LPL/Saunders C7700MX/670 Lamp Intermittent

Kevin Caulfield · Aug 28, 2017

Hi all,

I'm in the middle of a printing session. Right at the start I checked focus etc and had a sheet of paper ready in the easel. Pressed the timer switch and no lamp. So I opened the housing and replaced the lamp. Still no lamp lighting. So I checked the power supply just in case, even though the colour head is lighting up. No surprise, the 10A fuse was intact. So I put the housing back together and the lamp started working again. Printed a few sheets, all fine. Now it's stopped working again. Any clues as to how/why the lamp is working intermittently?
Thanks.

Molli · Aug 29, 2017

Hi Kevin,
What sort of shape is the lamp holder itself in? I was suddenly getting really long exposure times and a major part of the problem turned out to be a crumbling holder. I took it around to Mick's and he kindly cleaned the contact points for me which gave me around a stop or so more light. I'd have liked to have replaced it but neither Mick or I could find our way into that part of the casing to do so.
More pertinent to your question is that I had an occasional problem with the enlarger light failing to come on, but to be honest, I blamed it on my foot switch at the time. Given that it's not happened since the holder was given a little TLC, I'm now thinking the holder might have been the culprit there, also.
Let me know if you'd like me to post one up to you to see if it helps.

Kevin Caulfield · Aug 29, 2017

Hi Molli, thanks for your reply. The lamp holder seems to be in pretty good condition. I am the original owner but it's still nice to see that everything inside the lamp housing looks clean and new. Maybe the contacts could do with a clean though.

Molli · Aug 29, 2017

Hmmm, I'm afraid that's all I've got! I'm sure someone with a better grasp of, well, everything, will happen upon your question sooner or later and will, hopefully, give you a helpful answer. Good luck, I know how frustrating it is when things get all random in the darkroom, particularly right when one is on a roll and in the mood to get some serious work done!

Kevin Caulfield · Aug 29, 2017

Molli said:
Hmmm, I'm afraid that's all I've got! I'm sure someone with a better grasp of, well, everything, will happen upon your question sooner or later and will, hopefully, give you a helpful answer. Good luck, I know how frustrating it is when things get all random in the darkroom, particularly right when one is on a roll and in the mood to get some serious work done!

I appreciate your help, Molli. It pretty much has to be something like you suggested.

Kevin Caulfield · Aug 29, 2017

I'm a bit reluctant to squirt a bit of WD40 or RP7 onto the contacts but if that's what I should do please let me know. I will be grateful for any ideas. Thanks all.

Ozxplorer · Aug 29, 2017

Kevin, it may still be the transformer which is operating intermittently. Do you have access to another to use for a while so as to completely eliminate it as a cause? What about the mains supply power cable and the enlarger connection into the power supply?

tomfrh · Aug 29, 2017

I had very similar symptoms with my AC707 color enlarger. It was the ceramic lamp plug. It had a small crack and the lamp was only contacting intermittently.

I multimeter helped isolate the issue.

I ended up cutting off the plug and plugging the lamp prongs directly into the ends of the cut wire. A bit dodgy, but it hasn't missed a beat since!

teejay · Aug 29, 2017

Hi - I had exactly the same issue with my 6700 - was a complete PITA - would stop working...then start - issue was the lamp connector - I just cut it off and soldered in a new one in - just google "MR16 wire socket adapter"

Kevin Caulfield · Aug 29, 2017

teejay said:
Hi - I had exactly the same issue with my 6700 - was a complete PITA - would stop working...then start - issue was the lamp connector - I just cut it off and soldered in a new one in - just google "MR16 wire socket adapter"

Thanks, teejay, sounds like a plan.

Mick Fagan · Aug 29, 2017

Kevin, could be as simple as changing your socket with one of these, or a similar version at Jaycar.

https://www.jaycar.com.au/halogen-lamp-base/p/SL2735

Quite cheap per unit if you purchase 25 + of them.

Mick.

Kevin Caulfield · Aug 29, 2017

Yep, Mick, as per teejay's post, I already found that, thanks. I'll be at Jaycar Coburg shortly after opening time tomorrow. Thanks everybody!

Kevin Caulfield · Aug 29, 2017

Quite cheap per unit if you purchase 25 + of them.

