JOBO LPL 7415 - Bulb problem

serarsa · Jan 16, 2023

Hi everyone!

I'm having some problems using the Jobo LPL 7415.

I recently bought a new bulb for it since the old one died. It's a 24V 250w bulb (as indicated in the power suply).
Everything seems to work properly as the fan gets on once I start the enlarger trough the power supply... but the bulb won't turn on. I checked everything and there are no signs of broken cables and all is well connected.

Could someone help me out? I don't know if I should get another bulb or maybe is there something in the power supply broken?

scrufftie · Jan 17, 2023

Hi. I have experienced similar problems, which were caused by the bulb mount/socket. The connection was a bit loose and I managed to get mine working by wiggling the bulb a bit. It's not 100% satisfactory but the bulb connector is a pretty standard item and (should be) fairly simple to replace.

mpirie · Jan 17, 2023

The bulb itself could be faulty....use a multimeter and continuity test the filament.

Mike

Kino · Jan 17, 2023

Those pin-based bulb sockets are notorious for arcing and eventually burning out. I have had to replace several in enlargers and movie projectors.

Luckily, as Scrufftie states, if it is the socket, they are fairly simple to replace; most have two leads and twist-on wire nuts for the connections.

Here is the manual which shows the lamp replacement method: http://manuelsphoto.free.fr/LPL7451.pdf

Hopefully, replacing the lamp socket would be as easy as tracing the wires back to the connectors and attaching a new one.

If you can't find the exact Jobo/LPL socket, look for a OSRAM replacement; often they are the same.

Good luck.

koraks · Jan 19, 2023

In addition to the advice above, I'd suggest measuring the voltage on the lamp socket to verify it's being powered. If not, measure the output voltage on the power supply to exclude the possibility of a broken cable. If neither the cable nor the socket are the problem, the power supply itself will need to be inspected. Defects in such units are quite common.

BMbikerider · Jan 22, 2023

LPL Enlargers are good pieces of equipment. but they do have their problems with the socket and fixings in the head which have a tendency to corrode. Not so much as 'falling to bits corrosion' but enough to stop the free flow of power to the bulb. My current LPL7700 has had the transformer replaced and the holder for the bulb removed and replaced after the contacts were vapour blasted. Probably it is my darkroom because unless I am working there is no heating and a warm enlarger left to cool down in an unheated room tests the electrics beyond what is expected

MTGseattle · Jan 22, 2023

Adding to this. Let us assume a basement darkroom. What type of cover/bag would be appropriate to help prevent this stuff? Is a contractors garabage bag the easy budget solution? I've seen the semi-heavy plastic covers for the Beseler 23c, was there a saunders/LPL enlarger cover?

MattKing · Jan 22, 2023

The covers are more to keep dust off than anything else, although I guess they protect in case of water leaks as well.

JOBO LPL 7415 - Bulb problem

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