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geekhack Projects => Making Stuff Together! => Topic started by: lambreaux on Fri, 10 February 2017, 10:22:27

Title: Help with an IBM m2
Post by: lambreaux on Fri, 10 February 2017, 10:22:27

Ww

Title: Re: Help with an IBM m2
Post by: Tactile on Fri, 10 February 2017, 11:14:07

I think this is the trace where the cap connects. This is a photo from the Internet, this is not a photo of my controller.
[attach=1]

I am also working with am IBM M2 and will be opening mine back up today or tomorrow. When I do I'll have a much better view of the controller board. My problem is not with the capacitors, however, so all the traces on the PCB should be clean and easily visible.

Title: Re: Help with an IBM m2
Post by: Tactile on Fri, 10 February 2017, 12:00:43

I just opened my M2 and have confirmed the info in the above post. Those are the correct traces.

Title: Re: Help with an IBM m2
Post by: lambreaux on Fri, 10 February 2017, 12:16:50

Nn

Title: Re: Help with an IBM m2
Post by: Tactile on Fri, 10 February 2017, 12:24:00

There's another connection for that leg of the capacitor. See what I've added in this photo.
[attach=1]

Title: Re: Help with an IBM m2
Post by: rpavlik on Fri, 10 February 2017, 15:51:34

In case it wasn't easy to see, the test point/filled via at the end of that trace was circled. On the other hand, OP's board looks like that trace is destroyed, in which case you should just be able to solder right to the appropriate leg of the MCU - follow the skinny trace in any non-destroyed pic  ;) to see.

Through a schematic for a regular M (not an M2) and another post here (sorry, too many geekhack tabs open to link the right one :D ), combined with accidentally putting a 22uF cap in where the 2.2uF should go (and seeing it take a loooong time to go from "two lights on in bootup" to "ok, normal now"), I can confirm that top cap is the one that forms part of an "RC" network designed to keep the micro in reset long enough for power to stabilize. It's just a delay cap - nothing terribly fancy going on - so bodging it to the (presumably reset) pin on the micro is fine.

Title: Re: Help with an IBM m2
Post by: lambreaux on Fri, 10 February 2017, 16:36:14

Aa

Title: Re: Help with an IBM m2
Post by: Tactile on Fri, 10 February 2017, 16:54:04

Quote from: lambreaux on Fri, 10 February 2017, 16:36:14

On the other hand, I am afraid that the trace of negative connector (c3 in the photo) may also be damaged. Would there be another alternative way to solder it?

That leg of the capacitor just goes to ground so you can solder it anywhere on those big patches of ground plane. It would be best to keep the capacitor leads as short as you can but that lead can go just about anywhere.

Title: Re: Help with an IBM m2
Post by: lambreaux on Tue, 14 February 2017, 10:11:27

Q

Title: Re: Help with an IBM m2
Post by: Tactile on Tue, 14 February 2017, 12:13:32

Quote from: lambreaux on Tue, 14 February 2017, 10:11:27

Show Image

(http://i1382.photobucket.com/albums/ah260/mauricelambreaux/IMG_20170214_165007_zpsrjkkeeth.jpg)

I just changed the capacitors and this still does not work. I marked in the image where I attached the capacitor, the trace is very damaged, maybe the problem is another. Could you help me?

Thanks and best regards

This is a great excuse for me to give up on my M2 project!

If you'll PM me your address I'll send you a fully functional and non-modified IBM M2 controller. It'll be sent from the USA so I have no idea how long it will take to get to you but it's yours if you want it.

Title: Re: Help with an IBM m2
Post by: lambreaux on Tue, 14 February 2017, 12:36:37

[m

Title: Re: Help with an IBM m2
Post by: Tactile on Tue, 14 February 2017, 12:56:03

I think you missed a spot when you connected one of the caps.

[attach=1]

Title: Re: Help with an IBM m2
Post by: lambreaux on Tue, 14 February 2017, 13:45:13

V

Title: Re: Help with an IBM m2
Post by: Tactile on Tue, 14 February 2017, 14:18:01

That spot with the arrow is called a "via". The signal goes to that spot and then passes through the PCB to connect to a trace on the other side (or in the middle, in the case of a multi layer PCB). In the photo it appears to be a dead end but it's not. That spot connects to another trace "below" it, which you can't see.

I don't know where it goes from there. If you probe around you should be able to find it. It will seem like a hole filled with solder. The traces around it may be burned away but the hole will still be there. Since it is a hole it should be very easy to make a connection - much easier than soldering to a trace.

Title: Re: Help with an IBM m2
Post by: lambreaux on Tue, 14 February 2017, 17:28:16

It

Title: Re: Help with an IBM m2
Post by: lambreaux on Wed, 15 February 2017, 17:22:33

A