Hello. As the title states, I am a new user here. I was directed to these forums by the Basic Car Audio Electronics web site.
I have an issue, well, 2 actualy, with a Jensen 500w Bridgeable power amplifier. It's model XA 2250.
My more major issue is, if I have the level set to anything over half way, it will immediatly blow the inline fuse. It does not matter if it has remote or not. It's basically, plug the fuse in, and as soon as the blades complete the circuit, it blows the fuse. Again, ONLY when the level is set to over half way on the amp.
It is not dependant on what speakers I have connected. I've also been able to recreat it many times using my test bed consisting of a 500w computer power supply (sends the PSU into protect/short mode).
Problem #2. The right channel positive output doesnt' seem to have anything going to it. I dont know if thise is related to the original problem or not.
There is not scoring inside the amp, no debris, or any telling smell.
Any help is appreciated. I would like to get this corrected so I dont have to buy a new amp, being that I'm broke.
I have an issue, well, 2 actualy, with a Jensen 500w Bridgeable power amplifier. It's model XA 2250.
My more major issue is, if I have the level set to anything over half way, it will immediatly blow the inline fuse. It does not matter if it has remote or not. It's basically, plug the fuse in, and as soon as the blades complete the circuit, it blows the fuse. Again, ONLY when the level is set to over half way on the amp.
It is not dependant on what speakers I have connected. I've also been able to recreat it many times using my test bed consisting of a 500w computer power supply (sends the PSU into protect/short mode).
Problem #2. The right channel positive output doesnt' seem to have anything going to it. I dont know if thise is related to the original problem or not.
There is not scoring inside the amp, no debris, or any telling smell.
Any help is appreciated. I would like to get this corrected so I dont have to buy a new amp, being that I'm broke.
What do you mean by 'level' (gain control position, input level from head unit)?
Without the remote, no level control/input should make a difference. Are you sure the amp is switching off when remote voltage is removed?
At a low 'level' (where the fuse won't blow), are you saying that the left channel works properly but the right channel has no output? If so, have you tried moving all controls and switches to determine if a dirty contact is causing the right channel to lose signal?
Also try moving the RCAs where they plug into the amp. Sometimes they get loose and cause one channel to go out.
Do you have a multimeter?
Without the remote, no level control/input should make a difference. Are you sure the amp is switching off when remote voltage is removed?
At a low 'level' (where the fuse won't blow), are you saying that the left channel works properly but the right channel has no output? If so, have you tried moving all controls and switches to determine if a dirty contact is causing the right channel to lose signal?
Also try moving the RCAs where they plug into the amp. Sometimes they get loose and cause one channel to go out.
Do you have a multimeter?
Perry Babin said:
Alright, lemme see if I can answer this systematically.
The level I am talking about is on the amp itself, grouped with the High and Low pass filter setting knobs.
I'm fairly certain it's switching off, no power lights are on, and no output is there when I use an MP3 player with it.
The left and bridged both work fine when the amp isn't blowing fuses. The bridged uses the left channel + with the right channel -. And I have moved each and every switch and pot multiple times. I've used this amp to power everything from subs to mids and tweeters, using the appropriate settings for each
And I am fairly certain that it's not the cables since I have used quite a few different sets. And have also run it with just left and just right plugged in.
And last question, yes, I have a multimeter. I just wish I still had my good one, but that got stolen a while back, so the one I have will have to do.
Will the amp blow the fuse with nothing plugged into the RCA jacks?
Will it blow the fuse with the ipod plugged in but with no speakers connected?
A signal source with an isolated ground (like an ipod) can cause some amps to do strange things. Have you tried a different signal source (standard head unit)?
Pull the cover and measure the DC voltage from the left negative speaker terminal to the center leg of the output transistors. The output transistors are the large 3-legged devices under the clamps. Check all 8 of them with the remote on and with the remote off. Wait ~1 minute after removing the remote voltage before checking the voltage. You should read something near plus/minus 35v with the remote on and ~0v with the remote off.
With the amp disconnected from the supply, measure the resistance from the left - to the B+ terminal of the amp. It should read something significantly higher than 0 ohms.
Measure the resistance from the RCA shield to the L- speaker terminal. It should read ~0 ohms.
Measure the resistance from the chassis ground terminal to the L- speaker terminal. It should be well above 0 ohms.
Since the amplifier works properly in bridged mode, the power amplifier for the right channel is probably working properly. The fault is likely in-between the input circuit and the front end of the power amplifier circuit. It could be a defect in the muting circuit or a broken connection.
Will it blow the fuse with the ipod plugged in but with no speakers connected?
A signal source with an isolated ground (like an ipod) can cause some amps to do strange things. Have you tried a different signal source (standard head unit)?
