Hello All!
I have a Skar RP2000.1D that I am repairing. It had all the output fets shorted and also 3 of the power supply fets shorted, along with some of the gate resistors. I removed all the FETS, and was curious if I can check the gate waveforms with the FETS removed, or if the driver IC for the power supply needs them in place to get its power.
Just trying to learn while I wait for parts to arrive!
Thanks,
Mitch
Included is a stock photo of the guts. I'm at work right now and don't have the amp near me.
I have a Skar RP2000.1D that I am repairing. It had all the output fets shorted and also 3 of the power supply fets shorted, along with some of the gate resistors. I removed all the FETS, and was curious if I can check the gate waveforms with the FETS removed, or if the driver IC for the power supply needs them in place to get its power.
Just trying to learn while I wait for parts to arrive!
Thanks,
Mitch
Included is a stock photo of the guts. I'm at work right now and don't have the amp near me.
Attachments
There were two versions of this power supply circuit. One would switch the PS driver IC off if it didn't see rail voltage immediately after the IC switched on.
Are all of the PS FETs out of the board?
Please (and this applies to anyone who needs repair help) use your sig line to list all equipment you have, editing it as equipment changes. Include the model numbers.
Top of page, menu USER CP >> EDIT SIGNATURE
Oscilloscope (yes or no)
Multimeter(s)
Type of signal source (grounded RCA shields preferred).
Soldering iron
Desoldering pump
Power supply
2 ohm current limiting resistor (hollow cylindrical ceramic 100w preferred)
Are all of the PS FETs out of the board?
Please (and this applies to anyone who needs repair help) use your sig line to list all equipment you have, editing it as equipment changes. Include the model numbers.
Top of page, menu USER CP >> EDIT SIGNATURE
Oscilloscope (yes or no)
Multimeter(s)
Type of signal source (grounded RCA shields preferred).
Soldering iron
Desoldering pump
Power supply
2 ohm current limiting resistor (hollow cylindrical ceramic 100w preferred)
I updated my signature with as much information as I have currently. I'm not sure if it matters, but the board I have is identical to the stock photo above. I'm not by it currently, so if there is something I can check, it'll be tonight.
The PS FETs are out of the board, I just ordered replacements for all the FETS and resistors that I've found so far, won't be in until roughly Tuesday.
Thanks for the response.
The PS FETs are out of the board, I just ordered replacements for all the FETS and resistors that I've found so far, won't be in until roughly Tuesday.
Thanks for the response.
Currently I have all the PS FETs, Output FETs, and rectifiers out of the board. I measured the 494 and here is my results. I used Pin 7 as my ground reference.
Pin 1 - 0V
Pin 2 - 5V
Pin 3 - 4.45V
Pin 4 - .5MV
Pin 5 - 1.47 V (Checked with scope, good sawtooth pattern)
Pin 6 - 3.6 V
Pin 7 - 0V
Pin 8 - 12.05V
Pin 9 - 300MV
Pin 10 - 367MV
Pin 11 - 12V
Pin 12 - 12V
Pin 13 - 5V
Pin 14 - 5V
Pin 15 - 2.05V
Pin 16 - 3.88V
I'm assuming that my Pin 1 being low is what's causing it not to give me an output signal to my PS FETs. I tried to trace it and, for the life of me, cannot see where it goes. It comes out to a via, goes to the other side of the board and is connected to large block (not sure of the correct term) with many different things connected to it. I apologize for the less than perfect pictures, there is wire running right over the 494 and makes it difficult to get at.
Pin 1 - 0V
Pin 2 - 5V
Pin 3 - 4.45V
Pin 4 - .5MV
Pin 5 - 1.47 V (Checked with scope, good sawtooth pattern)
Pin 6 - 3.6 V
Pin 7 - 0V
Pin 8 - 12.05V
Pin 9 - 300MV
Pin 10 - 367MV
Pin 11 - 12V
Pin 12 - 12V
Pin 13 - 5V
Pin 14 - 5V
Pin 15 - 2.05V
Pin 16 - 3.88V
I'm assuming that my Pin 1 being low is what's causing it not to give me an output signal to my PS FETs. I tried to trace it and, for the life of me, cannot see where it goes. It comes out to a via, goes to the other side of the board and is connected to large block (not sure of the correct term) with many different things connected to it. I apologize for the less than perfect pictures, there is wire running right over the 494 and makes it difficult to get at.
Attachments
It's pin 16 that's causing the IC to shut down.
Follow it back and lift any PNP transistor that you find connected to that terminal.
It may be easier to install one FET per bank and allow the supply to produce rail voltage. If one of the FETs heats up, the drivers may be damaged.
Follow it back and lift any PNP transistor that you find connected to that terminal.
It may be easier to install one FET per bank and allow the supply to produce rail voltage. If one of the FETs heats up, the drivers may be damaged.
Ok, I went and re-read the TL494 information on the tutorial. Is the amp not using the Error Amplifier 1, so Pin 1 has 0 and 2 has 5?
So since Pin 16 is higher than pin 15, the Error Amplifier 2 goes high, which shuts down the duty cycle of pin 3?
I had it wrong in my head in the last post. Had the high and low backwards...
So since Pin 16 is higher than pin 15, the Error Amplifier 2 goes high, which shuts down the duty cycle of pin 3?
I had it wrong in my head in the last post. Had the high and low backwards...
The drive protection circuit is covered under item 44 on the PS troubleshooting page if you have the tutorial. The circuit board designations seem to be different for this amp but the circuit should be the same or similar.
I don't know if the following will help you remember or not (for some, visuals help). The circuit was for a dead simple power supply. Pins 13, 14, 15 and 2 are connected to 5v. Pins 1 and 16 are grounded. 1 and 16 must be below 2 and 15.
I don't know if the following will help you remember or not (for some, visuals help). The circuit was for a dead simple power supply. Pins 13, 14, 15 and 2 are connected to 5v. Pins 1 and 16 are grounded. 1 and 16 must be below 2 and 15.
