Digital pcb repair steps
 

Could some people give me their idea of the steps to take when
repairing a Digital system? Let's assume I don't have the schematic or
other paper on these boards. They are arcade game boards. On this one
particluar board I am working on it comes up with a work ram error. I
checked all of the RAMS and they check OK. What is the next step? Maybe
something with the address line? It is a system running on a 68000.
Also if I am checking pins on different chips with my scope what are
the levels that would point to a bad chip or node. Anything below .5
volts and above 4 volts? Still confused on this one,
Thanks
Uriah

Digital pcb repair steps
 

Russ wrote in message
oups.com...
Could some people give me their idea of the steps to take when
repairing a Digital system? Let's assume I don't have the schematic or
other paper on these boards. They are arcade game boards. On this one
particluar board I am working on it comes up with a work ram error. I
checked all of the RAMS and they check OK. What is the next step? Maybe
something with the address line? It is a system running on a 68000.
Also if I am checking pins on different chips with my scope what are
the levels that would point to a bad chip or node. Anything below .5
volts and above 4 volts? Still confused on this one,
Thanks
Uriah


obtain pinouts of all the chippery.
magnified inspection of all joints
continuity associated with all vias
check power rails are correct and at all chips
check oscillator is functioning
check all clock inputs have a signal
after that its more like divination, trying to isolate functional
/non-functional blocks, excessive heating of
chips/removal/checking/replacement etc

--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list on
http://home.graffiti.net/diverse:graffiti.net/

Digital pcb repair steps
 

Russ wrote:
Could some people give me their idea of the steps to take when
repairing a Digital system? Let's assume I don't have the schematic or
other paper on these boards. They are arcade game boards. On this one
particluar board I am working on it comes up with a work ram error. I
checked all of the RAMS and they check OK. What is the next step? Maybe
something with the address line? It is a system running on a 68000.
Also if I am checking pins on different chips with my scope what are
the levels that would point to a bad chip or node. Anything below .5
volts and above 4 volts? Still confused on this one,
Thanks
Uriah



There aren't any set steps to solving the problem beyond the basic
checks for voltage and stuck address lines. Repairing boards like this
is somewhat of an art, it just takes a lot of practice and a good
understanding of the building blocks used to create it.