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Old 6th January 2010, 06:35 AM   #21
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ok i replaced a fuse in that channel didnt notice it was blown on irf540 -3.08
irf9540 = 2.26

The bias pots for all 4 channels are fully counter cloclwise already didnt turn them at all . someone worked on this before i recieved it
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Old 6th January 2010, 06:44 AM   #22
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Those voltages don't look like they could be causing any problems.

Do all 540s read the same and all 9540s read the same in that channel?

Has the same output in one particular location failed repeatedly?
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Old 6th January 2010, 06:46 AM   #23
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all 540's and 9540's test the same in that channel. its when you hooked up the speaker wires that channel blows the outputs but i was using some new 540's and some old 9540's and some drivers were new some were old. Now everyting is brand new
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Old 6th January 2010, 06:50 AM   #24
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Does it still draw excessive current with no speakers connected?

If you don't know, measure the DC voltage across the 1.8 ohm resistor.
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Old 6th January 2010, 07:53 AM   #25
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ok the wierd thing is i put it back in the sink. Powerd it up and a big spark came for either the transformer or cap didnt see which one but the amp is up and playing on my bench right now. Working perfectly and not drawing much current like 4 amps while playing music at low vol
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Old 6th January 2010, 07:57 AM   #26
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ok figured out what it was i have to do 1 more thing to this amp and it should be good to go off to the next 1 i have to fix.
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Old 6th January 2010, 08:08 AM   #27
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Try moving the transformer to see if it does it again.

To set the bias, clamp everything down, insert the resistor in the B+ line and connect your multimeter across the resistor. Power up the amp and SLOWLY turn the bias clockwise until you just see the voltage across the resistor increase VERY slightly. You want the slightest increase possible.

Run the amp up to or very near thermal shutdown. You'll have to run the amp on direct B+ (no resistor in line) but every 5 minutes (give or take), insert the resistor in line and recheck the voltage across the resistor at idle. It should remain relatively close to the original voltage (after biasing all 4 channels).

If your amp meter on your supply has enough resolution at low current, you can monitor the current draw there.
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Old 11th January 2010, 05:04 AM   #28
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ok i do not get this amp. I replaced all of the outputs all of the drivers. some resistors and some caps and op amps I turned down the bias pots like u said and the amp worked fine

I put the amp together 100% so i could hook it up and set the bias.

Now the left channel is sending 29.68 volts on the output i checked the outputs they seem to test fine i checked the drivers they also seem to check fine. Wondering what i check from here
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Old 11th January 2010, 05:19 AM   #29
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Fuse blown?

Speaker wire color for that channel?

Voltage on op-amp for that channel?

Pin 1:
Pin 2:
Pin 3:
Pin 4:
Pin 5:
Pin 6:
Pin 7:
Pin 8:
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Old 11th January 2010, 05:51 AM   #30
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left channel thge wire is white
pin1=0.34
2= 0.5
3= 0.34
4= -17.41
5= 0.14
6=0.54
7=18.40
pin8= 18.49
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