On 2/12/2011 11:26 AM, Steve Hunt wrote:
> Jerry,
>
> I did get a quote from Omeg. Their part with the closest match would
> have been 220k with a reverse log taper, the correct size spindle bush,
> a genuine 1/4" spindle (not 6mm) and the correct length.
>
> They quoted £5.25 + 20% VAT each. Minimum order quantity of 10, then
> postage of £6.00 + 20% VAT.
>
> That would total over £70, and the pin spacing and length would still be
> wrong! So I'm sticking with the new linear pot I put in this morning.
>
> I doubt the Omeg part would have had quite the same taper as the
> original, anyway. Their normal log taper appears to be the simple
> "Commercial" taper comprising two linear sections of different gradient
> with a single break point; I guess their reverse log would be the same.
Probably achieved by laying down two different widths of resistive
material, or two different thicknesses, though that might leave a
perceptable edge about the middle of rotation.
>
> Just when I thought the projects had stopped, my cousin asked me to look
> over a Hallicrafters SX28 which he just bought on eBay. It's no hardship
> - those glowing dials, the smell, and the sound of that push-pull 6V6
> output stage are just magic :)
Watch out for electrolytics in odd places, like maybe a bias supply
created by a resistor in the plate winding centertap of the power
transfromer.
>
> 73,
> Steve G3TXQ
>
And if you run a single tone long enough you can get the screens of the
6V6 to incandescent temperature which is probably not good for their
logevity.
Good to know the linear pot is a practical solution for the original.
73, Jerry, K0CQ
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