Tag: comparator

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Bargain Bin USB-ODB Interface

ODB Adaptor
ODB Adaptor

This is a little bit of kit I got to talk to the Webasto TT-V I salvaged from a scrap Jaguar S-Type, and converts USB-RS232 to the standard car diagnostic ODB connector. (These are a much cheaper option at £4 than the official Webasto diagnostic adaptor & loom which is over £90.

PCB Top
PCB Top

There’s really not much to this adaptor, the only signals that are routed to the ODB connector seem to be the +12v on pin 16, K-Line on Pin 7 & L-Line on pin 15. The main IC here is a CH340 USB-Serial interface, with some glue logic in the form of an LM339 quad comparator.

PCB Reverse
PCB Reverse

The reverse side of the PCB only has the power indicator LED.

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Chicom “500W” ATX PSU

Cover Removed
Cover Removed

Here is a cheapo 500W rated ATX PSU that has totally borked itself, probably due to the unit NOT actually being capable of 500W. All 3 of the switching transistors were shorted, causing the ensuing carnage:

AC Input
AC Input

Here is the AC input to the PCB. Note the vapourised element inside the input fuse on the left. There is no PFC/filtering built into this supply, being as cheap as it is links have been installed in place of the RFI chokes.

Input Side
Input Side

Main filter capacitors & bridge rectifier diodes. PCB shows signs of excessive heating.

Filter Caps Removed
Filter Caps Removed

Filter capacitors have been removed from the PCB here, showing some cooked components. Resistor & diode next to the heatsink are the in the biasing network for the main switching transistors.

Heatsinks Removed
Heatsinks Removed

Heatsink has been removed, note the remaining pin from one of the switching transistors still attached to the PCB & not the transistor 🙂

Transformers
Transformers

Output side of the PSU, with heatsink removed. Main transformer on  the right, transformers centre & left are the 5vSB  transformer & feedback transformer.

Output Side
Output Side

Output side of the unit, filter capacitors, choke & rectifier diodes are visible here attached to their heatsink.

Comparator
Comparator

Comparator IC that deals with regulation of the outputs & overvoltage protection.