Super Chromega D Dichroic II troubleshooting

Hi all, I'm curious if anyone has some experiencing repairing the Super Chromega lamphouse/Chromegatrol power supply (the one with the built-in timer) and can provide some ideas about where to focus my efforts getting this thing working again. The hardware is new-to-me, and I've only put maybe an hour on it before it's crapped out on me.

Symptoms: the day it died, I was able to make a couple of test strips and one print. I set it up for a second print, and when I pressed the Expose switch nothing happened. Flipping to Focus mode does nothing. The fan and bezel light are both working, so that implies to me that there's something in the lamp power supply chain that's going wrong. I can't hear the transformer buzzing when I press the Expose switch.

I'm aware of the weakness of the lamp socket; I pulled the lamp and the contacts look pretty clean. I opened the power supply housing and didn't notice any obvious signs of damage in there. Anything else obvious I should be looking at?

I assume that you verify that the ligh bulb is good?

Chan Tran said:

I assume that you verify that the ligh bulb is good?

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Bulb looks good!

I don't think there is much information out there but I would try to search for a schematic diagram. Also I would verify that the bulb is good by checking its coninuity. I guess the bulb is 82V? Also I would try to verify that I don't have voltage at the bulb socket. Now I know the lamp is 24V. I believe it's just some loose connection or a bad bulb. As you said I believe the power gets to the primary winding of the transformer. I woud check and see if I have power at the secondary.

First, verify that the 24V 250W ELC lamp is, indeed, in good working condition. Use a multimeter to verify continuity through the filament. No continuity indicates a melted filament and requires a new lamp. Simply examining the lamp might—or might not—reveal a discontinuous filament.

Try reseating the 6-blade connector from the power supply to the lamp house. Two of these conductors carry the 24V circuit to the lamp.

Assuming that all connections are good, in FOCUS mode, the lamp will light if the filament is good. There’s little else to go wrong with respect to delivering current to the lamp.

In TIMER mode, there are several possible causes of the lamp failing to light.

The 120V 60Hz US/Canada version is the top drawing 412-040. The 230v 50Hz export version is 412-045.

Link to Chromegatrol schematic

Looking at the schematic and the OP said he heard the transformer buzzing so it's on. And unless the secondary winding is open he should have 24V at the secondary. If he has 24V at the secondary and bulb is good it's ony the connections or wiring between the tranformer and the lamp.

Chan Tran said:

Looking at the schematic and the OP said he heard the transformer buzzing so it's on. And unless the secondary winding is open he should have 24V at the secondary. If he has 24V at the secondary and bulb is good it's ony the connections or wiring between the tranformer and the lamp.

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Just to clarify, during the short time that the enlarger was working I did hear the transformer buzz; now that it's not working I no longer hear it.

backseatpilot said:

Just to clarify, during the short time that the enlarger was working I did hear the transformer buzz; now that it's not working I no longer hear it.

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So it means that the primary winding doesn't get power. Do you have a mulitmeter? Since it doesn't work on FOCUS the problem is fairly easy to diagnose.

Chan Tran said:

So it means that the primary winding doesn't get power. Do you have a mulitmeter? Since it doesn't work on FOCUS the problem is fairly easy to diagnose.

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Picking one up is on the errand list for this weekend. One of the questions I had was whether the primary winding would energize without a load on it.

backseatpilot said:

Picking one up is on the errand list for this weekend. One of the questions I had was whether the primary winding would energize without a load on it.

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It would energize and prduce the voltage on the secondary whether or not the secondary has a load on it.

There are several things in the Chromegatrol that could account for the symptoms described in post #1. If the relay had become defective, or if for some reason no current is sent to the solenoid of the relay, then the transformer would receive no current. In this case, the safelight socket would remain powered when triggering an exposure or engaging the FOCUS switch. This is easy to test by simply plugging a lamp into the safelight socket.

On the James Ollinger site is an account of repairing a Chromatrol that failed in the same manner as discussed in post #1. The problem was traced to two diodes that had failed.

Here’s the account on the Ollinger site.

http://www.jollinger.com/photo/enlargers/chromegatrol_repair.html

If the LM322N timer IC should need replacing, they are relatively inexpensive and readily available. For example,

https://www.ebay.com/sch/i.html?_nkw=lm322N+ic&_sacat=0&_from=R40&_trksid=p4624852.m570.l1312

I appreciate everyone's help - I learned a few things, notably that I have the -037 version of the Chromegatrol (luckily the extra proprietary ICs seem fine). I'm hoping the board layout and components are substantially the same as the other two versions. The zener diode is definitely shot, and it seems to have taken out the 5k resistor in parallel with it, so some parts are on order and I guess I'll see if I can remember how to solder.

Quick little follow up - I think this power supply has been tinkered with before! The housing says it's the -040 version, but the circuit board definitely has two extra ICs not in the wiring diagram (unless I'm misreading something about the rotary encoders... it's been a while). I was able to replace the zener diode with the same part, but Digikey is back-ordered on ceramic half watt resistors for some reason so I swapped it for a thin film resistor with the same specs. With my super rusty soldering skills, I was able to desolder the two bad parts and install the two new parts. And now it works again!

(Zener diode was 17 cents and the resistor was $3.47 if anyone's curious.)

backseatpilot said:

Quick little follow up - I think this power supply has been tinkered with before! The housing says it's the -040 version, but the circuit board definitely has two extra ICs not in the wiring diagram (unless I'm misreading something about the rotary encoders... it's been a while). I was able to replace the zener diode with the same part, but Digikey is back-ordered on ceramic half watt resistors for some reason so I swapped it for a thin film resistor with the same specs. With my super rusty soldering skills, I was able to desolder the two bad parts and install the two new parts. And now it works again!

(Zener diode was 17 cents and the resistor was $3.47 if anyone's curious.)

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Perfect outcome. I was getting my 2021 Subaru ready for the winter today. As near as I can tell there's not a grease fitting on it. Your mention of soldering reminded me of "chassis lubrication". Used to be, like soldering, a person could earn a living with these skills. Not any longer

Good to hear you're up and running!