Hi
What is the voltage on pin8,11. If voltage is 7-9v, drop must be happening on that 10 ohm resistor + transistor. And that I think is circuit for remote on. What voltage do you have for remote on?
Use scope to see if voltage drops on that transistor + resistor (10) There shouldn't be any, well very small, through goes all of the current for the circuit.
What is the voltage on pin8,11. If voltage is 7-9v, drop must be happening on that 10 ohm resistor + transistor. And that I think is circuit for remote on. What voltage do you have for remote on?
Use scope to see if voltage drops on that transistor + resistor (10) There shouldn't be any, well very small, through goes all of the current for the circuit.
I agree with Luka
Theres some wrong with
A) the A1273 transistor Circuit. I gather that there is more circuity around the Base of that transistor. Maybe to shut the amp down Protection. Measure the Base to emitter. It should be more than 1v other wise the transitor will start to turn Off.
B) The Collector of this Transistor should be close to Battery Voltage BTW whats the Voltage actually at the +Batt point on the schematic?
C) Are you sure you put the Driver Tansistor A1015 in correctly
That Bump at the waveform Bottom suggests to me that is not turning fully ON. I know you should not need to do this, But add a 1k resistor between the emitter and collector of the A1015 driver, Just to see if it helps the waveform.
As this type of driver stage technically wont clamp lower than 1.2v
but they always seam to.
As for that High pitched noise in the output of the amp.
Can you hear it when a Subwoffer driver is connected. As I am under the impression that This amp is for SUB only and as such usually have poorer quality output filters as Subs can pass on the noise of the switching pulses.
Cheers
Brett
Theres some wrong with
A) the A1273 transistor Circuit. I gather that there is more circuity around the Base of that transistor. Maybe to shut the amp down Protection. Measure the Base to emitter. It should be more than 1v other wise the transitor will start to turn Off.
B) The Collector of this Transistor should be close to Battery Voltage BTW whats the Voltage actually at the +Batt point on the schematic?
C) Are you sure you put the Driver Tansistor A1015 in correctly
That Bump at the waveform Bottom suggests to me that is not turning fully ON. I know you should not need to do this, But add a 1k resistor between the emitter and collector of the A1015 driver, Just to see if it helps the waveform.
As this type of driver stage technically wont clamp lower than 1.2v
but they always seam to.
As for that High pitched noise in the output of the amp.
Can you hear it when a Subwoffer driver is connected. As I am under the impression that This amp is for SUB only and as such usually have poorer quality output filters as Subs can pass on the noise of the switching pulses.
Cheers
Brett
The following was measured during hits hard enough to make the battery voltage sag.
voltage / v-drop on + batt: 12v / 1 to 2v
Voltage on Pin 8,11: 10 to 12v
voltage on Pin 12: ~10v
Voltage on Remote On: 11 to 12v
Voltage / v-drop on transistor collector: same as Pins 8,11
Voltage / v-drop on transistor base: 11v / 1v
Voltage / v-drop on transistor's emitter: 12v / 1 to 2v
a) There is no more circuitry around the base of this transistor in the area. If there is any additional circuitry, it occurs underneath some big caps. The trace I named +batt goes underneath the big caps, and I can't be sure what happens under there. I never see it emerge, but it shows continuity to the +batt terminal.
b) It is. Voltage / v-drop at +batt point: 12v / 1 to 1.5v
c) I'm quite sure the A1015s are in correctly. They had the same pinout as the originals (A1266), and they are all in the same direction as a Picture I took before I began repairs. I also drew which went where before taking out the old ones, and double checked as I took them out, so unless I royally screwed up, they are in correctly. Adding the resistor to the A1015 made only the slightest difference in the off portion of the waveform. It sloped to 0 just slightly harder, so little I almost didn't notice it. Image attached with before/after cut and paste into the same image. Top waveform is after, bottom is before resistor.
The 8" I've been using is a woofer, not a sub. I'll try later with an actual sub. I suspected as much as you said, about the poorer quality of output filters and the designers expecting the natural inductance of a sub to filter the remaining high frequencies.
voltage / v-drop on + batt: 12v / 1 to 2v
Voltage on Pin 8,11: 10 to 12v
voltage on Pin 12: ~10v
Voltage on Remote On: 11 to 12v
Voltage / v-drop on transistor collector: same as Pins 8,11
Voltage / v-drop on transistor base: 11v / 1v
Voltage / v-drop on transistor's emitter: 12v / 1 to 2v
a) There is no more circuitry around the base of this transistor in the area. If there is any additional circuitry, it occurs underneath some big caps. The trace I named +batt goes underneath the big caps, and I can't be sure what happens under there. I never see it emerge, but it shows continuity to the +batt terminal.
b) It is. Voltage / v-drop at +batt point: 12v / 1 to 1.5v
c) I'm quite sure the A1015s are in correctly. They had the same pinout as the originals (A1266), and they are all in the same direction as a Picture I took before I began repairs. I also drew which went where before taking out the old ones, and double checked as I took them out, so unless I royally screwed up, they are in correctly. Adding the resistor to the A1015 made only the slightest difference in the off portion of the waveform. It sloped to 0 just slightly harder, so little I almost didn't notice it. Image attached with before/after cut and paste into the same image. Top waveform is after, bottom is before resistor.
The 8" I've been using is a woofer, not a sub. I'll try later with an actual sub. I suspected as much as you said, about the poorer quality of output filters and the designers expecting the natural inductance of a sub to filter the remaining high frequencies.
Attachments
Yeah, Without knowing what this models waveform is normal. Call it fixed! And put it all back together.
I suspect its just the way its designed.
I personally use Proper Driver Chips form IR to drive fets. They have Mosfet output stages and Clamp really good.
Those little drivers in this amp cant handle much current.
Cheers
Brett
I suspect its just the way its designed.
I personally use Proper Driver Chips form IR to drive fets. They have Mosfet output stages and Clamp really good.
Those little drivers in this amp cant handle much current.
Cheers
Brett
I asked Perry about it (from bcae1.com/) and he said the buffer is a voltage follower, and it cannot output more V than supplied.
Since the output of the TL494 at pins 9 and 10 are at a peak of ~7.8 volts, even though the A1015's collectors are at 12 volts, the most the buffers can output is 7.8 - 0.6 = 7.2 volts. The 0.6 is typical diode voltage drop (the diode drop from the transistor), and the 7.8 volts is because it's a voltage follower and that's how much voltage is being applied to the base.
So I've buttoned it back up and am calling it fixed.
Thanks for all your help guys!
Since the output of the TL494 at pins 9 and 10 are at a peak of ~7.8 volts, even though the A1015's collectors are at 12 volts, the most the buffers can output is 7.8 - 0.6 = 7.2 volts. The 0.6 is typical diode voltage drop (the diode drop from the transistor), and the 7.8 volts is because it's a voltage follower and that's how much voltage is being applied to the base.
So I've buttoned it back up and am calling it fixed.
Thanks for all your help guys!
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.