Hi all,
My bass player got a 3520 model Marshall bass head (rack) off eBay a few weeks ago, gigged it a few times then it went off during rehearsals last week with the 2A mains fuse blown.
I've isolated the secondary windings from the diode bridge to see if its the toroidal PT shorted and the mains fuse doesn't blow with the secondaries isolated. Also measured the AC voltage across the secondary with 94vac end to end and 47vac from either end to the CT. I'm therefore thinking that the PT is fine and its something else thats drawing too much current in the power amp section - maybe the big 10,000uF can caps (they're 26 years old after all).
Any help/advice appreciated - I have minimal experience with solid state gear, I'm just a hobbyist amp guy into valve gear.
Schematic link... http://www.drtube.com/schematics/marshall/3520pwr.gif
My bass player got a 3520 model Marshall bass head (rack) off eBay a few weeks ago, gigged it a few times then it went off during rehearsals last week with the 2A mains fuse blown.
I've isolated the secondary windings from the diode bridge to see if its the toroidal PT shorted and the mains fuse doesn't blow with the secondaries isolated. Also measured the AC voltage across the secondary with 94vac end to end and 47vac from either end to the CT. I'm therefore thinking that the PT is fine and its something else thats drawing too much current in the power amp section - maybe the big 10,000uF can caps (they're 26 years old after all).
Any help/advice appreciated - I have minimal experience with solid state gear, I'm just a hobbyist amp guy into valve gear.
Schematic link... http://www.drtube.com/schematics/marshall/3520pwr.gif
Comment