29 October 2017

Failing old LCD displays

Following my recent interest in old numeric display technologies I came across old calculators, and started collecting them. In early 1970's there was a lot going on in the research of display technologies, so while Nixies were fading out, VFDs taking their place where there could be a lot of environmental light, LEDs and LCDs were entering the market.

Overheating causes early LED displays to fail faster, especially if run at full brightness.

Sharp EL-5103S
Early LCDs on the other hand lost the "vacuum" inside and became unusable. You can see the failure as a darkened area in the corners/border and there's nothing you can do.

But I wouldn't expect this kind of failure from my Sharp calculator made in late 1980's or the VHF transceiver of early 1990's! Unfortunately replacing an LCD is not easy and you can hardly fit a replacement in the same space. So these devices just turned into (my personal) museum pieces.

The upper area of the display shows signs of air leak.

Too bad for the scientific calculator that served me in high school and at the university. But it looks like a modern replacement costs less than 10€! And I will look for some old battery powered pocket calculator as well, possibly with LED display.

24 October 2017

Old instruments with a warm glow

With the purchase of the Philips PM6645 frequency counter I double the number of instruments sporting Nixies as display device in my lab.

Here they are, the PM2422 Multimeter and the PM6645 Counter both from Philips:

Philips PM2422 (left), Philips PM6645 (right).
I think the multimeter is slightly older than the counter, because the darker front panel looks more 1960's to me. It has a red-coated glass, while the 6645 has clear glass and clear tubes. Both devices are huge compared to today's standards, even if inside there is a lot of room. Probably back then workbench space was not an issue, maybe not an important cost in companies budgets?

Both Philips instruments sit on my oscilloscope, a Tektronix 7000 series, also from 1970's.

Why not add two more nixies in the picture with my biNixie clock?

19 October 2017

New toy: 500 MHz Philips frequency counter

At the Mercatino by ARI Biella in October 2017 my Nixie-radar noticed a frequency counter with as many as 9 tubes. It is a Philips PM6645 500 MHz device, with excellent sensitivity and 10 MHz OCXO reference. Considering that I had a 100 MHz kit-built counter, given the price and the specs I couldn't let it on the table.

At 80€ the beauty came home with me, an early Xmas present:

It mounts common ZM1005 Nixies. It is built with still commonly available parts in case something breaks

17 October 2017

Keeping jump wires in order during maintenance

I think this tip fits the "tribal knowledge" section launched at GQRP reflector and printed in SPRAT magazine.

There are some times when a lazy builder has used jump wires and pin headers to join two boards, rather than fitting proper block connectors. The situation is depicted in the picture below.

Then maintenance time comes, you don't remember neither the wiring scheme nor where the documentation is ...

So, you need to remove a bunch of jump wires but keep knowledge of their order. You have an easy option: take a picture and let them loose. Unfortunately they don't come in many colors, and some colors can be easily mixed up. And the simple idea kicks in: transfer one side of the jump wires on a free piece of pin headers so that they stay in the same color order but can be moved out of the way. The picture helps nevertheless, but order and wire bends will be preserved.

Now ... time to do some shopping for block connectors in various sizes!