My question was very simple, no need of any photo.
Pins 4 & 5 of J6901 go to that chip???
Pins 4 & 5 of J6901 go to that chip???
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iMac 2017 (18,3) fan on max loud, cpu on max
- Thread starter Georg3
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Then is a thermal interface too; just didn't identify that SMD code yet.
Diode mode to ground readings for these two lines.
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Unfortunatelly, we don't have exact schematic for this board.
Considering 00134 as guide, U5600/50 are both connected in the same bus.
If U5600 got damaged, it can block the communication on entire bus.
CPU proximity, as PSU temp are controlled directly by U5600.
TMP423 can control 3 remote sensors, plus its internal sensor.
You should check all its adiacent resistors.
The remote sensors are simple NPN transistors, connected as diode; more temp sensitive than a simple diode.
You should check/replace the sensor from PSU; all sensors connected to U5600 in fact.
Compare the readings with other sensors, connected to other temp interface (U5650).
Remove U5600 and check again the temps reported by macOS.
Considering 00134 as guide, U5600/50 are both connected in the same bus.
If U5600 got damaged, it can block the communication on entire bus.
CPU proximity, as PSU temp are controlled directly by U5600.
TMP423 can control 3 remote sensors, plus its internal sensor.
You should check all its adiacent resistors.
The remote sensors are simple NPN transistors, connected as diode; more temp sensitive than a simple diode.
You should check/replace the sensor from PSU; all sensors connected to U5600 in fact.
Compare the readings with other sensors, connected to other temp interface (U5650).
Remove U5600 and check again the temps reported by macOS.
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If I understand you correctly I solder B+C to PIN-5 and E to PIN-4 of J6901 and that should make the logic board think that the PSU temp sensors are connected as they should be even if the 7-pin data cable is disconnected?
If I don't have access to any donor MacBook or iMac boards can I buy an NPN from Digikey? If yes, could you help me find which one to buy?
If I don't have access to any donor MacBook or iMac boards can I buy an NPN from Digikey? If yes, could you help me find which one to buy?
Any NPN transistor should work.
You can use a plastic TO-92 case, with normal pins; more easy to accomodate on the board.
Of course, you can also try with a simple diode.
If the temp read by SMC from that sensor generates an issue, then may need to get one from other board; used as temp sensor too.
You can use a plastic TO-92 case, with normal pins; more easy to accomodate on the board.
Of course, you can also try with a simple diode.
If the temp read by SMC from that sensor generates an issue, then may need to get one from other board; used as temp sensor too.
@2informaticos can I just double check if I understood you correctly that I should solder the NPN transistor onto J6901 in a way that B+C are on PIN-5 and E is on PIN-4?
Yes, B+C at P line and E to N line.
@2informaticos YOU ARE A GENIUS!!!
The NPN transistor is giving the logic board the temp readings so it is not missing the 7-pin data cable, which means I can replace the original ACDC power supply with a DCDC supply so it can be battery powered!!
The NPN transistor is giving the logic board the temp readings so it is not missing the 7-pin data cable, which means I can replace the original ACDC power supply with a DCDC supply so it can be battery powered!!
Glad to hear you've solved it.
And thanks for feedback; someone else can find this useful...
And thanks for feedback; someone else can find this useful...
Thank you very much again! Battery powering it was the most important thing for me.
When I have free time I have to fix the other iMac, the one I started experimenting with and shorted out. As you suggested I'll go through the resistors on that data line to find out what is causing the "AC/DC T2 Sec Heatsink", "CPU Proximity", "CPU Backside" and "Skin" sensors to be missing.
If it is the SMC then do you think I might be able to find a replacement anywhere online?
When I have free time I have to fix the other iMac, the one I started experimenting with and shorted out. As you suggested I'll go through the resistors on that data line to find out what is causing the "AC/DC T2 Sec Heatsink", "CPU Proximity", "CPU Backside" and "Skin" sensors to be missing.
If it is the SMC then do you think I might be able to find a replacement anywhere online?