Wiring in a choke

[Pingu]

I have a crack with speedball and Panasonic 100Uf film caps. I have just bought a triad C7 X choke and was looking to install it when I finish checking the unit for dry joints. (No not ny build lol)
I assume it goes in place of the 270ohm resistor between u15 and u21, however I have seen photos on various site that have this resistor still in place but also with a choke. Should I remove the resistor when I wire the choke in or leave it in?
I’ve also added a little mains filter/spike suppresser with a Rifa  x/y capacitor block and vdr, don’t know if it makes any difference but was advised to do it on any project by a friend and it only cost a few pennies

[Deke609]

The Crack power supply has two 270 ohm resistors in its CRCRC filter. The Triad CX7 has a DC resistance of 270 ohms, so you would need to remove one of the two existing 270 ohm resistors and install the CX7 in its place.  Otherwise I think you'd be changing B+: installing the choke in parallel with a 270 ohm resistor would increase B+ and installing in series would decrease it - neither of which you want.

cheers, Derek

[Pingu]

Thanks Derek I see now all makes sense.
Those pix I saw probably had the 270ohm under the two caps removed not the one over the tranny. I don’t suppose it makes much difference which resistor it replaces, I’m only using one choke as it makes things so much easier with space available.
Thanks
Martin

[Deke609]

In PSUD2, either way reduces ripple to negligible levels - see attached pics of my very rough modelling of the Crack power supply (NOTE:  the current value of 90mA may be wrong - I used it as a ballpark estimate based on the CX7 rated max current of 90mA). 

It is interesting that the stock CRCRC filter already reduces ripple to about 1mV peak to peak. Adding the CX7 appears to knock that down further by a factor of 10.  I'll be curious to know whether you hear a difference.

cheers, Derek

[Pingu]

Thanks again Derek. Interesting traces and yes when it’s done sometime in January or February I’ll report back.
Would be good to hear others impressions of the choke mod as it so very cheap to do.
Martin