Thirty-seven years ago (1986), a Panasonic KX-W50TH Thermal Electronic Typewriter rolled off of an assembly line in Japan. It makes its way to North America and ends up in a construction contractor’s office for a number of years before ending up in storage. It is certain that the typewriter was quickly replaced by a computer and a dot matrix printer. Sadly, the owner did not use it much. How can I tell the history of this machine? The thermal typewriter uses heat to transfer letters from a thermal ribbon to the paper. The used ribbon is taken up by a spool into the ribbon cassette. Fast forward to 2020. The ribbon cassette gives up its secrets. The used portion of the ribbon shows where the letters were applied to the paper. Many invoices were printed using the Panasonic Typewriter. Because privacy is important, I shredded the ribbon. This typewriter is part of an overall hobby collection. Today, I use it with thermal paper to write notes and create labels.
About six months ago, the Pansonic typewriter no longer operated. Whether it was plugged in or powered with batteries, it would not turn on. This typewriter was destined for disposal. It barely saw any action, so why not try to fix it? I opened up the typewriter and traced its power, but I could not clearly narrow it down to a specific cause. I lack the tools to check more than voltage and resistance. Electronics that are over 30 years old often suffer from dried-out capacitors. Given the history of failures and a copy of the service manual, I gave it my best guess. One of the larger capacitors failed. I suspect the following capacitors may be the culprit:
- Large black 10,000 µF 16 V capacitor (upper right of the image)
- Light blue 3,300 µF 16 V capacitor (second from the right in the upper right of the image)
- Dark blue 4,700 µF 16 V capacitor (centre right)
Armed with a guess and some electronics background knowledge, two replacement capacitors (10,000 µF and 3,300 µF) were identified and ordered. I figured I could replace one at a time until the typewriter worked. I elected not to replace the 4,700 µF capacitor since it is not in line with the power input of the main circuit board. Parts are easier to source in the 21st century. Capacitors are much smaller today than they were in the past. Below, the image shows the replacement capacitors. You can find replacements at the same cost for one more many. Hard decision (first-world problems). At the rate of 35+ years to failure, the new capacitors (if stored properly) will keep this typewriter running for 350 years. Come on, laugh, that was funny.
The Panasonic KX-W50TH typewriter is easy to disassemble. The cover and the keyboard are easily separated with the removal of screws. Care must be taken when removing ribbon cables. They are delicate and hard to find. While dissembling the typewriter, plug in a soldering iron and have handy, desoldering braid, solder, and be patient.
As mentioned before, the replacement capacitors are smaller. Take care to measure the original capacitor’s height. You do not want the new one interfering with the keyboard. One very important consideration: match the capacitor to the old one. Choose the Farad number (typically µF) and the voltage. You can choose a higher voltage but do not change the Farad number. Take care to select a capacitor that is close to the original operating temperature range. In my case, I kept the values identical. As seen below, the new capacitor is physically smaller. Desolder the old capacitor and install the new capacitor. Take care with the positive and negative leads. Do not install the capacitor in reverse.
After the installation of the 10,000 µF 16 V capacitor, I reconnected the main display, attached power and turned on the typewriter. It worked! I could have stopped there, but I elected to perform preventative maintenance. I installed the 3,300 µF 16 V capacitor. After the second capacitor was put in place, one final power check was performed, and the typewriter passed the power on test. The typewriter was put back together and placed back into hobby service.
Items that I used to revive this typewriter (Amazon Affiliate Links Below):
- 10,000 µF 16 V Electrolytic Aluminium Capacitor (16×30 mm)
- 3,300 µF 16 V Electrolytic Aluminium Capacitor (13×20 mm)
- Vastar Soldering Iron
- KOTTO Third-Hand Professional Soldering Stand (optional)
- Fluke 117 Digital Multimeter
- KESTER Solder
- NTE Electronics SW02-10 No-Clean Solder Wick
