TECHNICAL MANUAL CROWBAR OPERATION - VERIFICATION TEST FIXTURE Printed: Rev. B: T.M. No.

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1 TECHNICAL MANUAL CROWBAR OPERATION - VERIFICATION TEST FIXTURE T.M. No Copyright 1999, 2002 Harris Corporation All rights reserved Printed: Rev. B:

2 Returns And Exchanges Damaged or undamaged equipment should not be returned unless written approval and a Return Authorization is received from HARRIS CORPORATION, Broadcast Systems Division. Special shipping instructions and coding will be provided to assure proper handling. Complete details regarding circumstances and reasons for return are to be included in the request for return. Custom equipment or special order equipment is not returnable. In those instances where return or exchange of equipment is at the request of the customer, or convenience of the customer, a restocking fee will be charged. All returns will be sent freight prepaid and properly insured by the customer. When communicating with HARRIS CORPORATION, Broadcast Systems Division, specify the HARRIS Order Number or Invoice Number. Unpacking Carefully unpack the equipment and preform a visual inspection to determine that no apparent damage was incurred during shipment. Retain the shipping materials until it has been determined that all received equipment is not damaged. Locate and retain all PACKING CHECK LISTs. Use the PACKING CHECK LIST to help locate and identify any components or assemblies which are removed for shipping and must be reinstalled. Also remove any shipping supports, straps, and packing materials prior to initial turn on. Technical Assistance HARRIS Technical and Troubleshooting assistance is available from HARRIS Field Service during normal business hours (8:00 AM - 5:00 PM Central Time). Emergency service is available 24 hours a day. Telephone 217/ to contact the Field Service Department or address correspondence to Field Service Department, HARRIS CORPORATION, Broadcast Systems Division, P.O. Box 4290, Quincy, Illinois , USA. Technical Support by tsupport@harris.com. The HARRIS factory may also be contacted through a FAX facility (217/ ). Replaceable Parts Service Replacement parts are available 24 hours a day, seven days a week from the HARRIS Service Parts Department. Telephone 217/ to contact the service parts department or address correspondence to Service Parts Department, HAR- RIS CORPORATION, Broadcast Systems Division, P.O. Box 4290, Quincy, Illinois , USA. The HARRIS factory may also be contacted through a FAX facility (217/ ). NOTE The # symbol used in the parts list means used with (e.g. #C001 = used with C001).

3 Guide to Using Harris Parts List Information The Harris Replaceable Parts List Index portrays a tree structure with the major items being leftmost in the index. The example below shows the Transmitter as the highest item in the tree structure. If you were to look at the bill of materials table for the Transmitter you would find the Control Cabinet, the PA Cabinet, and the Output Cabinet. In the Replaceable Parts List Index the Control Cabinet, PA Cabinet, and Output Cabinet show up one indentation level below the Transmitter and implies that they are used in the Transmitter. The Controller Board is indented one level below the Control Cabinet so it will show up in the bill of material for the Control Cabinet. The tree structure of this same index is shown to the right of the table and shows indentation level versus tree structure level. Example of Replaceable Parts List Index and equivalent tree structure: The part number of the item is shown to the right of the description as is the page in the manual where the bill for that part number starts. Inside the actual tables, four main headings are used: Table #-#. ITEM NAME - HARRIS PART NUMBER - this line gives the information that corresponds to the Replaceable Parts List Index entry; HARRIS P/N column gives the ten digit Harris part number (usually in ascending order); DESCRIPTION column gives a 25 character or less description of the part number; REF. SYMBOLS/EXPLANATIONS column 1) gives the reference designators for the item (i.e., C001, R102, etc.) that corresponds to the number found in the schematics (C001 in a bill of material is equivalent to C1 on the schematic) or 2) gives added information or further explanation (i.e., Used for 208V operation only, or Used for HT 10LS only, etc.). Inside the individual tables some standard conventions are used: A # symbol in front of a component such as #C001 under the REF. SYMBOLS/EXPLANATIONS column means that this item is used on or with C001 and is not the actual part number for C001. In the ten digit part numbers, if the last three numbers are 000, the item is a part that Harris has purchased and has not manufactured or modified. If the last three numbers are other than 000, the item is either manufactured by Harris or is purchased from a vendor and modified for use in the Harris product. The first three digits of the ten digit part number tell which family the part number belongs to - for example, all electrolytic (can) capacitors will be in the same family (524 xxxx 000). If an electrolytic (can) capacitor is found to have a 9xx xxxx xxx part number (a number outside of the normal family of numbers), it has probably been modified in some manner at the Harris factory and will therefore show up farther down into the individual parts list (because each table is normally sorted in ascending order). Most Harris made or modified assemblies will have 9xx xxxx xxx numbers associated with them. The term SEE HIGHER LEVEL BILL in the description column implies that the reference designated part number will show up in a bill that is higher in the tree structure. This is often the case for components that may be frequency determinant or voltage determinant and are called out in a higher level bill structure that is more customer dependent than the bill at a lower level

