Group 7 - Sony VCR

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VCR 3.JPG

Contents

Executive Summary

The objective of this project was to dissect and analyze the internal components and systems of a Sony VCR model number SLV-751HF. The page below documents the step by step process used to dissect and interpret the operation of the product. Before starting dissection, the VCR was tested for proper performances, and was found to be inoperable as a VHS cassette reader, but was able to receive input signals and output them to the TV. As the product was disassembled a log of parts and tools used was kept as a record of dissection information. Once disassembled, the VCR was analyzed and observed to determine how it operates. At this point the reasons for inoperability were discovered. After sufficient research and reassembly of the VCR, suggestions were made for improvements and modifications to maximize consumer satisfaction.

Introduction

A VCR provides an interface that allows users to view and hear recorded media. The Sony Model VCR provides a control interface that allow the user to control the functions of the VCR (play, pause, fast forward, etc.). Concurrently, the VCR has A/V and coaxial inputs and outputs that allow for a link between the viewing medium and another output device.

Members:

Before the Disassembly

Purpose of the VCR

The purpose of the VCR is to provide consumers with an affordable in-home method of viewing and recording VHS cassette tapes. A VCR can also be used to watch, record, or export external media sources via the coaxial and audio/visual inputs and outputs. For example, the VCR can receive cable transmitted TV stations, via the coaxial inputs, or view videos housed on a video camera through the A/V inputs.

Hypothesized Operation

A VCR operates by receiving power from a wall outlet, and converts it to usable electricity for the rest of the VCR. When a VHS tape is put in the cassette is put onto a reel, which spins the magnetic tape, progressively reading the data on this tape. This data is then converted to usable data, and then sent to the television screen through either the coaxial or A/V outputs.

Testing

The product was tested before disassembly, by plugging it into the wall outlet and turning it on. Immediately observed, was the fact that the VCR distributed power properly, as indicated by the lighting up and proper operation of the LCD display. A VHS cassette was then inserted into the tape loader, but was unable to be read, because it got stuck during a mechanical motion (assumedly being put into place for reading). The problem that arose during testing was assumed to be a mechanical glitch due to the knocking sound made from the VCR in a location near the front of the VCR, such as an arm hitting another arm, which would hopefully be easy to fix. The A/V and coax inputs and outputs were then tested by connecting an XBOX 360, and the cable signal from the wall, respectively to the VCR. Each was able to properly output a signal to the screen and speakers.

Assumed Components and Materials

Before dissecting the VCR assumptions were made about the components and materials. The estimated number of components was around thirty separate parts. Materials used were assumed to be:

  • Aluminum
  • Copper
  • Gold for circuitry
  • Plastics
  • LED lights
  • Magnetic alloys
  • Rubbers

Disassembly

This is the process we used to disassemble the VCR. Once the main shell pieces are removed most of the inside components can be removed in any order.

Step Number Part Removed Tool Used Ease of Removal Additional Notes
1 Bottom Screws Screw Driver Easy
2 Side Screws Screw Driver Easy
3 Bottom Plate Hand Easy Beginning steps of disasembly were easier than later steps
4 Top Housing Hand Easy
5 Back Screws Screw Driver Easy
6 Front Panel Clip Locks Easy
7 Back Panel Slide in Easy
8 Control Interface 1 Plastic Mount - Circuited Delicate
9 Power Supply Screwed in/ Wired Easy
10 Cassette Housing Screw Driver Relatively easy Many screws
11 Deck Board Bridge Pliers Delicate
12 Board Screw Driver Relatively Easy
13 Removal of Main Circuit board Hand Pliers Easy

Post-Disassembly

Parts List

This is a comprehensive list organizing all the parts that made up the VCR. The images are linked to other pages with components that have a quantity more than one.

