GEKCO SUBCARRIER REFERENCE OSCILLATOR MODEL SRO10 OPERATION/SERVICE MANUAL

Transcription

1 GEKCO MODEL SRO10 SUBCARRIER REFERENCE OSCILLATOR OPERATION/SERVICE MANUAL GEKCO Labs PO Box 642 Issaquah, WA (425) P/N REV 5/98 Copyright c 1998 GEKCO Labs All Rights Reserved Printed in the United States of America

2 GEKCO Page 1 Table Of Contents LIST OF FIGURES...1 INTRODUCTION...3 OPERATION...3 THEORY OF OPERATION...4 CIRCUIT DESCRIPTION...4 VIDEO INPUT...5 TV TIMING GENERATOR X SUBCARRIER PHASED LOCKED LOOP...5 CALIBRATION...5 REPLACEMENT PARTS LIST...6 CIRCUIT BOARD ASSEMBLY DRAWING...8 CIRCUIT BOARD X-RAY VIEWS...9 SCHEMATIC...11 SPECIFICATIONS...12 WARRANTY...13 List of Figures FIGURE 1: ONE LINE OF VIDEO SMPTE BARS...3 FIGURE 2: TYPICAL OPERATIONAL SETUP...4 FIGURE 3: BLOCK DIAGRAM...4 FIGURE 5. ASSEMBLY DRAWING...8 FIGURE 6. LAYER 1 TOP SIGNALS...9 FIGURE 7. LAYER 2 BOTTOM SIGNALS...10

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4 GEKCO Page 3 Introduction The SRO10 Subcarrier Reference Oscillator, allows you to obtain a good calibration reference source from any broadcast color video source or you can verify the subcarrier frequency of any color video source. Most modern VCR's and TV Tuners allow you to get to the baseband television signal which has a great reference signal as part of the NTSC Television signal specification. The signal we are talking about is the color burst reference signal that is exactly /- 10 Hz. See figure 1. The accuracy is required by the FCC for any broadcast television signal. Ok so I can get baseband video, how can I utilize the color burst since it only appears for approximately 9 cycles every TV line or 63.5 usecs. The answer is utilize a circuit that creates a continuous signal locked to the color burst. YELLOW CYAN GRAY +100 GREEN WHITE LEVEL (100 IRE) 100 IRE = 714 mv MAGENTA RED BLUE 140 IRE 1V p-p 20 IRE 3.58 MHZ COLOR BURST (9 CYCLES) BLACK LEVEL (7.5 IRE) BLANK LEVEL (0 IRE) 40 IRE 20 IRE 7.5 IRE SETUP OR PEDESTAL SYNC LEVEL (-40 IRE) COLOR BURST REFERENCE SIGNAL Figure 1: One Line of Video SMPTE Bars Operation Connect the power cable from the wall mount power transformer and the DC input connector on the SRO10. Next, plug the power transformer to a 120VAC wall outlet. The power LED indicates if the unit is operational. Setup the instrument as shown in Figure 2. Connect the video source to the video input connector. Loop through the video to some other source and terminate or just add a terminator to the video output connector or add the internal termination jumper. Connect the reference subcarrier output to the frequency

5 counter. Select the subcarrier frequency from the front panel to 1X for a 3.58 Mhz reference on a NTSC video source. The counter now reads the exact subcarrier color burst signal frequency. IN VIDEO OUT SUBCARRIER OUT DC INPUT 9-12VDC GEKCO MADE IN USA VIDEO IN REF OUT VIDEO SOURCE TUNER, VCR, ETC FREQUENCY COUNTER Figure 2: Typical Operational Setup The front panel switch can also be set to 4X for a reading of 4 times the color burst frequency. This unit has a phased locked loop that locks onto the color burst and creates a continuous subcarrier signal (3.58 MHz) or 4 times subcarrier ( Mhz). See Figure 2 for the block diagram. VIDEO IN TV TIMING GENERATOR 4 X SUBCARRIER PLL 4 X BURST GATE 1 X BUFFER Figure 3: Block Diagram Theory of Operation This design is broken into two blocks, the TV timing generator and the subcarrier phased locked loop (PLL). The first block generates a gate signal to tell the PLL when to sample the color burst signal and the next block samples the color burst and creates the 4 times (4 x) subcarrier output and divides that by 4 to create the subcarrier reference output (1 x). A switch allows selection of the 1x for 4 x output of the subcarrier oscillator. The transistor buffer isolates the outside equipment and allows the selected output to drive a low impedance load. Circuit Description