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5 THE CURRENTS AND VOLTAGES IN THIS EQUIPMENT ARE DANGEROUS. PERSONNEL MUST AT ALL TIMES OBSERVE SAFETY S, INSTRUCTIONS AND REGULATIONS. This manual is intended as a general guide for trained and qualified personnel who are aware of the dangers inherent in handling potentially hazardous electrical/electronic circuits. It is not intended to contain a complete statement of all safety precautions which should be observed by personnel in using this or other electronic equipment. The installation, operation, maintenance and service of this equipment involves risks both to personnel and equipment, and must be performed only by qualified personnel exercising due care. HARRIS CORPORATION shall not be responsible for injury or damage resulting from improper procedures or from the use of improperly trained or inexperienced personnel performing such tasks. During installation and operation of this equipment, local building codes and fire protection standards must be observed. The following National Fire Protection Association (NFPA) standards are recommended as reference: - Automatic Fire Detectors, No. 72E - Installation, Maintenance, and Use of Portable Fire Extinguishers, No Halogenated Fire Extinguishing Agent Systems, No. 12A ALWAYS DISCONNECT POWER BEFORE OPENING COVERS, DOORS, ENCLOSURES, GATES, PANELS OR SHIELDS. ALWAYS USE GROUNDING STICKS AND SHORT OUT HIGH VOLTAGE POINTS BEFORE SERVICING. NEVER MAKE INTERNAL ADJUSTMENTS, PERFORM MAINTE- NANCE OR SERVICE WHEN ALONE OR WHEN FATIGUED. Do not remove, short-circuit or tamper with interlock switches on access covers, doors, enclosures, gates, panels or shields. Keep away from live circuits, know your equipment and don t take chances. IN CASE OF EMERGENCY ENSURE THAT POWER HAS BEEN DISCONNECTED. IF OIL FILLED OR ELECTROLYTIC CAPACITORS ARE UTILIZED IN YOUR EQUIPMENT, AND IF A LEAK OR BULGE IS APPARENT ON THE CAPACITOR CASE WHEN THE UNIT IS OPENED FOR SERVICE OR MAINTENANCE, ALLOW THE UNIT TO COOL DOWN BEFORE ATTEMPTING TO RE- MOVE THE DEFECTIVE CAPACITOR. DO NOT ATTEMPT TO SERVICE A DEFECTIVE CAPACITOR WHILE IT IS HOT DUE TO THE POSSIBILITY OF A CASE RUPTURE AND SUBSEQUENT INJURY. FIRST-AID

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7 Personnel engaged in the installation, operation, maintenance or servicing of this equipment are urged to become familiar with first-aid theory and practices. The following information is not intended to be complete first-aid procedures, it is a brief and is only to be used as a reference. It is the duty of all personnel using the equipment to be prepared to give adequate Emergency First Aid and thereby prevent avoidable loss of life. Treatment of Electrical Burns 1. Extensive burned and broken skin a. Cover area with clean sheet or cloth. (Cleanest available cloth article.) b. Do not break blisters, remove tissue, remove adhered particles of clothing, or apply any salve or ointment. c. Treat victim for shock as required. d. Arrange transportation to a hospital as quickly as possible. e. If arms or legs are affected keep them elevated. NOTE If medical help will not be available within an hour and the victim is conscious and not vomiting, give him a weak solution of salt and soda: 1 level teaspoonful of salt and 1/2 level teaspoonful of baking soda to each quart of water (neither hot or cold). Allow victim to sip slowly about 4 ounces (a half of glass) over a period of 15 minutes. Discontinue fluid if vomiting occurs. (Do not give alcohol.) 2. Less severe burns - (1st & 2nd degree) a. Apply cool (not ice cold) compresses using the cleanest available cloth article. b. Do not break blisters, remove tissue, remove adhered particles of clothing, or apply salve or ointment. c. Apply clean dry dressing if necessary. d. Treat victim for shock as required. e. Arrange transportation to a hospital as quickly as possible. REFERENCE: f. If arms or legs are affected keep them elevated. ILLINOIS HEART ASSOCIATION AMERICAN RED CROSS STANDARD FIRST AID AND PERSONAL SAFETY MANUAL (SECOND EDITION)

