Durst 670

Steve906 · Feb 20, 2025

BobUK said:
I have shortened the quote.

Hello Steve.
Perhaps I have been lucky so far regards melting solder.

I would have thought the temperature of the lamp would be measured in front of the reflected element. Not around the back by the connectors. The front of the lamp would be hotter I think.

I ditched the correct connector due to arcing inside the tubes that the bulb pins go into.

Up to now things have gone well.

Possibly 500c could be reached if the bulbs are used in a slide projector for a long time continuous.

It would be nice to hear other peoples thoughts on this.

ps I will borrow one of those laser thermometers tomorrow, and see what it read.

These lamps have a dichroic reflector designed to transmit light forwards and heat back so they are less likely to damage delicate things being illuminated. The heat is also transmitted along the pins which is why they are always used with crimped/welded connectors, high temp ceramic holders, mica shields and heat resistant insulation.

BobUK · Feb 21, 2025

I managed to cadge a laser thermometer.
After leaving the lamp running for a solid 10 minutes the reflector was 110c .
The round boss that the pins are set in 90c .
The home made brass lugs 66c .

So in my case the lamp does get hot, but nowhere near 500c.
The 66c is not enough to melt solder.

There is an optional lamp saver facility on my enlarger timer. If the lamp is left on in the focus mode it switches off after 5 minutes. My test was a solid 10 minutes making me feel happy to leave the connections soldered.

The temperature is something to be aware of, and other less well ventilated head may possibly give cause for concern.

Well worth checking ones own set up, just for safety

Luckypete · Feb 22, 2025

Bearing in mind the comments above, and to my mind the over-complicated (IMO) multi crimped connectors in the light box which may well have degraded over the 40 years of this enlarger.

I replaced with the following ceramic connector and lamp holder.

I tinned and soldered all the wire ends and secured with the terminal screws.

The new bulb works fine (for now) and I have eliminated any connections issues in the light box.

It could be the transformer of course: I picked up a new (old) one from ebay and tested it OK – I now have a back-up.

I may well look for someone who could "upgrade" the electronics of the output stabilisation circuit of the spare, however back to printing and see what happens.

chatanooga · Tuesday at 5:05 AM

Luckypete said:
Bearing in mind the comments above, and to my mind the over-complicated (IMO) multi crimped connectors in the light box which may well have degraded over the 40 years of this enlarger.

I replaced with the following ceramic connector and lamp holder.

I tinned and soldered all the wire ends and secured with the terminal screws.

The new bulb works fine (for now) and I have eliminated any connections issues in the light box.

It could be the transformer of course: I picked up a new (old) one from ebay and tested it OK – I now have a back-up.

I may well look for someone who could "upgrade" the electronics of the output stabilisation circuit of the spare, however back to printing and see what happens.

Hi there, I'm just wondering did this lamp-holder replacement work out for you in the long term? I have the exact same problem - bulbs blowing very quickly - but replacing the ceramic holder did not fix the issue for me.

Durst 670

Steve906

BobUK

Luckypete

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