Well, I read through all of the other posts about this amp, and didn't find anything that described this problem.
Let's start here. I got this amp in a non-working state, the previous owner described a 'whistling noise' and capacitors 'looking bubbly'. I took a look, and they indeed did look bad (not just the plastic caps, the actual caps). So, I replaced capacitors C487, C488, C489, C255, C256, C258, and C259 with exact matches in relation to capacitance and voltage, used good quality ones from Digikey (I believe Panasonic, can check later but I generally go with them or Nichicon). I will not lie, those through-holes got me a bit -- had a few pull out, and used the obvious indication of "empty hole ends at traces" or "empty hole ends at empty board" to figure out what of the two layers was supposed to be connected where -- used a trick I learned from recapping Phoenix Gold MS-series boards to repair the now-missing through-hole connectors (can elaborate if needed). I made sure I had continuity everywhere there should be, in regards to the repaired through-holes, and replaced the aforementioned capacitors. However, the unit still exhibits the same symptoms -- when turned on (it will power up with a 15A fuse, and uses <1A at idle) the center LED comes on, the red LED comes on between the center and power terminals, and it emits a noise sort of like a desktop fan starting up with a minor obstacle (like the corner of a piece of paper) in it, stops (as if, in our metaphor, the paper was blown clear), then a high-pitched whine and hiss, as if you were to turn a receiver to the highest volume and play a ~12.5 kHz note (that is probably I'd say pretty close to the actual pitch). Note this comes from the actual amplifier itself, no speakers. I have tried to hook speakers to it, I get a very slight 'fuzz' if I hook one wire up and scrape the other wire on the terminal channel (like you would expect from a working amplifier with no input), and I have tried feeding it input, and still nothing. The knobs do not appear to affect idle power at all (gain, etc). Nothing looks burnt (aside the bad job I did at working on the board, but it's all repaired adequately). I can't seem to hear the source of the noise, but it appears to be coming from around where the two big metal 'bar' inserts are, near the spot between FET245-FET258. I could be wrong here though, it is very hard to try and pinpoint the sound.
Any ideas? I have basic-to-moderate component-level repair knowledge (can use a multimeter, solder reasonably well -- though haven't done my best work here I can say -- test components in or out of circuit, as necessary, replace SMD stuff as needed (and very begrudgingly), et cetera) Anything you have to offer would be extremely appreciated! Thanks in advance guys 🙂
Let's start here. I got this amp in a non-working state, the previous owner described a 'whistling noise' and capacitors 'looking bubbly'. I took a look, and they indeed did look bad (not just the plastic caps, the actual caps). So, I replaced capacitors C487, C488, C489, C255, C256, C258, and C259 with exact matches in relation to capacitance and voltage, used good quality ones from Digikey (I believe Panasonic, can check later but I generally go with them or Nichicon). I will not lie, those through-holes got me a bit -- had a few pull out, and used the obvious indication of "empty hole ends at traces" or "empty hole ends at empty board" to figure out what of the two layers was supposed to be connected where -- used a trick I learned from recapping Phoenix Gold MS-series boards to repair the now-missing through-hole connectors (can elaborate if needed). I made sure I had continuity everywhere there should be, in regards to the repaired through-holes, and replaced the aforementioned capacitors. However, the unit still exhibits the same symptoms -- when turned on (it will power up with a 15A fuse, and uses <1A at idle) the center LED comes on, the red LED comes on between the center and power terminals, and it emits a noise sort of like a desktop fan starting up with a minor obstacle (like the corner of a piece of paper) in it, stops (as if, in our metaphor, the paper was blown clear), then a high-pitched whine and hiss, as if you were to turn a receiver to the highest volume and play a ~12.5 kHz note (that is probably I'd say pretty close to the actual pitch). Note this comes from the actual amplifier itself, no speakers. I have tried to hook speakers to it, I get a very slight 'fuzz' if I hook one wire up and scrape the other wire on the terminal channel (like you would expect from a working amplifier with no input), and I have tried feeding it input, and still nothing. The knobs do not appear to affect idle power at all (gain, etc). Nothing looks burnt (aside the bad job I did at working on the board, but it's all repaired adequately). I can't seem to hear the source of the noise, but it appears to be coming from around where the two big metal 'bar' inserts are, near the spot between FET245-FET258. I could be wrong here though, it is very hard to try and pinpoint the sound.