Actually, still pretty cheap per unit, too,

Kevin Caulfield · Aug 29, 2017

Hey, thanks everybody for your help. I bought a replacement halogen lamp base from Jaycar this morning and have done the microsurgery on my enlarger and the operation was a great success. Thanks to Molli, teejay, Tom, Fred and Mick. I really appreciate your help.

mnemosyne · Aug 30, 2017

For the record: the ceramic sockets are subject to wear and should be replaced regularly (at least with every second change of lamp) because a worn socket can create all sorts of problems and will also shorten the life of a new lamp. There are cheap sockets out there that will fit mechanically but will not otherwise meet the load requirements of the lamp, so take care to use a quality one with the proper specs. And do not shorten the original leads of the socket ... Happy enlarging!

Kevin Caulfield · Aug 30, 2017

mnemosyne said:
For the record: the ceramic sockets are subject to wear and should be replaced regularly (at least with every second change of lamp) because a worn socket can create all sorts of problems and will also shorten the life of a new lamp. There are cheap sockets out there that will fit mechanically but will not otherwise meet the load requirements of the lamp, so take care to use a quality one with the proper specs. And do not shorten the original leads of the socket ... Happy enlarging!

Thanks, mnemosyne, for the info. Much appreciated. I should have bought more than just the two (one spare). I really appreciate the input.

Molli · Aug 30, 2017

Hi Kevin,
You mentioned 'microsurgery', does this mean you followed teejay's example and simply cut away the old holder and spliced in the new, or wee you able to access the 'point of origin', so to speak ?
I ask because I was unable to find a way in to where the tails e

Molli · Aug 30, 2017

(Sorry, posting issues here!) The remainder of the sentence, "... where the tails end in a connection point."

Ozxplorer · Aug 30, 2017

Mmmm! The suggested "hotfix" that worked in this instance seems like something I should anticipate needing to do at some future date... I will get a couple of spares to have ready to for my LPL C7700 Pro enlargers. Kevin, a useful post!. And, thanks for all suggestions...

Kevin Caulfield · Aug 30, 2017

Molli said:
(Sorry, posting issues here!) The remainder of the sentence, "... where the tails end in a connection point."

Hi Molli, yes, I had good access to the holder, and cut away the old and replaced with the new. The old and new holders are completely different shapes but obviously perform the same function. By the way, this enlarger was bought new by me maybe 19 years ago or so. Thanks again for your help. It was appreciated.

Kevin Caulfield · Aug 30, 2017

Ozxplorer said:
Mmmm! The suggested "hotfix" that worked in this instance seems like something I should anticipate needing to do at some future date... I will get a couple of spares to have ready to for my LPL C7700 Pro enlargers. Kevin, a useful post!. And, thanks for all suggestions...

Yes, Fred, it looks like something we all need to do occasionally. Follow Mick's link to Jaycar and you're all good. $4.95. Not bad for an enlarger refurbishment.

Molli · Aug 30, 2017

Kevin Caulfield said:
Hi Molli, yes, I had good access to the holder, and cut away the old and replaced with the new. The old and new holders are completely different shapes but obviously perform the same function. By the way, this enlarger was bought new by me maybe 19 years ago or so. Thanks again for your help. It was appreciated.

You're very welcome Thank you for your help, too! I'm thinking I must be missing something blindingly obvious because I have the C7700 also and I just can't see the connection point of those wire tails. If we ever get around to a Melbourne Meet Up, I'll have to pick your brains a bit, methinks. I'm glad to know it's an easy swap out, though; I bought four when I was looking to fix mine (including an emergency spare for locals in need ) and they're just languishing until I figure this out. It will be nice to see if I can get back to the exposure times I was using when I got the enlarger four years ago!

Kevin Caulfield · Aug 31, 2017

Molli said:
You're very welcome Thank you for your help, too! I'm thinking I must be missing something blindingly obvious because I have the C7700 also and I just can't see the connection point of those wire tails. If we ever get around to a Melbourne Meet Up, I'll have to pick your brains a bit, methinks. I'm glad to know it's an easy swap out, though; I bought four when I was looking to fix mine (including an emergency spare for locals in need ) and they're just languishing until I figure this out. It will be nice to see if I can get back to the exposure times I was using when I got the enlarger four years ago!

Hi Molli, I didn't mean to sound like an electronics guru, because I'm not. I just cut out the old lamp base, bared the wires, bared the wires of the new one, twisted them together and wrapped them in duct tape. I can take some piccies if it helps.

Kevin Caulfield · Aug 31, 2017

But specifically to your point, I don't think there is an obvious access point for the wire tails, hence my patch job.

SMBooth · Aug 31, 2017

For the record, I think WD40 is flammable so don't spray and turn on, dry/wipe clean first.

LPL/Saunders C7700MX/670 Lamp Intermittent

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