@mjtech01.bsky.social
I can remember when we'd go to the park with the children and take a bucket and spade or a ball. Now we have to take this.
May 16, 2025 at 3:25 PM
I can remember when we'd go to the park with the children and take a bucket and spade or a ball. Now we have to take this.
I'm sure I've got plenty of low-pF capacitors somewhere but lying on the bench was a strip of 47pF ones. Try sticking one in series with one of the existing crystal load capacitors to reduce it a bit. It works! The radio can talk to the others now. Happy offspring. /end
April 30, 2025 at 2:21 PM
I'm sure I've got plenty of low-pF capacitors somewhere but lying on the bench was a strip of 47pF ones. Try sticking one in series with one of the existing crystal load capacitors to reduce it a bit. It works! The radio can talk to the others now. Happy offspring. /end
The radio chip is a BK4819 and a data sheet is available. It says the master 26MHz crystal should be accurate to 2.5ppm, which is pretty ambitious for a toy. The example circuit diagram shows a trimmer on one leg of the crystal but that's not present in this radio. /4
April 30, 2025 at 2:21 PM
The radio chip is a BK4819 and a data sheet is available. It says the master 26MHz crystal should be accurate to 2.5ppm, which is pretty ambitious for a toy. The example circuit diagram shows a trimmer on one leg of the crystal but that's not present in this radio. /4
A check with the spectrum analyzer confirms this. The faulty one is about 10kHz low on each channel compared with the others. Doesn't sound like much at 446MHz but it matters for narrowband FM. /3
April 30, 2025 at 2:21 PM
A check with the spectrum analyzer confirms this. The faulty one is about 10kHz low on each channel compared with the others. Doesn't sound like much at 446MHz but it matters for narrowband FM. /3
Inside is this board. Neat, but there's not much to see and nothing to adjust. I had a feeling the radio was off frequency because it would sort of make contact when set to a different channel to the other set. /2
April 30, 2025 at 2:21 PM
Inside is this board. Neat, but there's not much to see and nothing to adjust. I had a feeling the radio was off frequency because it would sort of make contact when set to a different channel to the other set. /2
My children have these toy PMR446 walkie-talkies. We have three of them. Recently the blue and green one wouldn't communicate with the other two. Time for Dad to investigate. 🧵/1
April 30, 2025 at 2:21 PM
My children have these toy PMR446 walkie-talkies. We have three of them. Recently the blue and green one wouldn't communicate with the other two. Time for Dad to investigate. 🧵/1
Put it back together with nearly all the screws and it still works. Job done. /end
March 23, 2025 at 9:34 PM
Put it back together with nearly all the screws and it still works. Job done. /end
Add a bit of Kapton tape to try and prevent a recurrence of the fault. It's pretty certain to get dropped again! /7
March 23, 2025 at 9:34 PM
Add a bit of Kapton tape to try and prevent a recurrence of the fault. It's pretty certain to get dropped again! /7
Yay! It works. Son will be happy. /6
March 23, 2025 at 9:34 PM
Yay! It works. Son will be happy. /6
Add a bodge wire to the other side of the via through the convenient hole in the board. /5
March 23, 2025 at 9:34 PM
Add a bodge wire to the other side of the via through the convenient hole in the board. /5
Looks like a bit of damage to this via connected to pin 6 (CLK) of the serial Flash chip which presumably holds the firmware. That's going to cause problems. /4
March 23, 2025 at 9:34 PM
Looks like a bit of damage to this via connected to pin 6 (CLK) of the serial Flash chip which presumably holds the firmware. That's going to cause problems. /4
Looking at the construction closely, the pins of the printer motor come awfully close to the board just here (shown with the printer mechanism lifted a bit). /3
March 23, 2025 at 9:34 PM
Looking at the construction closely, the pins of the printer motor come awfully close to the board just here (shown with the printer mechanism lifted a bit). /3
It comes apart nice and easily with a few screws, and is quite neatly made inside. There's a main PCB with the camera, printer and screen connected by FFC connectors. This one fell on to a hard floor and now does nothing except blink the display backlight briefly. /2
March 23, 2025 at 9:34 PM
It comes apart nice and easily with a few screws, and is quite neatly made inside. There's a main PCB with the camera, printer and screen connected by FFC connectors. This one fell on to a hard floor and now does nothing except blink the display backlight briefly. /2
