Durst M305 transformer blown

Halford · Jul 8, 2010

Hi all,

So today I bought a Durst 305 colour enlarger from a reputable 2nd hand dealer.

I brought it home with great excitement, but when I plugged it in, the transformer (Durst EST 305) blew, making a popping sound and giving forth copious, smelly (and doubtless toxic) smoke.

However, until I killed the power, despite the smoke-billowing transformer, the enlarger lamp was still shining, so it wasn't a total failure.

Now, obviously I could take the whole thing back to the dealer and get a refund, but I'm quite taken with the idea of using this little enlarger, and I'm wondering if it might be feasible to repair the power supply or else replace it with something else. I imagine that any transformer which will give a 12V, 100W output would be okay, however I'm a bit puzzled by this power supply. It appears to give both a 12V and an 11V output on different pins of the 7-pin connector.

Does anyone have any experience with this kind of issue, and advice on whether it would be worth returning vs keeping the enlarger? I'd really appreciate constructive input.

Hal

ic-racer · Jul 8, 2010

Open it up an see what blew.

Is it a 120V unit plugged into your 220V mains?? (South Africa is 220V, right?)

French version of the manual does not say much about the power supply http://manuelsphoto.free.fr/durstm305.pdf

I have some schematics, but not for that one.

No fan, right? How about a little LED on the front?

Probably just need a generic 12V supply. A little wall-wart won't do, you need a transformer rated at 100VA at 12V to power that bulb.

ic-racer · Jul 8, 2010

Ok I did some French translation and it looks like it could be powered with either the TRA305 or the EST305. The TRA305 was just a transformer and the EST305 had a voltage regulator circuit in the box also. So, you should be able to run it off a generic power transformer, but a 100VA likely could cost some dollars.

Also, keep on the lookout for a TRA305 on e-bay etc.

Halford · Jul 8, 2010

Hi,

It's the EST 305, rated for 240V input -- the fuse is still intact and it was still generating an output voltage. Someone PMed the suggestion that it might be a blown cap in the voltage regulator circuit.

Do you think this sort of thing would do the trick? I can hopefully find something similar at a hardware store:

http://za.rs-online.com/web/search/searchBrowseAction.html?method=getProduct&R=0486126

Thanks,
Hal

ndrs · Jul 8, 2010

Yes, it will work, but if you can, try to find one rated for 150 W or more. You have to get rid of the Durst plug, though. I've been using a transformer for halogen lights (found it for €2 in a charity shop) with 100 W colour head, no problems at all.

fotch · Jul 8, 2010

Hal, your hardware stores may be different, but in the USA, they don't usually carry electronic components. Use to get capacitors at Radio Shack however, I think they are not the part suppliers they use to be.

There are other electronic parts suppliers that do carry a full assortment. Do you have any friends or acquaintances who are into Ham radio? They might be able to help. Maybe fine a Ham operator in your city or town and ask for help.

ic-racer · Jul 8, 2010

Halford said:
Hi,

It's the EST 305, rated for 240V input -- the fuse is still intact and it was still generating an output voltage. Someone PMed the suggestion that it might be a blown cap in the voltage regulator circuit.

Do you think this sort of thing would do the trick? I can hopefully find something similar at a hardware store:

http://za.rs-online.com/web/search/searchBrowseAction.html?method=getProduct&R=0486126

Thanks,
Hal

I'm not sure there. The larger Durst supplies that are regulated use a pulse-width-modulation circuit to control the voltage, rather than a big transformer. So, if the 'regulator' is blown, the whole thing is shot and shouldn't power up. But on the smaller power supplies, I don't know.

Based on the specs, that transformer you posted should work as a substitute.

It is also possible to get 12V by a large diode and a power resistor, some enlargers used that, but maybe not for 100W.

Whatever you do, don't trash the EST305. It may be repairable, or useful for parts to make on working unit out of two blown units.

You can take the cord off of the EST305 and hook that to the new transformer. You will want to keep the original connector on the M305 head, in case a Durst power supply shows up sometime.

Can you post a picture of the innards?

Halford · Jul 9, 2010

Thanks again for the input!

Here is a pic of the blown cap, and how it fits into the greater scheme of things. It's a PME217 on the HV side. These are still available, though I'm not sure if my local electronics store will stock them. I'm sure we can get something of the same specs (240V, 220nF). The electronics store I know best has this:

http://www.fort777.co.za/index.php?main_page=product_info&products_id=2619

(For reference, it's a CPS224 Class X2 suppression cap, with one model rated for 275V, 220nF)

Any reason anyone can think of that I shouldn't use this as a replacement?

Of course part of me wonders whether I shouldn't just wire the input straight to the transformer, but I suspect my enlarger lamp wouldn't last all that long if I did.

I really appreciate all the generous advice from you guys!

RH Designs · Jul 9, 2010

Halford said:
Do you think this sort of thing would do the trick? I can hopefully find something similar at a hardware store:

http://za.rs-online.com/web/search/searchBrowseAction.html?method=getProduct&R=0486126

Thanks,
Hal

That should work, yes. I've been using a similar transformer on my LPL7700 for years without problem, and you get a degree of voltage stabilisation thrown in for no extra charge!

Halford · Jul 9, 2010

Well, I decided to replace the blown cap instead of getting the lighting transformer -- a simply matter of R4 (< $1) vs R100 (> $10).

All seems well so far. I really appreciate all the help and feedback from you all!

And now I'm off to print

ic-racer · Jul 9, 2010

Halford said:
Well, I decided to replace the blown cap instead of getting the lighting transformer -- a simply matter of R4 (< $1) vs R100 (> $10).

All seems well so far. I really appreciate all the help and feedback from you all!

And now I'm off to print

Thats the way to do it, thanks for sharing. Good luck printing!

RH Designs · Jul 9, 2010

Glad you got it sorted!

fotch · Jul 9, 2010

Congratulation Halford, very resourceful.

gleaf · Feb 21, 2013

RE photo's: I see u for micro farads, 1000 x more capacitance than n nano... A bit higher voltage rating is no issue. Under capacitance will allow much higher ripple or if used as a time delay phase shifter) things will happen early. I assume nano was a typo? Best George.

Ralph Javins · Feb 21, 2013

Good morning, George;

Hal is OK. 0.22 ufd (micro-Farad) is the same thing as 220 nfd (nano-Farad). If it were the older 220 uufd or micro-micro-Farad (what is now called a pico-Farad), then we would have a real problem with the decimal point and it would be off by three (3) orders of magnitude. Hal is OK in this case.

Ribsy · May 14, 2020

Halford said:
Well, I decided to replace the blown cap instead of getting the lighting transformer -- a simply matter of R4 (< $1) vs R100 (> $10).

All seems well so far. I really appreciate all the help and feedback from you all!

And now I'm off to print

Hi - i have the exact same problem exactly. How did your repair solution work? Can you let me know what item you bought and how you repaired your item?

Thanks

Durst M305 transformer blown

Halford

ic-racer

ic-racer

Halford

ndrs

fotch

ic-racer

Halford

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