'm going to have to change systems completely.....

I'd swap out just the control module first and see if that's it. Then try a swap out of the power supply. I had something like this on the Ilford 400HL unit too. Seems my contrast switches were in need of removal and clean job. Once I did that it worked perfect, but the Ilford 500 system is different in that it uses the touch-pad setup. I used to have a Ilford 500 setup and never experienced any problems with it, but only used it for about two years.

On grade 5 you must have blue light only and full intensity. Hence I'd rather suspect connections. As said before, have a look to the bulb sockets, they carbonize over time and contact can be - or possibly get as inside temperature increases- not good enough.

You can use the 500CC controller with the 300W bulbs without any consequences as long as you get the equipement (PS and head) running for the 300W bulbs. The only slight difference might lay in the switch position related to the balance of power between the two lamps. Normal scenario (ie balanced power between the 2 bulbs) is the #1 position (#4 for 500CPM).

Good Luck

Does it get much brighter, or just a little, like a 10-15% difference in the resulting mid tone density? If the latter, then an ageing power supply, 500S, can cause this, especially with line voltage fluctuations. After putting an old-fashioned electro-mechanical voltage stabiliser and replacing my 500S I banished those fluctuations. But if it is more severe then I'd suspect connections.

I just reread your question, and I'm not so sure of my suggestion, as in my case the grade wasn't changing, it was the overall intensity, and a subtle clock drift... Good luck.