Rocket Questions

[billyjack37]

Does anyone know what the purpose of the two 100K 2 watt resistors that are attached from pin two to ground off the rectifier tube are for? Are they necessary? Lastly, would it be okay to use the center tap of the B+ secondaries for a standby switch instead of having all that AC going through the switch?

Thanks,

Bill

[Colossal]

Does anyone know what the purpose of the two 100K 2 watt resistors that are attached from pin two to ground off the rectifier tube are for? Are they necessary?

They are bleeder resistors. You can use a single 220k 2 or 3W metal oxide resistor. They allow the reservoir cap (the two 40uFs in parallel) to discharge when the mains power is turned off. This is a safety feature, allows for a little constant current demand, and are considered a good modern addition (so that the amp is not charged when the chassis is opened up for service). Cheap insurance and a courtesy.

Lastly, would it be okay to use the center tap of the B+ secondaries for a standby switch instead of having all that AC going through the switch?

I personally do not really care for the option of leaving the centertap open but some designs do that. Better to switch both legs of the PT secondaries with a DPDT switch. That way you are switching AC, not DC. Less potential for arcing on the switch.