I seek your assistance in resolving a left channel hum on a recently completed Crack 1.1.
Some background: when first powered up I managed to fry a 207 ohm resistor, from a bit of ham-fistedness (
https://forum.bottlehead.com/index.php?topic=11908.0). Following advice received here, I've replaced the fried resistor, and there now are indications of power coming to the appropriate terminals 1 - 10. However, while music does indeed play through the right channel, on the left there is only a hum. It occurs even in the absence of a music source, and with the volume pot set at zero.
I've searched the forum for posts on this topic and a common cause appears to be problems with the ground circuit. I re-flowed all the connectors for the black wires, but this did not address the problem. I cleaned the posts of the 12AU7, both physically and with contact cleaner and Caig deoxit; no change.
I've just re-tested the resistances and voltages, with the following result:
All resistances tested within spec
except the ground tab on the RCA jacks. This test yielded 0.5 ohms, not zero.
All non-zero voltages tested within spec. All terminals that should have returned 0 volts (3,6,8 and 10) yielded 0.5 mV.
I am out of my depth here and would be extremely grateful for any assistance you might offer.
Many thanks,
Steve R
