Hello everyone. I recieved this t30001 in for repair. It belongs to a friend of mine. The complaint was pulsing of the speakers and low output. I have not tested it for audio myself, but will soon I have a few other amps to finish up on.
I powered it up on the bench and there is a pulsing buzzing noise from the power supply and then when the protect light goes out there is a pulsing chirping noise from the output side.
I dont know alot about this particular amp and have never worked on a amp this big.
The only thing I have done so far is tested to see if thier was DC on the output terminals and there was not.
Just wondering if someone could point me in the right direction as in where to start???
Thanks again.
I powered it up on the bench and there is a pulsing buzzing noise from the power supply and then when the protect light goes out there is a pulsing chirping noise from the output side.
I dont know alot about this particular amp and have never worked on a amp this big.
The only thing I have done so far is tested to see if thier was DC on the output terminals and there was not.
Just wondering if someone could point me in the right direction as in where to start???
Thanks again.
Last edited:
OK just tested for sound. The amp does produce sound but it is very distorted and you can here the pulsing chirp from the speaker and the speaker pulses in and out the whole time.
My friend did indicate he had a previous problem with the cross over frequency pot and had it replaced. Apparentely they replaced it with the wrong one and had to bring it back to replace it with the right one.
He said the amp worked good then he hooked up some new subs and hit some hard notes dropping the volt meter to 8 volts in his ride and this is when the problem occurred.
The amp does not draw excess current but pulses while idling on my power supply amp meter but not much. You can hear the pulsing buzzing on the power supply side and the pulsing chirp on the output side, I tried with and without an input signal with same result.
I tried all the knobs and switches the only thing I noticed is the gain has to be all the way up for the sound to work, if its not all you here is the pulsing chirp and staticy squeelch noise.
Hope someone can steer me in the right direction......Thanks
My friend did indicate he had a previous problem with the cross over frequency pot and had it replaced. Apparentely they replaced it with the wrong one and had to bring it back to replace it with the right one.
He said the amp worked good then he hooked up some new subs and hit some hard notes dropping the volt meter to 8 volts in his ride and this is when the problem occurred.
The amp does not draw excess current but pulses while idling on my power supply amp meter but not much. You can hear the pulsing buzzing on the power supply side and the pulsing chirp on the output side, I tried with and without an input signal with same result.
I tried all the knobs and switches the only thing I noticed is the gain has to be all the way up for the sound to work, if its not all you here is the pulsing chirp and staticy squeelch noise.
Hope someone can steer me in the right direction......Thanks
Check the output pins of all of the op-amps, do any have significant DC?
Is the output filter inductor loose on the board?
Does having the subsonic filter on help?
With the black meter probe on leg 3 of Q431 and the red probe on the center leg of Q430, what is the voltage?
Does the voltage remain steady with and without driving a signal into a load?
Is the output filter inductor loose on the board?
Does having the subsonic filter on help?
With the black meter probe on leg 3 of Q431 and the red probe on the center leg of Q430, what is the voltage?
Does the voltage remain steady with and without driving a signal into a load?
Perry getting back to this amp the last question you had asked you want me to check if the voltage is steady with or without a signal driving a load?
If so you want me to hook a load to the amp with no signal and check the voltage too? Just want to be clear.
Output Filter Inductor loose on the board: NO
The sub sonic switch make a difference? : NO
Black Probe to leg 3 of Q431 and Red Probe to middle leg of Q430 I get a constant 117.8 VDC
Voltage remains steady with or without signal with or without a load between the legs you wanted tested and in accordance with how you requested.
I have not checked for dc voltage on the outputs for the op-amps yet.
I believe you want pins 1 and 7 on all the TL072C'S?
The sub sonic switch make a difference? : NO
Black Probe to leg 3 of Q431 and Red Probe to middle leg of Q430 I get a constant 117.8 VDC
Voltage remains steady with or without signal with or without a load between the legs you wanted tested and in accordance with how you requested.
I have not checked for dc voltage on the outputs for the op-amps yet.
I believe you want pins 1 and 7 on all the TL072C'S?
OK Perry bare with me here........................
U304
Pin 1: 2.171 vdc
Pin 7: -4.35 vdc and when tested makes amp go into protection
U306
Pin 7: -1.679 vdc
U307
Has no significant DC but testing pin 7 makes the amp go into protect.
All of the other op-amps have no more than 0.635 vdc on pins 1 and 7.
Thoughts????? Sounds like I may have a defective op-amp????
U304
Pin 1: 2.171 vdc
Pin 7: -4.35 vdc and when tested makes amp go into protection
U306
Pin 7: -1.679 vdc
U307
Has no significant DC but testing pin 7 makes the amp go into protect.
All of the other op-amps have no more than 0.635 vdc on pins 1 and 7.
Thoughts????? Sounds like I may have a defective op-amp????
Yes I do.
Although I may still need your help.
It kinda reminds me of a BD1500 with the bad op-amp you helped me fix along time ago. I am not sure but the wierd stuff the amp is doing with the pulsing and chirping and popping noises through the speaker.
Wierd thing is it has noises coming from the power supply side and the output side. The internal frequency or chirping sound coming from the output side is transfered to the speaker when its hooked up.
So how could the output switch from positive to negative? Could the op-amp be defective in a way that could cause this?
Although I may still need your help.
It kinda reminds me of a BD1500 with the bad op-amp you helped me fix along time ago. I am not sure but the wierd stuff the amp is doing with the pulsing and chirping and popping noises through the speaker.
Wierd thing is it has noises coming from the power supply side and the output side. The internal frequency or chirping sound coming from the output side is transfered to the speaker when its hooked up.
So how could the output switch from positive to negative? Could the op-amp be defective in a way that could cause this?
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.