Electronics > Repair

NOCO GB70 repair help

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jerryk:

--- Quote from: eurgenca on October 14, 2024, 05:55:58 am ---Well, this is the end, my friend.
Your CPU is busted. You will confirm that by lifting this pin, and if resistance is still low on CPU pin, then...
Here is a chance to invite other members. I don't ovn holtek programmer if someone have we can try to read content if not locked.

--- End quote ---

I have a Holtek programmer but if you look closely at the circuit board pics in the early posting, notice the lack of programming headers that is present on most all of the other NOCO jump pack line.  On the GB70 it's an OTP MCU so even if...The R series MCU in question is not for sale to the public and is only available to the OEM vendor (AFAIK).

I sure felt bad about being the grim reaper about the MCU but when you said to check the input protection diode I sure was hoping it was the only issue as this would have been such a simple fix.  I am curious as to why you checked pin 27 for resistance.  Typically that pin (PA5) is the latching circuit in the power on scheme on some of the other jump pack models.  From what I see on the GB70 it may be different.



Jerry

AN86:
Im not the expert in this stuff but there is something about it when somesaid its dead and i revive it.  It gives me satisfaction, its wierd i know but i like to fix stuff. And learn in the proces . If that 3 pin connector is responsible for those two big relays  it was logically to search from end of the problem to the top, if iyou know what i mean.  Maybe im wrong but continuity test on D17 beeps in both direction. 

And one crazy thing is if i put on continuity test and probe Lower left and upper pin on Q15 the big relay clicks.

Is that strange or not?

jerryk:
Not.  Disconnect your relay plug and then check D17 which is your flyback diode for the relay coils.  Using the continuity test on Q15's base you have activated the transistor that drives the output relays.  As a general rule I do not test for continuity on live circuit boards.  Randomly activating transistors can cause bad outcomes unless you fully understand the circuit.

Back to the problem at hand and since you are exploring you could do a resistance check across R305.  It should read 4.7K.

If you were closer I would be glad to go over that board in the remote chance there is something we are missing here.  The true test is as @eurgenca stated.  Carefully with power disconnected lift pin 27 and recheck resistance.

Jerry

jerryk:
Can you HOLD OFF on any more exploring of this circuit board until I test some things on my end. Pin 27 goes to R305 and P27 of the daughter board connector.

There is a chance that the short to ground at pin 27 is a problem is on the daughter board.  Your MCU may be OK!

I am going to remove the daughter board on the one that I have and trace that circuit down.

I will get back shortly and let you know what I find.

Of course the next question is are you capable of removing the daughter board?

Jerry

AN86:
I can hold my exploring. But i didnt tell one maybe crucial info, when i did explore with probing the Q15, i turn the booster on and than i probe again, when it click i have voltage on clamps around 16.3v and the leds flash from 25 to 100%.
Maybe this info is good maybe its useless but just in case. 

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