SpencerV1 was a fail for multiple reasons. For some reason I decided to try to do the project Manhattan style. With the amount of connections and wires I had problems with connections. In addition to that I used cheap Fets from ebay of dubious reliability. What ultimately killed it however was the discovery that my schematic had multiple fundamental flaws.
Reviewing the schematic
I think this problem arose when I tried to convert it to using a common anode display. I got confused during this process and never discovered my mistake in time.
V1 trying to display a 1
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I went though and hand checked the function of a few gates after it failed to work. Some of them seemed to not work not mater what but did after I swamped them with new ones. There were also one or two shorts from gate to source.
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good resolutions for the next assemblies :
* test each part before soldering
* test the circuit while assembly progresses
at least this should reduce the failure spotting time.
Good luck :-)
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Making a jig to test smd fets would be a hack in of it's self! It's also easier to avoid touching.. And for testing it while building.... I would need to go about building it differently. Due to it's nature there are a few gates that are very interconnected and shoot wires off off to later stages. I think constructing a circuit of this size in one go is okay. I don't want to go bigger however. Really need to get insulated tweezers probably.
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I bought an inexpensive (@$US20) tester from Aliexpress that automatically tests passive components and transistors. It can even determine ESR for capacitors and pinout and gain for transistors. I test all my discrete components now before using them. There are a number of sellers of these kinds of testers, including on eBay.
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What were the "dubious reliability" symptoms ?
FETs are very sensitive and fail easily anyway.
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