Re: [N8VEM: 15616]

[Sergey <skis...@gmail.com>]

Before you trash your Z80 please do a few more tests:
1. Check that Z80 has a valid power supply voltage. With a multimeter
set to V/DC, measure voltage between pins 11 (VCC, +5V) and 29 (GND).
If you're not measuring voltage about 5V (could be from 4.5V to 5.5V)
something is wrong with the power supply, something might be short
circuiting the power, or there is a soldering or PCB problem.
2. It is possible that Z80 is good, and it is getting valid power
(pins 11 and 29) and clock (pin 6), but still doesn't perform any bus
activity because /WAIT (pin 24), /BUSRQ (pin 25), or /RESET (pin 26)
signals are active. Measure logic level or voltage on these pins. Note
that they are active low, and so for a working system you should have
"high" logic signal or a voltage level > 2.7V. If one of them is logic
"low" or the voltage is close to 0V, you'll need to check the
corresponding circuit that generate the signal.