Labophot lamp mystery - solved

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blekenbleu
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Joined: Sat May 10, 2008 5:37 pm
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Labophot lamp mystery - solved

Post by blekenbleu »

I picked up a Labophot for parts; it had been dropped hard enough to break the head and crack its base;
however, the illumination base was intact except for a broken potentiometer (US$3 from Jameco),
https://www.jameco.com/z/RV24A02F-10-15 ... 91287.html
...but the lamp would not illuminate, despite having continuity between its G4 pins and power to its contacts.
Here is a Labophot lamp holder:
Image
Pins of a 20W 6V G4 halogen bulb slip into cast grooves behind those springy screwed shiny flat metal bits.

The problem turned out to be lost continuity from a G4 pin having eroded a groove into one of those shiny flat bits,
and that eroded corroded groove eventually became non-conductive. After scraping away that corrosion,
liberal application of rosin flux, solder and heat, that groove was filled with solder, restoring continuity and operation,
at least for awhile. This base will now be minimally modified to power an LED equivalent to 20W for diascopic
or 50W for episcopic illumination from under an Optiphot-66, hoping to keep costs < US$30.
Metaphot, Optiphot 1, 66; AO 10, 120, and EPIStar 2571
https://blekenbleu.github.io/microscope

blekenbleu
Posts: 146
Joined: Sat May 10, 2008 5:37 pm
Location: U.S.
Contact:

Re: Labophot lamp mystery - solved

Post by blekenbleu »

Finally getting back to LED upgrade, the polymer lamp mount is broken on one side:
Image
Being broken only one one side provides before/after evidence.

Pressure of spring-loaded lamp house contacts against screw flat heads seeming overwhelms aging brittle polymer.
Image

Bulb removed:
Image

Christmas gift Garrett Wade pen screwdriver bit nicely fits heat sink screws
Image

Hoping that J-B Weld filled epoxy will suffice to repair,
and wax paper works as a parting agent:
Image

... wrapped around contacts, with all extraneous parts removed
and cellophane tape over wax paper leading edge to ease insertion:
Image

C clamp to hold contacts in place while J-B Weld cures:
Image
J-B Weld had been opened unused for awhile; wasting some resin from which filler settled.

Mixed and ready(?) to apply:
Image

J-B Weld is difficult (at least, for me) to apply without drips:
Image
One should be prepared to sacrifice cotton swabs for cleanup.

Wants at least another dose applied, after this cures:
Image
Last edited by blekenbleu on Tue Dec 27, 2022 6:35 am, edited 1 time in total.
Metaphot, Optiphot 1, 66; AO 10, 120, and EPIStar 2571
https://blekenbleu.github.io/microscope

PeteM
Posts: 175
Joined: Sat Jan 05, 2019 12:06 am
Location: West Coast, USA

Re: Labophot lamp mystery - solved

Post by PeteM »

FWIW, I've seen the same failure in a couple other Labophots. Likely set down tilted back and the thin themoset plastic section cracked. The failures are different, but the lamp housings for the Labophot 2, and Optiphot 2 are also commonly damaged by users setting them down back end first.

A tiny aluminum angle as reinforcement, plus the JB Weld, has held up OK for the Labophot 1.

blekenbleu
Posts: 146
Joined: Sat May 10, 2008 5:37 pm
Location: U.S.
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Re: Labophot lamp mystery - solved

Post by blekenbleu »

PeteM wrote:
Mon Dec 26, 2022 3:57 pm
A tiny aluminum angle as reinforcement, plus the JB Weld, has held up OK for the Labophot 1.
That would have been better; J-B Weld by itself is not viscous enough to build up conveniently in just a few layers.
Metaphot, Optiphot 1, 66; AO 10, 120, and EPIStar 2571
https://blekenbleu.github.io/microscope

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