Hi all. I had an amp "Kicker KX 500.2" Class A/B 2 channel amp repaired by me with the valuable help of the guys here. The amp still works good.
Some weeks ago i noticed a small decrease at the overall performance of the amp. I simply ignored it because i had a lot of work. Yesterday i decided to have a look at it.
Normally the amplifier is connected bridged to 2 12" kicker subwoofers 8 ohms each, parallel, giving the amp a 4 ohm load.
I connected each sub to each channel, and i have checked each channel for signal, swapped rca cables and swapped subs, and all seemed to be fine, just the left channel being like 2/8 weaker than the right, testing both audio outpots. I just appeared that when you connected any signal or any sub to the LEFT RCA Channel (and oupot) sounded a bit weak.
Crossover variable setting works well at both channels, gain works at both channels.....but bass boost only works at RIGHT Channel, and yes , i know the bass boost setting only works with the low pass filter enabled. The left outpot does not change the sound, regardless from the bass boost setting, but the right works ok...amplifier in bridged mode (which i normally i have working) has bass boost.....
Even when the amp it is in bridged mode, if you connect any audio source to the left RCA input and try to use the bass boost, no changes at the sound at all.....if you connect audio to the right RCA, you have bass boost....
I just does not understand why the bass boost it does work at the right channel and doesnt work at the left in Stereo mode. Do im missing something.
Needless to say, i did the mods Mr. Babin suggested to me 2 years ago (rellocatting 2 transistors to the heatsink, the B649 ones if i remember right...) and all worked well from a long time.
I would like oppinions for this. Thank you guys.
Some weeks ago i noticed a small decrease at the overall performance of the amp. I simply ignored it because i had a lot of work. Yesterday i decided to have a look at it.
Normally the amplifier is connected bridged to 2 12" kicker subwoofers 8 ohms each, parallel, giving the amp a 4 ohm load.
I connected each sub to each channel, and i have checked each channel for signal, swapped rca cables and swapped subs, and all seemed to be fine, just the left channel being like 2/8 weaker than the right, testing both audio outpots. I just appeared that when you connected any signal or any sub to the LEFT RCA Channel (and oupot) sounded a bit weak.
Crossover variable setting works well at both channels, gain works at both channels.....but bass boost only works at RIGHT Channel, and yes , i know the bass boost setting only works with the low pass filter enabled. The left outpot does not change the sound, regardless from the bass boost setting, but the right works ok...amplifier in bridged mode (which i normally i have working) has bass boost.....
Even when the amp it is in bridged mode, if you connect any audio source to the left RCA input and try to use the bass boost, no changes at the sound at all.....if you connect audio to the right RCA, you have bass boost....
I just does not understand why the bass boost it does work at the right channel and doesnt work at the left in Stereo mode. Do im missing something.
Needless to say, i did the mods Mr. Babin suggested to me 2 years ago (rellocatting 2 transistors to the heatsink, the B649 ones if i remember right...) and all worked well from a long time.
I would like oppinions for this. Thank you guys.
Leave both RCAs plugged in and move the speaker to check for boost.
If you move the shaft of the pot to the side or push down on it, does the boostless channel ever have boost?
If you move the shaft of the pot to the side or push down on it, does the boostless channel ever have boost?
You may need to replace the drivers. 2SB649's and 2SD669's were UTC devices and over time, became weak and caused the channel to lose power. Usually the 2SB649 was the culpret. Do what Mr Babin instructs and if its not the gain pot which is a distinct possibility,you may want to replace all of the drivers, one complemetary pair per channel. We (Kicker) replace the devices with Head Tek 2SB649's and 2SD669's, there may be other substitute devices if the Head Tek is unavailable.You may find a good substitute on in this forum.
Hi, thanks in advance guys.
Mr. Babin, i moved back and forth the bass boost variable control (and up and down) without any changes at the sound of the faulty channel. Did many times without luck. I think i need to discard a mechanical problem with the potentiometer.
Maybe the voltage regulators are the problem ? i checked my voltages at 15 and -15 volts and i have 14.72 and -14.71 , but i did not went with any further testing.
Very weird, having boost at one channel and not at the other...all other controls works as expected at both channels.......
Any suggestion would be appreciated. Thanks a lot.
Mr. Babin, i moved back and forth the bass boost variable control (and up and down) without any changes at the sound of the faulty channel. Did many times without luck. I think i need to discard a mechanical problem with the potentiometer.
Maybe the voltage regulators are the problem ? i checked my voltages at 15 and -15 volts and i have 14.72 and -14.71 , but i did not went with any further testing.
Very weird, having boost at one channel and not at the other...all other controls works as expected at both channels.......
Any suggestion would be appreciated. Thanks a lot.