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9 1.1 Introduction The Crowbar Operation Verification Test Fixture provides a safe way to test the operation of the Harris Sigma and Sigma Plus transmitter crowbar circuit than previous methods available. It is an advanced troubleshooting method which should only be used by qualified personnel. It still requires the technician to deal with circuits which have voltages in excess of 36kV when operating and as such should be afforded the appropriate caution and respect. The purpose of the fixture is to short the -36kV supply to ground through a specific length of 36 gauge wire. The crowbar circuit in the transmitter should react quick enough to protect the wire. If the wire is blown, then the crowbar circuit is faulty and must be repaired. This test function goes beyond the functionality of the Crowbar Logic Test button in the transmitter. 1.2 Theory of Operation The IOT crowbar is in effect a high voltage shunt switch. Its purpose is to protect the IOT or Klystrode used in UHF television transmitters from adverse damage during fault conditions such as internal tube arcs. Under such conditions an unprotected tube will draw excessive current from the HV power supply and the energy storage capacitors which will additively contribute to effects causing possible damage to the tube. During a tube arc or HV cable fault the crowbar assembly detects the sudden rise in current drawn from the supply. This causes it Section I Introduction and Installation to self-trigger or turn on. The heart of the crowbar, a deuterium Thyratron, diverts any flow of energy from the supply away from the IOT thereby preventing further damage. Upon triggering, the crowbar informs the amplifier control that the crowbar has fired and there will most likely be a body current trip as well. In order to test that the Crowbar system is working properly, a fuse wire is connected between the cathode connection (- 36kV) on the IOT or Klystrode and a point that can be shorted to ground quickly. The process of shorting is relatively simple, however, the crowbar is floating at 36kV which causes considerable safety concerns. When the fixture is operated there are two (2) possible outcomes: a. If the Crowbar operates properly when the fixture shorts the -36kV, the contactor in the line control cabinet will disengage momentarily, then the transmitter will resume normal operation. In this case, the Crowbar has fired quick enough to protect the very fine gauge fuse wire on the test fixture and is therefore providing adequate protection to the tube. b. If the Crowbar fails to operate properly then the fuse wire on the fixture (from the -36kV supply to ground) will vaporize and a very loud BANG will be heard inside the amplifier cabinet (some smoke is also to be expected). The safety shields will protect the inside of the transmitter from the splatter of the fuse wire. In this case the crowbar either failed to operate or was too slow to react and is therefore not providing adequate protection to the IOT or Klystrode and should be repaired. Figure 1-1 Crowbar Operation Verification Test Fixture Rev. B: : Disconnect primary power prior to servicing.

10 1.3 Crowbar Test Fixture Construction The Crowbar Test Fixture is constructed primarily of non-conductive materials, see Figures 1-2 and 1-3. Operation of the switch is pneumatic and therefore the fixture requires no external power source or conductive wiring outside the transmitter cabinet. A pulse of air supplied by a foot pedal type air pump travels through a non-conductive tubing to a cylinder/piston assembly. The piston contact surface is connected via high voltage wire to the cathode connection on the crowbar assembly. THIS TEST FIXTURE IS USED TO SHORT THE 36kV POWER SUPPLY TO GROUND IN ORDER TO TEST THE OPERATION OF THE CROWBAR ASSEMBLY IN THE SIGMA SERIES TRANSMIT- TERS. BE SURE TO REMOVE ALL POWER, PLACE THE AMPLI- FIER CABINET ISOLATION SWITCH IN THE SHORT TO EARTH (GROUNDED) POSITION AND THEN USE THE GROUND STICK TO MAKE SURE NO VOLTAGE IS PRESENT BEFORE ATTEMPT- ING TO INSTALL OR REMOVE THIS TEST FIXTURE. The air pulse causes the piston to quickly rise and strike a stationary contact point on the fixture. The stationary contact is connected to one end of the fuse wire. The other end of the fuse wire is connected to the lower fuse wire terminal and in turn connected to a high voltage wire that gets connected to cabinet ground. The fixture is constructed so that it can be placed inside the high voltage compartment. Voltage standoffs are such that the fixture can safely be set onto a grounded or a high voltage surface. The tubing is of sufficient length, and dielectric resistance to allow the foot pedal to be placed safely outside the high voltage compartment. Tubing diameter is relatively small, this makes it possible to close safety panels and take full advantage of all safety interlocks during the test. Safety covers on the fixture are proven to catch the fuse wire splatter and prevent shorting of surrounding components should the crowbar fail to protect the wire during the test. Figure 1-2 Front View showing foot pump and HV lead Figure 1-3 Rear View showing Fuse wire and Ground Lead Rev. B: : Disconnect primary power prior to servicing.

