Chromegatrol Issue

[MattKing]

Nice self portrait George .

 

[George Nova Scotia]

I didn't even notice Looking a little gray around the edges!

 

[ca1945]

George, you sound like the man who may be able to help me. I very carefully ran the unit with the cover off and confirmed my suspicion that the sound I am hearing is the relay oscillating. I can also tell by looking at the inside and at the schematic that I do not want to touch something I shouldn't and end up in a casket. The obvious monster is the 660V C6 that is connected directly to the transformer. But there's also C3 at 1000V, and C2, C4, and C5 with high voltage ratings.

If the relay is oscillating, the relay at least works. Looking at the schematic, should I expect perhaps that diode CR2 is bad, allowing the relay to feedback on itself? I apologize if that doesn't make electrical sense.. I'm working with the most basic understanding here. If I read it correctly, the focus switch shouldn't use the relay at all.. the switch turns it on and off. But if CR2 is bad, then the voltage would flow back and trip the relay, and it would just oscillate, right?

I should note: the relay oscillates in both Focus and Expose modes. In expose, the timer is accurate, and opens and closes the circuit fine.

 

[Sirius Glass]

Before you touch it, let the capacitors bleed of the voltage or you will become a member of the big 660 club. Early in my career the engineers in the lab had become members of the big 500 club. i went months longer than everyone else then one day I reached around the box and became a member of the big 500 club. The jolt threw me across the room and slammed me spread eagle into a row of metal cabinets.

 

[MattKing]

Thank you guys so much! I was able to get those things back on track and now I can raise and lower the head all I want. Looking at your enlarger George I can tell where those springs should be.. do you happen to have a picture of what the springs attach to at the top on your unit? Maybe I can return this unit to its original configuration if I can see what the springs attach to.

Now if only I could fix the damn Chromegatrol..

Before you start moving the springs, be sure that you don't have an enlarger where someone has retro-fitted one set of springs (for a D6 like mine, as an example) to another model.

The springs may be common to more then one model, or maybe they are not.

 

[George Nova Scotia]

CA1945 I'm on the east coast and it's bedtime. I can have another look tomorrow unless Sirius has some ideas. Things I noted simple half wave rectifier, gnd is the neutral side of the AC line ( unless your AC is wired wrong then it's 120V) voltage reg is a Zener 33V = V+, the timer chip LM322N seems to out of production, might be hard to find. Google shows some sources, but not the common ones.

More thoughts tomorrow....

 

[George Nova Scotia]

First here are couple pictures of how the springs attach on my D5, as mentioned yours may have been replaced with a different type and maybe best left alone.

 

[George Nova Scotia]

Now in other news. I pulled my power supply up from the basement and plugged it in for the first time in a couple years (sadly it's just in storage till I decide what it's future will be.

It buzzes too. The relay looks solid, the timer works and seems pretty close for now and I have a steady 28VAC on the output terminals for the lamp. Right now my best guess is the transformer is buzzing. I don't know if this is normal or not, I suspect not. I've only tried this unit once when I first picked it up. It was a government surplus auction - I put in a low ball bid and won - not really expecting but spare parts for the other D5 I have set up.

I did make a quick video but still too big to upload, might have to find another spot.

Back to your OP. If you are measuring the correct voltage at the rear terminal for the lamp perhaps you have other problems. You said to tried a new bulb, but one problem that does show up is corrosion in the lamp socket - it may have to be replaced.

Anyone else have some comments re the noise (or anything else?) Perhaps the large capacitor connected across the transformer winding?

 

[George Nova Scotia]

One last thought. I carried the power supply back to the basement and hooked iT up. Much less noise, still a gentle hum, but not something I'd worry about. If the timer circuit is working, take a hard look at the lamp socket and the wiring.

Best of luck and be careful.

 

[ca1945]

I watched the relay with the cover off and the buzzing is most definitely the relay going back and forth rather than a transformer hum. You can actually see it whirring as it opens and closes itself. I know it's not supposed to do this, as it will most certainly wear the relay out exponentially faster. I uploaded a video to youtube of the buzz.. damn near impossible to see it on the video but the insides of the relay are what the noise is. [video]https://youtu.be/-M2zs-4uE0c[/video]

The socket for the lamp in the head looks great. No corrosion, no dust. Same thing with the terminals on the lamp itself. The insides of the power supply are another story..

