Your isolation transformer should be grounded. And pass the safety ground through to the UUT.
What should happen is the connection between the Neutral and the Ground must be broken. This connection is made back at your service entry panel. With that condition removed, it should not matter if you place a ground on either the Line or the Neutral on the secondary of the isolation transformer. This is no different than the old transformer based power system.
Maybe you can find a working 7904 power supply somewhere. There were many of those scopes made.
Does the power supply make a ticking sound when power is applied? Any visible signs of blown parts in the supply? Do you have continuity through the RFI filter on the scope?
You might say where you are located case someone is near you that can help.
Regards
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----- Original Message -----
From: "JJ" <jajustin@...>
To: <
[email protected]>
Sent: Friday, April 06, 2018 4:23 PM
Subject: [TekScopes] 7904 Mainframe damaged
Hello, I own a beautiful 7904 scope that I damaged when probing a stereo receiver. I didn't realize that my isolation transformer was earth grounded - forgot to remove the ground strap. So I effectively shorted out the scope by touching the probe's ground lead to a voltage node. The mainframe (without any plugins installed) doesn't power up. When the event happened, the scope remained on. But, after shutting it off, it wouldn't come back on. There's no activity - just dead.
I checked the fuse but I knew that wasn't going to be the problem since the surge came over the ground. I have the service manual. I was just wondering if there was an obvious place to start looking since this could have happened to others. I'm hoping that it's repairable - my heart is broken. I've used this scope for over 40 years. I'm a retired 70 year old electronics engineer. I guess I'm just getting old!
