Chromega Dichroic main light not working

[Wade Guisbert]

I have 2 used Chromega Dichroic II heads, and the main light in neither of the heads work. It is either the power source, lamp sockets, or something internal like circuit boards. Reason would tell me it is the power source, since I have only one old used power source (presently).

I have read other postings on this issue, but there is no information as to what the final solution was in those situations.

I have tried new lamp bulbs without success. I am purchasing a new lamp socket, and will probably buy a used power supply.

What has been others solutions?

Thanks!

[ic-racer]

Did they ever work?
Which power supply do you have? The 'standard' one has just a large step-down transformer in the box. A replacement transformer in the wattage needed would probably be around $200.

The Chromegatrol has a ferroresonant transformer that would be somewhat difficult to find a suitable replacement source, except, perhaps, Omega. If the timer circuit is bad, there is a schematic available on the web. It does not look that complicated. http://valuepig.com/docs/Chromegatrol.PDF

In both cases, there are no 'voltage controller' circuits to go bad.

The bulb can be changed over to 120v if all else fails.

Also, if you have the 'standard' power supply, you could check the DC resistance of the primary and secondary coils on the transformer. If I recall, when I last checked the primary windings I found about 0.9 ohms. The secondary was higher, 250 or so.

You may find some additional info here: http://www.apug.org/forums/forum43/6...a-ii-120v.html

[Wade Guisbert]

One of the heads worked, I'm not sure about the other one. I have the standard power supply. It looks old, the cord has "dry-rot". I bought it used on ebay several years ago, while I built and equipped a dark room.

I am a semi-retired dentist, not an engineer. I will replace stuff sequentially. I was just wondering which of the various elements of the enlarger was usually the weakest link, and go from there!

Thanks for suggesting a 120V lamp! I would have never thought to do that!

I'm still waiting for other's solution results!

[ic-racer]

One of the heads worked, I'm not sure about the other one. I have the standard power supply. It looks old, the cord has "dry-rot". I bought it used on ebay several years ago, while I built and equipped a dark room.

I am a semi-retired dentist, not an engineer. I will replace stuff sequentially. I was just wondering which of the various elements of the enlarger was usually the weakest link, and go from there!

Thanks for suggesting a 120V lamp! I would have never thought to do that!

I'm still waiting for other's solution results!

Maybe have a friend with a voltmeter/ohmmeter check things out. Bottom line is that that system is pretty simple and robust and should be able to keep working for years and years.

Weakest link would probably be cords, switches and connectors. The only other thing in the 'standard' power supply box is the transformer. Sure, transformers can blow, but that one is pretty reliable. As I recall, though, its primary circuit (120v) is not protected by a fuse. The fuse is on the secondary (24V) circuit up in the lamphouse.

[ic-racer]

I want to add friend of mine had the Omega Solid State timer on top of his power supply, and that timer blew the little SCR in there. That put the whole system down as he did not know to just remove the timer from the system to check it. The SCR was easily replaced ($1.87)
http://www.mouser.com/Search/Product...key526-NTE5455

As a note, when using the Omega Solid State timer, it is 'ON' and activating the relay when ever it is plugged in and in 'TIME' mode, even when sitting idle, so always turn it to OFF and/or turn the power supply to off or unplug it when not in use.

[Drew Wiley]

Always check the bulb socket too. Sometimes corrosion can occur where the bulb
pins insert.

[Wade Guisbert]

I did not find a guy with the electrical know-how to test the power supply. I bought a pristine Chromegatrol II on ebay for $250.00 ($1100.00 @ B&H), and all the heads work perfectly! I am really excited! This has been a long process. I gots lots of 4x5 slides and negs to play with! This is the best Christmas ever! (I've had 55 of them)

It was the old original power source all along, as I reasoned. Now I have a power source, voltage stabilizer, and digital timer all rolled into one. For only a quarter of the price of new!

[ic-racer]

Good to see this all work out OK!

[SteveKarr]

It's nice to get new things ... but a thought.
I have the 10x10 version and if the cooling blower/fan motor isn't connected it won't let the head light the lights.

Just a thought.