Omega Dichroic II head voltage stabilizer or power supply ?

[Jim C.]

I've blown two brand new ELC bulbs so far, once when I had the DiChro head set up, and now recently doing some
enlargements, both blown bulbs have had less than an 2 hours use. I'm down to my last new bulb, and I'm wondering where
or what could be causing the bulb failure, the bulb socket is fine, but when I hook a multimeter up to the socket I get a fluctuating
voltage that tops at 25.9vdc.

I'm wondering if the voltage stabilizer is the cause, does anyone have a pinout for the voltage stabilizer
connector and the power supply so that I can measure each ?

[Drew Wiley]

There are several potential culprits. Could be excess voltage fluctuations due to a bad power supply. Check the lamp sockets; these get old and bad. Commonly
junk bulbs are the issue. I'd never purchase Chinese el-cheapo bulbs, no matter what brand is on the box. They pop quick. It you touched the bulb with your fingers, the finger oil can make them pop. Moving an old enlarger might jostle something like an old fan and render the cooling inefficient. But I'd first measure
what kind of line fluctuation you have in the 115V line itself. A stabilizer can only buffer these a certain extent. How good is your multimeter? I always use a real
pro one worth a few hundred bucks. Also check the sockets and pins on the whole stabilizer system for corrosion or looseness. Most of these things are old enough to exhibit such issues. A bad contact here or there can wreak havoc.

[LabRat]

Let me expand on what Drew correctly said...

I had to maintain/service a bunch of these at a facility... Some would pop new bulbs quickly... The problem was usually some contact in the power chain turned slightly intermittent causing stress to the bulb... Starting at the timer (even the relays)/power supply/AC inputs/connecting cables (and sometimes inside of connectors) and right up to the bulb connector ALL need to be carefully checked for even very slight oxidation/pitting/arcing and carefully cleaned... (Some 600 or 800 emery paper wrapped around a popsicle stick and followed up with a shot of DeOxit D5 worked well for the connector pins, and the female pins shot with the D5 and rubbed with wooden toothpicks inside would leave a little mess of oxidation on the end of the wooden sticks...) For ALL the relays, get a relay burnishing tool strip, pop the covers off, and carefully rub the mating contacts with the tool, and follow with a shot of the D5... Shoot inside of ALL the switches, esp the timer and power!!!

But the usual culprit was that the bulb connector seemed fine, but after heating, the contacts would expand, becoming very slightly intermittent and slightly arc and oxidize, would turn out to be the problem and blow bulbs... (Get a few replacement bulb connectors, and replace them from time to time... They DON'T last forever, even though they still look good!!!!)

And check the fan system carefully... The fluctuating heat inside the head will expand/contract the contacts inside and create other thermal electrical and mechanical problems...

And sometimes entire batches of new bulbs were defective...

But all cleaned up they are good-to-go even if used hard... After that, the bulbs could be good for a year or two of very hard daily use...

Steve K

[LabRat]

Oh, I did I mention to check/clean the AC socket in the wall???

Steve K

[Jim C.]

Thanks Drew, LabRat.

The bulbs that blew were Impact brand from B&H, there was no scorching that would have
said to me that there may be a socket problem or that I touched the bulb, the filament in the Impact bulbs just
gave up, no discoloration, just a broken filament. It may be a bad batch of bulbs, too bad there is'nt any mechanism
in place to check if that was indeed the case. BH at the time didn't have any other brand but their house brand
in stock so I went with their house brand. Hopefully the Osram will last longer than 2 hours.

I would think that even if I had fluctuations in my mains they wouldn't be that severe but I'll check them when I get home.
The cooling fan in the head is working fine, and I didn't notice any heat on the head case.
I did Deoxit on the Omega timer, but I didn't do that for the power supply or the voltage stabilizer connections.
That's something I'll do next.

[ic-racer]

I've blown two brand new ELC bulbs so far, once when I had the DiChro head set up, and now recently doing some
enlargements, both blown bulbs have had less than an 2 hours use. I'm down to my last new bulb, and I'm wondering where
or what could be causing the bulb failure, the bulb socket is fine, but when I hook a multimeter up to the socket I get a fluctuating
voltage that tops at 25.9vdc.

I'm wondering if the voltage stabilizer is the cause, does anyone have a pinout for the voltage stabilizer
connector and the power supply so that I can measure each ?

Not enough information. What "voltage stabilizer?" I can only guess you are using 412-021 Standard Power Supply with the 404-841 Solid State Plug-in Voltage Stabilizer. If that is the case, I'd recommend removing the voltage stabilizer from the chain and report back the socket voltage readings.

[Jim C.]

Yes, it's the 412-021 power supply and the 404-841 stabilizer, I cleaned what I could inside the power supply and the stabilizer
and I did remove the stabilizer to see what voltages I was getting directly from the power supply.
Measuring at the lamp socket in the Dichro head with just the power supply connected I get 25 vdc
With the stabilizer connected I measure 19.1 vdc, which seems low to me, but the halogen lamp should run ok at that voltage.

[Vaughn]

Just thought I would mention this as an aside...

I had a row of eight 23C's that were constantly blowing bulbs...it was getting expensive (and frustrating for the students)! The campus electricians hooked something into the circuit the row of enlargers were on to measure any flucuations in the system, but could not find anything.

I finally got out my cheapo voltmeter and tested the out-put of each of the timers (Time-O-Lites, and perhaps a Beseler or two). I found a Time-O-Lite that was sending out a spike of high voltage when it shut off. If another enlarger in the row had its lamp on when the bad timer shut off, it would blow the lamp.

[Jim C.]

The timer seems fine I did all my voltage checking using the timer.
But that good info to know.

[Jim C.]

To add some closure to this thread, it seems that the bulbs were suspect, having switched to Osram bulbs
I've been happily enlarging for more than the 2 hours I was getting from the Impact brand bulbs.

I also bought the bulbs from Bulbs America, good service, very good prices.

[brucetaylor]

Good thread. Bulb quality can be a huge factor. We use Osram bulbs only at work. Had a customer complain about the cost when he found cheap ones online. It's no bargain to do the job twice.

[Jim C.]

Actually the Impact brand bulbs were about 10 bucks each, not exactly expensive, but not cheap.
I replaced the last of the Impact bulbs with an Osram ordered from McMaster ($20) but hoping
that it was the bulbs and not the hardware I bought Osram spares from Bulb America ( $6) just in case it
was the hardware. So far it was the Impact bulbs, the Osrams are working great.

[bob carnie]

Just a little aside , handling of the bulbs is very important , use cotton gloves when putting them in.

[denverjims]

Sorry to be a little late to this party, but I had a similar problem with the power supply I got when I bought my Chromega on the big auction site. Unlike you EE types I never did figure it out, but discovered that I could "Frankenstein" my old Beseler color head PS I had kept for "just in case" to the Chromega head. Switched to the ELJ bulbs the Beseler used (same socket as ELC ) and it worked fine for years after I re-calibrated exposure times.

Just had to figure out which leads did what on both ends. Another way to de-dermis a feline.