[Coco] 2 wasted cpus?

[camillus Blockx]

Good to hear you have a coco 3, now you can test your cpu's  in that coco,
that is if the cpu is not soldered in place.
If it is soldered in place there is still a way to test, rather awkward but
doable.

Attache an 1 kohm resistor ( brown black red ) on a piece of wire like this:

------------------------------|--------------------[
    ]--------------------
wire +- 12 inch               resistor lead      1 K Ohm R         resistor
lead

Do this 2 x

Take one of the cpu's you bought and bend carefully pin40 up, so it makes
no contact withe lower cpu.
Place the cpu on top of the cpu in the coco 3, and press it downso it sits
snug into the socket together with the original cpu. Now solder one of the
earlier made wire and resistor to an ground lever, ( + side of nearby
capacitor) and attach the resistor side to pin 40 on the BOTTOM cpu. This
 will HALT the bottom cpu so it will not effect the test)

Now the other wire you connect to a nearby - side of a capacitor and the
resistor side to the upper cpu pin 40,

- from capacitor or supply
-----------------------------------wire-----------------------res 1k
------------------- pin 40 cpu on bottom
+from capacitor or supply
-----------------------------------wire-----------------------res 1k
------------------- pin 40 cpu on upper

Do not connect any pin directly to any supply connection ALWAYS use
resistor ( at least 1Kohm )

Apply power and see if you get a working image, try reset if not from the
first try. Possible you need to press a bit on the upper cpu to make shure
it makes good contact. If you have good screen cpu is OK, else needs more
testing.

After power down do the same with the second cpu

Hope this makes sence to you

Good luck

If you decide to trow the board away,i will take it and pay for Shipping

thnx


On Thu, Mar 7, 2013 at 12:10 PM, Luis Antoniosi (CoCoDemus) <
retrocanada76 at gmail.com> wrote:

> i applied only to one side, it's is very difficult to put solder on top,
> you can't reach with solder tip, and the socket's round metal legs covers
> the solder points. I use a socket like these:
>
>
> http://image.made-in-china.com/43f34j00uBeapAfrfwqm/IC-Socket-Machined-Pin-0110-.jpg
>
>
> But I tested the traces from top and bottom and all seem to have continuity
> until their components or vias.
>
> sending the board to you probably would cost more than buying anoter coco2
> on ebay. I already have a coco3, I just want to fix my coco2b. Thanxs for
> the help.
>
> Felipe.
>
>
>
> On Thu, Mar 7, 2013 at 12:58 PM, camillus Blockx <camillus.b.58 at gmail.com
> >wrote:
>
> > The best way to know if your cpu's are busted is to put them in an other
> > coco and test it.
> >
> > Also worth to mention is when you placed the machiened socket did you
> > solder it on both sides?
> > Go with a thin solderwire and add a little more solder tobottom and top
> > side on the pins of the cpusocket.
> > This makes sure that plated thrue holes are making goodcontact. Use also
> a
> > fine solderpoint for this.
> >
> > good luck
> >
> > ( I would like to help you, but I do not know if you live close to
> Indiana,
> > Valparaiso area )
> > You can buy a coco 3 128k for $75+ S/H, so don't know if you want to send
> > your board to me, I test and if damaged try to repair it, and send it
> back
> > to you. The cost would only be Shipping and parts, if needed.
> >
> > Just let me know ok
> >
> > camillus
> >
> >
> >
> > On Thu, Mar 7, 2013 at 2:32 AM, Arthur Flexser <flexser at fiu.edu> wrote:
> >
> > > It's also conceivable that you have a cold solder joint, depending on
> > > how exactly you tested continuity.  (Another possibility is a cracked
> > > or damaged trace on the motherboard.)  Try testing the continuity
> > > between each pin and someplace the trace beneath it goes to.  If you
> > > just tested continuity between the pin and the glob of solder beneath
> > > it, a cold solder joint might not be detected.  A close examination
> > > under a magnifying glass might turn up a problem more quickly.  So
> > > might reheating all the connections to see if the problem goes away.
> > >
> > > Art
> > >
> > > On Thu, Mar 7, 2013 at 1:02 AM, Retro Canada <retrocanada76 at gmail.com>
> > > wrote:
> > > > just got my 2 mc68b09e cpus from jameco. removed the defective cpu
> from
> > > my coco2, installed a machined socket but when i test both cpus all i
> get
> > > is garbled screeen. with vdg checkerboard and at signs. the same if i
> > > remove and turn it on without the cpu.
> > > >
> > > > i checked the continuity on all pins seems fine. cpu is receiving 5v
> > and
> > > making some heat.
> > > >
> > > > so did i get 2 busted  cpus?
> > > >
> > > > Sent from my iPhone
> > > >
> > > > --
> > > > Coco mailing list
> > > > Coco at maltedmedia.com
> > > > http://five.pairlist.net/mailman/listinfo/coco
> > >
> > > --
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> > >
> >
> > --
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> >
>
>
>
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