8x10 Super Chromega F info requested please

**Erik Larsen** · 9-Mar-2011, 18:48

Hi all,

I have an 8x10 Super Chromega Dichroic II lamphouse with corresponding power supply and power relay and use it with a Darkroom Automation timer. Everything works fine as far as I can tell, but the "lamp failure indicator" lights on the power supply are all lit up indicating that all 4 bulbs are burnt out which isn't the case. The problem is that the "lamp failure indicator" lights throw out a lot of white light which I'm sure can contribute to fogging my paper. I have placed tape over them to solve the fogging issue, but I would like to know if one of my bulbs actually is burnt out so I would like to fix the issue if possible. I've looked in the power supply for obvious signs of problems and it looks brand new inside with no discolored wires, but honestly I don't know what I'm looking for. Does anyone know what to look for to diagnose the problem? Any help would be greatly appreciated.

One last question if I may. The fan is designed to run as long as the power supply's power button is on and I have read that it is supposed to run after the exposure is over to dissipate heat. I can rig it so it goes off when the bulbs go off by hooking it to the power relay which I would prefer if it isn't significantly shortening the life of the bulbs? The fan is pretty loud (ceiling mounted squirrel cage enclosure) and it would be nice to work with out the fan running after the exposure is made. What do you folks think?
thanks for any help.
regards
Erik

**ic-racer** · 9-Mar-2011, 19:12

The four 250W lamps are wired in series. So, when one blows, all 4 would go out. Thats why you need the indicators. They tell which of the 4 is blown. The indicator lights are wired in series with each lamp. There is a resistor made of #17 nichrome wire wound on a 3/16" mandrel in parallel with each indicator lamp. Perhaps those resistors are fried, causing the indicator lamps to light all the time. I think those wire-wound resistors may allow the other 3 250W lamps to continue to function but if the lamp is not replace soon perhaps those resistors can overheat.

There is a thermostat in the head but it is connected to the timer circuit and is normally closed. Above 130 F it opens and prevents you from making any more exposures.

I'd probably just use the main switch as a blower on/off switch and turn it off after you think its cooled off.

My Durst has a termostat on the blowers for the overrun of the blowers after long exposure, but it almost never stays on for more than a minute or so. For exposures less than a minute the blower usually just stops when the exposure stops.

**Erik Larsen** · 9-Mar-2011, 19:37

thanks Ic racer, this unit has a safety feature that turns the lights off if it gets too hot making me think I might be ok. My exposures are usually 15 to 45 seconds and the lights are only of for a long time if I am composing/focusing. I just do not want to be stupid and ruin something in the lamphouse that I can't replace easily.

I don't know what's up with the "lamp failure indicator" lights. All bulbs light up so no "lamp failure indicator" lights should be on. The indicator failure lights are suppose to tell me if, and which bulb is not working, but it is telling me that all bulbs are burnt out. Here is a pdf of what it looks like. Any clue why they are on?

**Erik Larsen** · 9-Mar-2011, 19:43

Hey Ic, I could have sworn that I read a different post a second ago

The fan can be run by the power relay, not power supply if I want it to turn off when the bulbs turn off. It is basically controlled by the timer this way. If I do it the way it is supposed to(via power supply) then the fan runs as long as the power button is on on the power supply.

Any way to tell by looking if the resistors are not working? I'm not an electrician, but I have stayed at a holiday inn

regards
Erik

**Erik Larsen** · 9-Mar-2011, 20:06

Hi Ic, please disregard, as I unplugged and plugged the bulbs back in and all is well in enlarger land again. Thanks for thinking it through however.
erik

**ic-racer** · 10-Mar-2011, 20:50

Originally Posted by Erik Larsen

Hi Ic, please disregard, as I unplugged and plugged the bulbs back in and all is well in enlarger land again. Thanks for thinking it through however.
erik

Yes I had changed my post after tracing out the thermostat wiring on the schematic. Glad to hear it is working again.