Durst EST 305 information

Bumba · Feb 17, 2020

Hi, I was looking for some information on the Durst EST 305 stabilizer.

My questions are:
How stable is the output voltage? Is there any variation at all at output?
How prone are the capacitors to blowing? I've seen a few reports online about the capacitor going kaput. It seems fairly easy and cheap to replace.

Thanks for any help

One more thing. Does anyone know what this connection is? It looks like what the enlarger plugs into but there's the same on the other side. On my TRA it has a UK plug in its place.

mpirie · Feb 18, 2020

I can't comment on the stability of the output, but capacitors do have a lifespan and they then become a weak link in the power supply.

If you're worried about it and capable, then you can replace the capacitors (probably electrolytic) with new versions.

The connector is a shrouded IEC plug, similar to the cables used in kettles and heavy duty electrical equipment because it carries an earth as well as live and neutral.

Mike

AgX · Feb 18, 2020

mpirie said:
The connector is a shrouded IEC plug, similar to the cables used in kettles and heavy duty electrical equipment because it carries an earth as well as live and neutral.

At first sight yes, but

-) that cable is for the connection to the mains. And there is no mains wall-outlet with such connector. These connectors are only used at devices themselves.

(An exception to this rule may be propriatary cable dividers, as these connectors are smaller than the round continental european 3-plug mains connectors.)

-) that transformner is double insulated and does not need earthing, it thus has in other configurations only a 2-plug "Euro" mains plug.
The connector in question may be an outdated 2-plug version, but still then it could not be connected to wall-outlets.

I am puzzled...

mpirie · Feb 18, 2020

An IEC cable with a 3-pin 13A plug on one end and an IEC male plug on the other will fit to the cable shown above. A very common cable and method of extending reach.

The transformer may be insulated and in a plastic case, but it will have a through-earth because it is connecting to a metal enlarger chassis. So the chassis earth will need to pass through inside the PSU case to common earth. That's why it has a 3-pin connector and not a 2-pin connector.

2-pin Euro plugs are used where the case of mains powered equipment is plastic, so cannot become live in the event of an internal wiring fault.

If the OP can post a picture of the connector from the opposite side, then we'll see it's 3-pin IEC. You can see the wiring diagram of the plug on the top label.

Mike

AgX · Feb 18, 2020

mpirie said:
An IEC cable with a 3-pin 13A plug on one end and an IEC male plug on the other will fit to the cable shown above. A very common cable and method of extending reach.

The transformer may be insulated and in a plastic case, but it will have a through-earth because it is connecting to a metal enlarger chassis. So the chassis earth will need to pass through inside the PSU case to common earth. That's why it has a 3-pin connector and not a 2-pin connector.

-) Yes, as I indicated in my post one may use such connectors also to extend cables.
But why would Durst use such connector on a device wich is intented to be connected to a wall-outlet (or same connector at a timer) ? But the screw holes are sealed, what one would not find at a tinkerer mounting that connector.

-) A metal casing etc. of device powered by a dividing transformer (as in this case) does not need an earthing. One may consider such though for earthing static electricity.

mpirie · Feb 18, 2020

We're assuming Durst fitted the connector......it is possible that someone else fitted the IEC connector......i've done it myself on occasion.

Mike

Bumba · Feb 18, 2020

Hi thanks for the information everyone. It looks like an IEC connection but I've asked the eBay seller for more photos of it to be sure. I've seen other Durst transformers with them on so it's a possibility that they were made by Durst like this but I'm not sure why if that was the case.

Bumba · Jul 8, 2020

Hi, I'm back but I didn't want to make a new thread.

I managed to pick up one of these Durst EST 305 transformers but when I plugged it in, it blew my bulb. It was definitely the bulb because I had a spare so I replaced the bulb and plugged in my Durst TRA 305 (the unstabilised version of this transformer) and all was good again.

Any idea what the problem is with the EST? Its definitely compatible with my enlarger which is the Durst M370

Thanks

AgX · Jul 8, 2020

The problem was with the lamp itself.
Incandescent lamps typically "blow" at switching on, as then higher currents run than in continuous operation. Likely your lamp was near the end of its life. Transport likely added fractures to the tungsten wire, so that it burned trough at very first switching on.

Bumba · Jul 9, 2020

I don't think it was the lamp because it was a fairly new lamp which had been working well with my TRA transformer. The second I try my new EST transformer then it blew. The EST isn't in best condition so I'm thinking it's not effectively stepping down the voltage.

Durst EST 305 information

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