Durst L1840 Enlarger 8x10 10x10--Everything you wanted to know...

[swmcl]

So the overall aim of the CLS1840 power supply is to produce a somewhat regulated RMS voltage (and hence power to a stable resistive load) ?

Are there some big LC filters in there ? In other words, how dc is the supply to the lamps?

I know there are later Durst enlargers with dc supplies but they are smaller units. Are you saying the CLS300, 1840 and 2000 are regulated dc psu's ? At what power?

A little question to enlarge my understanding ... what is the range of variation on the lamps and why the variation? Was it to just trim the lamp output a little (say + or - half a stop) or was it to make more drastic variations? I would've thought the colour of the light would change if the variation was too extreme. Perhaps the circuit you describe isn't adjustable but just varies to account for line voltage changes ?

I'm also a bit concerned with chopped waveforms myself...

Thanks so far!

Cheers,

Steve

Cheers,

Steve

[Degroto]

Is this followup from this 2011 thread? ( http://www.largeformatphotography.in...arger&p=751071 )
If so I congratulate you on your persistence. Have you had a chance to see if the CLS301 turns on?

Indeed it is. I'll post an updat in there as well

[ic-racer]

So the overall aim of the CLS1840 power supply is to produce a somewhat regulated RMS voltage (and hence power to a stable resistive load) ?

Are there some big LC filters in there ? In other words, how dc is the supply to the lamps?

I know there are later Durst enlargers with dc supplies but they are smaller units. Are you saying the CLS300, 1840 and 2000 are regulated dc psu's ? At what power?

A little question to enlarge my understanding ... what is the range of variation on the lamps and why the variation? Was it to just trim the lamp output a little (say + or - half a stop) or was it to make more drastic variations? I would've thought the colour of the light would change if the variation was too extreme. Perhaps the circuit you describe isn't adjustable but just varies to account for line voltage changes ?

I'm also a bit concerned with chopped waveforms myself...

Thanks so far!

Cheers,

Steve

Cheers,

Steve

Technically the lamp is powered by AC, not DC. The AC pulse is not the sine-wave from the mains, but a chopped up pulse from the Thyrisors. Kind of related to "Switching" power supplies and Pulse-wave modulated LED dimmer circuits. So, no, it is not a heavily filtered DC powering the lamps. The Thyristor are connected straight to the mains and chop parts of the main AC wave. If the Thyristors were stuck full on then the full 220V would hit the 120V lamp and fry it.

In terms of the principle behind the regulation, yes it is all about lamp color and lamp voltage. The exact voltage you set is a trade-off between lamp life and intensity. Since the lamps cost so much, some advocate setting the voltage a little lower. Once the trimmer is set for a certain voltage to the lamp, it maintains the exact voltage to the lamp + or - one percent of the total voltage. This ensures the lamp color is exactly the same each time the enlarger is used.

From the manual:

The EST1000 voltage stabiliser [sic] keeps the output constant over an input range from 180 to 260 volts...it compensates voltage fluctuations from +10% to -15% within 0.3 second.

In the picture the lamp is indicated by the circle with the "X" in it. TH2 and TH3 are the thyristors.

[swmcl]

Thank you for the block diagram.

My circuit is pretty different in function but I think I'll persist. The voltage stabilisation is a bit irrelevant here. The voltage is pretty constant over hours generally.

Thanks again.

We're not talking zero crossing detection in these old circuits are we ... ? and we're not talking of a series resistor set for 'just glow' to greatly reduce inrush current ... ?

Hmmm.

[ic-racer]

My circuit is pretty different in function but I think I'll persist.

What is your circuit from? Durst?

We're not talking zero crossing detection in these old circuits are we ... ?

Yes , zero detection to synch to pulses of the Thyristors to the mains sine wave.

and we're not talking of a series resistor set for 'just glow' to greatly reduce inrush current ... ?

In the CLS1840 and CLS2000 the lamp has current flowing through it , not from resistors but from the Thyristor circuit, pulsing ever so slightly at rest to keep the filament warm, but it does not glow. These heads also have an electronic shutter in addition to that. So the lamp lights up a second before the shutter opens and then the shutter closes before the lamp is extinguished.

[swmcl]

No my circuit is of my own design. I have no reference. I need to build from scratch unless someone can give me a heads-up.

Cheers,

Steve

[old time photo]

Just make sure you protect the enlarger with the recommended breaker size.
You will be using a lower size for the enlarger. In other words you would want
a sub panel

[swmcl]

Have no fear! It'll be more than adequately specified for safety and performance.

Cheers,

[ic-racer]

No my circuit is of my own design. I have no reference. I need to build from scratch unless someone can give me a heads-up.

Cheers,

Steve

I'd use a lamp that can be powered off the wall current.

[Degroto]

So I have finally my build up my Durst L184 again but this time it will stay that way. I have updated my topic as well:
http://www.largeformatphotography.in...arger&p=751071

And you can read a bit more about it on my new blog:
http://allthingsanalogue.weebly.com/blog/darkroom

I have a little trouble connecting my powersupply and the timer. I tried it but the light does not react to the timer. It stays on. Any thoughts? I will post a photo later with the different setups I have tried. Thanks in advance.