Perry
I have a bd1501 that I thought I had finish repairing. I had output the rail switchers and audio were switching properly. So i removed the pot from u17 and reattached r31 &35. I powered up tha amp and notice it was drawing around 5 amps. I checked and made sure outputs weren't getting hot and proceeded with checking the output with a 60hz signal. Amplifier produced clean output. I switched the 0/180 button and poof there went the rail switchers and 24.9 ohm resistors. Now that I have repaired it again I am at the same problem. I am going to replace u3 &u4 and see if it fix the problem. Any ideas....
I have a bd1501 that I thought I had finish repairing. I had output the rail switchers and audio were switching properly. So i removed the pot from u17 and reattached r31 &35. I powered up tha amp and notice it was drawing around 5 amps. I checked and made sure outputs weren't getting hot and proceeded with checking the output with a 60hz signal. Amplifier produced clean output. I switched the 0/180 button and poof there went the rail switchers and 24.9 ohm resistors. Now that I have repaired it again I am at the same problem. I am going to replace u3 &u4 and see if it fix the problem. Any ideas....
When you power it up again, make sure that the output on U17 (no input signal) is essentially a straight line on the scope. If you see excessive oscillation or noise on that pin shut the amp down and re-check the connections on the resistors and the IC.
Before I tried that I un hooked r35, powered it up same thing. Okay It has a few random spikes but other than that the output is steaight. Even when the r31 and 35 out of the circuit it is around 3 to 4 amps. Seems like when it is forced to - or + voltage manually it has less current draw.
3.37amps at idle. Amp is out of the heatsink. Let amp stayed powered to watch current draw. Noticed the audio outputs are starting to get warm but rail switchers are not. When I got the amp the rail switchers and powersupply fets were toast. I have replaced the audio outputs, u8, or u9.
Okay fets went pop again......uhggggg. amp plays perfectly fine on rockford 12" 4 ohm sub. I can give it up to 52 amps on powersupply. It blows the rail switchers like a firecracker when you flip the 0/180 phase switch.. hmmmm any thoughts. I have definitely perfected the art of popping FETS this week. Haha
These amps are sensitive to high frequency input to the class D section. It's likely that the 0/180 switch has dirty contacts and is driving a signal that would sound sort of 'scratchy'. After removing the defective FETs, look at the signal on the output pin of U4 to see if you see a noisy signal when you move the switch. If you do, clean the switch to see if you can get it to switch properly. If you cannot, replace it. For testing, you could solder a jumper in place of the switch to confirm that the amp is otherwise working properly.
Okay I will try that I already replaced u4 & u3 before I blew the fets. This is the pro series bd1501. I did think the 3.7 amps at idle was high. Giving it one more chance out opto couplers running low on parts.. expensive learning curve huh...I blew the fets last time I switched that switch. This time atleast it didn't take the 24.9 ohm resistors with them. Its pretty instantaneous on the. Fets blowi g when you switch the phase 0/180
Perry I replaced the switch and fets this morning and the ic driver. Powerd unit up and idle current was around 3.2 amps. I also replaced both voltage regulators closest to the switches. Had nice audio output. Disconnected speaker and audio input. Flipped subsonic filter switch and rail switchers go boom. Any ideas
Did you confirm that the switch was switching cleanly while the output transistors were out of the circuit?
9.73 is the supply voltage likely.
You would only check to see if there was significant DC on the output pins of the op-amps. Should be pins 1 and 7. Pins 4 and 8 are the supply pins.
Do any of the switches have DC on the metal casing?
As Perry mentioned did you confirm the switches were switching cleanly with the output removed?
It almost sounds like a defective op-amp somewhere sending a spike of DC into the class D input.
You would only check to see if there was significant DC on the output pins of the op-amps. Should be pins 1 and 7. Pins 4 and 8 are the supply pins.
Do any of the switches have DC on the metal casing?
As Perry mentioned did you confirm the switches were switching cleanly with the output removed?
It almost sounds like a defective op-amp somewhere sending a spike of DC into the class D input.
The outputs swing from -8.48 to 8.26 when pot is installed. I did not check for dc on the housing of the switch. I replaced the switches to rule outn scratchy ones. I will remove the mesha board with outputs and check ti see if there is a spike.
New old-stock components are not necessarily up to spec. You need to switch it back and forth while the outputs are out of the circuit or the output stage is disconnected from U4 to confirm that there is no significant noise as you move the switch from one position to another. Switch it slowly and repeatedly as you watch the output from U4.
2v is OK but you'd want 2ms.
You should see the audio signal and nothing else. If you see a short burst of high frequency noise, that could cause problems. A slight DC pulse isn't a problem, well it isn't a problem that's going to cause the amp to fail. The problem that causes the outputs to fail is a high frequency signal being driven into the output stage.
You should see the audio signal and nothing else. If you see a short burst of high frequency noise, that could cause problems. A slight DC pulse isn't a problem, well it isn't a problem that's going to cause the amp to fail. The problem that causes the outputs to fail is a high frequency signal being driven into the output stage.
Okay guys,
There is no dc voltage on the housing of the switches and no spikes on pin 1 and 7 of u4. I did notice that the output on u17 is around 2v. I am guessing this value is off since outputs are removed. When I place scope prone on pin 6 and switch position sometimes it changes sometimes it doesn't eventually back to 2v. Sometimes it jumps to 9v or -9v then back to the 2v.
There is no dc voltage on the housing of the switches and no spikes on pin 1 and 7 of u4. I did notice that the output on u17 is around 2v. I am guessing this value is off since outputs are removed. When I place scope prone on pin 6 and switch position sometimes it changes sometimes it doesn't eventually back to 2v. Sometimes it jumps to 9v or -9v then back to the 2v.
Well I haved replaced. U3, u4, u5, u17, u18, u21, u6, u7, u8, ic drivers, optocouplers, rail switchers, and half of the powersupply fets......there is no money in this one for it has depleated my parts inventory..haha
This is goung to be the expensive lesson to learn...
This is goung to be the expensive lesson to learn...
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