NOCO GB70 repair help

[AN86]

Hello, a friend of mine give NOCO GB70 to me. Its dead,
Just red light is iluminated, dont charge, cant turn on.
I open it and on quick look, its all ok. Battery is on 11.8V ,its not full but i guess its not empty either. Fuse is good, not burned.
Can you give me some directions if there is any know fault or where to look for problem.

Thanks in advance.

[jerryk]

First - Disconnect the JST connection from the battery to the board.
Second - Do not try to desolder any components as parts of the main board are still under power.
From there can you post a photo the board and the date code of the device which is printed on the side of the case.  Good new is the battery is still viable.  The GB70 can blow the relays and that can be a daunting repair.  However, most of the time it's not terrible to repair.  As a start, confirm all switches are functional.

Jerry

[eurgenca]

Which red 25% or !.

[AN86]

Thanks for fast repay.
Switches are ok. I tested that first.  This evening ill take a picture of the board numbers. "!" Error light is on.

[jerryk]

Also disconnect both the relay and NTC plugs and check both for proper function.

Jerry

[AN86]

I fall a sleep evening so i didnt do anything, i did take a picture before i left to work.
Idid try to disconnect everything and start it but nothing happen.
Its dead as before

[jerryk]

It will not start with any of the plugs disconnected.  If able you need to check the resistance across the NTC and the relay coils.  If you have a 12V power supply power the relay coil and check that the relay is engaging and it's internal points are making a connection. Do this with the cables disconnected from the board.  Then check each cell voltage and make sure they are even.  Then reconnect all cords and check that there is power to S1 On/Off switch.  If the switch is powered then press it and see that it powers up IC6 which is the LDO that powers the microcontroller.  The LDO output should be 3.3V.  This should get you started.

Be careful when probing this board under power.  The Holtek MCU's seem to zap quite easily.  Under no condition do you want to remove any of the board components under power.  This means you have unplug all connection plugs and desolder the black ground wire that's connected to the board below the R106 in your photo.

Good luck - Jerry

[AN86]

Thanks for directions. Ill put kids to sleep in hour or two and start to test.
In meanwhile i test as i believe is temperature sensor for battery.
2 pin  connector and it said around 15-16kiloohm. So i believe this part is working.  Was 16.8 a bit later was colder few degrees and it was 15.3.

Later ill try test and ill post what i find.

Thanks

Edit:
All cells are 3.7v

[AN86]

I did the test you recommended. Big two relays are working, connected tham to 12V and they clicked and continuity test said it connects inside the relay, but testing IC6 is strange. I measure and write it on the picture I attached. Did i measure  something wrong or there is the problem? Since you said Holtek MCU is a little tricky to measure i decide to leave it as it is for now.

[jerryk]

Those measurements are definitely wrong.  You have a short to ground on the board somewhere and just hope it's not at the MCU.   Can you read me the number off the MCU.  I think I know what it is but you need to identify the input pins and the measure the resistance across the input decoupling capacitor.

Also this fits the error you are seeing.  I assume the red error light was solid?

Jerry 

[AN86]

Now it dont even illuminate "!".  But if i need 3.3v and i have 1.2 that drops to 0.7 in few sec then its definitely a problem.
 I add picture of the oder side of the board. I hope the number helps. It said veersion G, its blocked by the wire in the picture.

[AN86]

MCU picture

[jerryk]

C21 should be your decoupling capacitor to VDD and VSS.  With all plugs removed can you check the resistance across C21.  It should read around 4K.  It should not read in the low ohms region.  When you tested your relays did you disconnect all plugs?

Jerry

[AN86]

On C21 it reads 3.4 ohm. And continuity test is beeping.
When tested relays i disconnect all plugs, didnt want to risk anything.  How can i know the rating of this component? I believe its capacitor according to looks and C name on it.

[jerryk]

Your MCU is most likely shorted as in failed.  I don't recall the capacitance value of C21 but the symptoms here are not good.

The LDO which is IC6 has a direct path from its output to pin24 on the MCU which is VDD.  I doubt the short is at the capacitor but you would have to remove it to be sure.

Jerry

[AN86]

Guess ill have to remove capacitor and see. Ill do it and let tou know what i find out, and hope for best

[AN86]

I did remove capacitor and replace it with lets say similar, i know its not good choice but i wanted to see if there will be any difference, and it didnt make a difference. But i notice something. On the board next to the IC6, which gives output of 1.2 and than drop to 0.8V, there is a probably test dot that said 3.3v. and when i probe it i have exactly as on the output pin on IC6, and then another test spot that has label 12v and on that spot i have 0.004V which is crazy and i guess maybe there is a problem. On the cylindrical capacitor behind the board near that spot i dont have 12v only ground. And capacitor is polarised. Ill try to snoop around. Picture attached just in case i didnt explain good.

[jerryk]

Your voltage regulator IC6 is shorted between the output and ground. This can further drain your battery. Odds are the short is at the MCU. Can you measure the temperature of IC6 by chance?

Jerry

[AN86]

I have that ebay digital laser thermometer. I try with him and let you know.

[eurgenca]

Check ZD2 and ZD5 for short. Usually 5V1 diode go short. If so replace it and if you are lucky you good to go.

[AN86]

ZD2 is beeping on continuity test. And on diode test on DMM it said 0.002V. but continuity test is beeping so i guess its bad.
Is there any value specific i need to ask in store?

 

[jerryk]

You cannot test ZD2 in circuit.  You have already taken the resistance at C21 which was 3.4 ohms so this will be the same at ZD2.  The only way to test ZD2 under current conditions is the remove it.  FWIW if ZD2 is shorted when you remove it your jump pack will start working if was the only issue.  Once you remove ZD2 if no change in symptoms then check the resistance again across C21 or ZD2 pads and see if it is still 3.4ohms or thereabouts.

Jerry

[eurgenca]

Like I told you. Replace ZD2 with 5V1 diode, and if you LUCKY you are good to go, but probably not. Next step is to check douther board if you will have problems with charging. If CPU is bad you are stuck.