Component Model Number Quantity Material Manufacturing Process Photo Images Cad Images
Power supply MBP No. 062749 1 Aluminum, plastic, copper, ceramics, glass Print circuit board, insert components, solder, add housing
100 2107.JPG
Part4.jpg
Circuit boards MF-173 1-646-740-13, MD -56 1-646-862-22, MF- 172 1-646-743-13, MA-144 1-646-739-13, HF-27 1-646-751-12, RP-149 1-646-749-12, CM-14 1-630-505-21, SR-440- 68- 120- 0294-01, MF-171 1-646- 742-13, BA 6440FP 304 191, MM 8V-0, GCMK-C2X 12 Polytetrafloroethylene, copper, epoxy Etching, lamination, drill holes, soldering, plating and coding, screen printing, protection CB's 1-12 CB's 1-12
Control panel 3951072 1 Plastic, aluminum, rubber Plastic mold, insert components, solder
100 2138.JPG
Part9.jpg
Wire bundles - 6 Copper, plastic Dyed copper wire, insulated, bundled
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Power cord KDK-F 1 Copper, plastic Dyed copper wire, wires braided, insulated, ends attached
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Tape deck 3041 1 Aluminum, plastic, rubber Mold gears, print circuit boards, shape metal components, assemble
100 2108.JPG
Part15.jpg
Tape loader 34154-12 1 Aluminum, plastic, lubricant Mold gears, shape metal components, assemble
100 2141.JPG
Part14.jpg
Housing 3-703-845-21 1 Aluminum Cut and shape metal sheets
100 2140.JPG
Part11.jpg
Frame SVM010384 1 Plastic Molded
100 2136.JPG
Part1.jpg
Connections/bridges EL005088 6 Copper, plastic Cut copper, mold plastic to ends C/B 1-6 -
Display 1-519-745-11 1 Polarized film, glass substrate, liquid crystal, electrode film, filter film, plastic Formed, molded, assembled
100 2104 2.jpg
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Rear panel cover 3-951-081-9 1 Plastic Molded, text printed
100 2139.JPG
Part2.jpg
Feet 55-44 2 Plastic, rubber Molded plastic, added rubber
100 2134.JPG
Part13.jpg
Spacers - 2 Plastic Molded S 1-2 S 1-2
Base - 1 Aluminum Cut aluminum sheets
100 2137.JPG
Part10.jpg

Parts Description

Each part has its own functional goal to meet as well as preform and be physically appealing to its consumers.