Any ideas? I have basic-to-moderate component-level repair knowledge (can use a multimeter, solder reasonably well -- though haven't done my best work here I can say -- test components in or out of circuit, as necessary, replace SMD stuff as needed (and very begrudgingly), et cetera) Anything you have to offer would be extremely appreciated! Thanks in advance guys 🙂
hi there any reply on your post as I am sitting withdrew same problem but my Amp goes on and plays but just a very irritating high frequency sound coming thru the subs. Pls let me know if anyone replied.
Thanks
Basskiller
Thanks
Basskiller
I am back, finally got back to this amp. I did a bit of voltage measurement here and there, and before I go any further it is probably a good idea to link this picture.
http://i.fixya.net/uploads/images/3258a8b.jpg
I will reference this pic that someone else posted as I go.
The first thing to note is both of the LED's described in that link are on. I'm not sure what either mean, they don't correspond to anything outside of the case I don't think. Anyone know what they do?
The second thing to note is when it powers up it makes like an 'metal on metal drag' noise, or like dragging a fork against a knife blade, approximately. More of an 'electronic' sound, though. Almost like a 'teleporter' or "sword unsheathing' might sound in a movie, I should say; and very high-pitched. It seems to 'fizzle out'/crackle a bit and stop; then a high-pitched tone comes from the board, maybe 10k tone. It only draws .8 or .9 amps, according to my meter, while running. None of the transistors seem to test blown, I don't see any obvious physical damage on the board. The center leg of the transistors (as seen in the bottom-left corner) throws +12v constantly. The transistor in the middle of the right side, I am not sure which leg but it is throwing +78v constant. Anyone have any ideas where to go from here?
I forgot to mention, I do not believe that there is 'oscillation', as in how you normally see voltage rise and drop on a transistor, which is why I took note of the transistors. I will have to double-check, but I do not believe there is any significant amount of DC voltage being thrown on the outputs. It does not play anything if a signal is put into it.
http://i.fixya.net/uploads/images/3258a8b.jpg
I will reference this pic that someone else posted as I go.
The first thing to note is both of the LED's described in that link are on. I'm not sure what either mean, they don't correspond to anything outside of the case I don't think. Anyone know what they do?
The second thing to note is when it powers up it makes like an 'metal on metal drag' noise, or like dragging a fork against a knife blade, approximately. More of an 'electronic' sound, though. Almost like a 'teleporter' or "sword unsheathing' might sound in a movie, I should say; and very high-pitched. It seems to 'fizzle out'/crackle a bit and stop; then a high-pitched tone comes from the board, maybe 10k tone. It only draws .8 or .9 amps, according to my meter, while running. None of the transistors seem to test blown, I don't see any obvious physical damage on the board. The center leg of the transistors (as seen in the bottom-left corner) throws +12v constantly. The transistor in the middle of the right side, I am not sure which leg but it is throwing +78v constant. Anyone have any ideas where to go from here?
I forgot to mention, I do not believe that there is 'oscillation', as in how you normally see voltage rise and drop on a transistor, which is why I took note of the transistors. I will have to double-check, but I do not believe there is any significant amount of DC voltage being thrown on the outputs. It does not play anything if a signal is put into it.
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I'm being a double-posting ******* here, but after reading through thread after thread it kinda sounds like this here, the second post by Skew, except the fact that I have 2 lit LED's, the one nearer to the power terminals, and the one in the middle of all the capacitors in a bundle.
Forgot to include the link.
http://www.diyaudio.com/forums/car-audio/184937-amp-repair-question-mtx-1501d.html
http://www.diyaudio.com/forums/car-audio/184937-amp-repair-question-mtx-1501d.html
Be careful in that some class d amps wont oscillate without a speaker/load connected.
I sold an irs2092 based and the buyer complained it didn't work when he tested it.
It just sat at +17VDC on the output.
He hadn't connected a speaker in case the amp was faulty !
I sold an irs2092 based and the buyer complained it didn't work when he tested it.
It just sat at +17VDC on the output.
He hadn't connected a speaker in case the amp was faulty !
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