| AudioAddicted |
Hi everybody.
I have a pioneer Power Amplifier for Car use.(it is supplied at 12V).
Well this amp came in my hands from a friend of mine. It is a used amp but it is really good. and I liked that gift. But when i connect it to the 12V power suply it doesn't make any thing at all.....just like dead..... No led turns on and there is no sound at the loudspeaker, it doesn't even warm up just a little bit (at the supply transistors and the amp FET-s. It works with PWM power supply in the DC/AC converter). Well i can not figure it out what to do with that. I really don't want to send it to rubish cause it is a real quality stuff. when i opened it up there were no signs of burns inside.Can u help me? Ill send u some photos tomorow for further detail. thanks in advance. |
|
|
| keith721 |
| Is there an additional line that should be connected to your head unit? Typically, these power amps get their voltage directly from the battery, but won't switch on unless they see power on a separate line. Typically, they use the same line that raises your power antenna. |
|
|
| Stocker |
| If it's labelled in english, there may be a terminal near the power connections called "remote", for the remote turn-on lead. When the head unit turns on this lead goes to "12V" and the amplifier senses the voltage and turns on. Jumper this to the 12V supply on the (+) and it should turn on if all else is well. |
|
|
| AudioAddicted |
NO there is no other line to connect to the head unit.(U mean the remote control, don't u? The one that turns on the amp if connected to the positive pole of the battery). Usually it is suited between the positive and the negative pins of the supply in the amp. Did I understood that well? Correct me if I am wrong.
I am afraid there is something at the DC/AC converter in the supply unit of the amp and I really don't understand that mess. There are some of IC-s and plenty of little transistors there. Any one of them can be dead and I think I can not find which one without your help.
Sorry about the photos that I promised before but I had some trouble with the rechargable batteries of the camera. Something with the charger. I'll fix that tonight and the photos will be available the next morning. |
|
|
| AudioAddicted |
Hello everybody,
As I promised yesterday, I brought some photos of my Pioneer.
I tried to connect it to a dual voltage transformer, as u can guess, +18v, -18v so that I could understand if the supply DC/AC converter had died too. (I have done that before successfully) well it wont give a sign of life even now. I think I have got to find a remote line to connect to the +12V but I can't find it. THEORETICALLY it should switch on after i connect it to the +12v.
Now it's in your hands. Help me please!!! |
|
|
| AudioAddicted |
| another photo |
|
|
| AudioAddicted |
| circuit photo |
|
|
| AudioAddicted |
Sorry I am new in this forum and maybe i am not posting at the right place, but I wanted to ask a simple question:
Which model of pioneer amp is the one on the photo below? Any identification code will be helpful. |
|
|
| Perry Babin |
The amp appears to be the same as a Pioneer GM-1000/2000. It may be labeled differently outside of the US.
There is a 4 pin plug. The two center pins labeled acc and B/R need 12 volts for the amp to power up. Connect them to a 12 volt power source via a 3 amp fuse. |
|
|
| AudioAddicted |
| thanks Perry Babin that was it. when I connected the B/R and ACC to +12v the amp switched on. I was delighted till the time i proved it to some music. I can't understand where is the point. When I play it to really low volume (at about 5-10%) it sounds OK in quality but when I get it a little bit louder then the music comes out with some distortion like scratching on something. It is really noticeable. I THINK there is something at the preamp maybe. a friend of mine has the same problem too, identically. what should I do now? I don't know where to check for any blown transistor or op amp. |
|
|
| Perry Babin |
Check the voltage across the B+ and ground terminals on the amp when it sounds distorted. It shouldn't drop much below 12 volts with the engine off. With the engine running, the voltage should remain above 13v.
Turn the gains up and down and listen carefully to the system at both low and high gain. If the distortion begins at the same position on the volume control, the problem is likely in the head unit. If the distortion begins at the same output level (the level of sound you hear, not the volume position), the amp is likely at fault.
These tests won't mean much if the voltage is dropping too much. If you have low voltage, fix that problem first. |
|
|
| AudioAddicted |
first of all lets make clear that my amp isn't mounted in the car. I have it at home where i use as audio source my PC computer. The amp is fed by a 220 to 12V transformer with an ac/dc converter of 25 amperes. It's a long time i have been using this supply unit and it is tested with a lot of other amplifiers with the same audio source (my PC), I mean that I am sure it isn't the supply that causes the problem.
Well i have tried "playing" with gain and other features of the amp like bridged or not bridged and high pass, full, or low pass and the result is always the same:
the distortion comes at the same level of the sound I hear. I don't think there is a problem at the main FET transistors. they are really ok. I am afraid there is something at the preamp, but i can't say what. Thats why I need your help. |
|
|
| Perry Babin |
| Distortion is very difficult to troubleshoot without seeing waveforms and tracing the signal. I'd recommend that you reassemble it fully and try it in a vehicle. |
|
|
| AudioAddicted |
| I don't think trying it in a vehicle will make any difference. It will give the same result, I am sure. the supply I am using is absolutely OK. The distortion is like the sound from a loudspeaker driven by an amp when the amp's power is exceeded but I am sure there are not the main FET transistors of the output power, so I guess there is any operational amp at the preamp which puts in distorted signal into the power amp. what do you think? |
|
|
| heiki |
| quote: | Originally posted by AudioAddicted
I don't think trying it in a vehicle will make any difference. It will give the same result, I am sure. the supply I am using is absolutely OK. The distortion is like the sound from a loudspeaker driven by an amp when the amp's power is exceeded but I am sure there are not the main FET transistors of the output power, so I guess there is any operational amp at the preamp which puts in distorted signal into the power amp. what do you think? |
First of all, sorry for bringing up this old thread.
I have the same amplifier, and also exactly the same problem. Distortion begins at under 1V from speaker output, and I couldn't get clean sinewave to scope at all.
FET's get +-20.7V, and it doesn't drop as the volume rises.
The amplifier driver IC uPC1298V gets stable +-19.0V, which is one volt under recommended voltage from datasheet (+-20 to 46V). Could that be a problem? |
|
|
| heiki |
| Here is 1khz sine wave from speaker output. |
|
|
| Perry Babin |
Is the signal going into the 1298 clean?
Is the output of the other channel clean? |
|
|
| heiki |
| Input signal in 1298 is distorted and both channels have same problem. |
|
|
| Perry Babin |
| Trace the signal back. ICs 2, 4 and 5 are the only other ICs in the circuit (assuming this is precisely like the GM-1000). The output pins of the ICs are 2 and 8. Which of the outputs are noisy/distorted? |
|
|
| heiki |
| I found out, that after turning on the amplifier, signal from the source gets distorted. |
|
|
| Perry Babin |
If you connect the ground clip of your scope probe to the shield of the RCAs, is the noise level reduced?
Is the signal source's ground connected to the power supply ground? |
|
|
|
