Owner stated this amp goes into protect. This is a Type 4 amp. It works until the amp draws about 15A from the bench. Input power voltage changes dont affect the outcome. When it pulls over this, the output waveform gets badly distorted and the amp also makes a slight buzzing sound. If pushed the amp will protect (DC offset?).
Any thoughts as to why the amp works <15A draw? Idles at 2A. Nothing shorted afaik.
Photo at terminals under load. 65hz sine wave.
Any thoughts as to why the amp works <15A draw? Idles at 2A. Nothing shorted afaik.
Photo at terminals under load. 65hz sine wave.
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It looks like it's either low-voltage protection or over-current protection.
What is the circuit board designation of the LM393 near the 494 driver IC?
Are the two shunt resistors near the output filter inductors in series between the inductors and the speaker terminals?
I'm assuming that this is like the skar RP-2000.1 since I have no photos.
What is the circuit board designation of the LM393 near the 494 driver IC?
Are the two shunt resistors near the output filter inductors in series between the inductors and the speaker terminals?
I'm assuming that this is like the skar RP-2000.1 since I have no photos.
LM393 is U7.
This board looks near identical to the RED board on the type 4 pages, only the board in this amp is actually dark-brown.
There are no driver cards in this amp. Everything is on the main PCB.
-YES
This board looks near identical to the RED board on the type 4 pages, only the board in this amp is actually dark-brown.
There are no driver cards in this amp. Everything is on the main PCB.
If you take the audio signal from the inductor side of those shunt resistors, that should bypass the over-current protection and may eliminate it as a problem.
I installed a solder/bridge from the inductor to the positive speaker terminal, bypassing the shunt resistor; and the issue remains.
I also notice the 3w 1k resistor between speaker terminals appears to have gotten very hot at one point. Its slightly brown in the middle but still measuring fine. Probably DC caused.
I also notice the 3w 1k resistor between speaker terminals appears to have gotten very hot at one point. Its slightly brown in the middle but still measuring fine. Probably DC caused.
With the bridge, does it go into protect at precisely the same output level?
Does pin 1 of U7 go high on protect?
Does pin 1 of U7 go high on protect?
Yes precisely same output level with the bridge.
Pin1 of U7:
At idle: 5.0vDC
When output distorts: 5.15vDC
Unloaded: Stays at 5vDC even at clipping
Pin1 of U7:
At idle: 5.0vDC
When output distorts: 5.15vDC
Unloaded: Stays at 5vDC even at clipping
Its pretty straight. Maybe a little wobble but not a lockable signal.
I found C3, a small SMD cap connected to pin #8 of the TL494 detached from the PCB. It was barely hanging on to glue at one of the PS toroids. Re-attached, and it would SEEM that this amp is fixed and able to go full clip at 4-ohms (70A draw). Will test further.
I found C3, a small SMD cap connected to pin #8 of the TL494 detached from the PCB. It was barely hanging on to glue at one of the PS toroids. Re-attached, and it would SEEM that this amp is fixed and able to go full clip at 4-ohms (70A draw). Will test further.
There are two capacitors on pin 8, 11 and 12. They connect across the supply and ground. Was the electrolytic cap the one soldered?
Yes c3 is a small electrolytic cap. This amp needs new filter caps as the ones in it look to have vented. I’m going to replace them later today.
I removed the terminal bridge from previous post and the problem returned but this time at about 60A draw. At this point I’m thinking new filter caps may help.
I removed the terminal bridge from previous post and the problem returned but this time at about 60A draw. At this point I’m thinking new filter caps may help.