possible logic board failure

[jasongoldworthy]

hi guys

can I ask how common is it for the PCH to go bad on an iMac ?

I already have a question open on here but id like to know how common it is for the logic board to go bad on an iMac that didn't see much use ?


thanks

jason

 

[Lifeisabeach]

hi guys

can I ask how common is it for the PCH to go bad on an iMac ?

I already have a question open on here but id like to know how common it is for the logic board to go bad on an iMac that didn't see much use ?

I don't know statistically how common it is, but it does happen. Some particular models have been more prone to it than others due to whatever engineering issues plagued them that year.

 

[jasongoldworthy]

hi thanks for the reply.

I only ask as I'm sure a 2017 iMac should have lasted longer than it has ?


as the logic board has failed but from what I've been told its the PCH on there that's bad and apple want £400+ to repair it.

thanks again

 

[pigoo3]

Just talking from a purely statistical point of view...just about nothing is 100%. Even if the logic board failure rate was 1 in a million...somebody...somewhere will be that 1 person. We don't want to be that 1 person...but it's got to be someone.

Also...it is possible that unforeseen parameters such as high humidity...high environmental temps...sudden bumps...dirty internals...liquid spills...etc can theoretically cause logic board failures.

AND...one big thing many folks may not consider...is "electricity quality". Either daily electricity quality to someone's home or business...or electrical issues due to surges in the system...or surges/spikes due to weather.

Nick

 

[Lifeisabeach]

Agreed with Nick 100%.

 

[ferrarr]

Anything (everything?), can die at any time.

 

[techiesteve]

At work I see logic board failures, but not that many compared to other faults, and all faults together are likely only a very small percentage of units manufactured. Everything from vintage products to M1 based Mac's. I have likely stated this before, but long ago I worked for an MOD contractor. Even using defence standard approved components and extensive inspections and testing, still the odd failure can, and did occur. The post above is correct - "Anything (everything?), can die at any time."

Edit. If the iMac was purchased within the UK or Europe from Apple and by a consumer, not a business, the original purchaser can make a European Consumer Law Claim to cover the repair. The original invoice or receipt will be required and a claim form has to be completed with the approved repairer. If there are signs that the iMac has been opened/worked on not by Apple or an AASP, that may effect the ability to claim.

 

[jasongoldworthy]

thanks Steve yeah sadly that's put it out of a claim option as I have opened her up myself to find out if the PSU was the problem lol

but I thought id ask if you guys have heard of the PCH failing on the iMac logic boards ?

as its a new one on me.

 

[techiesteve]

When either an AASP or ARS diagnoses a defective logic board it is simply replaced with an exchange board. The defective board is then shipped back to Apple. It's the fastest way to get a Mac reliably up and running. There is no feedback as to what originally failed.

 

[pigoo3]

Totally sympathize with you Jason...and totally agree. A 2017 iMac logic board should last a lot longer than 3-4 years. Many of us are using 8-10 year old Apple computers...and everything is fine.

Here's some data on failure rates. It's not the most current data...but can give some idea of what sort of failure rates are "normal" for the computing industry. As can be seen in the article...between 2010 & 2015...failure rate of Apple portable computers was between 7-9%...with the worst competitor brand failure rate (Lenovo Y Series) being 23%:

Laptop Reliability: Can You Count On Your Computer? - Consumer Reports

Which laptop brands and models have the fewest repairs? Consumer Reports surveys our readership to get the answers to laptop reliability.

www.consumerreports.org

Nick

p.s. Apologies for the "partial" linked article. Looks like we need to be a Consumers Reports member to be able to read the whole article. But what we can read is pretty interesting.

 

[jasongoldworthy]

thanks for the reply again nick.

the sad part is everywhere in the USA I can get the logic board but sadly nobody in the UK here has one for sale and I think that's because its the 4k retina model

 

[pigoo3]

the sad part is everywhere in the USA I can get the logic board but sadly nobody in the UK here has one for sale and I think that's because its the 4k retina model

Have you checked eBay UK? Maybe you can find one there that's not working properly...but has a good logic board (maybe has a damaged display or something like that).

Nick

 

[jasongoldworthy]

thanks nick ill search for one in that condition I don't mind if it has a smashed display as long as the logic board is bad


one more question guys could the CPU be the reason that im seeing no sign of life on the logic board ??

 

[pigoo3]

one more question guys could the CPU be the reason that I'm seeing no sign of life on the logic board ??

I was going to ask about the certainty the logic board is really dead/the issue (you sounded pretty confident the logic board was the issue...so I didn't ask further). Did you have a seperate thread posted here exploring this (maybe I missed it).

As far as the CPU. With a 2017 iMac...is the CPU socketed/removable?

If it's soldered to the logic board...and the true problem was a dead CPU...replacing just the CPU would be pretty difficult (unsoldering it & soldering in a replacement). If the CPU is socketed...then it would be a easy replacement (after getting the iMac opened up)...which isn't very easy either.

Nick

 

[jasongoldworthy]

hi nick

I was told by based on its issue from a local repair shop that the PCH is the problem.

but im wondering if a dead CPU would appear as no diagnostic led's lit on the logic board ?

because I can always throw in another i5 7400

I just didn't think of checking that before forking out £350 for a damaged machine with a good logic board

 

[pigoo3]

but im wondering if a dead CPU would appear as no diagnostic led's lit on the logic board ?

I read your other thread where you mentioned none of the logic board diagnostic LEDs are lit. Not sure if you have the proper diagnostic LED definitions for a 2017 iMac...below I attached a screenshot of the diagnostic LED definitions for a 2019 iMac (they may be the same for a 2017). Hopefully it's readable.

None of the diagnostic LED definitions specifically address working/non-working CPU...mostly only if the logic board is communicating properly with other components of the iMac. As you know...logic boards are very complex...can't really say if the logic board issue is solely due to a problem CPU (can only test this by replacing the CPU by itself).

If i5 7400 CPU's are cheap...you could test the CPU replacement theory by replacing the CPU.

In the other thread it was also mentioned that you got this 2017 iMac from someone else (already dead)...I was assuming it was your iMac. If you got it already dead...then almost anything could have happened to it prior to you getting it. As I mentioned earlier in the thread...problems could be due to the iMac:

* being dropped
* liquid spill
* "bad quality" electricity/electrical surges
* bad weather/thunderstorms
* etc

Here's the screenshot of the diagnostic LED definitions for a 27" 2019 iMac:



HTH,

Nick

 

[jasongoldworthy]

hi nick thanks again

ive followed the guide on the led's and no change even after a CPU change.

I have tested the original CPU and its fine.

so it must be a bad logic board.

I have voltages coming out of the PSU and I have voltages going back from the signal cable.

but no led's illuminate at all.

 

[jasongoldworthy]

Hi guys I sourced a replacement logic board from the book yard

and I’m now getting the power light but the 2nd light is blinking on every few seconds ??

many ideas ?

cheers