Reviving (jump-starting) a dead R.O.GNT Speaker Lithion-Ion Battery

I recently had to revive a (as it at first seemed) dead Li-Ion battery. It was the battery of a newly bought R.O.GNT external speaker which refused to work or even charge. The device was DOA (dead on arrival) but it was so cheap that sending it back would have cost more than I’ve paid for it.

The speaker has an internal Lithium-Ion battery to allow mobile usage. My guess was that this battery slowly discharged while waiting for a buyer and at some point the undervoltage protection kicked in. Normally this protection should prevent a defective cell from being charged. In my case I hoped the cell would still be okay and survive a jump-start. It was successfully done before in other cases. Continue reading “Reviving (jump-starting) a dead R.O.GNT Speaker Lithion-Ion Battery”

Ripped off JTAG header pads on my dev FritzBox [FAIL]

Ugh… this is so disappointing. I tried to solder a ribbon cable to the JTAG header of my “development” FritzBox 7270. Right during the process I accidentally bumped against the bare PCB. It fell off the table and the already soldered cables ripped off some of the pads. Here’s a photo after removing the remaining cables:

FritzBox Ripped-off JTAG pads

I’m unsure how to continue. I followed the traces but so far did not find adequate vias or pads to solder to. At the moment I’m trying to not brick the FritzBox and therefore do not need a JTAG connection… again…

Partly-homemade MVG Tram Model

My sons are big “MVG Trambahn” fans. MVG, or Münchener Verkehrsgesellschaft, is the transport corporation responsible for most of the public transport (subways, trams, buses) here in Munich.

My sons favorite vehicle is the tram and they always wished to have one to play with. Well, I tried to fulfill their wish but the MVG does not sell toys. At their Trambahn Museum collector’s items are being sold but they are far too fragile (and too expensive) to let my sons play with them.

I was lucky and after some searching found a light blue tram (Amazon link) as a basis. After removing all the pseudo-advertising stickers I used my vinyl cutting machine and a SVG version of the MVG logo to create a rather realistic looking tram. See for yourself…

MVG Tram Model

The models’ dimensions are about 46 x 6 x 10 cm (L x W x H). The color of the original trams is a bit darker and their logo is white instead of black. (I did not have white vinyl when modding the tram and my sons don’t care.) Also the newer tram models have more than three segments.

USB Voltage and Current Meter [Review]

I recently bought a few powerbanks to replace by self-made battery-packs and to have an “emergency” power supply for my iPad. (I always forget to charge my iPad during the day and get angry about myself in the evening.)

To test the power consumption on my devices (without always hanging a volt meter in series to my devices) I’ve bought a USB voltage and current meter. The device is simple to use – just stick it in between the device you want to test and your computer/ charger/ powerbank. Its OLED display shows the voltage, current, power, and capacity (nice, but why?) of the attached device.   Continue reading “USB Voltage and Current Meter [Review]”

RFM26W Breakout Board – First Dirty PCB Manufacturing Service Test

This is partly a review of the Dirty PCB manufacturing service (“Dirt Cheap Dirty Boards” as they call it) as this is my first order. I usually let my boards being manufactured at Seeed Studio or iTeadStudio, but hearing a lot about Dirty PCB lately made me curious and so I ordered a small RFM26W breakout board.

They provide all you need (including Design Rules and CAM export) for Eagle CAD on their web side. For $14 you not only get around 10 boards (12 in my case) but also 6 different colors to choose from.

I did not opt for a fast delivery and so the package took 2 1/2 weeks from China to Germany. (Manufacturing the PCB took four days.) Continue reading “RFM26W Breakout Board – First Dirty PCB Manufacturing Service Test”

HIF6A-60PA-1.27DS as Replacement for JAE PICL-60P-LT Sharp-PC Connector

Needing a replacement for the long ago discontinued Sharp-PC connector JAE PICL-60P-LT, I dug through a lot of datasheets and finally found a pin-compatible one:

Hirose HIF6A-60PA-1.27DS – Datasheet
Hirose HIF6A-60PA-1.27DS – Digi-Key Link

The connector fits good enough for my purposes. If necessary removing a bit of the plastic case left and right of the pins improves the connectivity as the replacement connector is a bit broader.

There is also a version with mounting holes (HIF6B-60PA-1.27DSL) which I will also try to get my hands on (currently not in stock).

My original solution was to use a 2×30 1.27×2.54 pin header as shown in this post, but the narrow space between the pins led to serious constraints in designing a new interface board (more about that when it’s ready).

Unbricking a HP LaserJet M1212nf stuck in an “initialization loop”

I recently helped to repair a bricked HP LaserJet M1212nf printer that was stuck in an “initialization loop”. It booted up normally, but after 10-20 seconds the printer stopped to accept any kind of commands and the text “initializing” was shown on the LC-Display. It then restarted and the whole boot/init started over again and again.

My first approach was to make a hard reset, i.e. set the printer to factory defaults. This can be achieved by:

  1. Turning off the printer
  2. Pressing and holding the “Start Copy” and the “Cancel” button. (Easy, both are below each other.)
  3. Turning on the printer

After setting the initial configs (language, country) the initialization loop reappeared —  the problem was not fixed by the hard reset.

Next, I tried to reinstall the latest firmware which failed due to the loop — there simply was not enough time to upload the firmware I would guess.

I then tried to find out if there is some kind of low level bootloader that would accept a firmware image (many devices nowadays have such a semi-failsafe mode) when the printer is turned on — but did not find any info on that either.

My final approach was just to try out if there would be a firmware upload possibility right after a hard reset (steps as described above). I had recognized that the initial settings/configs right after a hard reset were not affected by the reboot loop. To my surprise this actually worked. I was able to upload the firmware when the first init-setting appeared. After updating the firmware the loop was gone and the printer worked again as before.

I hope this description helps others who are also affected by this problem as I have not yet seen any other solution in the HP forum. I can only guess how the “initializing loop” occurred: maybe an automatic firmware update failed and bricked the printer. Anyways, the 200+ MB printer driver software by HP is a PITA and their web site is a maze…