FM/CL1909 in MN base

ebuchner

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May 28, 2017
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This is probably a decade late to the game, but I'm pleased with the result. I wasn't entirely satisfied with a bi-pin MN base since it was prone to oxidation/resistance problems. I finally got around to doing this and now have improved electrical contact and substantially more mechanical stability.
IRM1KRD


https://imgur.com/IRM1KRD
 

konifans

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Jan 1, 2015
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What do you mean by oxidation problem?
What kind of glue did you use for this lamp assembly? Be careful most of the glues in the market cannot resist the heat...
 

ebuchner

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May 28, 2017
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The spring contacts in the bi-pin holder and the leads of the lamp tended to develop an oxide scale at the high operating temperatures, which tended to render the unit inoperable after fairly short runtimes. The adhesive used in this case is an inexpensive silica-filled sodium silicate based adhesive (read as muffler paste). The use of this adhesive was based on the fact that ultra-high temperature refractory cements are typically a zirconia filled sodium silicate based adhesive. Since I'm not looking at temperatures exceeding 500 to 600 °C or so, I opted for the less expensive silica filled option.

In the case of the above unit, the internal electrical connections are made with crimps, which have so far performed extremely well, but may still be susceptible to oxidation and scaling at extended runtimes. In the future, whenever I extend the leads on the lamps I will probably employ a spot-weld for even greater reliability,
 

mamelo

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Sep 25, 2011
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Trying to understand. Did you put the adhesive on the bulb contacts or did you use it to fill gaps to seal the contacts from air / oxygen? Thanks.
 

ebuchner

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May 28, 2017
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It is applied such that it holds the lamp in place and *should* seal the crimp connections from contact with the air. I'm couldn't apply it too thickly in the neck of the mounting around the wires, since thick sections of refractory cement won't cure without exposure to air. I'm assuming there are some cracks/leaks, which is why I still think I should opt for spot welds for extending the leads of the bulb next time. The lead-to-spring connections are fairly robust solder joints, so I'm not concerned about those connections.
 
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