Solid State Guitar Amp Forum | DIY Guitar Amplifiers

Solid State Amplifiers => Tubes and Hybrids => Topic started by: Psabin8951 on November 05, 2019, 04:15:27 PM

Title: JTM60 Combo rectified diodes fried
Post by: Psabin8951 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?
Title: Re: JTM60 Combo rectified diodes fried
Post by: Enzo 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.
Title: Re: JTM60 Combo rectified diodes fried
Post by: trobbins on November 06, 2019, 06:24:10 PM
Was the mains or HT secondary fuse blown?
Are the power transformer windings ok?