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Author Topic: JTM60 Combo rectified diodes fried  (Read 282 times)

Psabin8951

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JTM60 Combo rectified diodes fried
« on: November 05, 2019, 04:15:27 PM »
I have just been given a JTM60 combo.
Its HT rectified diodes D105,106,107,108 are all blown (literally!).
Obviously I can replace these but what would have caused this?

Enzo

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Re: JTM60 Combo rectified diodes fried
« Reply #1 on: November 05, 2019, 04:54:39 PM »
Possibly nothing.  One diode shorts from random component failure, and causes the others to fail.  Otherwise, a shorted power tube is the first source of damage in a repair until shown otherwise.  Beyond that and all farther down the list would be anything to short the B+ to ground, like bad filter, bad flyback diode, shorted OT, and so on.

trobbins

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Re: JTM60 Combo rectified diodes fried
« Reply #2 on: November 06, 2019, 06:24:10 PM »
Was the mains or HT secondary fuse blown?
Are the power transformer windings ok?

 

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