AIU Issues Redux

I'm sure GGG will clarify.  But based on your symptom, I'm guessing he's referring to one of the black IC chips circled.  These are generic readily-available components about 50 cents each (shipping will be more than the part!).  Kind of a soldering nuisance to replace them though...

Being thru-hole parts, they'll be a whole lot easier to do than the smaller SMT parts.

What I do with thru-hole parts is I clip all the leads right at the chip and then just heat up a connection and pull the legs out one at a time.  A lot easier than trying to remove the whole chip.  Clean the holes out and plop the new chip in.  This makes short work of cleaning the holes.

Charly, Call MTH Service.  The tech notes are not very good, but they can point to the most likely chips based on the specific issues.  Which bank, all banks, etc...   G

So how does this play out in the real world?   So the "tech notes are not very good" and even GGG is suggesting kicking it back to MTH Service!  Given two-way shipping costs and related overhead costs does this effectively mean the ~$100 AIU is a consumable item (if not under warranty)?

There was another recent my AIU does not work thread where the solution was the purchase of a replacement AIU.  In that case I suggested making some simple voltage measurements but concluded any further troubleshooting would require an oscilloscope and lots of spare time...

No I am saying I rarely work on a AIU hence have limited experience with the fault methodology, and as you say why waste all the time backward engineering it if your going to see one in 5 years.   On the other hand, MTH service has worked on plenty of them an therefore may be able to point to the specific chip.  Plus they have the prints.  Saves time and effort.  They know what chips control what relays.  Or just replace all the chips.  I am not saying send it to them, rather get phone tech support.  NO CHARGE.

ASC notes give you the basics and basic/common fault.  Charly's issue is beyond the first symptom which was repaired.  

And yes some items are not worth repairing at any level given parts and even a modest labor rate can push an item over the replacement cost.  Operating cabooses, simple accessories under $70, etc...  G 

stan2004 posted:

There was another recent my AIU does not work thread where the solution was the purchase of a replacement AIU.  In that case I suggested making some simple voltage measurements but concluded any further troubleshooting would require an oscilloscope and lots of spare time...

Yeah, that was mine.   Based on what I was able to buy a new(used) one for, the cost/benefit of repairing a very long out of warranty AIU became obvious.

Now that I have 2 good working ones again, I may call MTH service and see if they can give me guidance on where to look next on my old bad one, and use it as a hands on learning item for future knowledge.

So are the chips that Stan has circled at least in the ballpark?  All ten of the accessory relays are not working.  Thanks guys for all your input and knowledge.  It is very much appreciated.  Is there anything specific I can ask about when calling MTH Tech. Service?