Ok, here is the problem. I have 2 Kenwood kac-728s which are 2ch "600w" amps. Anyway one of them, when hooked up to two 10" kenwood tornado subs, has this problem: It works fine up until about 1/4 volume, however when you get over that, it cuts out on every thump of bass and then turns on again just in time for the next thump. I took the back cover off and noticed that the power relay clicks off on every bass peek. I double checked every connection and tried different hookups with the subs such as 1 sub on each channel in stereo also bridged them in series so that they were 8ohm to put less of a load and same thing happened in every instance after that I took off this amp and hooked up the other one and everything was fine. I'm pretty sure it’s something with the amp internally. I got this amp off ebay and this was the first time I tried it on so I don’t know what could have been done to it. I was wondering if anyone had any ideas with what might be wrong with it or is it a lost cause?!
Replies (1)
Swez on 07/25/2003 09:26:48
Can you inspect that relay for pitted or worn contacts? In some cases, the contact points can pip or burn and cause the solinoid to loose connections under high load conditions. A thin finger nail file or emery cloth may clean up the contacts. If not, consider replacing that relay.
Also, there could be an electrical problem in the power supply. If that circuit loses power, it will open and the amp will shut down as well. Could just be a loose/cold solder joint.
Also, the PC board may have a few bad solder joints. Look for grainy soldering connections on the back side of the board. You may have to clean the board first with IPA (Rubbing alcohol) and a tooth brush to find them. Many boards use a no clean solder that leaves a brownish gold colored residue. Over time, this residue can effect performance of the board by high resistance problems or "intermetallic" migration than can cause minor shorts in the board. This is caused by heat and high humidity in most cases.
You'll need a bright light, a stong magnifying glass and a powerful soldering pencile/gun (60 watts or more). Use fresh electronics grade solder w/ an RMA flux. When re-soldering is completed, re clean the board with IPA, allow to fully dry (hair dryer) And then reinstall the board into the casing and test it.
Use 60/40 alloy soldering wire... is best and a small diameter (0.50 dia) or less is good. Kester and Alpha Metals both make very good solders.
Look here: http://www.partsexpress.com/pe/showdetl.cfm?&User_ID=13736129&St=1082&St2=-66132481&St3=91390843&DS_ID=3&Product_ID=10609&DID=7
If all else fails, a trip to the repair shop maybe needed.
Swez
Replies (1)
Swez on 07/25/2003 09:26:48
Can you inspect that relay for pitted or worn contacts? In some cases, the contact points can pip or burn and cause the solinoid to loose connections under high load conditions. A thin finger nail file or emery cloth may clean up the contacts. If not, consider replacing that relay.
Also, there could be an electrical problem in the power supply. If that circuit loses power, it will open and the amp will shut down as well. Could just be a loose/cold solder joint.
Also, the PC board may have a few bad solder joints. Look for grainy soldering connections on the back side of the board. You may have to clean the board first with IPA (Rubbing alcohol) and a tooth brush to find them. Many boards use a no clean solder that leaves a brownish gold colored residue. Over time, this residue can effect performance of the board by high resistance problems or "intermetallic" migration than can cause minor shorts in the board. This is caused by heat and high humidity in most cases.
You'll need a bright light, a stong magnifying glass and a powerful soldering pencile/gun (60 watts or more). Use fresh electronics grade solder w/ an RMA flux. When re-soldering is completed, re clean the board with IPA, allow to fully dry (hair dryer) And then reinstall the board into the casing and test it.
Use 60/40 alloy soldering wire... is best and a small diameter (0.50 dia) or less is good. Kester and Alpha Metals both make very good solders.
Look here: http://www.partsexpress.com/pe/showdetl.cfm?&User_ID=13736129&St=1082&St2=-66132481&St3=91390843&DS_ID=3&Product_ID=10609&DID=7
If all else fails, a trip to the repair shop maybe needed.
Swez
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