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Removed the SIO card, now I am getting in12 78 Is it possible that the SIO card interfering with input port 12? SIO card is a new one, assembled with great caution and seem to be working fine, except

When I use the instructions on page 24, Examine Input Port, Press 5 12, read in12 78, instead I am getting blinking FF. Is this normal? Does this indicate in have an HW problem?

The comment on TTL was a generalization. Also likely any Nmos chips and others will be dead. That will include most of the parts like the Ram chip, uSD is plugged in, and as mentioned already most

Thanks Allison. I have replaced the 74SL259 with a new one, but didn’t make any difference. [email protected]> wrote:

Any TTL (74LS259) will react very badly with overvoltage. Most of the CMOS may tolerate it. Allison

Now that the Front Panel is working, I need to fix the SIO card which I think accidentally destroyed during the troubleshooting of the Front Panel. SIO card received 9V instead of 5V now all LEDs are

I originally used FJN3303 transistors, which have internal 22k+22k resistors. When Mouser stopped stocking the thru-hole versions, I had to switch to FJN3305 with internal 4.7k+10k resistors. I

Hi all! To add another data point to the problem, I'm using DTC114ES for Q2/Q3, and DTA114ES for Q5 (all with 10k + 10k resistors) and R4 is 22k. Edit:? R4 is of course 10k.? I confused it with R4

Thanks Lee, a 22K resistor in parallel with R4 A between pins 1 and 2 solved the problem with S8. [email protected]> wrote:

Kerem Kapkin wrote: Correct. This provides a debounced pushbutton to clock counter U2A. Either is fine; you just don't want to leave a CMOS input floating. Or J2 pin 10 also works. With this setup,

Here is the recommended setup for standalone testing of the front panel, just to make sure it is the correct start. -J2 Pin 9 [/out] is connected to 3 components. 0.1uF cap other end ground, momentary

Nothing is actually getting hot on mine. Barely perceptible warmth would be a better way to put it. I'm powering it directly from the USB port on my laptop. Actually I just got a new laptop and it's

OK, that's correct. You have enough 5v power. That's also correct. 74LS145 input D (pin 12) is always low when the interrupt handler is working. The inputs to it count from 0-7 and repeat. If the Z80

I cannot get S8 work no matter what. While running FFF1 sequence it is using 92mA current at 5V supply. While testing with the logic probe, 74LS145 inputs to A(15), B(14) and C(13) are fine but D(12)

Ah; that may be a hint. The Z80MC runs *cold". Everything is CMOS, nothing gets hot. What are you using for a power supply? Could its voltage be insufficient? USB supplies are often weak, and the

I thought that there was a pattern to the failure I'm experiencing but now I'm not so sure. One thing I did notice, when the chips are cold, it seems to work. Once it warms up, the problems occur

I started a new thread for this issue. I thought that there was a pattern to the failure I'm experiencing but now I'm not so sure. One thing I did notice, when the chips are cold, it seems to

I also have an issue with the 8 not working, but i chalked it up to me messing up the build. I will try to see if I can find time to test out your theory this weekend. -=- Brett Sent from Proton

Hi Lee, I will try your suggestion. I have the front panel on my breadboard now with your suggestions for testing. Have a safe trip, when you are back we can reconnect for

You're the second person to mention problems with the "8" key. I haven't seen it myself, and from the schematic, can't imagine what could be wrong that only affects the "8" and not the other keys in