No response in terminal

[Kipper Klank]

There seems to be no response in the terminal in PUTTY or Teraterm
Power light on board is solid. How do I diagnose a problem like this? I have checked every joint where i have soldered and no crossed wires. it worked fine one day. Then another day....huh.... Kinda like my Arduino: not in sync error. Idk.

[Kipper Klank]

The baud rate is correct. The cable works fine. I have powered the board externally then internally using the ftdi. The reset button has no effect on the the ftdi. How would I tell if the board is working but the serial io is the problem? Maby?

[Kipper Klank]

I have also begun to take notice that the hex inverters in the clock and ram are getting warm...but oh so slightly....is that supposed to happen?

[Hans Van Slooten]

No, that's not normal. That could be a short or something wrong with
your power supply. If any of the ICs get too hot (especially the EPROM
in my experience) it could ruin them.

Hans

On Fri, Jan 27, 2017 at 4:41 PM, Kipper Klank <delph...@gmail.com> wrote:
> I have also begun to take notice that the hex inverters in the clock and ram are getting warm...but oh so slightly....is that supposed to happen?
>

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[Spencer Owen]

Hi Kipper,

If it was working one day and now isn't, think carefully about what might have changed.  Have you removed any boards and maybe put them in the wrong way?  Is the computer/terminal software/cable/comm port set up the same?  Are you running it from the same power supply?

Take a look at http://rc2014.co.uk/troubleshooting/ for a more exhaustive list of things to check.

(Oh, and nothing is supposed to get warm)

Spencer

On 30 January 2017 at 16:24, Hans Van Slooten <vans...@gmail.com> wrote:

No, that's not normal. That could be a short or something wrong with
your power supply. If any of the ICs get too hot (especially the EPROM
in my experience) it could ruin them.

Hans

On Fri, Jan 27, 2017 at 4:41 PM, Kipper Klank <delph...@gmail.com> wrote:
> I have also begun to take notice that the hex inverters in the clock and ram are getting warm...but oh so slightly....is that supposed to happen?
>
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[Kipper Klank]

I have gone through every possible situation that I can think of that might cause this problem. The only
Thing I can think of is that I test the IC individualy. What kind of equipment can do this. And how would I use it. Thank you for helping me,

Kipper.

[n.a.m...@gmail.com]

Hi Kipper,

I don't know what equipment you have but I'll assume you have a multimeter that can read DC voltage.

So the first step is to check if the Z80 gets a clock. Unfortunately, very few multi-meters can read AC signals above 100kHz properly so you need to construct an AC probe to read the 7+ MHz clock signal. Luckily, this is easy and cheap to do.

You take two 100k resistors, a 10 nF capacitor, a 1N4148 diode and to construct the following signal tracer:

The component values are not critical at all. If you have 10k resistors, use 10k resistors. If you have a 100nF capacitor, use 100 nF.

Connect the 'signal' end to the CLK signal on the bus of the RC2014 and the GND to the GND pin of the bus. Set your multimeter to DC volts. The meter will read more than 1 V if there is a changing signal on the CLK and much less (it should show something close to 0V) if there is a static signal (either 5V or 0V).

If there is a clock - good! If not, well, there's your problem! :)

Now you can check whether the CPU is running a program. If it is, the address lines should be changing, so now connect the probe to a low-numbered address line, such as A2. If the meter shows 0V, the CPU is not fetching data and might be broken.

If the CPU is fetching data, connect the probe to the a couple of data lines. If you see changing signals, the ROM and/or RAM are probably working. If not, probe the chip select/enable pins on the ROM and RAM chips etc.

If the ROM/RAM board are working, probe the serial output pin on the 68B50. This is more difficult to do, because that pin will only change if the Z80 is accessing the serial port. You'll have to keep resetting the RC2014 to get serial activity while looking at your multimeter.

These tests above will give you more information where the problem lies.

Of course, if you have an oscilloscope, use that to actually look at the signals instead of using the probe! :)

Good luck! Let us know how you get on!

Note to Spencer: if you ever do a re-design of the serial board, it would be helpful to include an LED to show serial activity.
Preferably with a circuit that lights up the LED a little longer, so one can actually see light even if a single byte is sent at 115200 baud :).

Regards,
Niels.

[Spencer Owen]

Hi Niels,

That signal tracer looks like a nice neat thing.  Because I've got a nice scope to play with I haven't bothered trying to read active data signals with a multimeter.  But I'm tempted to build one of these to test out, because, well, why not :)  

It'll probably be worth me putting a link back to this post on the RC2014 troubleshooting page too.

Tx and Rx LEDs on the new Serial Module is a good idea too.  It should be easy enough to get them to light just when data is passing, although I'd have to look in to staying on a little longer.  As you say, a byte at 115200 doesn't take very long and I don't think my eyesight is calibrated to spot that ;-)

Also, as a quick follow up to Kipper, if you have a breadboard and jumper leads then the gates individual logic chips can be tested.  Check out the data sheets for 74LS04 and 74LS32, plug them in to a breadboard, apply 5v and Gnd, then you can manually apply high or low signals to the different gate inputs and check that the output does what it says in the truth table.  The bigger chips aren't so easy :-)

Cheers

Spencer

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[Niels Moseley]

Hi Spencer,

Feel free to copy/paste from the post for the RC2014 troubleshooting page.

Regards,
Niels.

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[PianoMatt]

One thing I found useful was being able to test the chips to make sure I hadn't borked them with ESD. The TL866 EEPROM programmer also doubles as a chip tester, and can test the ROM, RAM and logic ICs through the programming software. Also useful is the Hobby Components logic analyser. They are about £12 on Amazon UK right now and I can't recommend them enough.

[Spencer Owen]

Thanks Niels,

The troubleshooting page has been updated :-)  

http://rc2014.co.uk/troubleshooting/troubleshooting-with-a-multimeter/

Cheers

Spencer

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