[sdiy] Spare MN3009 for Juno 106

[rsdio at audiobanshee.com]

On Jun 17, 2018, at 12:17 AM, Michael Zacherl wrote:
> On 17 Jun 2018, at 02:35, rsdio wrote:
>> It’s cheap enough to literally divide the original resistor values by 4 and just spend a few pennies more to keep the delay times as close to original as possible.
> 
> good point, but were the original components as close at all?

We’re at the edge.

I started with the assumption that the original components were +/-5%, and noticed that using the standard value 2.2 kΩ resistor value increased this error to +13%. That’s out of spec.

Even if the originals were +/-10%, the 2.2 kΩ replacement would have to be 2.5% tolerance or better to stay entirely within the original range.

The issue is that when you scale the resistance, you can only retain the original relaxed tolerance if the new value is centered within the original range. If you round the new calculated resistance up or down to a nearby standard value, then the tolerance has to be tightened up to stick within the original range.

Fortunately, as my investigation revealed, the cost is minimal to maintain the same (or better) tolerances.

Brian Willoughby