 

[George Nova Scotia]

It sounds a bit different than mine. If the relay is chattering the DC supply(what there is of it) is likely bad. There is one large cap on the board - have a look at it is it bulging or vented? I had a look at my board earlier, not a easy thing to work on. Looks like a pain to remove and no silkscreen labels on the parts. Every part will have to traced out to ID them. Have a good look for any damaged or burnt parts, has it been repaired before. CR1, C2, CR5 would be prime suspects. I'm not sure what you have for test gear or your experience with this type of thing so don't go beyond what you are sure of. CR1 is connected directly to the hot 120VAC line with the neutral line playing the role of circuit GND. Nice way to blow up test gear if you aren't sure what is going on.

I assume the timing function doesn't work?

 

[ca1945]

The timing function actually works perfectly. If I set a value with the pots and the multiplier dipswitch, it counts off like a champ.

Take a look at this: looks like a scorch mark and a damaged trace on a cap. No idea which one..

 

[Sirius Glass]

Since there is a scorch mark, you should probably replace that capacitor [those capacitors].

 

[George Nova Scotia]

I'd have to go get mine again and the trip to the basement and back to the second floor would just about do my knees for now. I believe that is R2 1.5K 5W it likely runs warm. The main filter cap is toward the center of board, just visible grey. There is a lot of dirt there, that cap may have vented. The board needs to cleaned and the cap replaced, diodes checked etc. The timer working is a good sign, sourcing that IC might be fun. Time to get some parts and warm up the soldering iron.

I can take a second look tomorrow (later today for me) long distance troubleshooting is tough.

 

[ic-racer]

A while back I re-did a 'standard' Omega timer (the one that sits on top of the Power Tower). That one was non-digital and was fixed by replacing the SCR. I replaced the electrolytic caps at the same time. You should be able to get that Chromegatrol running if the transformer still works, all the parts are available. Doesn't seem like the IC is bad but it is not that hard to find: http://www.ebay.com/itm/LM322N-LM322-Precision-Timer-IC-/270658505020

 

[SMBooth]

I had this issue and after changing the relay (didn't fix it) i changed the lamp. Problem fixed. Have you actually replaced the lamp , sorry I didn't read through the thread.

 

[DREW WILEY]

Mine finally acted up after 35 years of use (and I bought the thing used to begin with!). I solved the problem by throwing out the whole rig
and picking up an enlarger worth fifty times as much, at least new. My cost = free, but quite an ordeal to pick up and install in my own digs.

 

[ca1945]

Well, the problem was solved by means of an exchange with a working (and much cleaner) Chromegatrol. This stopped my troubleshooting from going further, but my next steps were to take off the board, clean it and re-cap the scorched one. It sat long enough that I felt safer about the caps and attempting to discharge them.

Thanks for all the helpful input. One thing I didn't put in the thread was my thought that with modern IC voltage regulators and DIY microcontrollers like Arduinos, am I totally out of my mind assuming that it wouldn't be a huge deal to make a replacement for the Chromegatrol that weighed a fraction of what it weighs, takes up a lot less space, is digitally controlled, and costs very little? We're not talking high voltage vacuum tube power supplies.. it can't take much to get stable 24V.

And further on that note, anyone ever explored swapping halogens for high powered white LEDs?
Benefits:
-not having to worry about UV/IR
-no heat (no fan!)
-no need for voltage regulation or really much of any demanding power requirements.
-much longer life

Cons:
-possibly not as much output, though I would think there are small and bright enough arrays to do the job
-color temperature (again, I feel like there are full spectrum options available)

I'm down to try both ideas at some point.

 

[DREW WILEY]

LED's are relatively weak compared to halogens, and you're not realistically going to print color with them. It's a bit more complicated than
you envision at this point. For example, any relatively young technology might have component replacement issues down the line, until more standardization kicks in. LED's at this point in time are more realistic as an option to cold lights rather than colorheads. Don't bet on long life
either. Gotta do your homework. It still relatively adolescent technology, with a lot of foibles and Darwin Award distribution. Things are just
starting to shake out. By contrast, there is a mountain of Omega gear still out there to cannibalize from.

