[sdiy] The fatman is finished...

[Scott Gravenhorst]

There's more inline, but I do have one important question:  Are you sure the
5 volt supply is 5 volts, AND that it is properly regulated/filtered?  A
supply with noise can have an _average_ DC voltage that could appear correct
on a DMM, however if there's a problem with it, you might have 60 Hz
appearing on the rail from bad filtering, wrong resistor size, or excessive
load.  If your signal tracer has a series cap, try listening to the 5 volt
(to ground) supply rail.  Or you could try to measure AC volts with the DMM.
 There should be very little AC volts on the supply.  I don't have a spec for
that, but measure that and let us know what it says...  This is another place
where an oscope is wonderfully superior to a DMM.  If you've got a serious
problem with 60 Hz noise, you'll hear it with the tracer and you'll see it on
the DMM set to AC volts.

I've put other comments inline below...

Gabriel Lindeborg <gabriel.lindeborg at sverige.nu> wrote:
>Hi Crow!
>
> > The Old Crow wrote:
>> It sounds like the 8031 is not running.  Check to see if there is a
>> processor clock at IC1 pin 18 (or 19, whichever is the internal osc
>> output)...
>
>The up seems to be running as I get totaly different power up behavior 
>when I remove the crystal.
>
>>or check for the ALE strobe pulses at pin 30.
>
>The ALE output stays at a constant 0V as far as I can tell with the 
>simple multimeter I got at hand.

ALE (Address Latch Enable) will toggle with each bus access, so this will
toggle very fast (megahertz rate) and you won't see it with a multimeter. 
Here's where you need a scope.

>
>> Are C2 and C3 the
>> listed 33pF values?
>
>Yep, marked 33 anyway...
>
>> Check for solder bridges, cracked traces, etc. in the 
>> IC1/IC2/IC3 === MCU/latch/ROM connections.  Check IC4 connections as well.
>
>The soldering and traces has been scrutinezed w. a loupe, over and over 
>again (I feel pretty confident w. the soldering as I have soldered for a 
>living some years ago).
>
>I'll try to reburn the 2764... but then again the power up behavior 
>should be constant if thats the problem, shouldn´t it?

If you can burn, you should be able to verify.  No?

>//Gabriel - I wish I had a scope at home...

Borrow one ?

---------------------------------------------------------
- Where merit is not rewarded, excellence fades.
- Hydrogen is pointless without solar.
- What good are laws that only lawyers understand?
- The media's credibility should always be questioned.
- The only good terrorist is a dead terrorist.
- Governments do nothing well, save collect taxes.

-- Scott Gravenhorst | LegoManiac / Lego Trains / RIS 1.5
-- Linux Rex         | RedWebMail by RedStarWare
-- FatMan: home1.gte.net/res0658s/FatMan/
-- NonFatMan: home1.gte.net/res0658s/electronics/
-- Autodidactic Master of Arcane and Hidden Knowledge.