Pull the cover and measure the DC voltage from the left negative speaker terminal to the center leg of the output transistors. The output transistors are the large 3-legged devices under the clamps. Check all 8 of them with the remote on and with the remote off. Wait ~1 minute after removing the remote voltage before checking the voltage. You should read something near plus/minus 35v with the remote on and ~0v with the remote off.
With the amp disconnected from the supply, measure the resistance from the left - to the B+ terminal of the amp. It should read something significantly higher than 0 ohms.
Measure the resistance from the RCA shield to the L- speaker terminal. It should read ~0 ohms.
Measure the resistance from the chassis ground terminal to the L- speaker terminal. It should be well above 0 ohms.
Since the amplifier works properly in bridged mode, the power amplifier for the right channel is probably working properly. The fault is likely in-between the input circuit and the front end of the power amplifier circuit. It could be a defect in the muting circuit or a broken connection.
Yes, it blows the fuse with nothing at all plugged in. And I was using it with my standard pioneer hu. I only plugged in my mp3 player when I was tinkerying around with it.
And how do you want me to measure it. With the level down to the point where it's stable? Or what? Cause if I dont, all it will be getting is the negative and remote.
And what exactly do you mean by RCA shield? the outer ring on the input connector?
And how do you want me to measure it. With the level down to the point where it's stable? Or what? Cause if I dont, all it will be getting is the negative and remote.
And what exactly do you mean by RCA shield? the outer ring on the input connector?
to my understanding
our friends problem should be located not in the outputs but mostly in the power supply .....
should be one of the mosfets leacky or something and at low levels is working and then more current draw drives to almost shortcircuit .....
it could just as well be a mosfet drive issue and goes on ....
but from what i see here our friend will be not able to locate such a problem ....
mostly issues like that are no cable/gain.source related .....
our friends problem should be located not in the outputs but mostly in the power supply .....
should be one of the mosfets leacky or something and at low levels is working and then more current draw drives to almost shortcircuit .....
it could just as well be a mosfet drive issue and goes on ....
but from what i see here our friend will be not able to locate such a problem ....
mostly issues like that are no cable/gain.source related .....
Re: to my understanding
Well, thank you for writing me off before I've even managed to really start this project. I cannot tell you how much your faith in me fills me with joy!
Anyways, back to the real problem at hand: Apparently, the last time I tried this, the amp actualy managed to blow out my PSU, and I dont have another one. So doing anything on the bench is out.
Also, I have one fuse, and as I said before, I am broke... So it looks like I am going to have to put this project off untill I can either pick up another PSU or grab some more fuses.
sakis said:
Well, thank you for writing me off before I've even managed to really start this project. I cannot tell you how much your faith in me fills me with joy!
Anyways, back to the real problem at hand: Apparently, the last time I tried this, the amp actualy managed to blow out my PSU, and I dont have another one. So doing anything on the bench is out.
Also, I have one fuse, and as I said before, I am broke... So it looks like I am going to have to put this project off untill I can either pick up another PSU or grab some more fuses.
Okay, so quick update. Had to grab my multimeter from the car. Was trying to figure out what's up with my power door locks on my old 89 S10 Blazer...
Anyways, I've got the readings.
The first reading: Left - terminal to 12v B+ terminal gives a a 1010 reading that steadily goes up 1 ohm per every 30-40 seconds.
The second reading: Left - to RCA Sleeve. All of them, both input and output, produce a good 0ohm reading.
The last test. Left- to chassis ground... Give a no connection reading. A clue maybe? Same with the Right- to chassis ground.
Edit, just tested the chassis ground strap itself and it's got a good 0ohm connection so it's not broken inside the jacket..
Edit #2. Shouldn't the power - terminal have a connection to the ground strap? Cause I'm not getting any reading between the 2.
Anyways, I've got the readings.
The first reading: Left - terminal to 12v B+ terminal gives a a 1010 reading that steadily goes up 1 ohm per every 30-40 seconds.
The second reading: Left - to RCA Sleeve. All of them, both input and output, produce a good 0ohm reading.
The last test. Left- to chassis ground... Give a no connection reading. A clue maybe? Same with the Right- to chassis ground.
Edit, just tested the chassis ground strap itself and it's got a good 0ohm connection so it's not broken inside the jacket..
Edit #2. Shouldn't the power - terminal have a connection to the ground strap? Cause I'm not getting any reading between the 2.
Well, we can now write off problem #2. It's not actualy a problem, it's a fricken design feature, flaw, take your pick...
It's not actualy a stereo amp, even though it claims to be. the right positive and left negative are mapped on the board in series... So it doesn't matter if I use this in bridged mode or not... Grr... Ohh well... No biggy...
It's not actualy a stereo amp, even though it claims to be. the right positive and left negative are mapped on the board in series... So it doesn't matter if I use this in bridged mode or not... Grr... Ohh well... No biggy...
