Heater Wire Center Tap & Output Tranformer B+ Connection Questions

[Jman]

Hi,

I am building a 5E3 Tweed Deluxe and the power transformer I am using does not have a center tap for the heater wires, so I will need to create an artificial one using two 100 Ohm resisters. I know the two resistors need to come off the pilot light assembly where the heater wires meet the pilot light assembly. But, where should I ground them to? In looking at pictures of a Clark Beautfort, it looks like they simply ground them by soldering them to the back of the pilot light assembly. Is this how it is done or is there a better way to do it?

Also, is it better to connect the B+ wire from the output transformer to the board where the 4.7K & left most 16uf filter cap come to a junction or run the B+ wire to the standby switch?

Thanks for your help!

[Jazz P Bass]

Heater Ground

The two 100 ohm resistors meet at chassis ground.

[Wilder Amplification]

Hi,

I am building a 5E3 Tweed Deluxe and the power transformer I am using does not have a center tap for the heater wires, so I will need to create an artificial one using two 100 Ohm resisters. I know the two resistors need to come off the pilot light assembly where the heater wires meet the pilot light assembly. But, where should I ground them to? In looking at pictures of a Clark Beautfort, it looks like they simply ground them by soldering them to the back of the pilot light assembly. Is this how it is done or is there a better way to do it?

Also, is it better to connect the B+ wire from the output transformer to the board where the 4.7K & left most 16uf filter cap come to a junction or run the B+ wire to the standby switch?

Thanks for your help!

Better to have your OT CT wire on the filter cap as this is where the power tubes pull current from.

[tubeswell]

Hi Jman

To get a quieter amp, you can run your 2 x 100R resistors from either side of the heater winding to the 6V6 cathode(s). This will elevate the heaters at the 6V6 cathode voltage (about 18-20V), which should quieten down any possible heater noise from the pre-amp filaments.

Or you can make a voltage divider off your B+ line at your 1st (reservoir) filter cap, and run your 2 x 100R artificial ground reference resistors to that. If you are going to do this, figure on using about 220k overall between the B+ and the ground, and it will double as a bleeder network for discharging the filter caps. Within this 220k itself, if you aim for a voltage divider than gives you (say) up to about 60VDC elevation at the knee assuming a B+ of around 360VDC or so, then you will need an 18% divider (60/360 = ~18%). So if the overall resistance needed is 220k (for the overall divider to double as a good bleeder network), then 18% (of 220k) will be 39.6k (say 39k) for the ground leg, which means you will need ~180k for the upper resistor (39k + 180k = 219k, which is close enough). Use a 10uF - 47uF 100V electrolytic cap to ground in parallel with the 39k in order to decouple any ripple at the knee of the divider.

[Jman]

Thanks

Thanks for your input, this helped a lot!