Zone VI VC Head, trouble

[dajaab]

Hi Everybody,

I own a Zone VI VC cold head but sadly one of the bulb, the green, doesn't work anymore.
Does anyone have an idea of where I can repair this head or at least have the schematic ?
The bulb is not broken, I think it's an electronic trouble but values on IC are erased ;-(

I can not resign myself to giving up this head, any help would be welcome

Thanks

[Eric Woodbury]

A schematic would be great. I've never seen one of these. I did own an Aristo VC head for a bit. It wasn't very complicated, but I don't know that Fred's is the same. You said no part numbers on the ICs, so you've looked under the hood. Perhaps post a few pix. One of the outside to see the controls and a few of the guts.

EW

[Luis-F-S]

PM Richard Ritter, hopefully, he can chime in. Also, the company that bought out Aristo has some replacement bulbs for some of their heads. Google is your friend. L

[dajaab]

I asked Richard Ritter, he said he wasn't at Zone VI/Calumet when this lamp was designed. He don't know.
LightSources sells remplacement bulbs but I'm pretty sure it's not the bulb, I think it's an electronic trouble. Maybe I'm wrong ?

Here some pictures
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[Eric Woodbury]

Dajaab, Does one lamp work and not the other? I don't see any obviously burnt parts. Do you? Does it smell? Those are signs of major failure, but from what I see, it looks ok. People sand off part numbers to hide their design, but those 14p packages surrounded by resistors are probably quad opamps of the cheapest kind. I doubt they are damaged either, as once they are in a circuit, they are pretty tough.

Ask LightSources if they have a schematic.

Does this unit have photo diodes monitoring the lamp intensity? You would be able to see these mounted near the tubes in the lamp house. If so, that would account for some of the circuitry. It seems like a lot of parts for what it does.

Somebody here should have some insight. Obviously I'm worthless without a schematic or unit in front of me.

[Chuck Pere]

If each head is driven by similar circuitry maybe you can figure out some comparison checks between the working and non-working circuits. Start at the tubes and work back? You would need the proper test equipment plus be careful with high voltages.

[Eric Woodbury]

If you put a meter on the high voltage, make sure the meter can take it. Most meters are limited to 600V. It should be noted on the front of the meter. You can put a voltage divider at the front end with a couple (or more) of 10 Meg resistors. This will protect the meter. If you aren't familiar with any of this, then find ham radio neighbor or EE student.

Oh, you should check any wires from the pots (potentiometers) and switches Make sure none broken.

[Leigh]

Speaking as one with limited experience with Z VI heads, but LOTS of experience with vintage electronics...

The components with the highest probability of failure are the two blue electrolytic capacitors at bottom center of the first photo. These commonly fail at 10 to 20 years of age. Those in your head are much older.

They're relatively easy to replace, with two leads soldered to traces on the underside of the board. These caps are polarity sensitive. Normally the negative side is identified with dashes in that black line on the side. The lead closest to that line is the negative; the other is the positive.

Electrolytic caps have two values that the replacement must match, the capacitance and the voltage.
Capacitance is usually in microfarads, like 22uF (22mfd) or 47uF. Voltage is DC volts like 200DCV.

Your replacements must also match mechanically, specifically the diameter and lead spacing.
You may have some leeway in the height (length).

You can get replacements from Mouser Electronics:
https://www.mouser.com/Passive-Components/Capacitors/Aluminum-Electrolytic-Capacitors/Aluminum-Electrolytic-Capacitors-Leaded/_/N-75hqwZ1yzvvqx?P=1z0yp7wZ1z0z7l5
They show capacitance units as uF, same as mfd.


Here some pictures
178875

- Leigh

[Eric Woodbury]

Leigh, I agree, but I'll guess that those two caps are ok. If they failed it would take out the whole unit, not just the green tube, as they appear to be part of the plus/minus power than runs the entire board. Also, if they had failed, the tops would be puckered (typically). It is capacitor heating that kills caps, not time. It is the current in and out, heating the ESR of the cap. This unit doesn't seem to have a lot of hours on it, based on the fine condition of the chassis box.

Without more info and/or schematic, everything is speculation. I sure hope a schematic is found.

[dajaab]

Thanks to all for your interest

Some news:

I checked the two photo diodes, they go from 300K to 500Kohms when they are facing the lights
Same behavior for both, I think they are ok

I reversed the wiring of the lamps, the wires that went on the blue now go on the green.
And now, he green bulb works instead of the blue bulb.
So this first high voltage transformer works, and when I increase or reduce with the Hard control potentiometer on the control box, the intensity changes.

