Saba Compact Clock A - washed up - no joy

As announced, I washed with hot tap water the Saba Compact Clock A PCB covered with NiCd electrolyte spill.

I would say that 80% of the alien material has gone away and most tracks shine again. A ceramic capacitor was split in half and I had previously removed a trimmer that was badly damaged.

I reconnected the transformer and, unfortunately but expectedly, the clock does not power up at all. Not even a mildly reassuring sequence of "000".

Probing around with the DVM I spotted open diodes in the area closest to the was-backup-battery. And since I have no pinout of the microchip, let alone a datasheet, I have no idea which pin is not being fed correctly.

I might replace few 1N4148 here and there and fit a new 100k trimmer. If nothing happens I will leave a note to the future myself inside the device of what has been found and done, and the Saba Compact Clock A will join my collection of electronic items from 1980's.

It can be fixed. With patience and time. Do I really want to?


PS: the display is not a simple LED, and I need the microchip to work again so that I can measure voltage values!

PPS: according to the blogging platform, this is my 500th post!

Saba Compact Clock A clean-up from NiCd spill

During a ful immersion into my pile of electronic junk I noticed an alarm clock radio from early 80's: SABA Compact Clock A. Since it was not my target I skipped over it, just to come back the next day and pick it up for further analysis and putting it back into service.

The display is LED, not VFD. Nevermind. The whole thing powers up but radio and clock don't work, so a look inside was desperatly needed.

The battery still in place and visible leak.

Horror! The radio contained a NiCd backup battery that has leaked over 1/3rd of the PCB. It is all dry now, in small crystals. According to many online discussions the dry electrolyte (KOH) will come off easily with a brush and then some simple chemical solution.

I will try a first cleaning round without becoming obsessed about it. If it doesn't work out then I might fit into the case a custom alarm clock built with modern technology that reuses the AC transformer, the display and the loudspeaker.

Solder side. The green protective layer comes off.

One thing is sure: I must tidy up my desk because I have KOH crystals all over and it needs a thorough cleaning!

Six VFD tubes (IV-3) in a row

Work on old display technology continues. I spent few nights trying to align six VFD tubes on a piece of veroboard. The result looks neat but very hard to keep proper alignment when soldering 10 pins per tube.

So I dropped the idea of using veroboard and, given the very cheap prices for prototype PCBs, I will try to design one myself.

Originally I wanted to draw many single-tube boards, but I will probably go for a full board that includes driver transistor arrays (ULN2003).

A local OM will help me producing the files for the PCB factory, so hopefully I will save a little time on that step.

Compact power supplies for our circuits

While wondering around Aliexpress offers I stumbled upon a black box coded "HLK-PM01" that is said to be a 90-260Vac to 5Vdc at 600 mA output.

There is also an interesting 3.3V @1 A as HLK-PM03 and 12V @600 mA as HLK-PM12. The producer has even a website www.hlktech.net.

These blocks are the best solution so far I have encountered for DIY projects that need to run off an AC outlet, let alone the bulky "USB" chargers. And HLK-PM03 provides 3.3V that are needed for ESP8266-based projects.

I've ordered a couple of 3.3V modules, also because an positive review you can find on a .dk website (for HLK-PM01).

Veroboard at last!

When I was in primary school, at the age of 9 or 10, I received this book as a present:

Italian edition of "Science fun" by Usborne Publishing 1981

It shows simple electronics, chimics and physics experiments. All electronic circuits were supposed to be built on what I later found to be called "Veroboard": a multihole board with fully connected rows that could be easily interrupted with a drill bit or so. I searched all local shops to no avail. I resorted into building those circuits with componets sitcked in soft PVC food containers and showing them at school.

Now, more than 30 years later, in the local shop I tried asking for a "breadboard with connected rows", for the childish fun of asking, and ... what a surprise! They had it! Given the smell it was probably built long time ago. When I sat in the car after my shopping session I even though something was melting!

Now I have found out that I can shop online for "Veroboard" and get some more of it probably slightly cheaper than the local shop. Curiously most sellers are in UK and not in Far East. I had stopped looking for it too long ago.

Today I am using Veroboard in my VFD Clock transformation project, to simplify wiring between the four tubes that are connected in parallel next to each other.

Striped print on Epson inkjet printer

We own an Epson XP-215 inkjet printer/scanner/copier. We print/copy very seldomly and very few pages each time. One of these days I had to copy a drawing and it came out with wide horizontal white areas. A second copy of the same document was even worse!

In order to better understand the problem I created a simple print with increasing numbers, one per line, and you see the result on the right.

Initially I suspected something had gotten into the printer cylinders and periodically moved paper away from the print head, but further prints were even worse. With the help of an Internet search engine I found and watched some tutorials that showed how to clean nozzles that had dried ink all around.

All you need is a piece of kitchen paper, some liquid for cleaning glass (windows) and thin gloves (else you loose sensitivity in your fingers). The quest for these tutorials is left as an exercise to the reader.

Around the black ink nozzle there was something that looked like dry ink. I removed it with the method mentioned above.

Once I re-installed ink cartridges the first test print came out like this:

Almost completely readable. Almost. Then I did a print head check printout (from the Epson tool on Windows). Then after 10 minutes I printed again and everything looked normal.

Mission completed. 60€ printer saved from dumping within one year from purchase. Happy family members.

biNixie clock: completed.

Less than six months, from first purchase to a completed device. This is a personal record!

In May 2015 I bought some Burroughs B5092 Nixie tubes. Since I couldn't build something meaningful out of three working tubes I opted for a dual-digit clock, and a third B5092 stays as spare.

Inside a decoupage light-wooden box I fit the two sockets, a perfboard with K155DI BCD decoder/drivers, an Arduino clone board with DS1307 RTC and a lumos.sk high voltage PSU.

This clock has been built with components of the Cold War era, from both sides of the wall, mixed with modern microcontrollers and switching power supply.

The firmware shows HH, MM and SS. Every hour all symbols are looped once in a basic cathode de-poisoning routine. I have not implemented any other fancy feature like fading, DST auto.adjust, night mode and so on: it is a simple addictive clock.

Yes, I caught people staring at the box for few cycles before asking what are those numbers.

Edit March 2016: the schematic diagram is now available.

TIL305 on driver's back

Fast forward to the arrival of ATtiny4313 through few design considerations about controlling TIL305 displays "remotely", and a couple of these dot-matrix displays have jumped on the back of their drivers according to the drawing published earlier on this blog.

Meanwhile I have also completed the onboard font with 0-9 numbers and 7 possible symbols (check the ASCII table and you will see there are seven "holes" between number 9 and capital letter A).

For this first release I have left out current limiting resistors on anodes, so I rely on the average current since in the worst case each pixel is ON only 1/7th of the time. The resulting "component" is compact and TIL305 displays can sit next to each other without short circuits.

With proper fuse settings the ATtiny4313 works between 1.8 V and 6 V, so intensity can be controlled through either "pixel ON time" or DC power supply (but not through PWM dimming).