  • Power supply
-The power supply's purpose is to convert household outlet power into usable forms for the VCR's components to use. It's built compactly to fit behind the tape deck and it's circuit board within the frame. It's gray and the metal is unfinished since its out of view inside the housing. The power supply is inside a metal shell to protect the surround plastic and other electrical components inside the frame near by.
  • Circuit boards
-The boards provide a circuit path to all the components in the VCR as well as hold most of the electrical components. It's built to hold all the necessary pieces in an organized and compact fashion without expanding the overall size of the unit. It's also unfinished and exposing all its wires to visually see where the paths are going and to keep as open to cooling as possible. The boards are made from the certain materials to remain sturdy for components and durable to heat changes.
  • Control panel
-The control panel allows for user input into the system to control its function. It's built to look good to personal preferences while providing useful operations. It's smooth and painted with easy to read text. The panel has to blend into the unit and be useful to the users.
  • Wire bundles
-The wire bundles carry electrical signals through the unit. It's built to easily make connections between boards and components. They are multicolored strands. The bundles are light and flexible to make it easy to work around other parts of the VCR like the frame and have easy recognition with it's colors.
  • Power cord
-The power cord carries the electrical power from outlets to the power supply in the back of the unit. It's built to give the user a way of powering the VCR in any location in a home. It's painted black in color to blend in and not be noticeable upon focus and draw attention away from it. The cord is flexible and easy to work with in small, varying environments.
  • Tape Deck
-The tape deck's purpose is to hold VHS tapes and record the information into signals that the VCR uses to display its pictures and sound. It's built to fit the VHS tapes and be able to feed the tape through its readers and wind back up into the VHS. It's unfinished metal exposed along with its plastic components. The deck is made from metal to hold all its components and take the stress of the tape feeding through its parts as well as the VHS spinning its feeders on its parts.
  • Tape Loader
-The tape loader feeds the tape onto the deck as well as ejecting the tape when the user wants to remove it. It's built snugly hold VHS tapes and secure it to the tape deck. It's plastic is painted black so it blends in when people insert and remove tapes it blends in. The loader has a metal surround the tape to remove the chances of breaking that might happen to plastic over time lifting and moving VHS tapes.
  • Housing
-The housing protects the components inside of the VCR. It's built to fit over all the components and frame and keep users out while having openings for ventilation in high heat areas. It painted a stone gray color to look good in appearance and match the rest of its outside visible parts. The housing is made from aluminum to be durable in movement and absorb heat off the components.
  • Frame
-The frame gives a rigid support to attach all the components to as well as seal off the system. It's built to fit all the parts and maximize space while keeping its overall size small. It's painted black to provide a contrast to all the components inside of the VHS. The frame gives the unit's components protection from damage and space out the parts to minimize heat.
  • Connections/bridges
-The connections/bridges provide connections between board's circuits. It's built to fit inside the frame and fit onto the circuit boards. It's exposed wire and plastic since users wont see the part. The connections/bridges are flexible to allow for different distances between boards to be connected with the same part.
  • Display
-The display shows the user what the VCR is currently doing as well as provide useful information about the VHS tape or other things it may be doing. It's built to fit in front of the unit while being large enough to read. It's made to match the rest of the parts in the front and flow with the overall look of the unit. The display's clear coating allows users to read the light material and process data.
  • Rear panel cover
-The rear panel cover is to provide information on the inputs and outputs on the back off the VCR. It's built to fit on the back of the frame where all the plugs come out of the unit from one of the circuit boards. It's black in color to match the frame. The panel is made separate from the frame because its easier to print the information on a small cut piece of plastic instead of the large frame.
  • Feet
-The feet provide a balance to the system so it sits level in its location. It's built to fit underneath the VCR and be the same height as the feet on the base piece. They're black to match the unit and not be noticeable. The feet have rubber on the bottom to give the unit grip so it doesn't move around once you set it in place.
  • Spacers
-The spacers provide rigidity in the unit in areas where pressure by a user carrying it may damage components inside the VCR. It's made to fit in its two different locations. The are white in color to be easily identifiable. The spacers protect important parts from harm and hold weak areas together in the unit.
  • Base
-The Base seals the bottom of the VCR. It's made to fit the frame of the unit. It's unfinished metal since it's underneath and not noticeable. The base is hard and gives some support to components attached to the frame and heat sinks the boards while keeping them off the ground with its feet.

Assembly

We mostly reversed the order in which we removed each part from the frame and put the surrounding panels back on.

Step Number Process Ease Of Placement Tools Used
1 Motherboard screwed on to housing Fairly easy Phillips head screw driver
2 Tape deck screwed onto the housing Fairly easy with some complications due to tight spaces for some of the screws and a holding bracket that was misplaced but then later found Phillips head screw driver, pliers
3 Tape loader put in place on top of the tape deck Fairly easy Phillips head screw driver
4 The converter box was then put in place Easy Phillips head screw driver, pliers to hold up screws
5 Power converter was put in place Fairly easy, trouble with locating where ground cable was to be connected Phillips head screw driver
6 Back panel put in place Easy Phillips head screw driver
7 circuit board for user interface put into place Fairly easy Hands to clip panel into place
8 All wires reconnected across all boards Average, there were some missing wires before our dissection Hands
9 User input panel put into place Fairly easy Part clipped in by hand
10 Bottom housing screwed into bottom of the frame Fairly easy Phillips head screw driver
11 Top housing screwed into top of the frame Fairly easy Phillips head screw driver
12 Feet screwed onto bottom housing Fairly easy Phillips head screw driver

Assembly Diagram

This image assists with placement of the major components inside the frame and outer surrounding pieces. As explain in our assembly processes, the circuit boards will be the first to get placed inside the frame from the bottom and in front of the frame. Then the power supply can be added and all the wire bundles and connections/bridges attached. Finally all the main body panels are added and secured into place. Its that simple and can be done with no more than a pair of hands and a Phillips screwdriver.