I checked the input voltages, both of these two transformers are well fed in 110V,
They each have a red and black cable, of small section, the control circuit I guess ?

I reversed these two control circuits, I still have the green lamp which works. But this time I can reduce or increase its intensity with the Soft control button on the control box.

I conclude that:
the two high voltages are supplied with 110v in primary section, (I can't check output)
the two control circuits red and black work,
the two bulb work if I reverse the wiring of the lamps,

it can only be the high voltage that is absent on the second transformer ? Transformer HS ?

What do you think ?
An idea where can I find this part?

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[Eric Woodbury]

Can you measure resistance on primary and/or secondary of HV transformers? Depending on wiring, you may need to disconnect the primary on the suspect to measure. On the secondary is the tube, which will look like an open circuit if the voltage is off.

Is there any kind of visible label on the transformer? Is that what's under the white covers?

[dajaab]

I don't understand:

Primary (non disconnected) 68 Ohms on both
Secondary (disconnected) 148 Ohms on both
??
Same values but only one works ?

I have to disconnect primary on both to be sure but my wife wants to go to Sushi bar, so next tomorrow ;-(

[Eric Woodbury]

Sushi more fun that this.

Looks as though the transformers are good. That very good. Xfmrs are hard to replace.

Secondary only has the tube on it and we know that works. Good.

How is the primary driven? There must be a triac between the main (120VAC from wall) and the load (primary of xfmrs). Do you see something like this?

[dajaab]

I definitively need to disconnect primary, they are connect in parallel !!

[Eric Woodbury]

"They" being both the xfmrs?

How many wires coming and going from these transformers? I assumed 2 for primary and 2 for secondary. I just want to make sure they didn't do something tricky. Based on the 120VAC on the primary, I doubt it.

Do you know what a triac looks like? Do you see any there?

[Chuck Pere]

Are the HV transformers under the white case? Can you remove the top to see inside. Looks like you have control wiring running into the case.

[dajaab]

Good morning

No information on HT transformer, no way to open it
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178897

I unsoldered them, same value on primary or secondary, 450K Primary, 148 Ohms secondary
I think there is a capacitor inside because if I wait with my fluke, value increase slowly.

I draw a schematic:
178898

there are three TO220 type, one on radiator, both without dissipator still have value but I'm unable to read something without desoldering.
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[dajaab]

I don't see any connection between these TO220 and primary circuit for HT

there are also these component plugged in parallel, one on Power input, one one Timer input.
I don't know what it it ? A big resistor 1.2 KOhms ?

178900

[dajaab]

I think both primary are still energized to stay warm and ready. the red and black wires control the secondary and allow the variation of the power for the lamp.
When I turn the head on, both primary are powered by 110v.
I guess the TO220, triac or transistor, only controls the red, black circuit ?

I really care about this VC Zone VI. It comes from a complete darkroom that I bought from the Christopher Voelker's widow, a Los Angeles photographer. He worked a lot for film and television studios, only in B&W argentic, he photographed a lot of artists, David Lynch, Ringo Star, Beyonce... I saw a little of his work, it was beautiful, nice contrast, nice light. He was paraplegic which did not prevent him from setting up his own studio and having a great career. He unfortunately had a tragic end four years ago.
To use again its Beseler 45 MX and its VC Head Zone VI would make me very pleasure, it is just symbolic.

[Eric Woodbury]

Dajaab, Given that there are six wires to the transformer, then I wouldn't expect the triacs. You are right that you have a primary, a secondary, and a control. winding. What is the resistance on the control (red/black) winding? My guess is your transformer is some form of a saturable core reactor. The current in the red/black would control saturation of the transformer, thus changing its impedance controlling current to the load. These were used in the ZVI Cold light Stabilizer.

Could we get some more close pix of the circuit board, much like that partial above?

I'll do all I can at distance to help. More fun than the paperwork staring me in the face.

[dajaab]

No resistance between Black and red, on both. open circuit ?

tell me if these pictures work for you:

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178905

178906

[Eric Woodbury]

Not sure where to go next. A few notes. I see 7 alterations to the circuit. 4 on the bottom and 3 diodes added in parallel to resistors.

The Relay is a 2 pole (under 2Adc) relay. Do you hear the relay click when you do something?

