Marshall MG100HDFX Question

[dimefan0908]

I just replaced a volume pod on my Marshall MG100HDFX head but the wires that run from the transformer to the board and plug in to positions W4 W5 W6 W7 W8 and W9 got mixed up. Now it pops fuses, I have read alot of posts that point to the same problem whit the TD7293 chip on the back of the heat sink going bad as well. The amp worked fine other than alot of bad noise and weird response from the overdrive volume pod (that is untill I got my hands on it). I have looked all over the internet and called a few shops around here with no luck of finding which order these wires go. There are 2 Red,2Blue,a Black and a Brown wire. If anyone out there could send me information or a picture of the wires from the transformer to board of a good working amp I would greatly appreciate it. Thank you for any and all help. Jeremy

[Prairie Dawg]

Originally Posted by dimefan0908

I just replaced a volume pod on my Marshall MG100HDFX head but the wires that run from the transformer to the board and plug in to positions W4 W5 W6 W7 W8 and W9 got mixed up. Now it pops fuses, I have read alot of posts that point to the same problem whit the TD7293 chip on the back of the heat sink going bad as well. The amp worked fine other than alot of bad noise and weird response from the overdrive volume pod (that is untill I got my hands on it). I have looked all over the internet and called a few shops around here with no luck of finding which order these wires go. There are 2 Red,2Blue,a Black and a Brown wire. If anyone out there could send me information or a picture of the wires from the transformer to board of a good working amp I would greatly appreciate it. Thank you for any and all help. Jeremy

I wish I'd seen this post yesterday, I had one on hand until about 6:00 PM last night dammit. I even had my camera on the bench and said to myself "naaaaaaaaaaah no reason to document any of this stuff." It never fails.

I was amazed at the volume that could be gotten out of that matchbook sized chunk of silicon.

I hate when that s**t happens.

[dimefan0908]

Originally Posted by Prairie Dawg

I wish I'd seen this post yesterday, I had one on hand until about 6:00 PM last night dammit. I even had my camera on the bench and said to myself "naaaaaaaaaaah no reason to document any of this stuff." It never fails.

I was amazed at the volume that could be gotten out of that matchbook sized chunk of silicon.

I hate when that s**t happens.

Isn't that the way it always goes! A day late and dollar short gotta love it. If you happen to get another one in within the week let me know please. Thanks

[Enzo]

Leave the wires disconnected. Use an ohm meter to determine which ones are windings. Obviously the two reds and the two blues are, but the others must be their center taps - find out which is which.

Then, being very careful, power up the transformer, still not connected, and measure the AC voltages between the wires. I would guess the red ones were the higjh voltage and the blue ones the low voltage, but it could be the other way - find out.

Now you look at the schematic. W4,W5 appear to be the high voltage connections with W6 as the center tap. And W7,W8 are the low voltage with W9 the center tap.

Now that we know what everything is, shove the right wires on the right posts.

[ParthaD]

In case you still need it...

I happened to have one open waiting to replace the power module which is out of stock at Marshall. In case you're confused about the 2 blue and the 2 red, they go in the same order as they exit the xfrmr, the leftmost red on the leftmost post and same for the blue.

Please feel free to ask any other questions.