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14th February 2009, 04:43 AM
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#1 |
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diyAudio Member
Join Date: Feb 2009
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mtx 500d problems
ive got a old school mtx 500d that powers up, and has sound, but isnt real loud. it makes a sub flex in and out slowly...
now on the board there is a row of black transistors that get really hot. i think one of the ic chips near the rca jacks is getting a little hot too......i can get a pic of it in a few min... |
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14th February 2009, 10:55 AM
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#2 |
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diyAudio Member
Join Date: Feb 2009
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hey perry , does this help any?
494 Pin 1: 2.349 Pin 2: 2.346 Pin 3: 3.484 Pin 4: 0.448 Pin 5: 1.482 Pin 6: 3.271 Pin 7: 000.6mv Pin 8: 10.95 Pin 9: 000.6mv Pin 10: 000.6mv Pin 11: 10.95 Pin 12: 10.98 Pin 13: 4.88 Pin 14: 4.88 Pin 15: 04.87 Pin 16: 000.6mv 339 i probed this ic in the same order as the 949 Pin 1: 4.67 Pin 2: 4.67 Pin 3: 10.98 Pin 4: 4.87 Pin 5: 6.68 Pin 6: 3.516 Pin 7: 04.88 Pin 8: 1.054 Pin 9: 3.362 Pin 10: 04.61 Pin 11: 3.362 Pin 12: 001.0 Pin 13: 001.6 Pin 14: 4.67 |
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14th February 2009, 03:07 PM
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#3 |
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diyAudio Member
Join Date: Feb 2009
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the 4 parts in the row gets so hot you cant touch them....and the 2 op amps (i believe) get hot but you can touch them for a few seconds...
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14th February 2009, 06:20 PM
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#4 |
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diyAudio Member
Join Date: Nov 2003
Location: Louisiana
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With you black meter probe on a negative speaker terminal, what is the DC voltage on pins 4 and 7 of those two op-amps?
__________________
Links >> Basic Car Audio Amp Repair --- Basic Car Audio Electronics --- Basic Transistor Testing --- Basic Switching Power Supply Design --- Basic Computer Skills << Links |
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16th February 2009, 11:45 AM
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#5 |
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diyAudio Member
Join Date: Feb 2009
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in the pic this is the lower opamp
pin 4 -030.0mv . its start at around 070.0 and slowly drops pin 7 reads 000.1mv ...starts at 000.9 and drops off to 000.1mv and bounces from 000.0 mv to 000.1 top opamp pin 4 reads -012.6 but it starts at 085.00 and drops down slowly pin 7 000.1mv ...it does the same thing as the other opamp drops and bounces also i noticed that most all of the transistors on the board like the ones i have boxed in the pic get very hot.. |
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16th February 2009, 11:45 AM
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#6 |
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diyAudio Member
Join Date: Feb 2009
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scratch those readings...i think my dmm has bit the dust on me.....it bounces all over the place with just the negative probe on the negative speaker terminal....lol..
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20th February 2009, 01:40 AM
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#7 |
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diyAudio Member
Join Date: Feb 2009
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ok, i bought a fluke meter....hope these are better readings..
494 Pin 1: 2.357 Pin 2: 2.354 Pin 3: 3.521 Pin 4: .449 Pin 5: 1.486 Pin 6: 3.275 Pin 7: 0.001 Pin 8: 11.24 Pin 9: 0.001 Pin 10: 0.001 Pin 11:11.18 Pin 12: 11.19 Pin 13: 4.923 Pin 14: 4.923 Pin 15: 4.923 Pin 16: 0.001 339 i probed this ic in the same order as the 949 Pin 1: 4.719 Pin 2: 4.719 Pin 3: 11.22 Pin 4: 4.923 Pin 5: 6.841 Pin 6: 3.573 Pin 7: 4.923 Pin 8: .8879 Pin 9: 3.372 Pin 10: 4.681 Pin 11: 3.372 Pin 12: .001 Pin 13: .002 Pin 14: 4.719 op amp pin 4 -18.04 pin 7 fluctuates from .017 to - .045 op amp pin 4 18.05 pin 7 fluctuates from .039 to - .040 |
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20th February 2009, 02:02 AM
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#8 |
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diyAudio Member
Join Date: Nov 2003
Location: Louisiana
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What DC voltage do you have on pin 8 of the op-amps?
If it's ~18v, the regulators (Q2, Q61, Q3 and Q62) are OK and the transistors are running hot as usual. This was a real weak point with these amps. If you adjust the gain, does that make the woofers move in and out?
__________________
Links >> Basic Car Audio Amp Repair --- Basic Car Audio Electronics --- Basic Transistor Testing --- Basic Switching Power Supply Design --- Basic Computer Skills << Links |
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20th February 2009, 03:54 AM
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#9 |
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diyAudio Member
Join Date: Feb 2009
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yes the speakers are moving in and out when you move the gain. pretty much all the time.... the speakers are popping if you turn the gain to high making the sound cut off , then back on...
pin 8 on each opamp is reading 17.15 |
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20th February 2009, 04:03 AM
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#10 |
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diyAudio Member
Join Date: Nov 2003
Location: Louisiana
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What is the DC voltage on the 1st pin (left side in photo) of the 2155?
What is the DC voltage on pins 1 and 7 of the op-amp directly above the 2155 (in the photo)?
__________________
Links >> Basic Car Audio Amp Repair --- Basic Car Audio Electronics --- Basic Transistor Testing --- Basic Switching Power Supply Design --- Basic Computer Skills << Links |
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