Help unsoldering xenon tube for Snap On timing light.

[Clark Coe]

Today I asked friends that are electronic techs to do the soldering to replace the xenon flash tube on a Snap On MT1261 timing light.
Problem is they cannot get the solder to melt and release the old tube. Tried 850 degrees F setting on the solder gun and cannot get the solder to go liquid.
Anyone done this before? What is this stuff?...silver solder? Sonic welded?



Back story on this situation is that I have borrowed this timing light from a friend. I was mapping the timing curve on my distributor and kept the timing light firing for a long time as I wrote down the rpm and degrees of advance. I think excessive heat built up and burned out the flash bulb. There was enough heat to unsolder the reflective shield behind the bulb.

[Cyclone Joe]

If it is anywhere a recent build, its probably silver solder or tin without lead.  Crank up the heat, since the modern solder has a higher melt temperature than the lead-based formulations.  I just hope its not a multi-layered board for your sake, otherwise you're fighting a loosing battle.

Joe

[WConley]

I would just cut the existing tube leads off with a Dremel disc.  Then you should be able to lay the new tube in alongside the cut-off tube leads and solder them together.

Stuff these days is not meant to be fixed.  I just got a low-battery warning on a smoke detector in my house.  Instead of being able to change the battery, you have to slide a plastic tab over to "deactivate" the unit.  That's the only way to shut it up.  Yup - that breaks a component inside and you have to go buy a new unit. 

[preaction]

How old was the detector ? Like everything they have a service life.

[WConley]

The smoke detector was about seven years old. 

Funny - other ones that came with the house have batteries you can change.  I know they work fine because my wife doesn't turn up the vent fan over our kitchen stove very high.  The resulting smoke tests the detectors a few times a month...

[Clark Coe]

So far I am not convinced that standard 60/40 electrical solder would be appropriate. The white ceramic stands suggest a higher temperature level environment. A glob of molten solder on the tip of a 850 degree Fahrenheit soldering gun does not melt into that fused joint between the xenon tube lead and the ceramic standoff.

I am considering unsoldering the vertical leads from the PCB and trying an oxy acetylene torch to disassemble the old flash tube from the vertical leads.

[shady]

the reason you can't unsolder it is because the lamp is not soldered in the first place. it was probably brazed on. the lamp gets too hot for solder. A replacement lamp should come already mounted to the ceramic stand offs & all you would have to do is solder the whole assembly to the pc board under it.

[Clark Coe]

The vertical white isolators are not ceramic, but are very heat resistant. They melted a little when we tried to unsolder the flash tube. The joint at each electrode end of the xenon tube must be sonic welded or brazed. I am planning to cut the tube free with a Dremel tool like WConley suggested and then try silver solder.



This has not been my month for electronics. The 6 CD changer in my Ford Five Hundred ate two CDs ( Jeff Beck and Stevie Ray Vaughn ) and then said goodbye.
The cheap boombox in my garage has decided to stop playing CD also!