18-06-2020, 06:37 PM
Just as an update I have now checked the ESRs of all the electrolytics including the dual 50uF - these are all good. I have initially checked the blue/brown leads of the primary - 9.7R (I'm going to disconnect chassis from the cab tomorrow to check the others). I have also check the DC ohms resistance across the dual 50uF - no issues there as the resistance was initially 140kR and rising. I have also checked the amp on a lamp limiter initially with and without the valves. With no valves, no light at all from the 100watt bulb. With the valves in place (just a quick check before dismantling), the lamp was very dim but grew brighter as the hum grew (does this suggest anything or nothing?).
I will be using the variac tomorrow when the chassis is out (I will need to either put a socket to the variac or take the plug off the amp).
I have also checked all of the connections and cannot see anything loose, broken or touching the chassis.
I must admit I'm feeling somewhat down about this now.
Ho hum (and lots of it!).
Rob
I will be using the variac tomorrow when the chassis is out (I will need to either put a socket to the variac or take the plug off the amp).
I have also checked all of the connections and cannot see anything loose, broken or touching the chassis.
I must admit I'm feeling somewhat down about this now.
Ho hum (and lots of it!).
Rob
if all else fails...read the instructions!
