The power amp section has blown parts. You will likely find they use a chip like the TDA7293 as the power amp output and it will be blown, shorted causing the fuse to blow. These cost $6 from Digikey.com. Find a competent tech to replace it and use heat sink compound. Verify the part before ordering one. They come with leads bent either way so make sure you get the one with a matching suffix letter. When firing up after repair, put a 60 watt light bulb in series with the hot power lead to act as a current limiter... saves blowing fuses if there is another problem.
Testimonial: "Awesome. Helped me out a lot! Me being a greenhorn when it comes to electronic, I appreciate it!!!"
Okay cool. Also one more think is there detailed schematics for this amp out there somewhere or a components list. Thank you so much!!!
Here is your schematic:
http://elektrotanya.com/marshall_mg100df...
Scroll down to "get manual" and click on it to download. Ignore other download links that are for other PDF readers, etc.
Hello again, I replaced the TDA7293 power amp chip in my Marshall. I put a new fuse in and bang it went. Saw some sparks and a bang noise and the smell of burnt components lol. Do you have any other idea as what may have caused this. Would there be a possible short in the fan that cause it to blow again. The new TDA7293 is toast along with the new fuse. Could there be a problem with the power supply and ground? Thank you again.
Check C5 right near the TDA7293. Also when restarting an amp, you put a 100 watt lamp in series with the power cord. This acts as a current limiter and saves fuses and further parts while troubleshooting. There is also a possibility this problem backed up into the power supply. Leaving thee power module out, and using the series lamp in the power cord, measure the voltages in the power supply. If there is excessive drain, the lamp will light to save the fuse. If the unit runs wih the lamp extingished, then verify the electrolytics on the power module. If the TDA7293 shows that it went, capacitor C5 OR possibility of a solder bridge during replacement would be about the only possibility. "Candle" the board with a bright light to verify there are no solder bridges on the TDA7293 leads before re-installing.
Get back to me on this.
Sorry to be asking so many questions I am just starting out when it comes to electronic repairs. I appreciate everything you have told me! For C5 checking to see if it is burned out you mean? Also I took off the second blown TDA7293 my PCB chip of that section has some burn marks on it from the TDA where it fried. Should I get a new output section. Some of the rings on the PCB came off as well. Also how would I run a 100 Watt light bulb in series with the power cable?? Sorry once again just starting out on electronic repairs. I want to be able to do this lol.
Thank you so much!,
- Joe
Do you know where I can get a replacement PCB for the output section of this amp. When I removed the second TDA it has a small amount of black on it from where it blew.
Thanks
Joe
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