Diagnostics

Power LED is not steady

Power LED comes on but flickers from time to time

The board is sensitive to supply voltages lower than 5V, and some power supplies don’t quite deliver that. Try some other supplies. Or check your supply as we show in this video:

Duration: 3m14s

Alternatively, you can try if a different USB power cable helps in combination with your supply.

System doesn’t start

Blinkenlights don’t come on
Blinkenlights come on in random state and stay there
Blinkenlights change briefly but then nothing happens

If the Power LED is lit and stable, but still the computer doesn’t start properly, the most likely cause is a poor soldering connection for one of the pins. If this is the case, the system may work perfectly fine on one day, and be completely broken on another. Look for these joints with a loupe or by taking pictures with a smartphone.

You can also troubleshoot with a multimeter. This Excel sheet gives reference voltages: Troubleshooting-1.xls.

 

There are two sheets, each with instructions at the bottom. (If you have a small screen you may miss those.)

In general, pay closest attention to the ground pins. Those are always a bit more difficult to solder, especially when using a lower wattage soldering iron. The reason is that these pins are connected to a larger body of copper and that draws away more heat compared to other pins.

You should also check if the EPROM and RAM chips are seated firmly, and none of their pins are bent or misplaced.

If the LEDs light up in some arbitrary pattern and then briefly change, that is evidence of code trying to execute. If all four LEDs stay off, it is also possible that the RAM is not seated.

If none of this helps, you might want to check that there is no short between pins. For example, some leads on the back side might be touching.

As a final resort, backside cleaning might be an option. Sometimes excessive leftovers of soldering flux can cause problems. The reason is that, depending on its composition, flux may be conductive. Removing flux is a tedious job, and advice on the Internet on it varies widely. Don’t follow Internet advice, but get advice from the store where you bought your soldering materials. The potential need for cleaning and the required method depends on those.

For your reference, consider this: 1. We have seen boards with copious amounts of flux on them that worked perfectly fine. 2. We haven’ t heard back of anyone yet who had to do this to make his Gigatron work.

In summary: if you can’t find the bad soldering joint or short, assume you have missed it and look for it again.

Low voltage from clock generator

At the end of assembly step 3, the clock voltage is low and unstable

This is the symptom for a cable break in the probe cable. The voltage on the USB power input will appear correct. Try a different multimeter.

Slow performance

Pictures runs slow
Racer screen updates slowly
The Mandelbrot clock drifts several minutes per day

Check if you have not accidentally disabled the retro scan lines without realising it. Most applications need the retro lines enabled to work well. Toggle between modes with the [Select] button.

Anything else

We have a user forum for support where we hang out with other Gigatron builders to discuss new ideas. The forum has a dedicated section for support on kit assembly. If none of the above solves your issue, you can ask for advice in there. Maybe somebody has already experienced the same thing and can help you right away. Of course, there are also the contact methods that are listed in the Assembly Manual, but you might get a quicker response in the forum.