Help! no signal! Marshall JTM60 - Page 2

rynestyne · 24th April 2006, 06:58 PM

Well, i did replace the HT fuse and the amp played for about 30 seconds before blowing the fuse again. I have been told this could be caused by worn out tubes. The amp has mullard el34 power tubes and JJ 83 preamp tubes. Would it most likely be the power tubes or preamp?

Netlist · 24th April 2006, 07:37 PM

Good. Assuming you replaced the fuse with a correct spare, something seems to be wrong with the electronics.
The HT fuse is the 500mA slow blow. If it were faulty rectifiers, D105 - D108, the fuse would probably blow instantly. Worn out tubes can be but first check capacitors like C112, C111, C110, C109.

/Hugo

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24th April 2006, 06:58 PM	#11
rynestyne diyAudio Member Join Date: Apr 2006 Location: San Antonio, Texas	Well, i did replace the HT fuse and the amp played for about 30 seconds before blowing the fuse again. I have been told this could be caused by worn out tubes. The amp has mullard el34 power tubes and JJ 83 preamp tubes. Would it most likely be the power tubes or preamp?

24th April 2006, 07:37 PM	#12
Netlist diyAudio Moderator Emeritus Join Date: Jan 2003	Good. Assuming you replaced the fuse with a correct spare, something seems to be wrong with the electronics. The HT fuse is the 500mA slow blow. If it were faulty rectifiers, D105 - D108, the fuse would probably blow instantly. Worn out tubes can be but first check capacitors like C112, C111, C110, C109. /Hugo