6 GEKCO Page 5 Video Input The color composite video input signal is connected to J6 and can be looped through to J4 or terminated by Jumper JP2 into 75 ohms. The video is AC coupled by C14 to IC3 the LM1881 sync seperator. The composite video is also AC coupled to IC1, the MC44144 PLL, used to lock on to the color burst signal. TV Timing Generator The main use in this circuit for the LM1881 is to generate the color burst gate signal. The sync seperator strips the composite sync signal and generates the Burst Gate signal from the trailing edge of composite sync. This signal is approximately 4.8 us long, negative true. The Hex Invertor, IC2, is used to invert the negtive true burst gate pulse to a positive true signal required by the MC44144 PLL I.C. The resistor network of R7 and C9 is used for the Vertical Sync seperation. This feature is not necessary for this application but is shown in case you need the Vertical Sync operation for something else. 4 X Subcarrier Phased Locked Loop The MC44144 is designed to implement the color sync function in a video system. The 4 X Subcarrier Phased Locked Loop (PLL) is used to generate the continuous subcarrier frequency from the momentary color burst input. When a NTSC/PAL composite video is applied with a burst gate signal the IC will phase lock a Voltage Controlled Crystal Osciillator (VCXO) to the color burst. Both 4X and 1X subcarrier frequency outputs are provided by the IC. The VCXO operates from a 4X subcarrier crystal and is typically +/- 350 Hz of pull-in. The burst gate pulse from the Sync Seperator tells the PLL when to sample and lock the subcarrier oscillator to the input video. You can see that the PLL is only locked for a short time during the video line. Only 4.8 us out of 63.5 us or about 7.5% of the time. C11, C10 and R6 form the phase detector loop filter. The filter is designed for the time ratio mentioned and should work for PAL timing also even though the author has not verified that. The crystal network of Y1 and C8 provides the reference 4 X subcarrier for the VCXO. The 4X and 1X outputs are coupled by C6 and C7 and can be selected by SW1. The buffer circuit of Q1 and the bias network of R3,R4 and R5 with the output coupling of C4 allows the signal to be available to a 50 ohm load, if necessary. Calibration A dual channel oscilloscope is required for best setup. Connect a broadcast color video signal to J6 connect a BNC cable from J4 to your oscilloscope channel 1 using a BNC T connector and terminate it with a 75 ohm terminator. Setup the oscilloscope to view the color burst signal and magnified so that the burst cycles are easily viewable. Plug in the power transformer to power up the unit. Connect the other oscilloscope channel probe to the reference output J3. Select SW1 so that the 1 X subcarrier output is viewed on channel 2. Adjust C8 so that the reference output and channel 2 is locked to the color burst on the incoming video. Note where the adjustment of C8 causes a loss of lock at each extreme, and center C8 between the loss of lock positions.

7 Replacement Parts List Table 1. Replacement Parts List Item Qty Reference Part No. Description Value 1 1 R Resistor, carbon film, 1/2 w, 5% 33 ohm 2 1 R Resistor, carbon film, 1/4w, 5% 330 ohm 3 1 R Resistor, carbon film, 1/4w, 5% 3900 ohm 4 1 R Resistor, carbon film, 1/4w, 5% 18k ohm 5 1 R Resistor, carbon film, 1/4w, 5% 51 ohm 6 1 R Resistor, carbon film, 1/4W, 5% 47k ohm 7 1 R Resistor, carbon film, 1/4W, 5% 680k ohm 8 1 R Resistor, carbon film, 1/4w, 1% 75 ohm 9 9 C1, C2, C4, C5, C9, C10, C12, C13, C Capacitor, mono ceramic, 50v, radial lead ls.1 0.1uF, CAPR / C6, C Capacitor, mono ceramic, COG, radial lead ls pF, 100v, CAPR / C Capacitor, mono ceramic, COG, radial lead ls.1 470pF, 50v, CAPR / C Capacitor, tantalum, 16v, radial lead 47uF, 16V, PCAPR C Capacitor, trimmer pF trimmer cap, SG3004, CAPTR D Diode power 1N LED LED, Green PCB Mount 16 1 SW Switch, Toggle SPDT PCB Mount 17 1 VR Integrated Circuit, Voltage Regulator, TO-220 LM340T-5V, 5V, TO Q Transistor, NPN, TO-92 2N Y Crystal, HC49, MHz

