820-01700 PPVCC_S0_CPU normal resistance to ground/diode reading?

[karoliens]

I am working on this board that has some water damage though not around this rail but I measured it anyway to rule out that CPU is not fried.
Resistance to ground on PPVCC_S0_CPU rail is 2Ohm and in diode mode it shows 0V.
What is the normal reading on that rail?
TIA

[mon2]

Re: 820-01700 PPVCC_S0_CPU normal resistance to ground/diode reading?

I think you may be ok here at 2 ohms. We had an a1398 with 1 ohm to ground and it was working fine.

Also review this thread:

https://boards.rossmanngroup.com/thr...-ground.37575/

[karoliens]

Re: 820-01700 PPVCC_S0_CPU normal resistance to ground/diode reading?

I think you may be ok here at 2 ohms. We had an a1398 with 1 ohm to ground and it was working fine.

Also review this thread:

https://boards.rossmanngroup.com/thr...-ground.37575/

Thank you for a quick reply. I've read that thread already but I was hoping maybe someone remembers from the top of their head normal reading on that rail.

I'll hook it up to the power supply and I see what it shows. With older MacBooks that use MagSafe1 and MaSafe2 I've cut the cable with lightning connector ant connected it to the power supply for troubleshooting.

Do I need to buy genuine USB-C charging brick to do the same for these newer models as well?

[mon2]

Re: 820-01700 PPVCC_S0_CPU normal resistance to ground/diode reading?

You do not require the genuine USB-C power supply to power the macbook models. We have used LVSUN 90-95W models with success.

Power delivery is an industry specification but you should purchase a unit with 20V support. More power the better. A branded version is preferred over no names. We have met LVSUN at past trade fairs in HK and they are a solid company. At the fair, we purchased this unit for ~$18 USD. It retails for ~60+ USD in the market. The unit worked well till we applied it to a butchered logic board from Ebay - Ebay refunded our money in full and allowed us to keep the macbook sold by this hack.

[karoliens]

Re: 820-01700 PPVCC_S0_CPU normal resistance to ground/diode reading?

You do not require the genuine USB-C power supply to power the macbook models. We have used LVSUN 90-95W models with success.

Power delivery is an industry specification but you should purchase a unit with 20V support. More power the better. A branded version is preferred over no names. We have met LVSUN at past trade fairs in HK and they are a solid company. At the fair, we purchased this unit for ~$18 USD. It retails for ~60+ USD in the market. The unit worked well till we applied it to a butchered logic board from Ebay - Ebay refunded our money in full and allowed us to keep the macbook sold by this hack.

So you just cut the end of non-genuine USB-C brick and connect it to PSU? I suppose I could also use USB-C ammeter. I've see Louis using one for troubleshooting.

[mon2]

Re: 820-01700 PPVCC_S0_CPU normal resistance to ground/diode reading?

No - no cutting required.

Normal use is to use the power adapter as-is. To monitor the voltage and current draw from the external power adapter, apply a USB Type C meter / dongle like the T66C from RD (we use this one in the shop):

Works very well and is accurate (our white meter which is cheaper fails to show us low current draw yet the T66C works fine):

https://www.aliexpress.com/item/32968303350.html

This one is cheaper but shows 0mA while the true current draw is 28mA-30mA on the T66C:

https://www.aliexpress.com/item/3306...d=0LXuSrx85Qze

So your external power adapter will plug into this meter -> the meter plugs into your macbook or any Type C product -> meter will offer the details of the power delivery contract being used with a live update on the current draw.

Be sure that you select the BIDIRECTIONAL designs like the above otherwise, the meter will not function properly.

Beside the above, there are these Type C cable heads that may work for your PSU use (personally do not recommend it but is an option):

https://www.aliexpress.com/item/1005...d=Why2vY2PzlFP

The above should be close but as noted, not recommended. The Type C spec is required to send out 5v by default -> after the ACE controller IC on the logic board negotiating, the external power adapter then shifts from 5v upto 20v. With this PSU cable, you will always be sending out 20v so IMHO, it is not an accurate representation of what the official adapter will be doing.

Still recommend that you purchase a quality 100W PD compliant adapter with 20v support + the TC66C tool. Rest are extra gravy if you choose to buy them.

Here is another option that may be better than the above cable only solution:

https://www.aliexpress.com/item/1005...d=m8cyIZpv6V4U

So for this to work @ 20V 5A, you MUST purchase a suitable E-marker style cable with PD support. If you DO NOT, the cable will be a passive one and max current is 3A. Just a FYI. Then apply your PSU to this brick -> then the USB C e-marker cable to the TC66C to monitor the voltage / current -> dock to your macbook. Now your PSU is driving the setup.

Personally have never used this product so no idea on how well it will work. </Disclosure>

[karoliens]

Re: 820-01700 PPVCC_S0_CPU normal resistance to ground/diode reading?

Thank you for explanation.