28 February 2016

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!

25 February 2016

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!

23 February 2016

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.

20 February 2016

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).