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Wednesday, 26 December 2018

More Counting with Nixies


As part of my TEAS which I described previously, I have acquired a further HP Counter/Timer as "spares" for the one I already have (yes, this is part of the condition it seems).

So, I started with the normal replacement of the electrolytic capacitors in the PSU and then did some debugging of the electronics itself. I found one of the 4 bit latches to be suspect so I removed it:

It didn't work out well for the poor thing, but removing DIL devices from through hole boards can be quite tricky at times. I did manage to remove some working parts from another board I have:

although removing the Nixie socket was extremely challenging, and I ended up prizing off the top plastic part and removing one pin at a time.

So, in the broken unit we now have:

A socketed replacement for U9 - this was the chip I suspected of being bad.

I have also inserted sockets for the "Option 001" which is the addition of the extra digit and then used parts from the spare board above to create this option. You also have to move a resistor that drives the Overflow electronics to that it does this one decade higher.

You have to admire the design and build quality of these units, they certainly don't come like this anymore:

The unit has had a good clean and everything now seems to be working:

The top unit is the newly repaired item, the one on the bottom is from last time.

Now, what next?

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