1D is an MMBTA42. That would be wrong from the limited information I have.
In the only photos I have of a similar board (SMD IR2184, not DIP). it uses two 2D transistors (MMBTA92). Your board may need or the circuit may have been changed because the 4D can withstand more voltage.
I believe the two TL072s are correct (or at least usable in this circuit).
In the only photos I have of a similar board (SMD IR2184, not DIP). it uses two 2D transistors (MMBTA92). Your board may need or the circuit may have been changed because the 4D can withstand more voltage.
I believe the two TL072s are correct (or at least usable in this circuit).
Some people use low voltage for the rails when troubleshooting. I would expect the voltage on the transistor Q1 to be greater. The base and emitter are going to be near the low voltage (6.8v?) but the collector should be very near negative rail. If negative rail is near -200(?), the collector and the input to the 2184 should be within 12v of the negative rail.
I stated Q1 as the transistor but in the diagram, I don't see how pin 7 of the op-amp can drive the transistor to drive the input of the 2184 as its drawn. Did you use your meter to confirm that the diagram was accurate? I can't do that because I don't have a board here.
I stated Q1 as the transistor but in the diagram, I don't see how pin 7 of the op-amp can drive the transistor to drive the input of the 2184 as its drawn. Did you use your meter to confirm that the diagram was accurate? I can't do that because I don't have a board here.
Hey Perry, we spent time comparing some voltages on bills board with my working board.
One anomaly that we found is the source pin for Q81 (J111-D74ZCT) seems to be lower than mine. The source pin connects to the SD pin for the IR2184 through a 100ohm resistor. My voltage is 5.12V and bills is 3.8V. Q81 appears to be some sort of a protection/muting transistor.
I went to your tutorial under Class D type 3, where it has the SWF image of the DWM3640 driver board which includes the IRS21844S. The shutdown/protection pin should be 4-5V above negative rail. When we check my board, that holds true. When we check bills board, it only reads 3.8V and not the 4-5V that it should be. We're just going off the ground pin of the voltage regulator that supplies its voltage to the Q81 to get our 5.12 or 3.8V.
Question is, where does that voltage come from? My assumption is that its coming from the IR2184/driver card as an output to the Q81 transistor since it's connected to the source pin, but I'm not totally sure. I thought the SD pin was an input and usually when those pins go high they cause a shutdown. This seems to be opposite.
One anomaly that we found is the source pin for Q81 (J111-D74ZCT) seems to be lower than mine. The source pin connects to the SD pin for the IR2184 through a 100ohm resistor. My voltage is 5.12V and bills is 3.8V. Q81 appears to be some sort of a protection/muting transistor.
I went to your tutorial under Class D type 3, where it has the SWF image of the DWM3640 driver board which includes the IRS21844S. The shutdown/protection pin should be 4-5V above negative rail. When we check my board, that holds true. When we check bills board, it only reads 3.8V and not the 4-5V that it should be. We're just going off the ground pin of the voltage regulator that supplies its voltage to the Q81 to get our 5.12 or 3.8V.
Question is, where does that voltage come from? My assumption is that its coming from the IR2184/driver card as an output to the Q81 transistor since it's connected to the source pin, but I'm not totally sure. I thought the SD pin was an input and usually when those pins go high they cause a shutdown. This seems to be opposite.
Look at the internal diagram of the IC and it shows a pullup resistor to an internal 5v supply.
The J111 (if that's what it is) pulls the voltage on the SD pin down to the negative rail initially but when the power supply powers up, a negative-rectifying diode charges a capacitor negatively and when the negative voltage reaches a threshold, the voltage on the SD pin is released and it rises to the voltage that it's pulled to internally.
On that same 'type 3' page, you also saw that the 21844 has a threshold of about 2.1v so I'd expect that the voltage is OK but if it's not pulling up far enough (no j111 in the circuit), I'd expect that the IC was defective (even if new).
Some ICs need a high to shutdown but most that have an overline on the SD shut down when the pin is pulled low.
The J111 (if that's what it is) pulls the voltage on the SD pin down to the negative rail initially but when the power supply powers up, a negative-rectifying diode charges a capacitor negatively and when the negative voltage reaches a threshold, the voltage on the SD pin is released and it rises to the voltage that it's pulled to internally.
On that same 'type 3' page, you also saw that the 21844 has a threshold of about 2.1v so I'd expect that the voltage is OK but if it's not pulling up far enough (no j111 in the circuit), I'd expect that the IC was defective (even if new).
Some ICs need a high to shutdown but most that have an overline on the SD shut down when the pin is pulled low.
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