WTB 100k mono pot with a 3mm diameter shaft

[TheFinisher]

Hi guys
Unfortunately one of the 2 mono volume pots on my vintage preamp broke off at the legs yesterday .
It’s Bourns 51CAAE28S20 which are no longer made .
The problem is that it’s shaft is only 3mm in diameter so I’m struggling to find a replacement
100k
3mm shaft ( 15mm in length )
Mono
It had 3 legs

 

[cabirio]

See if this one will work, per the datasheet the "C" after the 51 indicates a 3.18 mm / 1/8" shaft rather than 3 mm (that would be "S"):

https://eu.mouser.com/ProductDetail/Bourns/51CAD-E24-A20L?qs=MVHXLImBVS9uqPWHQLo7Bw==

 

[RM]

Or just enlarge the bushing from 1/8” to something more appropriate like 4 or 6mm.

R

 

[TheFinisher]

Thanks Cabrio , that’s the closest I’ve seen , I’ll keep it in my mouser shopping basket should a 3mm one not come available.
I could always grind down the shaft a little or bore out the bushes that fits on it .
Cheers

 

[TheFinisher]

Or just enlarge the bushing from 1/8” to something more appropriate like 4 or 6mm.

R

I hear what you’re saying and I have considered that but when drilling out the bush i would have to be very precise otherwise when turning the pot it would be off centre.
The other alternative is that i get some bushes made with 6.5mm at one end ( most shafts are 6mm ) and 3.5mm at the other end.

 

[cabirio]

I meant that yours is also 51C..., so it should be 3.2 mm rather than 3?

 

[TheFinisher]

Oh I didn’t know that the 51c represented a measurement. Thanks 👍🏻

 

[cabirio]

On page 4 of the datasheet you have the whole order code explained: https://www.bourns.com/pdfs/50.pdf

 

[TheFinisher]

I’ve now ordered 2 of them , thanks mate , one old preamp saved .

 

[TheFinisher]

Well thanks to you guys ( especially cabirio ) the correct pots arrived today BUT now I have installed them even though I fitted the knobs at the minimum position when I turn on the preamp the volume is at maximum! I’m obviously doing something wrong and my suspicion is that the middle and left pin ( looking from the back ) should be linked when soldered to the board? It did kind of look like they may have been linked originally but then I presumed it was a blob of solder that shouldn’t be there so I removed it , now I have maximum volume 😩

 

[TheFinisher]

Now sorted. 👍🏻

 

[cabirio]

Great news! Just curious, what was it?

 

[TheFinisher]

The left and the middle leg needed to be soldered together.

 

[TheFinisher]