MicrobeHunter.com Microscopy Forum

I have a new-to-me biological Labophot with the standard halogen lamp which appears to not be as bright as it could/should. It does light up pretty brightly on max setting of on/off/adjustment wheel, but is out completely when turning down past the '4' value on the wheel. I checked the bulb, it is an Osram 6V 20watt. I have a manual from here which talks about adjusting the trim pot on the lamp circuit. How involved is it to get access to the trim pot? Anybody done this? Thanks.

Its electrical location is shown on Fig.52 and it will either be an open unit or a little block with a screwdriver slot … almost certainly mounted on a printed circuit board.

Sorry, I’ve never seen inside a Labophot, but it looks like the board should be inside the base.

MichaelG.
.
Edit: __ I would suggest you start here: https://lavinia.as.arizona.edu/~mtuell/ ... 20base.php
… from which it appears that there is no PCB !
… and unfortunately the photos are not very clear
… if you get that far, and take some decent photos, I’m sure we can spot a trim-pot if there is one lurking in the rats nest of wiring.

MichaelG. wrote: ↑

Sun Jan 22, 2023 7:08 pm

… if you get that far, and take some decent photos, I’m sure we can spot a trim-pot if there is one lurking in the rats nest of wiring.

Not the one on the SE corner of the base in the first (leftmost) image of the top row ? that brightness knob ?

Looking at picture 1, top left, of the Arizona.edu site of the disassembled Labophot, I see the illumination intensity dial set at '5' and the lamp glowing a dull amber which is about what mine does. Maybe that is normal?

And as

MichaelG. wrote: ↑

Sun Jan 22, 2023 7:08 pm

it appears that there is no PCB !

mentioned - that conflicts with the manual I referenced, which specifically refers to a PCB, which the Optiphot has, but the Labophot does not. So - I don't have a good repair manual for this part of the Labophot. Looking at the schematic in Fig. 52 of the manual I do have, there does not appear to be a trim pot, so maybe adjustment is not possible. Anybody confirm this?

Labophot 2 has a PCB for the 6v 30w
I've seen PSU parts sold for Labophot 1, I was under the impression they only use a thyristor.
I don't have one to check.
I only have the 2.

Possibly, the pot needs to be cleaned. I don't think there is a trim pot.

The LED kit is a very tidy retrofit and works very well.

lorez

deleted, unrelevant post

lorez2 wrote: ↑

Sun Jan 22, 2023 11:34 pm

Possibly, the pot needs to be cleaned.

I have some contact cleaner and am familiar with cleaning pots - I'll clean the pot, and if that doesn't change anything try the LED route. It would be easy to mount a little LED chip in place of the halogen bulb, and put the controls outside the microscope base in a separate box. Thanks.

I decided to put an LED in place of the bulb. For now, I'm keeping all the original parts on the scope except the bulb and the fuse, the fuse removed for precaution as will be apparent. I mounted the LED on a 1" square piece of 1/4" thick rubber (auto body bondo squeegee) and stuck two pieces of wire in the bottom in place of the original bulb contacts. The wire just to provide a mount, and the rubber for insulation in case somehow those contacts get energized. (With the fuse removed, not very likely) I put the new lamp into the lamp housing in place of the original bulb and just ran the wires out the side. I put the control power supply, on/off switch and dimmer pot in a separate box - this is an upscale version of a plywood one I made previously, this one is a solid block of walnut. Inside and outside views It works great, and I can revert to the original equipment easily if I change my mind about LED's.

First Class Job!

lorez