Repairing MTX 1501d - Help a newb

scoob8000 · 18th January 2009, 04:25 PM

So I finally got the cajones up to try to fix this smoked mtx 1501d I got scammed on.

Replaced all the 75339 fets (all shorted out) and a couple melted poly caps right near them.

There's also a cracked (looks like physical damage) diode I replaced that leads to the fet in the center of the board.

I think the previous abuser of this amp "modded" it, since Q240 is missing.

So on first power up (no speakers, no inputs) I get the power led and about 3 seconds later LED238 near the input section lights up.

LED399 in the center of the large caps never lights.

Trying my test again with a speaker connected and an audio source. Soon as LED238 lights I get a very faint buzzing on the speaker. (About .1 volts on the dmm).

No idea where to go now.

Mass Car Audio · 19th January 2009, 06:03 AM

Have you check the gate resistors ? I noticed most of the time when the mosfets transistors blown the gate resistors go to. Take your DMM and check all the resistors that are in front of the mosfets.

http://www.samengstrom.com/nxl/10116...e_page.en.html

scoob8000 · 19th January 2009, 10:55 AM

doh!

I should of thought of that. (I had to replace one on that 6100d I was messing with)

There two of them, and they're both open.

I'll have to see if I can clean them up. They're a little dirty from the magic smoke, as if they weren't hard enough to read to begin with.

Mass Car Audio · 19th January 2009, 05:26 PM

I have that problem all the time man, if I cant see the colors on the resistors I just take the resistor number thats printed on the PCB and phone in to the manufacture and they will look it up in their service manuals.

scoob8000 · 22nd January 2009, 11:31 AM

Does "39R2" sound about right? I got one clean as I could and can still barely ready it with a magnifying glass.

Is there a size to these little smd resistors? Last time I ordered SMD diode's, they were too small to even cover both solder pads.

dmarrow · 9th May 2013, 09:25 PM

Where can I find an owners manual for an MTX 1501D thunder elite

18th January 2009, 04:25 PM	#1
scoob8000 diyAudio Member Join Date: Nov 2008	Repairing MTX 1501d - Help a newb So I finally got the cajones up to try to fix this smoked mtx 1501d I got scammed on. Replaced all the 75339 fets (all shorted out) and a couple melted poly caps right near them. There's also a cracked (looks like physical damage) diode I replaced that leads to the fet in the center of the board. I think the previous abuser of this amp "modded" it, since Q240 is missing. So on first power up (no speakers, no inputs) I get the power led and about 3 seconds later LED238 near the input section lights up. LED399 in the center of the large caps never lights. Trying my test again with a speaker connected and an audio source. Soon as LED238 lights I get a very faint buzzing on the speaker. (About .1 volts on the dmm). No idea where to go now.

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19th January 2009, 06:03 AM	#2
Mass Car Audio diyAudio Member Join Date: Nov 2008	Have you check the gate resistors ? I noticed most of the time when the mosfets transistors blown the gate resistors go to. Take your DMM and check all the resistors that are in front of the mosfets. http://www.samengstrom.com/nxl/10116...e_page.en.html

19th January 2009, 10:55 AM	#3
scoob8000 diyAudio Member Join Date: Nov 2008	doh! I should of thought of that. (I had to replace one on that 6100d I was messing with) There two of them, and they're both open. I'll have to see if I can clean them up. They're a little dirty from the magic smoke, as if they weren't hard enough to read to begin with.

19th January 2009, 05:26 PM	#4
Mass Car Audio diyAudio Member Join Date: Nov 2008	I have that problem all the time man, if I cant see the colors on the resistors I just take the resistor number thats printed on the PCB and phone in to the manufacture and they will look it up in their service manuals.

22nd January 2009, 11:31 AM	#5
scoob8000 diyAudio Member Join Date: Nov 2008	Does "39R2" sound about right? I got one clean as I could and can still barely ready it with a magnifying glass. Is there a size to these little smd resistors? Last time I ordered SMD diode's, they were too small to even cover both solder pads.

9th May 2013, 09:25 PM	#6
dmarrow diyAudio Member Join Date: Mar 2013	Where can I find an owners manual for an MTX 1501D thunder elite