Help! Marshal MG50DFX Anybody Anyideas

thomas7037 · 10th August 2005, 09:43 AM

My marshal amp recently stopped working so I decide to fix it. I replaced the main amp chip a TDA 7293 along with all of the other pre amp chip including many TL027`s when I put the amp on now it works all of the time but is very quiet? Can anybody shed light on my problems? I also noticed two leds in the amp one green and one red, are they for test purposes? should they light up?
Cheers for any help offered

Enzo · 11th August 2005, 02:29 AM

Look at pin 4 of the module ribbon, or pin 9 of the 7293 itself. This is the standby pin. There should be a positive voltage there - maybe 3-5v or something. When the big chip fails sometimes it damages the mute circuit.

On the main board somewhere is a small transistor and a zener that control this line. Shorted zener will leave the chip muted.

Something to check.

10th August 2005, 09:43 AM	#1
thomas7037 diyAudio Member Join Date: Aug 2005	Help! Marshal MG50DFX Anybody Anyideas My marshal amp recently stopped working so I decide to fix it. I replaced the main amp chip a TDA 7293 along with all of the other pre amp chip including many TL027`s when I put the amp on now it works all of the time but is very quiet? Can anybody shed light on my problems? I also noticed two leds in the amp one green and one red, are they for test purposes? should they light up? Cheers for any help offered

Thread Tools	Search this Thread
Show Printable Version Email this Page	Search this Thread: Advanced Search

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
Marshall MG50DFX Schematic wanted...	fuzzy	Solid State	1	12th February 2009 03:35 PM

New To Site?	Need Help?
Register to Participate Search Privacy Statement Contact Us	Frequently Asked Questions Did you forget your password? Mark Forums Read


	Please consider donating to help us continue to serve you. Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving

11th August 2005, 02:29 AM	#2
Enzo diyAudio Member Join Date: Sep 2004 Location: Lansing, Michigan	Look at pin 4 of the module ribbon, or pin 9 of the 7293 itself. This is the standby pin. There should be a positive voltage there - maybe 3-5v or something. When the big chip fails sometimes it damages the mute circuit. On the main board somewhere is a small transistor and a zener that control this line. Shorted zener will leave the chip muted. Something to check.