D
Dave
- Jan 1, 1970
- 0
Standard prototype nightmare. You assemble a multi layer board with lots of
high pin count SM devices, plus lots of decoupling caps and so on. Final
check before power on - AAAAAAggghhh ! fractional ohm short between the
ground and power planes !!. The pcb is (probably) ok, because you did some
basic checks on it before you started assembling (and it was 'tested').
So, does anyone have any magic recipes for recovering from this ?
It may be a solder bridge or two, or a bad component (I've seen an 0603 cap
that was a solid short.)
Does measuring resistances help ? - ground/power planes are pretty low
impedance to start with
Even with reasonable tools, removing and replacing high pin count (100 -
200+) devices is somewhat risky.
I seem to remember that HP had a 'current sniffer' that enabled you to
inject pulses and track them. Would that work with a plane/plane short ?
Could you do something similar with a signal generator and a Spectrum
Analyser with a suitable probe ?
Dave
high pin count SM devices, plus lots of decoupling caps and so on. Final
check before power on - AAAAAAggghhh ! fractional ohm short between the
ground and power planes !!. The pcb is (probably) ok, because you did some
basic checks on it before you started assembling (and it was 'tested').
So, does anyone have any magic recipes for recovering from this ?
It may be a solder bridge or two, or a bad component (I've seen an 0603 cap
that was a solid short.)
Does measuring resistances help ? - ground/power planes are pretty low
impedance to start with
Even with reasonable tools, removing and replacing high pin count (100 -
200+) devices is somewhat risky.
I seem to remember that HP had a 'current sniffer' that enabled you to
inject pulses and track them. Would that work with a plane/plane short ?
Could you do something similar with a signal generator and a Spectrum
Analyser with a suitable probe ?
Dave