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Old 8th August 2015, 04:22 PM
davidgc davidgc is offline
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Default Durst Mod 70 - dim light

I have started to use the Mod 70 and set it up yesterday for the first time.
After some reasonable printing I became more and more frustrated when I could not get a print to expose correctly. I thought it was either me not trusting the initial test strip or I was using some very old paper won with some equipment on an auction (that had provided good prints in the past).
This morning all was well when I was getting the prints I was hoping for, well exposed with contrast, then as the day has gone on the prints have become underexposed and low contrast even at Grade 5.
I have changed the bulb and the same thing is happening. Also, during the day I noticed that the light increased its power all by itself, while in focus mode. I know it cannot be the paper as I am using just opened Ilford 5x7 MGVC.
It also appears to be intermittent as I undertook a further test strip, after sometime away, to find a test strip print as you would expect.
I do not have a voltage stabiliser and I am using it with the RH Designs f stop clock.
It has been getting warm in my darkroom (the bathroom) with no ventilation or means of cooling. I have now pulled the blackout down to ventilate and cool the room.
I may have sent this thread too early as my actions may prove the answer. However, I would like to know if anybody else has had a similar experience and found an answer ?
My feeling is that the enlarger has a built in power-down mode when it gets too hot or has been used for a prolonged period.

Thanks, David
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Old 8th August 2015, 04:39 PM
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which head do you have?
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Old 8th August 2015, 04:44 PM
Mike O'Pray Mike O'Pray is offline
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You may be right but unless the lamp is on for most of the time, the actual light time is only a matter of seconds each time and cumulatively only a small part of your session in the darkroom. I'd have thought that the enlarger and lamp would be able to sustain its power.

There are a number of options:

1. The lamp is on its last legs and about to expire. This can show up as a fluctuating brightness during the exposure. Does the Durst 70 use the twin pronged halogen lamps as does the M605? I have certainly seen this effect with these lamps

2. If it is a halogen lamp is the connector to the twin prongs a ceramic two holed plug? If so then arcing within the ceramic plug from a blackness that forms within the plug may the problem. Try using a large darning needle in the plug holes to clean the holes or better still use a small round file to clean the holes out and clean the lamp's prongs as well

3. Your mention of lack of contrast and the need for an increasing grade over the session makes me wonder if the developer is exhausting. It happened to me once. Try dumping your developer and making up fresh and using immediately.

In fact unless you have a Nova processor I'd be inclined to use and dump developer after that day's use when used in trays.

Some developers are said to last several days in trays but most if not all of the common ones such as Ilford MG developer deteriorate after a full days use. If might even be that if you have done a lot of prints, it is volume exhausted more than time exhausted. Make sure you haven't exceeded the maker's recommended use.

Let us know how it goes

Mike
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Old 8th August 2015, 04:51 PM
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as he's told us he can see the light changing brightness I think its safe to assume that its something to do with the electronics or bulb and since he's changed the bulb that leaves the electronics.

If it a B+W head then it must be your timer or electricity supply. And note the B+W head doesn't require a transformer. It uses a normal 240Volt 75W bulb.

If its a colour or vario head then its most likely the built in transformer or the lamp unit but it could be your timer or electricity supply. Can't tell you which.

But first check all connectors and wiring connections.

Do your normal house lights have a tendancy to flicker or adjust brightness of their own accord?
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Last edited by Argentum; 8th August 2015 at 05:03 PM.
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Old 8th August 2015, 05:06 PM
davidgc davidgc is offline
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Thanks for the quick responses. I am just about to return and test the enlarger from 'cold'.
It is the B+W head with one halogen bulb. Both bulb connections were furry and I only cleaned the bulb connectors. But even after this it did give one good test strip. I re-bottled the chemicals last night, but if all fails after my next session, I will mix new developer and, try the enlarger with a direct mains connection and clean out the connections.
Looks like I will miss the start of Indiana Jones ...
I do hope it is not the electronics.
Thanks again.
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Old 8th August 2015, 06:15 PM
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looking at the manual found here:

http://www.film-and-darkroom-user.or...ead.php?t=7629

the B+W head on page 7 which is section 2.0 can be seen in the diagram as "Moodular 70 BW".

Is that the head you have or do you have the one on the right listed as "Modular 70 Vario".

There is a very big difference between the two and I can't be specific without knowing exactly which you have.

The BW head does NOT use a halogen bulb and if yours does then its not a BW head or if it is then someone has altered it.

Note: The vario head is only for black and white but its not called a B+W head. The vario head uses a halogen bulb.
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Old 8th August 2015, 07:04 PM
davidgc davidgc is offline
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Well, I have changed the developer, cleaned the connections and used a cable direct to the mains and, the prints are still lacking in exposure and contrast.
I have attached a picture taken with my phone showing the different stages of today. The top 4 all show this mornings work with varied levels of exposure and contrast. The bottom left shows the typical print I am experiencing and the bottom right a short reprieve later in the afternoon. There are more (I must have done at least 20) though at a larger f stop there is less of a problem but when closed down 3 stops I get the washed out look and even on a test strip starting at 50 secs there is little difference in contrast.
The prints are 5x7.
I think it is the electronics ...

Just seen your new thread Argentum (thanks for your time).
I have the Modular 70 Vario with Halogen Photo Optic Lamp HLX 64627 EFP 12 v 100w and the inside looks like the picture on the top of p14. But it does not have the tracking handle as shown on the Vario at the bottom of p16, it has the handle.


David
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Old 8th August 2015, 07:06 PM
paulc paulc is offline
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Quote:
Originally Posted by davidgc View Post
It is the B+W head with one halogen bulb. Both bulb connections were furry and I only cleaned the bulb connectors.
It may well be worth replacing the lamp holder - If you have a local specialist lighting store (not a B&Q type outlet), they might have a suitable holder available from stock.
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Old 8th August 2015, 07:32 PM
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So that is the "Modular 70 Lumo" unit with built in transformer.

If light output is changing of its own accord then most likely its the transformer playing up but it could be the timer or power supply voltage fluctuations. If it were the latter then you'd probably notice your house lights changing brightness by themselves. And unfortunately that leaves the timer or transformer. I'd guess the tranformer but can't be sure.

I think Keith Tapscott just had a problem with a Lumo unit. I don't know if he's got it fixed or not or what the final outcome was but if he's looking in you might get a suggestion or two.

But still worth checking all connectors to plugs and cables to be sure its not something as simple as that. Move canles and plugs while lamp is on to see if it makes a difference to light output.
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Old 8th August 2015, 07:56 PM
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there should be a white light lever on the right of the vario unit which lifts the Y+M filters in or out of the light path. Is that working properly?

On the left of the lumo unit there should be a dial with a plus and minus sign marked on side of lumo. That dials in or out 60 white light density units (+ or - 2 stops) 30 units being equal to 0.3 logD but its not marked as that. Just + or - which gives 2 stops more or less of brightness which is useful for adjusting print times for your prefered fstop.
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