I found the resister value which was 7.7k ohms.
Unsure about this amp though. Initially powered up with a 2 ohm resistor and did not power up. I think the voltage was too low at about 10.3 to 10.6. So I moved on to a 10 amp fuse and 12.8v and crossed my fingers. Initially drew 6 amps of current and slowly over the course of 2 minutes the current dropped down to 4.5 amps and is sitting idle at 4.5 amps. I do see audio on the speaker terminals with with the scope. I also can feel the heat coming off the largest inductor nearest the driver board. I pushed and twisted on it and didn't see any change.
*** from the time it took me to write (10 - 15 minutes) the the current is slowly rising to now 4.57amps.
Every mosfet is new in the audio section, all drive and pulldown resistors in the audio section replaced with 1% resistors. Both audio driver boards rebuild with new 1 ohm 1% resistors, changed every drive transistor to ksa1220ay and ksc2690ay, the 12v zenners were shot so those got changed too. This amp was in extremely bad shape when I received it.
1. Is it normal for an amp to idle at 4.5 amps?
2. Is it normal for the inductor to run hott at idle?
3. Where would I start to look for current draw?
Unsure about this amp though. Initially powered up with a 2 ohm resistor and did not power up. I think the voltage was too low at about 10.3 to 10.6. So I moved on to a 10 amp fuse and 12.8v and crossed my fingers. Initially drew 6 amps of current and slowly over the course of 2 minutes the current dropped down to 4.5 amps and is sitting idle at 4.5 amps. I do see audio on the speaker terminals with with the scope. I also can feel the heat coming off the largest inductor nearest the driver board. I pushed and twisted on it and didn't see any change.
*** from the time it took me to write (10 - 15 minutes) the the current is slowly rising to now 4.57amps.
Every mosfet is new in the audio section, all drive and pulldown resistors in the audio section replaced with 1% resistors. Both audio driver boards rebuild with new 1 ohm 1% resistors, changed every drive transistor to ksa1220ay and ksc2690ay, the 12v zenners were shot so those got changed too. This amp was in extremely bad shape when I received it.
1. Is it normal for an amp to idle at 4.5 amps?
2. Is it normal for the inductor to run hott at idle?
3. Where would I start to look for current draw?
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I dont if it makes a difference but the + 12v regulator is at 11.96v and the negative is at -12.22. Something maybe pulling the positive one down?
The resistor colors looked like blue, gray brown... Are you sure it's 7.7k?
The inductors should heat at the same rate. Does the signal from the outputs driving each one look the same?
22v on pin 1 is likely OK.
The regulators have a tolerance (± marked value) that could account for the difference. It's also sometimes due to the grounding point. Did you measure from the ground leg of the regulator to the output pin or did you use a different grounding point?
I don't know what the idle current should be. What N-channel outputs did you use?
The inductors in some amps run hot but the identical inductors should operate at the same temperature.
The inductors should heat at the same rate. Does the signal from the outputs driving each one look the same?
22v on pin 1 is likely OK.
The regulators have a tolerance (± marked value) that could account for the difference. It's also sometimes due to the grounding point. Did you measure from the ground leg of the regulator to the output pin or did you use a different grounding point?
I don't know what the idle current should be. What N-channel outputs did you use?
The inductors in some amps run hot but the identical inductors should operate at the same temperature.
I lifted the leg of a similar resistor and it tested exactly 7.7k ohms. I was able to push the 2 ends on the broken one together and it also did give me a reading of exactly 7.7k ohms.
1. After checking the outputs I found r314 10ohm resistor measuring 2kohms so That was out of tolerance by a landslide. That will teach me to check new parts before I put them in.
2. I measured from both negative power terminal and the ground pin of the regulator. The windings on the transformer were really loose so I snubbed them up tighter put some epoxy to hold them in and replaced the regulator. 18 volts going in now 12.03 coming out.
3. I used vishay irf9640pbf's and used IRFB31N20D's. I know I read somewhere you said this amp does not like irf640s because they run hot and is it something to do with high gate capacitance making them harder to driver? Maybe I'm mixed up there. I don't recall.
After replace I replaced the resistor and fet the amp starts up with 6 amps and slowly makes it's way to 4.4Amps idle at 12.75V . All the drive signals look good so in my case the ksa1220ay and ksc1690ay drivers were an excellent substitute. Plays audio under heavy load for and hour now and the inductors seem even in heat dissapation. Thanks Perry.
1. After checking the outputs I found r314 10ohm resistor measuring 2kohms so That was out of tolerance by a landslide. That will teach me to check new parts before I put them in.
2. I measured from both negative power terminal and the ground pin of the regulator. The windings on the transformer were really loose so I snubbed them up tighter put some epoxy to hold them in and replaced the regulator. 18 volts going in now 12.03 coming out.
3. I used vishay irf9640pbf's and used IRFB31N20D's. I know I read somewhere you said this amp does not like irf640s because they run hot and is it something to do with high gate capacitance making them harder to driver? Maybe I'm mixed up there. I don't recall.
After replace I replaced the resistor and fet the amp starts up with 6 amps and slowly makes it's way to 4.4Amps idle at 12.75V . All the drive signals look good so in my case the ksa1220ay and ksc1690ay drivers were an excellent substitute. Plays audio under heavy load for and hour now and the inductors seem even in heat dissapation. Thanks Perry.
The 640s are not as good as the 640N (for switching amps) which aren't generally as good as the IRFB31N20D (in this type of amp).
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