 

[ic-racer]

The chromegatrol is heavy because of the ferroresonant voltage stabilizing transformer which is simple and reliable. Sure, you can replace that with a switching power supply that is lighter, but I don't think it will be simple or as reliable.

 

[ca1945]

Drew: A single halogen vs a single LED would be a pointless exercise; the halogen would murder that contest. But the thing about LEDs is that you could put a bunch them together in a small space. You can't do that with halogen bulbs.

LEDs have been around for decades. It's a simple technology. Higher power white LEDs and driver chips are newer, but the complications are in the manufacturing process, not in the implementation (which is what counts). They aren't that much more difficult to implement than a light bulb, and driver chips for something like this aren't any more complex than the ancient timer chips used on the Chromegatrol. There's a reason all of the street lights in my town are spewing out ugly white LED light instead of sodium vapor light.

I have no idea if you could get enough lumens out of an LED package that would fit in the same size as an ELC halogen bulb. But it seems worth a try. No ones going to get a Darwin award doing it haha.. the worst that could happen is you waste like 15 bucks on some components and find out you can't get enough light, or you smoke an LED. That's a lot better than accidentally putting a fingerprint on a halogen bulb and having it blow glass all over the place when you least expect it. And reliability? I don't think anyone can say that a halogen bulb is going to have a life expectancy that can compete with an LED component. I'm not saying LEDs (especially high output ones) are going to last forever by any stretch of the imagination, but all they have to do is last longer than a halogen. They are not expensive so replacement is a non issue.

There may be a mountain of omega gear, but there's several oceans of cheap electrical components. I wouldn't have to scour ebay and pray that I'm getting something good or order something from Canada. I could have a brand new component at my door in a day or two. Certainly wouldn't have to pay the shipping cost for the Chromegatrol's gigantic transformer. When you know exactly how your equipment was designed and how it works, you can fix it yourself for next to nothing.

ic-racer: if it's reliable then how come mine wasn't, and these units in particlar required a special write up from John Ollinger? I know it wasn't to do with the transformer itself, but that's beside the point. These things aren't cheap (comparatively) used.. certainly not the shipping either. Brand new 24V switching supplies are < $20. More importantly, they weigh under a pound.

Everyone: I'm not an EE. I'm an electrical idiot, if that wasn't apparent by the dumb questions I ask. But I'm definitely going to try and see if I can get some LEDs to match the power of a halogen (or come close). And if I can, I'll print with it, and see if their "white" spectrum is white enough.

I'm not really confident it's going to work. But not attempting because LEDs are some new poorly understood technology that's unreliable and dangerous doesn't make sense. If anything, it's safer because I won't have to be poking around the innards of high voltage equipment trying to figure out what went wrong with them!

If it doesn't work out, then I'm out a few bucks.. but I'll have learned a lot in the process.

 

[George Nova Scotia]

There are some designs out there for LED heads, mainly for BW variable contrast printing using blue & green LEDs. One challenge is that that LEDs are by nature narrow band devices or have holes in the spectrum. I don't know if any has tried to make are head for colour work, should be doable just have to get the right mix. Second challenge is still heat, LED don't like heat. High power means the LEDs are usually mounted directly to a heat sink.
Best of luck and please keep us informed. Lots of our equipment is getting very old and sooner or later something will have to give. One thing on my todo list is to look at designing a controller/timer for the Ilford 500 system. The power supplies are still fixable the controller I'm not sure about.

 

[ic-racer]

ic-racer: if it's reliable then how come mine wasn't,

I suspect the regulated power supply is fine; the timer needs repair.

 

[paul ron]

Now here is something I learned from old radios... some parts like that 5w resistor run very hot n over the years the solder joints let go causing it to run even hotter n burning the PC. Ive touched up solder joints n the units run fine ever after. Also check to see if the traces are burned n replace them with hard wire. Ive seen this too many times with flyback transformers.

The other thing, use a higher temp solder. Most electronic solders today are low temp for delicate computer work.

Look up how to properly bleed off heavy caps? You think low voltage cant hurt..but the large cap will grab you n fry your brains! high voltage doesn't let go.. it contracts your muscles n forces you to hang on.

An old tube man taught me to work on an off balanced stool tilted backwards n also work with one hand. if the bastard grabbed me, the stool will fall over n help me get free.... saved my life once! still have 8 more lives left.

just a thought.