8 GEKCO Page PS Connector, Power 2.1mm, PCB Mount 21 3 J3, J4, J Connector, BNC, 75 ohm, PC Mount 22 2 X1, X Socket, IC, Dip X Socket, IC, Dip k, 32k X 8bit 256k, 32k X 8bit 256k, 32k X 8bit 256k, 32k X 8bit 24 1 U Integrated Circuit, Sub. Ref. Osc., Motorola, MC44144P, DIP U Integrated Circuit, Hex Invertor 74HC04, DIP U I.C, Sync Seperator, LM1881N, DIP A Printed Circuit Board SRO10 Rev A 28 1 T Transformer Wall Mount Operation/Service Manual Rev 5/98

9 Circuit Board Assembly Drawing Figure 4. Assembly Drawing

10 GEKCO Page 9 Circuit Board X-RAY Views Figure 5. Layer 1 Top Signals

11 Figure 6. Layer 2 Bottom Signals

12 SRO10 Schematic SRO10DS970910

13 Specifications Signal Video Input Connectors Impedance Subcarrier Ref. VCXO Oscillator Oscillator Lock In Range Electrical Characteristics Reference Output Level Power Requirements DC Input 2 BNC Loop Through 75 ohms BNC +/- 350 Hz >300 mv P-P 80 ma 120 VAC Wall Power Transformer Provided Physical Characteristics Dimensions mm in. Width Height Depth Weight kg lbs Net Shipping

14 SRO10 Warranty YOUR GEKCO FACTORY ASSEMBLED PRODUCT ONE YEAR LIMITED WARRANTY Welcome to GEKCO products. We believe you will be pleased with the performance of your product. Please read this consumer protection plan carefully. It is a LIMITED WARRANTY as defined in the U.S. Consumer Product Warranty and Federal Trade Commission Improvement Act. This warranty gives you specific legal rights, and you may also have other rights which vary from state to state. GEKCO S RESPONSIBILITY PARTS - Replacement for factory defective parts will be supplied free for one year from date of purchase. Replacement parts are warranted for the remaining portion of the original warranty period. You can obtain warranty parts direct from GEKCO by writing or telephoning us at (425) We will pay the shipping charges to get those parts to you... anywhere in the world. SERVICE LABOR - For a period of one year from the date of purchase, any malfunction caused by factory defective parts or workmanship will be corrected at no charge to you. You must deliver the unit at your expense to GEKCO. TECHNICAL CONSULTATION - You will receive free consultation on any problem you might encounter in the use of your GEKCO product. Just drop us a line or give us a call. Sorry, we cannot accept collect calls. NOT COVERED - Repair service, adjustments and calibrations due to misuse, abuse or negligence are not covered by this waranty. Unauthorized modification of the product or of any furnished component will void this waranty in its entirety. This waranty does not include reimbursement for inconvenience, installation, set-up time, lost of use, or unauthorized service. This waranty covers only GEKCO factory assembled products and is not extended to other equipment and components that a customer uses in conjunction with our products. SUCH REPAIR AND/OR PARTS REPLACMENT SHALL BE THE SOLE REMEDY OF THE CUSTOMER AND THERE SHALL BE NO LIABILITY ON THE PART OF GEKCO FOR ANY SPECIAL, INDIRECT, INCIDENTAL OR CONSEQUENTIAL DAMAGES, INCLUDING BUT NOT LIMITED TO ANY LOSS OF BUSINESS OR PROFITS, WHETHER OR NOT FORESEEABLE. Some states do not allow the exclusion or limitation of incidental or consequential damages, so the above limitation or exclusion may not apply to you. OWNERS RESPONSIBILITY EFFECTIVE WARANTY DATE - Waranty begins on the date of first consumer purchase. You must supply a copy of your proof of purchase when you request warranty service or parts. OPERATING MANUAL - Read your operating instructions carefully so that you will fully understand the proper operation and function of your unit. ACCESSORY EQUIPMENT - Performance malfunctions involving connections to (or interfacing with) other non-gekco equipment are not covered by this warranty and are the owner s responsibility. SHIPPING UNITS - Follow the packing instructions published in your manual. Damage due to inadequate packing can not be repaired under warranty. If you are not satisfied with our service (warranty or otherwise) or our products, write directly to GEKCO, CUSTOMER SERVICE, PO Box 642, Issaquah WA We will make certain your problems receive immediate, personal attention. GEKCO reserves the right to discontinue products and to change specifications at any time without incurring any obligation to incorporate new features in products previously sold. SRO10DS970910