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Shorted primary?

10/25/2004 11:15 PM
Mark Lavelle
Shorted primary?
I think the 270EX in my Verberator may have a short in the primary. My secondaries are *way* low even with all the tubes removed (e.g., under 80 VAC across the red leads), and I've already been through a couple of fuses on the primary side after not finding any shorts on the secondary side of the circuit.  
Does anyone out there have a 270EX they can measure? I'm getting less than 3 ohms across the primaries (a 270DAX I've got measures 5.2 ohms).  
Any other suggestions are welcome, too, of course...
10/26/2004 4:01 AM

Disconnect the secondaries altogether so only the primary is connected to the mains. Put an ammeter in place of the fuse, or leave the fuse and connect the meter across the power switch so you can measure draw. The unloaded tranny should not draw more than a tiny bit of current. if it draws moderate or heavy current, then there is trouble inside it.  
You may have removed the tubes, but with the secondaries connected, you still are applying voltage to filter caps and rectifiers, heater related parts, and so on.  
Make sure to check the tranny cold for shorts between windings and from each winding to frame.  
And don't forget to remove any surge suppressor MOVs from the mains input and any death caps. I usually disconnect the primary and connect it to the mains via test leads for this stuff.
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