11 November 2018

Reviving a ceiling lamp from CFL to LED

We've had at home a ceiling lamp for about 10 years, and for the last 4 years it has misbehaved. It contains two 55W CFL tubes with an external HV power supply by OSRAM (Quicktronic Professional QTP-DL 2x55 GII).

The defect was that it would switch off after about 15 minutes of operation and it would restart only after a rather long while. In any case it was not usable at all.

The original configuration.
I tried replacing the gas-filled elements without success, so the culprit must have been the embedded power supply. Since I am still developing my spider superpowers, working upside down on the ceiling is not my thing so I pulled down the lamp on the table. Still about 15 minutes of operation even without the front glass (in case it was a heat issue).

I took apart the power supply case and looked for the obvious, that obviously wasn't that obvious. I simply reconnected everything with the power supply out of its case and it would run for hours. HA! Maybe a cold solder joint failed with heat cycles over time and moving the circuit around sort-of fixed it.

I took my chances and put everything into the metal case, and still working. So I secured the case back to the lamp and ... 5 seconds of operation!

Enough. Either I got another identical power supply or I had to find something else. My readers probably already guessed which one I picked! "Something else", of course.

The lamp base is metallic and hidden against the ceiling so it can be drilled as needed to accomodate a different setup.

Few searches later I learned that there are LED replacements for neon tubes, and they include the power supply too. I chose two circular replacements whose total equivalent power would get close to the original 110W.

Of course I had a look inside the power supply, that is very simple since it has to light up a series of LEDs:

The LED strip power supply.

And the final look, up on the ceiling before placing the cover glass:

Final config. Notice something "light"?
Now the two light sources are independent, so if one fails the lamp will still work at 50% luminosity. If you look closely at the last picture you will see LEDs are "on", dim, but "on". Even with a single wire attached, the culprit is probably some leak of the long driving wire towards ground. I couldn't get rid of it by swapping the two cables, so I consider it as a night light undocumented feature.

We don't use that lamp very often, so hopefully it will last another 10 years!

06 November 2018

Elka 135, calculator from Bulgaria

Meet the Elka 135 scientific calculator! I bought this marvel in FN 2018 fair. Batteries had leaked inside, so this was the fault to fix (yet again).

There are few pages online that describe this calculator made in Bulgaria. I like the 8-digit LED display. It can be powered from an external 6V DC source through a 3,5mm audio jack (!!).

Using a variable voltage power supply I could confirm that it works down to 4.5V and a small "L" appears in the leftmost position: this means I can use this calculator with USB power, without fully restoring the battery contacts.

Few keys are bouncy resulting in double-triple press, but I am not sure whether they were like that in the original, non-damaged calculator.

More complex operations take some time, and the left position in the display keeps updating until the result is ready.

This device is quite power hungry, because of the LED display, but modern batteries (or USB power) can handle it.

26 October 2018

Industria Macchine Elettroniche IME-141 - eeeeeerror

I let my daughter play with IME-141 calculator. Since a calculator is boring if you don't have maths to do, she pressed few buttons at the same time and this is the result:

It never occurred to me I could to that "test". Now I try it on every calculator just for the fun of it.

And for the curious, a close-up of display VFD tubes. I really like the shape of segments. The vertical filament is visible too.

06 October 2018

FM radio for the bathroom - followup

This is a follow-up to my previous post about an FM radio for the bathroom morning routine.

The good old Samsung Galaxy S (i9000) does a wonderful job. Its stand-by time is more than a week even if we leave the GSM_RF part powered all the time (otherwise we would need to switch it on every time we need the FM radio). The loudspeaker volume and quality are very pleasant.

I even found a smaller 3.5mm jack to sacrifice and now it looks even better without effect on the received signal.

Long live radio!

Case closed :)

13 September 2018

Rethinking my mobile setup

Alright, the shortened UHF-only Nagoya UT-106 is back in service.

I added a piece of RG-58 with PL-259 so that I could measure SWR. But just the fact of terminating the coax with a PL-259 made me think of a way to fit the QYT KT-8900 mobile in the new car in place of a handheld.

While the large glass roof drastically reduces the flat metallic area for a magmount antenna, it does not block RF either. Since the only place for a small magmount is above driver's head, the antenna cable would be in the way of the passenger because I don't leave the antenna outside when the car is unattended, go figure. But there is plenty of space in the back of the car. Yes, inside, but with all those transparencies (be it glass or plastic), RF-wise it is almost like being outside.

The plan is to place the magmount base on a metallic surface and let it rest on the parcel shelf. At home I found an L-shaped 40 cm long iron piece that can be forced between the back seat and the shelf. SWR of this combo is 1.5:1 on the FT-817. So far so good.

Will it work?

06 September 2018

Nagoya UT-106 intermittent signal

Now that I was enjoying trouble-free mobile HAMming, my modified Nagoya UT-106 developed a fault causing intermittent reception. Moving the coax near the RTX would restore/loose the signal, so probably something has broken in the coax. Since the handheld lays on the passenger's seat, holding the microphone causes it to move around and put some stress on the cable.

I will cut out the broken part and try to resolder the SMA connector. Before that I will fit a PL-259 so that I can try the whole setup with a more powerful RTX as well as measure SWR.

03 September 2018

FM radio for the morning routine: September 2018 attempt

Following my previous post on two attempts at joining the morning news and the morning bathroom routine, in both cases something is too wrong. Memory lost and instable signal are no-go.

Initially I admitted my failure to provide a suitable device and let the family member head to the shop to look for a replacement. Then an idea strike: why not use the FM radio into that old Samsung Galaxy S phone that was gathering dust? Just fit a 3.5mm jack (with enough wire) to behave as an antenna and set the output through the internal loudspeaker.

Bingo! While an overkill, it is battery powered, rechargeable and does not loose memory when the battery goes flat (but you can monitor it easily). It has more than enough audio power to fill the bathroom and costs nothing. Last but not least there is a self power-off setting at 30 minutes! The only drawback is that the RF-GSM part has to be ON to receive FM radio. But that works even without a SIM card inserted.

As shown in the picture, if the FM station is close/strong enough a 3.5mm jack alone acts as a perfect antenna (picture shows a 5mm to 3.5mm adapter). Probably it also helps not to overload the input stages resulting in better reception!

Let's see how long this solution lasts.

Note. I know I could have used an Android app to listen to the Internet streaming transmission. But who knows if there is still a working app around for Android 4.x? And how it would compare with power consumption? And the current over-the-air solution works even during power outages.