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All Electronics $1 Scrounging Board

PCB-31 When I was shopping for some goodies at All Electronics I came across a circuit card they were selling for $1. The description indicated that the board included two voltage regulators, a crystal and assorted parts. I like to scrounge and look up the parts used in consumer electronics so I purchased one of these just to scrounge. It’s like a grab bag of parts that engineers really use…

In this short article I provide some high-resolution pictures of the board using the PCB scanning method described in this previous article. I remove parts using the scrounging methods described here, and I list the parts I thought were worth removing, with data sheet links.

BoardComponent1 This picture shows the component side of the board. There are several interesting IC’s and transistors to scrounge. Notice the two voltage regulators that are bent over in the middle right of the picture, just above them is what looks like transformer. This is actually a large inductor which I am sure will come in handy on a future project.

Since this board was part of a multi-disk CD player I expected to find some motor driver ICs. There were two of these ICs, one large power transistor, and several smaller signal transistors on the component side of the board.

Although there were a lot of aluminum electrolytic capacitors I only removed the largest one. These are fairly cheap to purchase so I skipped over them. The short legs would have made them difficult to re-use anyway.

BoardSolder1 The board also had some PCB-mount pushbutton switches and four 20K potentiometers (pots) which were very much worth the effort to remove. I noticed two through-hole parts as well. One was an Atmel serial EEPROM and the other was a neat dual motor driver IC.

The solder side of this board has a large number of surface mount components. The resistors are marked with values so they are easily reusable. For the caps you would need to use a capacitance meter. These parts are glued on so it takes slightly more effort to remove them. I used a hot air embossing tool to heat the board and a pair of small tweezers to wiggle the parts off.

I only took the large tantalum cap and the surface mount transistors from this side of the board.

The Tools:


To do the scrounging job I used the tools pictured here. Yes I really do wear safety glasses when I do this work. Please take care of your eyes, it only takes one accident to lose an eye and this is dangerous work. Read all the information on my scrounging pages here and anything else you can find before you start.

I actually used two pairs of pliers: one to hold the part and one to hold the PCB while it was heated. A soldering iron and solder wick were used to remove the regulators but it was so much easier to heat the board up and pull the parts with the hot air gun that I soon dropped the solder wick method. A small pair of tweezers were used for the surface mount ICs and parts. Heating the area with the heat gun then removing the parts with the tweezers was fairly easy. Larger parts, like the connectors and POTs required a pair of long nose pliers.

The Loot:


Scrounging this board was fun and definitely worth the effort. I picked up some new lab stock and learned a bit about CD players in the process. Here is what I collected.

Qty Description
2 PCB Pushbuttons
1 Large inductor (looks like a transformer)
4 PCB pots, 20K
1 4.7uF SMT Tantalum Cap
1 16.9344MHz Crystal
1 4.19MHz Ceramic Resonator
1 1000uF 16V Aluminum Electrolytic Cap
Many Smaller Aluminum Electrolytic Caps
1 8-Pin DIN connector
1 Leaded power diode
1 Leaded 2.2 Ohm 1W resistor
1 SIP connectors and mating cable with PCB termination
1 7805A TO-220 5V Linear Regulator
1 7808A TO-220 8V Linear Regulator
1 TO-220 NPN Power Transistor with Beta of about 150
1 TO-92 NPN Transistor with beta of about 50
1 Small (TO-92 like) NPN Transistor with beta of about 150
14 SMT Transistors or diodes
1 Thermistor with negative coefficient (not sure)
1 Atmel 92C46 in 8-Pin Dip – 1K-Bit Serial EEProm
1 LB1649 – Dual Bidirectional Motor Driver
1 JRC 2100 – Unknown 8-Pin SOIC
1 A393F – 8Pin SOIC Dual Comparator from KEC
1 SM5871AS – Digital audio Sigma Delta D/A Converter
1 KA9258D – 4-Channel Motor Driver – designed to do many functions in a CD ROM drive related to head focus control.
1 KA9201 RF AMP for CD Player. Handles the optical sensor that reads a CD.
1 KA8309B Servo Signal Processor for CD Player.
1 AKD-77CW N45 – Unknown
1 KS9210 – Digital Signal Processor – Designed specifically for CD Players

Looking up the parts

JRC2100ADD-77CWSeveral of these parts are very specific to CDROM players and not of much use for hobby electronics but it was interesting to look at the data sheets.

I found most of the parts without much trouble but there were these two I could not find any information on. See if you can find anything. They are shown below, hopefully you can read the part data from the scans.

Comments Please:
Can you find a data sheet for these two mystery parts?

Have a good source for data sheets online? I normally use Octopart but for these special parts I end up with a lot of sites that try to get you to register, only to find out they don’t even have the part data sheet you were looking for.

Any other articles about scrounging parts form PCBs?

Crazy Idea:
Wouldn’t be neat if there was a database of parts that located them in electronics that we could scrounge. Enter a part you are looking for and get a list of the common devices that include one. Or maybe enter in the device you are about to toss to see what interesting parts might be inside. There could even be a recycling Craig’s List kind of thing where people that were looking for specific parts could connect with people that were throwing away stuff that had those parts.

Posted in Discovering, Parts, Scrounging, Scrounging Parts, Workshop Tools.

7 Responses

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  1. Richard Sim says

    I have a strong suspicion that the second mystery IC is related to the NEC UPD7510*, which replaced the Daewoo DMC42C/P4008.

  2. rsbohn says

    I like the idea of a component scavenger database. Perhaps you could just do a hi-resolution scan of the boards and upload it to Evernote. Evernote does good OCR and searchable images. You would just have to put a note on the picture, where the board came from.

    Read about my struggles with a difficult Mega8:

  3. Mr. Meval says

    If you need a surface mount to bread board you can cut out that portion of the PCB, solder the part back on and add wires. It’s not perfect but it works. You do need to either take the part off or cover it with something prior to sawing to try and keep ESD at bay depending on the part. Once that is cut out just solder thirty gauge wire to it and then solder those to a header or even a socket for breadboarding.

  4. Thomas says

    Regarding the first unknown part:

    If you happen to know that JRC (Japan Radio Company, founded 1915) is a historic brand used these days by NJR (New Japan Radio Company, “New” since 1959 🙂 ), and that NJR these days uses IC codes starting with NJx and not JRC any more, you pretty easily end up at:

    To quote:

    > NJM2100 is a low supply voltage and low saturation output
    > voltage (±2.0VP-P at supply voltage ±2.5V) operational
    > amplifier. It is applicable to handy type CD,radio
    > cassette CD,and portable DAT,that are digital audio
    > apparatus that require the 5V single supply operation and
    > high output voltage.

    You could compare the datasheet with how the IC on the board is connected to get a first indication if the 2100 on your board could be a NJM2100.

  5. Joseph Yumul says

    😀 maybe i can earn a lot of money selling sacrap boards

  6. Berni says

    I once had a site that had lists of parts in devices down to the last component.But i lost it

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