Bottlehead Forum

Bottlehead Kits => Crack => Topic started by: Jim R. on August 04, 2010, 03:36:45 PM

Title: Filament wiring routing question
Post by: Jim R. on August 04, 2010, 03:36:45 PM

Is it critical (in terms of noise pickup) where the filament wires are routed?  There is no description in the manual and I assume it is shown in a picture somewhere, but I'd prefer to run the wires across the pt winding and through the gap between transformer terminals 7 and 9, but not sure if hum pickup will be an issue or not -- trying to keep them further from the input signal wiring.

Thanks,

Jim

Title: Re: Filament wiring routing question
Post by: Grainger49 on August 05, 2010, 03:02:49 AM

The routing should keep some distance, maybe  a finger's width, from the signal wires.  It is always best for signal and AC to cross at 90 degrees.  I run them in a loop to arrange that they cross the grid or plate wires that way.  Running the two parallel can cause hum pickup.

I also push heater wires against the top plate as flat as I can and hot glue them down if necessary.

Title: Re: Filament wiring routing question
Post by: Jim R. on August 05, 2010, 03:14:41 AM

Grainger,

Thanks, I understand that, just looking for specifics for the Crack and whether running the wires over the transsformer winding is going to be a problem or not.  In other words, what do the pictures in the manual show.

Thanks,

Jim

Title: Re: Filament wiring routing question
Post by: pro_crip on August 05, 2010, 05:15:08 AM

In the crack manual, on page 18, there is a pic that shows the heater wires, as a twisted pair, running from the terminals on the power transformer, 4 and 5. They run alongside the transformer along the top plate straight to tube socket b. Then, the twisted pair separates so the black wire is attached to B7L and the red wire is attached to B8L. Next page shows a pic of the wiring to tube socket A. A red wire is attached to B8 and a black wire to B7 and then they're twisted again. The twisted pair runs underneath the terminal strips, along the top of the plate. Once underneath the second strip the the wires are separated again. Black goes straight to A9, the red loops alongside the socket, to A4 and A5. HTH.

Rich

Title: Re: Filament wiring routing question
Post by: Jim R. on August 05, 2010, 05:39:49 AM

Hi Rich,

Great -- thanks.  So the wires from terminals 4 and 5 run alongside the transformer close to the 6 lug terminal strip?

I'm doing something a little different with the 9 pin heaters as I have a DPDT switch which allows me to toggle the filament configuration so that different tubes can be used.

Thanks,

Jim

Title: Re: Filament wiring routing question
Post by: pro_crip on August 05, 2010, 06:12:52 AM

Yeah, the pic shows the twisted pair running right alongside the power transformer. Additionally, in the same pic, it shows the twisted pair running between the bolt holding the 6 terminal strip and the terminals on the power transformer. It is literally a straight shot the whole way.

Rich

Title: Re: Filament wiring routing question
Post by: Jim R. on August 05, 2010, 06:24:38 AM

Rich,

Excellent!  Thank you again.

-- Jim