Macbook Pro mid 2010 resistor values

Shaky McSoldering

macrumors newbie
Original poster
May 12, 2016
3
0
London
Hello,
I am an ex-lurker, sub-genius type person who is trying to repair a MBP that appears to have a few problems.

I can't seem to find a dedicated mothrboard repair forum here, so apologies for the inappropriately positioned new thread, if anyone can suggest a better place for it I would be glad to delete/move the post.

The first problem that there is no light on the magsafe connector.

I do have Board View and schematic files for the motherboard which is an:

A1286 - EMC 2253 - 820-2850-a - K18.

I am going through the G3 Hot circuit diagnosing the components but I notice that my schematic PDF (pg. 64) does not specify the resistances for some of the resistors.

For example R6990, R6992 and R6993 are specified as

'''5%

MF-LF

1/16W

402'''

This gives me a lot of useful information, but no Ohm value to measure.

I have looked at the schematics for other MBP boards, some have the Ohms, but the circuits are different and include diodes.

Could someone please help me with the resistance values for these components?
 

MacTech68

macrumors 68020
Mar 16, 2008
2,268
175
Australia, Perth
I could be reading it wrong, but if you look a little closer, you'll see a 0 (zero) above R6993, a 1 above R6990, and a 0 (zero) above R6992.

I'm going to assume these are the values in Ohms, so

R6990 = 1 Ohm 1/16W 0402
R6992 = zero Ohm 1/16W 0402
R6993 = zero Ohm 1/16W 0402

I guess it's just the strange way it's annotated. I must admit, it had me for a short while. :)
 

Shaky McSoldering

macrumors newbie
Original poster
May 12, 2016
3
0
London
Thanks for the reply!
I did see the ones and zeros on the schematic, but they seemed fishy to me.

All the other resistances that I checked in the 100+ page document did specify the unit, so I thought it was a misprint.
thinking maybe my schematic is a hokey pre-production version.

I am too much of a scared newb to replace the components without the validation of someone who knows better.

Mr. Rossman does say that the first two resistors are basically fuses, so maybe I will give it a go.
I just don't want to end up doing more expensive damage.

My basic problem is that PP3V42_G3H is giving me .612 volts at probe point 918.
 

Shaky McSoldering

macrumors newbie
Original poster
May 12, 2016
3
0
London
Ah yes, but I needed to know the reference values,
which as far as I was concerned were not on the schematic.

What I see is:
R6990 1.2 ohms
R6992 .3 ohms
R6993 .2 ohms

If the ones and zeros theory is correct (which seems very likely) and the tolerances are 5% then all of these look like they need replacing.
I would love to see what a fresh 0 Ohm resistor should read on a meter, as in what is 5% of zero?

Some new ones are on the way anyway, hopefully I will have them for the weekend.
I will let you know how I get on, thanks for the help.
 

chown33

Moderator
Staff member
Aug 9, 2009
8,840
5,263
vertical
Ah yes, but I needed to know the reference values,
which as far as I was concerned were not on the schematic.

What I see is:
R6990 1.2 ohms
R6992 .3 ohms
R6993 .2 ohms

If the ones and zeros theory is correct (which seems very likely) and the tolerances are 5% then all of these look like they need replacing.
I would love to see what a fresh 0 Ohm resistor should read on a meter, as in what is 5% of zero?

Some new ones are on the way anyway, hopefully I will have them for the weekend.
I will let you know how I get on, thanks for the help.
Zero ohm resistors are cheap. Touch the probes of your meter together. What's the reading?

Probe cables have non-zero resistance.
 
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RobertBrush

macrumors newbie
Aug 15, 2020
1
0
Hello Everyone,

similar issue, similar guy. Could somebody help me figure out if there is a potential resistor missing here?
(See picture).

I have a mid 2010-15" Mac Pro lying here that allows clicking but the tracking (mousemovement) doesn't work.
(A1286 EMC 2353 820-2565a)

Following Rossman's guide I figured it might have to do with the Booster and I couldn't read any voltage coming through and noticed something missing.

Which resistor could this be and what ohm value does it have?

Cheers

Robert
 

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