Silvertone 1482 heater voltage & popping
My Silvertone 1482 has recently been re-capped and re-tubed (except the 6X4 and the 12AU6). Has been purring like a kitten, sounding really great, switched it on today to be met with the occational popping and a hum through the speaker. The hum gets a little louder when i turn up either of the volume controls but then stays at a constant volume even if i turn the controls to max. The popping is very intermitent, have been through with my trusty chop stick and can't make it happen by touching any componants. I've pulled tubes, replaced tubes, makes no difference. The only tube i don't
have a spare of is the 6X4 rectifier which is original 1965. The tubes sockets have been cleaned and tensioned and all the remaining resistors are within spec.
I did take some voltage measurements and the heater voltage to the tubes is reading 3.15vac....should be 6.3vac. The plate on V1 is 113v...correct going by the schematic i have, the plate on V2 is 184v...the schematic gives 138v, so seems a bit high.
The paltes on the 6v6's are 358v & 358v and the cathode current 35.3ma and 35.2ma....seems a bit high for a pair of 6v6's????
Am i right in thinking that the bias is set by the 270ohm 5w resistor to ground from the cathode of one of the 6v6's (they share this?). The resistor reads 268ohms and is new and good.
I realise there's a few different questions here but to sum up.
I have popping!
I have hum!
I have low heater current!
I have possibly a high bias setting!
Could most of this be caused by a failing rectifier tube....do they tend to do this or do they either work or not.
Many thanks in advance.