These common yellow stir-plates by Thermo Scientific/Cimarec have plastic potentiometer shafts, knobs easily broken off.

But Thermo no longer sells the replacement pot assembly! The pots themselves aren't sold anywhere either. It's an OEM part from CTS Electrocomponents, with a big plastic spacer and extra-long shaft. And power switch.

BUT, we can dissect the broken pot and reconstruct it. Keep the shell, but use internal parts from other pots.

Buy these 100K pots:

450D104-8-ND (digikey)

450T328F104A1C1 (digikey)

The long plastic shaft from the 450D104 can be cut down and used to replace the (too short) metal one. And, the rotor-assembly from the metal one will work inside the original Thermo pot.

Here at Chem Dept. the undergrads occasionally shear off the pot-knobs. Should we just throw away a perfectly good $500 stirplate?!! We can fix this.

Other repair parts are still available, see
https://www.labequipmentparts.com/la...272&f=5&m=1987

William Beaty wrote:

But Thermo no longer sells the replacement pot assembly! The pots
themselves aren't sold anywhere either. It's an OEM part from CTS
Electrocomponents, with a big plastic spacer and extra-long shaft. And
power switch.


That doesn't surprise me, CTS used to sell a universal line of pots which
were like a do-it-yourself construction.

You ordered the pot body (ohms, linear/taper, spade or eyelet) then selected
the shaft (metal/plastic, stub or up to 6/7 inches).

Some of the options were two bodies could click together making a dual one,
then they had a shaft (split or half-moon) that fit both straight through
and or a hollow one for the front and a solid thin one to the rear.

Some could even mount a power switch on the back, turn to click on or
push-pull.

It was a clever design but really made for repairs rather than production
but I could see in small enough quantities it might of been cheaper than
ordering custom built ones.

It was all snap and click, no screwing around with e or c-clips.

-bruce

On 11/29/18 6:52 AM, wrote:
William Beaty wrote:

But Thermo no longer sells the replacement pot assembly! The pots
themselves aren't sold anywhere either. It's an OEM part from CTS
Electrocomponents, with a big plastic spacer and extra-long shaft. And
power switch.


That doesn't surprise me, CTS used to sell a universal line of pots which
were like a do-it-yourself construction.

You ordered the pot body (ohms, linear/taper, spade or eyelet) then selected
the shaft (metal/plastic, stub or up to 6/7 inches).

Some of the options were two bodies could click together making a dual one,
then they had a shaft (split or half-moon) that fit both straight through
and or a hollow one for the front and a solid thin one to the rear.

Some could even mount a power switch on the back, turn to click on or
push-pull.

It was a clever design but really made for repairs rather than production
but I could see in small enough quantities it might of been cheaper than
ordering custom built ones.

It was all snap and click, no screwing around with e or c-clips.

-bruce


I still have a box of Allen-Bradley DIY pots from eBay.

Cheers

Phil Hobbs


--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510

http://electrooptical.net
http://hobbs-eo.com