Asm0004.jpg
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Post-Assembly

How the VCR Works

Viewing a VHS tape

This video shows how a VCR loads a tape onto the tray and pulls the tape around its reading components. This isn't the VCR shown throughout the page that model was non-functioning from the outset of the project.

<embed src="http://www.youtube.com/v/z8wBTTHKaQA&hl=en&fs=1" type="application/x-shockwave-flash" allowscriptaccess="always" allowfullscreen="true" width="425" height="344"></embed>


The tape deck contains many rotating heads on it that each serve its own function. The first one that a VHS tape will pass is the erasing head on the left hand side. This piece clears the material off the tape before reaching the writing head. The writing head is the large silver drum in the back portion. It's angled a bit so the groves along the head can etch frames of video into the tape. Next it reaches a cleaning brush that wipes away access material before the optical head. This is where the etches are processed into images that we see on TV screens. Finally the tape reaches and audio head that translates sounds off the tape. The tape then gets wound back up into the VHS tape. The audio and video signals read from the tape are then sent a converter box which relays the signals to the motherboard. The motherboard relays the signals to the A/V and coaxial outputs for viewing on a television or other compatible medium.

Controlling the VCR

When the user wants to preform an operation on the VCR they press a button on the control panel. This signal is then sent through jumpers to the circuit board with the LCD display. This signal is relayed to the motherboard where it is processes and sent back to the display to show what action was taken as well as to the circuit board under the tape deck which performs the operation on the VHS tape.

Power

The VCR runs on 120 V alternating current not in excess of 25 A. This current is converted by the power supply to direct current that the VCR can use.

Analyses and Testing

Model Assumptions

  • A VCR will on average be used 3 times a week
  • Product lifespan 10 years

Calculations

  • 3 uses/week*52 weeks/year*10 years = 15,600 uses
  • 15,600 uses * 3 =46800 uses (error allowance)

Procedure

  • Test one out of every 1,000 tape loaders
  • Use a machine to simulate inserting and ejecting tape
  • If tape loader reaches 50,000 then pass the batch
  • If tape loader fails before 50,000 further testing required

Further testing

  • Test 5 tape decks of the group of 1000 that failed
  • If one of 5 fails discard batch
  • If all 5 tape decks pass, release batch
  • Maintain record of pass/fail, and batches tested for future reference

Reflection on Disassembly/Assembly

The disassembly and reassembly, were hardly labor intensive, requiring only use of hand, a Phillips head screwdriver, and pliers on rare occasion. The reason for such ease in deconstruction and reconstruction was, the product is designed in separate modular components. Reassembling the VCR was almost the exact reverse of the dissection, although many different reassembly processes could have been chosen. The steps used to put the VCR back together were chosen based upon the initial deconstruction by the group. In rebuilding the VCR the same screwdriver was used, however, it was manageable to put the product back together, without reusing the pliers. The entire product was reassembled to the original configuration initially given, with the exception of a repaired gear in the tape loader, which originally did not work.

Design Changes

For the time period

  • Make the device smaller
- Layered printing of circuit boards
- Reduce empty space by stacking circuit boards and including a fan for cooling
- Smaller front control panel by reducing the size of large buttons
  • Second tape deck for recording or dual play of VHS tapes
  • Include a receiver for better audio quality and amplification

Modern Improvements

  • Include DVD player for recording VHS to DVD and convenience of an all in one media player
  • MP3 Line in to allow music playback

Recommendations

  • Manufacture
- Plastic clips to hold secure circuit boards to frame to reduce manufacture time and separate components
  • Maintenance
- Use more durable backings of buttons to reduce  tendency to break and malfunction over time 
  • Recycle
- Use more plastic parts for ease of recycling

References

External Links

Video from HowStuffWorks.com