We have a couple of these toy digital cameras. They take terrible photos and videos and print out on thermal paper, and the children love them (also because they play Snake). This one broke today. Time for daddy to fix it. 🧵/1
March 23, 2025 at 9:34 PM
We have a couple of these toy digital cameras. They take terrible photos and videos and print out on thermal paper, and the children love them (also because they play Snake). This one broke today. Time for daddy to fix it. 🧵/1
The permanent field magnet is cylindrical and hides inside the armature, making the motor slimmer. The whole thing is a marvel of precision, especially as it only costs a few pence. /end
March 18, 2025 at 8:46 PM
The permanent field magnet is cylindrical and hides inside the armature, making the motor slimmer. The whole thing is a marvel of precision, especially as it only costs a few pence. /end
The armature is entirely self-supporting, with no core at all. This makes it very light and able to spin at high speed, though I think the windings may be prone to damage. The commutator on this one is thoroughly worn out. /4
March 18, 2025 at 8:46 PM
The armature is entirely self-supporting, with no core at all. This makes it very light and able to spin at high speed, though I think the windings may be prone to damage. The commutator on this one is thoroughly worn out. /4
The brushes look pretty conventional. These motors are sold in CW and CCW directions, though in practice they work both ways. /3
March 18, 2025 at 8:46 PM
The brushes look pretty conventional. These motors are sold in CW and CCW directions, though in practice they work both ways. /3
A bit of Dremel action soon has the commutator end off and the armature removed. I think the outer casing is brass, not steel. /2
March 18, 2025 at 8:46 PM
A bit of Dremel action soon has the commutator end off and the armature removed. I think the outer casing is brass, not steel. /2
My childrens' model aircraft use these tiny coreless motors. I wondered what was inside a worn-out one. 🧵/1
March 18, 2025 at 8:46 PM
My childrens' model aircraft use these tiny coreless motors. I wondered what was inside a worn-out one. 🧵/1
Graphical version of Impetus is now playable on the BBC Micro, though there's still work to do. youtu.be/jPlgj_LknpE
February 16, 2025 at 7:12 PM
Graphical version of Impetus is now playable on the BBC Micro, though there's still work to do. youtu.be/jPlgj_LknpE
Progress on getting Inufuto game "Impetus" running on the BBC Micro in graphics mode 5. To make it fit, code is all in a sideways RAM bank, level data is in normal RAM, so there's 34K to play with instead of 19K.
February 14, 2025 at 10:05 PM
Progress on getting Inufuto game "Impetus" running on the BBC Micro in graphics mode 5. To make it fit, code is all in a sideways RAM bank, level data is in normal RAM, so there's 34K to play with instead of 19K.
This one is a BG (British General) socket and having pulled it apart I'm favourably impressed by the USB power supply. There's a decent creepage distance between primary and secondary. The components are decent quality and not crammed in. I'm satisfied with its safety.
December 29, 2024 at 11:01 AM
This one is a BG (British General) socket and having pulled it apart I'm favourably impressed by the USB power supply. There's a decent creepage distance between primary and secondary. The components are decent quality and not crammed in. I'm satisfied with its safety.
Simplest solution is a replacement socket. I don't want to leave one with broken plastic where it could be a safety hazard. But at least I win a nice little USB power supply board.
December 23, 2024 at 12:05 PM
Simplest solution is a replacement socket. I don't want to leave one with broken plastic where it could be a safety hazard. But at least I win a nice little USB power supply board.
It looks like some cheap and nasty charger or travel adapter has lost a piece of its live pin, and forcing it out has broken a chunk off the plastic socket front. Now no pin can fit in. /2
December 23, 2024 at 12:05 PM
It looks like some cheap and nasty charger or travel adapter has lost a piece of its live pin, and forcing it out has broken a chunk off the plastic socket front. Now no pin can fit in. /2
I've just pulled this 13A socket apart to see why a plug won't go in. It's in a room used by guests. 🧵/1
December 23, 2024 at 12:05 PM
I've just pulled this 13A socket apart to see why a plug won't go in. It's in a room used by guests. 🧵/1