I'm not convinced.
I have a junk preamp board here and the pot had to be turned hard into both of the high and low stops for it to read as 0 ohms between the wiper and the high/low terminals. To get it to read a as 1/2 of it's rated resistance when it's centered (as it should) I had to push down hard on the knob. The pot looks and feels flawless but neither section is good.
Using the attached diagram, confirm that you read 0 ohms between the wiper and the corresponding high/low terminals when the pot is in either extreme position. Then set the pot in the center position and confirm that you read approximately 9k ohms between the wiper and the corresponding high/low terminals. Do this without touching the knob or shaft of the pot.
I have a junk preamp board here and the pot had to be turned hard into both of the high and low stops for it to read as 0 ohms between the wiper and the high/low terminals. To get it to read a as 1/2 of it's rated resistance when it's centered (as it should) I had to push down hard on the knob. The pot looks and feels flawless but neither section is good.
Using the attached diagram, confirm that you read 0 ohms between the wiper and the corresponding high/low terminals when the pot is in either extreme position. Then set the pot in the center position and confirm that you read approximately 9k ohms between the wiper and the corresponding high/low terminals. Do this without touching the knob or shaft of the pot.
Attachments
Im back with the testing results:
B WIPER / B Low = 0.01 ohms wide open
B WIPER / BHigh = 19.38 k ohms wide closed
B WIPER / Center shaft Position = 9.09 k ohms
All the previous readings are reversed when moving the pot. It looks like B WIPER operates correctly.
But A WIPER gave me infinite ohms (no reading) at A Low and A High, regardless of the pot position.
I think this is the culprit , right ? what would be a suitable replacement for this part ?
Here are some pictures of my tests ...(not all were included)
Thanks in advance.
B WIPER / B Low = 0.01 ohms wide open
B WIPER / BHigh = 19.38 k ohms wide closed
B WIPER / Center shaft Position = 9.09 k ohms
All the previous readings are reversed when moving the pot. It looks like B WIPER operates correctly.
But A WIPER gave me infinite ohms (no reading) at A Low and A High, regardless of the pot position.
I think this is the culprit , right ? what would be a suitable replacement for this part ?
Here are some pictures of my tests ...(not all were included)
Thanks in advance.
Attachments
Yep. it looks like its toast...or not ? it doesnt looks good....or what if i do a good cleaning ?
Removed and dissassembled the pot from the preamp board.
It says B20K, that is the name of the replacement , right ? or there are another suitable replacement ?
Thanks a bunch,
Removed and dissassembled the pot from the preamp board.
It says B20K, that is the name of the replacement , right ? or there are another suitable replacement ?
Thanks a bunch,
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Last edited:
B is the taper of the resistive elements. 20K is the resistance of the elements.
If the problem was an intermittent connection to the wiper, cleaning may help but if the pot is open across the element, it's not likely to be salvaged.
You can wire two individual 20k pots to see if thew circuit is otherwise OK.
Maybe PapaZBill can help. He's a repair tech at Kicker.
If the problem was an intermittent connection to the wiper, cleaning may help but if the pot is open across the element, it's not likely to be salvaged.
You can wire two individual 20k pots to see if thew circuit is otherwise OK.
Maybe PapaZBill can help. He's a repair tech at Kicker.
These ports always go bad on the kickers.Last time i got that problem i went ahead and change all of them.
KX 500.2
I used a port like this,but i got it from Allied Electronics.The shaf was longer so i
cut on it.
RK12L12C0A0A ALPS | Mouser
KX 500.2
I used a port like this,but i got it from Allied Electronics.The shaf was longer so i
cut on it.
RK12L12C0A0A ALPS | Mouser
Thanks for all the responses.
I did some cleaning of the pot, and the metal parts. Reassembled and tested , and i got readings at A WIPER, very similar to B WIPER. Checked if i had a smooth measurement and looked ok. I decided to reinstall at the preamp board and reassemble amplifier, and yep, it worked as normal. Both bass boost channels are now operating correctly. Even i got rid of a very faint sound at that faulty channel.
I will be looking for replacements anyway, i understand this is a temporary fix, but definitively this was the problem.
Thanks for all the responses. Thank you guys !!!
I did some cleaning of the pot, and the metal parts. Reassembled and tested , and i got readings at A WIPER, very similar to B WIPER. Checked if i had a smooth measurement and looked ok. I decided to reinstall at the preamp board and reassemble amplifier, and yep, it worked as normal. Both bass boost channels are now operating correctly. Even i got rid of a very faint sound at that faulty channel.
I will be looking for replacements anyway, i understand this is a temporary fix, but definitively this was the problem.
Thanks for all the responses. Thank you guys !!!
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