The amp is a stereo amp. The L- and R+ are connected to ground (secondary ground). The L+ and R- are independent.
Everything else is OK (from the resistance readings you posted). I expected that you'd have less than 1000 ohms from chassis ground to the L- but it's not really important.
Let us know when you get a new supply. If you want another computer supply, you can probably get a used one from a computer repair shop for just a few bucks. To help protect the new supply, insert a 5 amp fuse in series with the B+ line feeding the amp. If you amp has only one fuse, you can replace the on-board fuse with the 5A fuse.
Until then, look for loose/broken connections. Broken or failing connections will typically have a crack/ring all around the solder connection.
Everything else is OK (from the resistance readings you posted). I expected that you'd have less than 1000 ohms from chassis ground to the L- but it's not really important.
Let us know when you get a new supply. If you want another computer supply, you can probably get a used one from a computer repair shop for just a few bucks. To help protect the new supply, insert a 5 amp fuse in series with the B+ line feeding the amp. If you amp has only one fuse, you can replace the on-board fuse with the 5A fuse.
Until then, look for loose/broken connections. Broken or failing connections will typically have a crack/ring all around the solder connection.
Yeah, I've looked the board over 10+ times, and have had my fiancee, who took a couple classes in electronics in college, look it over as well.
I'm gonna head over to our local Deseret Industries (THE Thrift store here in morman city) and see if I can pick up a 300+ watt PSU for cheap.
But alas, it is my 21st birthday tomarrow, so I really dont think I'll be getting much done
Hopefully I wont be too 
to do anything the next day though.
Question though, having the R+ connecting to ground, wouldn't that throw the right channel speaker out of phase?
I'm gonna head over to our local Deseret Industries (THE Thrift store here in morman city) and see if I can pick up a 300+ watt PSU for cheap.
But alas, it is my 21st birthday tomarrow, so I really dont think I'll be getting much done
Hopefully I wont be too to do anything the next day though.Question though, having the R+ connecting to ground, wouldn't that throw the right channel speaker out of phase?
You connect the wires just as shown above/below the terminal block.
The phase is relative. A negative (inverted) signal on the negative terminal is the same as a positive signal (of equal amplitude) on the positive terminal.
For more detailed information, read the following page:
http://www.bcae1.com/bridging.htm
The phase is relative. A negative (inverted) signal on the negative terminal is the same as a positive signal (of equal amplitude) on the positive terminal.
For more detailed information, read the following page:
http://www.bcae1.com/bridging.htm
Okay, that section explained alot of things enough that I have drawn my own conclusion to help understand it. You'll have to realize that I am a computer geek, with only a limited experiance in home audio. I have however repaired my father's SAE T102 a few times, as well as my Sansui 7900Z.
And, as both amps are non bridgeable, and supply the correct amount of power to the speakers attached to each of them, I've never really had to worry about bridging, or phase.
On a more on topic note, I have finally picked up some new fuses, and new wiring (the old stuff I hooked up quickly, and didn't take the time to hide it or anything) so tomarrow, as long as the wheather wasn't like it was today, I will wire it all up, and get those voltage readings.
And, on a completely off topic note, I got a $25 wally world gift card for my birthday (hence the new fuses and fuse block and wiring) and managed to get some automotive grade black carpet, and just finished carpeting up my twin 12 home made box! I'm happy. Lemme know if you wanna see picks of it.
And, as both amps are non bridgeable, and supply the correct amount of power to the speakers attached to each of them, I've never really had to worry about bridging, or phase.
On a more on topic note, I have finally picked up some new fuses, and new wiring (the old stuff I hooked up quickly, and didn't take the time to hide it or anything) so tomarrow, as long as the wheather wasn't like it was today, I will wire it all up, and get those voltage readings.
And, on a completely off topic note, I got a $25 wally world gift card for my birthday (hence the new fuses and fuse block and wiring) and managed to get some automotive grade black carpet, and just finished carpeting up my twin 12 home made box! I'm happy. Lemme know if you wanna see picks of it.
Bad news...
Got the wiring all set up, spent 2 hours just doing the wiring...
Get it all set up, go to put the fuse in, and there's a loud crack from inside the amp. About the same as a firecracker. Open it up and one of the fets has cracked...
The cost to replace them all, compared to the cost of finding a good used amp pretty much warrents that I am not going to be fixing it.
Thanks for the help anyway.
Got the wiring all set up, spent 2 hours just doing the wiring...
Get it all set up, go to put the fuse in, and there's a loud crack from inside the amp. About the same as a firecracker. Open it up and one of the fets has cracked...
The cost to replace them all, compared to the cost of finding a good used amp pretty much warrents that I am not going to be fixing it.
Thanks for the help anyway.
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