Electronics > Repair

NOCO GB70 repair help

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AN86:
I think its megaohms its big M on the multimeter.
But maybe im wrong, il take a picture and post it.

I test it all with all plugs disconnected

--- Quote from: AN86 on October 14, 2024, 05:12:11 pm ---...Maybe im wrong but continuity test on D17 beeps in both direction. 


--- End quote ---

I did measure D17 few posts before. and it seems like its bad also. Correct me if im wrong.
So far i didnt get diodes i order from the internet, but ill try to solder regular one not SMD just for testing only and let you know.

jerryk:

--- Quote from: AN86 on October 23, 2024, 03:54:31 pm ---I did measure D17 few posts before. and it seems like its bad also. Correct me if im wrong.

--- End quote ---

Possible confusion on my part.
In your earlier post you were testing things with the relay plug engaged since you activated Q15 via a continuity test and the relay engaged.  As long as all plugs are currently disconnected and D17 measures as a low resistance short in either direction the diode D17 is faulty.  If this is the case, then you can replace it with a 1N4148 or similar.  Keep in mind it's the flyback diode for the main relays and needs to be installed before you attempt to activate those relays.

Jerry

AN86:
Diodes finally came from post office. Ill change both ones and post if its working or not. 

AN86:
Got strucked with feaver so i was offline for a few days.

I did change diodes but still the same. No right signal on that transistor that engage the big relay.

jerryk:
It would be helpful if you would refer to any diode, transistors or other circuit component by the silk screen label on the board.

You said you replaced "diodes but still the same".  Can you tell me which diodes you replaced and what diode did you use as the replacement?  The only defective diode I'm aware of in this discussion is ZD2 which is a 5V1 Zener diode.  I'm not sure what other diode you replaced.  As for ZD2 you have already replaced it with a 5V1 (axial lead) diode so putting the original smd version in it's place would do nothing.  It's just a protection diode for the MCU and you could remove it and your circuit would still not change in it's behavior.

As for "No right signal on that transistor that engage the big relay."  If you checked the test point near the label R74 after holding down the boost/override button for three seconds and did not see 3.3V then you need to remove R74 and try that test again.  The purpose of this test is to completely isolate pin 11 from any possible ground faults down stream of the pin.  If you have R74 removed and after a three second press of the boost/override switch you get the flashing leds from 25% to 100% but no 3.3V at that test point then I cannot see any other fault possibility than the MCU.

Good Luck - Jerry

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