There are 4 adjustable resistors, white with slotted screws on top next to black connector. Is there a calibration proceedure that requires adjustment by the user? I'd guess not and that it was pre-adjusted since it was for a known lamp.

The 14-pin black parts with "ST" on them are quad opamps. Something generic probably, such as an LM324.

U5, in the corner, is a Motorola part ("M"), probably logic, and not fully utilized. Not all pins are connected. Probably an oscillator since there is X1 right there.

Can you read U6 part number? Wipe with a wet Qtip maybe. (actually, this won't matter, just curious).

I see no signs of heat or distress. Half of you circuit works. Both tubes are good. You can reassembly with transformers swapped to see that they are both okay. I don't understand the transformers or why the red/black are open, but they are the same.

I recently fixed a product sent to me. It was a 30-year-old timer. It had a bad capacitor in it. Shorted. It was not a large value cap, but a little one. I'm not worried about the dipped tantalums (such as C5 and C9), nor any of the blue ones, big or small. The little yellow ones are a concern, especially C9 and C14. Perhaps measure across these for a low value on your ohm meter. I'd try not to fold them down as they can be a bit brittle and you don't want to bugger up where the leads enter the yellow part.

Other than that, I got nothing until you have a schematic. I know you really want this to work. Troubleshooting like this is tedious.

[cuypers1807]

I have a 8x10 Zone VI enlarger with a aging cold head and I am considering upgrading to a Heiland LED head. It is pricy but would last a lifetime and would be more versatile and reliable than the current fluorescent bulbs.

[Keith Pitman]

I have a 8x10 Zone VI enlarger with a aging cold head and I am considering upgrading to a Heiland LED head. It is pricy but would last a lifetime and would be more versatile and reliable than the current fluorescent bulbs.

Ditto.

[Eric Woodbury]

Same here, except mine is a Beseler 810 (sort of) and I'm almost done with my LED head. Here's a couple very early pix of beginnings.

1st pic is 3 of 9 green LEDs lit.
2nd pic is 1 blue LED lit and diffusor material
3rd pic is placement of 18 LEDs

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[dajaab]

it's sentimental, as I explained before, and it's a nice challenge, no ?
I use a Heiland Led head on my Focomat V35 and a split grade head on my De Vere 504. Both are connected to the same Heiland Split grade unit.
It works perfectly and I know Leds are almost for life !

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178934
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I bought some leds 35w for another project but I already thought to make an LED head for my huge Durst 1840.
How do you choose the colors green and blue, don't you have to respect a specific color temperature?
What power do you use?

Eric, do you think that if I sent you that head you could do something?
My only fear is to break one of the tubes during transport

[dajaab]

Led like this ?

178937

10w et 35w 36v

[Eric Woodbury]

It is a good challenge, but until we have more info, I'm stuck.

I've never seen those LED modules before.

I buy the 3-up LED stars from LED supply. They are CREE. I bought the green and ROYAL BLUE. You need the royal blue at highest contrast so you don't 'leak' any into the green sensitive area. The plain blue LEDs are too close to the green spectrum. My power supply is 200W, which I now estimate to be about 4X too bright. We'll know soon.

If you use BLUE LEDs, be careful. They are very bright and your eye doesn't stop down as much as they should because it doesn't see that blue very well. Use sunglasses.

I'm sorry I can't work directly on your power supply. I have so many projects to finish and I have a damn disease that competes for my time and emotional energy. You seem to be doing pretty well. If you swap the known good transformer into the bad position and it works, then you'll know the xfmr is good. Having to find another of those could be a deal breaker unless there is a manufacturer's name on it. Then check those caps.

Maybe post a schematic request over at Photrio if you can't find one otherwise.

Best, EW

[Chuck Pere]

From your trouble shooting it appears that the "transformer" unit is bad. Since it's bad anyway maybe you can figure out how to open up that white case to see what's inside. Might be some replaceable components in there.

[sepiareverb]

The minimal range of contrast was always my bugaboo with the Zone VI. I upgraded to an LPL machine for up to 4x5 and adapted a Kienzle head to the 810, never missed the ZVI "VC" head.

Sentimental isn't my thing anymore.

[J.B. Harlin]

I have done a lot of research on the neon VC heads, both Zone VI and Aristo. The HV supply in the Zone VI head is a solid state dimmable neon power supply. The older iron core transformers were used in the Aristo units. Though I have never seen a Zone VI 5x7 head I do have the 8x10 and have made two major modifications over the years to it.

