I'm in the process of testing a Thandar TG501 signal generator. Part of my testing is to do a PAT inspection on it as i'm selling it on. Need to make sure its safe.
I performed an earth bond test on it with a test current of about 10A and it failed. The way it failed though was telling: it basically had an earth bond resistance of 0.1R, then went up and up till it went practically open circuit! Indicating that the earth bond couldn't hold the 10A current and and clearly not liked the ordeal.
Sure enough when I cracked it open, there was a lifted charred track. Tracing this track, it when to the outer of the 50R output BNC on one side of the break and to chassis on the other. The BNC on closer inspection is isolated from the metalwork withe a plastic collar.
Now I've PAT inspected signal generators before by testing at the BNC shield, and they have survived the ordeal, but this is a new one on me cos the BNC outer goes to earth via 0V which is connected to the mains earth (So says schematics in the service manual). Yet there is an earth wire directly to the chassis. And all BNC's are like this on it.
Question is: do I repair the break and leave it as it was designed or do I solder a wire from mains earth to all BNC Outers?