Measuring Tape Teardown

Had taken out a cheap measuring tape from my tool kit for some measurements earlier this week. These are the ones which spring back when you release them. Turns out my darn tape won’t coil back. It was stuck with the entire section hanging out. Then I thought why not, let’s open it up and see what’s happening.

Measuring Tape Teardown
Measuring Tape Teardown
Measuring Tape Teardown
Measuring Tape Teardown

Measuring tape consists of a metallic yellow/white unit with black markings(Usually high contrast colours are used for easy reading). It’s coiled all along a central hub. The magic happens in the central hub which consists of a tightly coiled spring(Guessing it’s made of some form of spring steel) which rotates in the other direction (Creating more tension) when the tape is pulled out. The length of the coil of the spring is almost the same as the measurement tape itself. When released, the spring coils back pulling the entire tape back in a snap. An elegant design which looks simple enough. Seems that in my unit, the spring steel part is broken. It’s not really worth repairing these by cutting the spring steel and reattaching, as a new one will cost you only around INR 100($1.2), but sure you can repair it if you want to, be ready to deal with unwinding a mangled tape though.

Measuring Tape Patent

When I searched the patent databases, I found the potentially first design of this tape which was filed more than 150+ years ago in 1864. Patent No. US45372A. Nice to see that a design engineered that far back is still relevant and fully functional today.

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Boat Rocker Headphone Teardown and Fault Diagnosis

Boat Headphone Teardown
Boat Headphone Teardown
Boat Headphone Teardown
Boat Headphone Teardown

A friend of mine dropped off a pretty old pair of wireless Bluetooth Boat Rocker headphones which were not working. The power LED turns ON but it’s unresponsive after that. Opened it up and first did a charge test with a USB current meter and found that there was no current taken from the power supply. That’s usually bad news, as that could potentially mean that the battery is bust or the main chip is blown. I opened up the battery compartment and there was no bulging of the battery. The battery was showing voltage, which was slightly low, but nothing too concerning. Then I desoldered the battery and connected a spare battery right on the PCB. Then plugged in the USB meter and voila the new battery is charging. Turned out the culprit was a faulty positive battery wire running all along the headband. It had no continuity and it was broken in between. Replacing that thin wire should get the headphones backup. The device wasn’t turning ON as the main chip couldn’t detect the battery due to the broken wire, even though it was getting external power.

Coming to the circuit analysis, these BLE headphones contain a Bluetooth chip from the Taiwanese manufacturer Airoha (AB1510). It’s a DSP chip with 48MIPS. It has all the bells and whistles for audio input, processing and outputs. It has a BLE PCB antenna. The great part of this chip is a built-in battery charge controller capable of charging at 400mA with protection. This eliminates the need for an external charging circuitry altogether. I couldn’t find a pricing for these chips though. If anyone knows please do comment. The other main IC is 24C128A, which is a 2-wire Serial EEPROM from Microchip to mostly store audio presets I suppose. The LiPo battery has a capacity of 450mAh. All in all, a reasonably well-designed headphone.

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