What I found to be the short coming (as mentioned here) of the Zone VI VC head is the lack of full contrast control. This puzzled me until I went into the 8x10 unit I have and took a very close look at how it was designed. What they did was design two control circuits. One for the blue grid and one for the green grid. They use a dimmable solid state neon power supply on each grid, B & G. What they added was a photocell sensor to control and stabilize the light output of each grid. The problem is, there is no way to keep one sensor from seeing the light from the other grid. So the two circuits interact and fight each other. My 8x10 had blue and green filters added in front of each photo cell, I believe in an attempt to minimize the crosstalk. But this is still not adequate to stop all interaction. So as you increase say the green, the blue gets turned down. And the opposite happens when you turn up the blue. I was never able to totally isolate the interaction. I tried moving the sensors and even adding a light pipe directly to the associated grid. There was always interaction. I ended up removing all of the original circuitry and using two iron core transformers with associated dimmers like Aristo used. I used one photo cell sensor and a Zone VI Compensating Timer and all was well. We used this setup for over 10 years and it worked as expected.

In 2016, after a lot of research, I finally was convinced there were suitable green and blue LEDs that would work for VC printing. I tested several LEDs and then built a replacement head for the original modified Zone VI on our 8x10 enlarger. It has worked very well. If you are interested in that project, here is a link to the BLOG post.

http://www.jbhphoto.com/blog/2016/07/02/leds-vc-printing

Hope this helps. . .

[dajaab]

Thanks J.B
I'm gonna check this link
BTW, I love your work

[J.B. Harlin]

Thanks for the kind words!!!

One other thing, those two gold 1.2K ohm, probably 25W resistors are heaters. Neon is most efficient (most light output) at a temp of about 112-115 deg F. The round button with the disk cap across it is the thermostat. This is why the head needs to warm up in order to help stabilize the light output. If the grids get cold enough they will not start immediately either. Neon, or cold cathode lighting is fascinating.

[David E. Rose]

I use my Zone IV head in split exposure mode. I expose the green and the blue lights separately, using the length of the exposure for each to vary the contrast. I did this partly because the individual lamps never had equal output, even when new. You might try this as an alternative to trying to get balanced output from both tubes at the same time.

[J.B. Harlin]

I use my Zone IV head in split exposure mode. I expose the green and the blue lights separately, using the length of the exposure for each to vary the contrast. I did this partly because the individual lamps never had equal output, even when new. You might try this as an alternative to trying to get balanced output from both tubes at the same time.

Split printing will work great. You only use one grid at a time and you have a built in stabilizer for each which will assure repeatability. They should have made this a feature, since the adjustable VC mode did not work very well.

[dajaab]

It's a very good idea.
Just need to find a high voltage switch to alternate blue or green neon since I have only one High voltage transformer in working condition

[J.B. Harlin]

It's a very good idea.
Just need to find a high voltage switch to alternate blue or green neon since I have only one High voltage transformer in working condition


I would be very hesitant switching that kind of voltage. Are there any markings on the failed power supply?

[Eric Woodbury]

BTW, it's NOT neon. It's a cold-cathode florescent lamp or CCFL.

I agree with Harlin, although switching these voltages with MOSFETs is possible, working on such things is dangerous. Do we know yet that the xfmrs are bad? Have you reversed them in the setup? Is there any number or symbol on the xfmr? If the xfmr is bad, it may be replaceable. Could be the easy solution since so far there is no schematic.

(For various reasons, my money is on the electronics being bad.)

e

[dajaab]

High voltage but low amperage, no ?
I admit it's a weird option.
I didn't have time this week to try to reverse the xfmrs, I'll do that tomorrow
But no number, no symbol, nothing, nada

[Eric Woodbury]

Yes on the volts amps thing. Volts times amps is power (watts).

I'd guess these CCFLs are hundreds of volts with a bit of a kicker at turn on. Once the tube starts, it becomes low impedance and the voltage would drop. Neon is typically 10 to 20 kV. If you touched, either would both make you tingle and let you know you're alive. A most unpleasant sensation.

[dajaab]

Same trouble when I reverse xfmrs, I guess one is bad.
I'm gonna sell the two cold-cathode florescent lamps (thank Eric) and one xfmr, maybe someone needs these, and keep the body to try to build a new head with green and blue LEDs.
I have one question for those who have built LED heads, do you use a red LED instead of the red safety filter ?
With a foot switch it's very useful for dodging and burning