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  #11  
Old 12th May 2021, 12:34 PM
Nat Polton Nat Polton is offline
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https://www.ebay.co.uk/itm/260815358...sAAOxyBjBTU~Mo

The Link for the above post.

Cheers.
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  #12  
Old 12th May 2021, 12:50 PM
John King John King is offline
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Quote:
Originally Posted by mpirie View Post
To clean the lamp holder contacts, i'd recommend Servisol electrical contact cleaner rather than WD40.

Your fuse is likely to be 20mm glass. The rating should be impressed on the fuse caps, 240VAC and 1A or 2A.

If ordering from RS (Maplins used to be a good local source) then i'd suggest getting anti-surge fuses, they are built to take the "shock" of high demand for a short time before blowing, so are better suited for transformers etc.

Mike

PS If all fails, drop me a PM and i'm sure i can find a spare for you.

RS Have them at a ridiculously cheap price a pack of 10 cost £1.96. The postage costs more so I will collect from the Gateshead warehouse. The actual size needed is 32mm x 6.3mm (measured with vernier calipers) a lot bigger than the ones you suggested. The amp rating is stamped on the transformer box.

Now that is sorted, I will clean up the two spare ceramic holders. WD 40 was used on the 1st one with specific purpose, it provides good lubrication when doing the cleaning and any residue from the WD40 should help to delay any further corrosion.

Last edited by John King; 12th May 2021 at 01:03 PM.
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  #13  
Old 12th May 2021, 01:49 PM
Svend Svend is offline
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Quote:
Originally Posted by mpirie View Post
To clean the lamp holder contacts, i'd recommend Servisol electrical contact cleaner rather than WD40.
+1 to contact cleaner. This stuff is a staple in my shop. I keep two kinds on hand -- one simple contact cleaner that leaves no residue, and a second type that leaves a light coating of corrosion inhibitor behind. I'll use one or the other depending on need. I'm not familiar with Servisol brand, but in general these are great products. For heavy corrosion I may use a piece of fine emery paper to clean things up.
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  #14  
Old 12th May 2021, 04:10 PM
John King John King is offline
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Quote:
Originally Posted by Svend View Post
+1 to contact cleaner. This stuff is a staple in my shop. I keep two kinds on hand -- one simple contact cleaner that leaves no residue, and a second type that leaves a light coating of corrosion inhibitor behind. I'll use one or the other depending on need. I'm not familiar with Servisol brand, but in general these are great products. For heavy corrosion I may use a piece of fine emery paper to clean things up.
Good idea, but tell me how do you get a piece of emery paper, or wet and dry production paper into a hole approx .75mm diameter? A camel and eye of a needle come to mind! The way I did it worked and will work again. WD40 was fine.
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  #15  
Old 12th May 2021, 05:05 PM
Svend Svend is offline
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Brute force, John Anything is possible if the hammer is big enough.
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  #16  
Old 13th May 2021, 03:41 PM
Nat Polton Nat Polton is offline
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I have used dental flossing brushes a few times on small parts.
They are like very tiny nylon bottle brushes.
Available in Chemists and large supermarkets. Look around the toothbrush and tooth paste section. Quite cheap as well.
They are available in different sizes. These are 0.4 mm.
Used with contact cleaner they may be of use.
If you still have your own teeth you will find them very handy after a bacon sandwich.

Cheers.

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  #17  
Old 13th May 2021, 06:49 PM
John King John King is offline
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Default Not really any use

Nat, I appreciate your info (I already use them to clear bacon from my teeth)

However the holes in the ceramic holder do not pass right through the holder and are only deep enough to take the pins in the base of the bulb. A relatively soft dental hygiene brush. would not have cleared corrosion.

I have sorted it now anyway and the light is steady and quite a bit brighter as well, now the corrosion has been cleared.

Thanks.
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  #18  
Old 19th May 2021, 11:24 AM
John King John King is offline
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Default At Last

The problem I thought I had sorted out proved not to be so. I have messed around with bulbs, ceramic holders, timer and still the problem came back after a short while, time and time again

Then a eureka moment last night. As I was about to give up and putting things away, I moved the transformer and accidentally touched the 2 min plug at the back where cable to the enlarger head is connected to and - BOY was it hot?

It was almost too hot to hold. I left it until this morning and checked it with a volt meter and the voltage was down to around 9-to-10 and and the readout was fluctuating as I move the probes. Obviously there was a high resistance which was causing the problem.

I swapped this over with a different LPL transformer, but with the same output and fitted it to the 7700 and the problem has gone.

I will remove the back of the device and check to see if the plug has any spare cable and fit a replacement micro plug to get it back up and running safely again. Hopefully it shouldn't be too difficult.
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  #19  
Old 19th May 2021, 01:18 PM
John King John King is offline
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Default Ceramic Bulb Holders

As the genuine LPL ones do not seem to be available anymore, I have found that the ones sold by RK photo as spares, intended to fit the Meopta range of colour enlargers are 99% identical and will take the 100w 12v bulb
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  #20  
Old 19th May 2021, 01:58 PM
Mike O'Pray Mike O'Pray is online now
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Some great info here from all parties. Glad it is all fixed John. I had read that a very small jeweller's round file will fit the hole and should have the necessary friction

Mike
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