11 1.4 When Do I Use the Test Fixture? The Crowbar Test Fixture should be used whenever there is a doubt as to the operation of the crowbar assembly. Several necessary instances would be: a. Before replacing an IOT or Klystrode b. After replacing the thyratron or doing any work on the crowbar assembly or high voltage wiring. c. Anytime there is a high voltage arc in the transmitter, especially if an excessive amount of damage occurred due to the arc. 1.5 Test Fixture Preparation Test Fixture preparation basically consists of installing a piece of wire and making sure the fixture is clean. Read the following steps carefully to avoid any possible problems. Step 1. Install a piece of fuse wire on the test fixture (if necessary). The wire is 36 gauge bare copper (a roll of wire is included with the kit), although enamel insulated wire is also acceptable. To install the wire, simply back the hex nuts away from the acorn nuts on the end of the posts. Wrap at least one turn around the post as close to the acorn nut as possible and finger tighten the hex nut to secure the wire. CAUTION DO NOT LEAVE A TAIL OF WIRE STICKING OUT ON EITHER END AS SHOWN IN FIGURE 1-4. MAKE SURE THE WIRE IS WRAPPED TIGHTLY AROUND THE POST AS IN FIGURE 1-5. ANY WIRE STICKING OUT COULD CAUSE UNDESIRED CORONA ARCING. Step 2. Once the wire is installed, replace and secure all shields in place. Be sure to clean the shields and fixture if the wire has previously been burnt open. Failure to thoroughly clean the fixture could result in an arc to ground that bypasses the wire. DO NOT OPERATE THE TEST FIXTURE WITHOUT ALL SHIELDS IN PLACE. Step 3. Step 4. Practice. It is a good idea at this point to practice pulsing the rubber air pump to see just what it takes to activate the fixture. The idea is to get a quick but firm hit on the stationary contact. It is not necessary to Stomp on the air pump. As you will see it only takes a good firm step. This also confirms that the fixture is working (not sticking). Check position of the plunger lug and make certain that it is working freely. For best results, the lug should be facing away from the plate so that the cable can flex freely. DUE TO THE DANGEROUSLY HIGH VOLTAGES INVOLVED BE SURE TO READ ALL OF THE INSTRUCTIONS CAREFULLY AND FOLLOW ALL LABELS PRINTED ON THE FIXTURE. Figure 1-4 Improper Installation of the Fuse Wire Figure 1-5 Proper Installation of Fuse Wire Rev. B: : Disconnect primary power prior to servicing.

12 1.6 Crowbar Test Fixture Installation The following is a step by step procedure for installing and operating the test fixture in the Sigma Plus and Sigma CD series transmitter. NOTE If you have a Sigma Classic, please refer to the Sigma Classic procedure later in this chapter. Please read and understand the entire procedure before proceeding. THIS TEST FIXTURE IS USED TO SHORT THE 36kV POWER SUPPLY TO GROUND IN ORDER TO TEST THE OPERATION OF THE CROWBAR ASSEMBLY IN THE SIGMA SERIES TRANSMIT- TERS. BE SURE TO REMOVE ALL POWER, PLACE THE AMPLI- FIER CABINET-ISOLATION SWITCH IN THE EARTH (GROUNDED) POSITION AND THEN USE THE GROUND STICK TO MAKE SURE NO VOLTAGE IS PRESENT BEFORE ATTEMPT- ING TO INSTALL OR REMOVE THIS TEST FIXTURE. Step 1. Step 2. Step 3. Shut the transmitter off and remove all power from the transmitter by disengaging the breakers on the line control cabinet. Also lockout the line control cabinet and remove the key. Place the Isolation Switch, on the rear of the amplifier cabinet, in the SHORT TO EARTH (grounded) position. Remove the lower right-hand door (when viewing from the back) from the rear of the amplifier cabinet. Use the shorting stick to ground all exposed areas where voltage could be present. If in doubt, short it out! Leave the ground stick hanging on the high voltage side of the crowbar unit as shown in Figure 1-6. Figure 1-6 Ground all surfaces with which personnel could come into contact Rev. B: : Disconnect primary power prior to servicing.

13 Step 4. Place the test fixture on top of the crowbar assembly as shown in Figure 1-7. Step 5. Connect the HV lead attached to the lower end of the fuse wire to the ground strap running up the inside of the cabinet wall as shown in Figure 1-8. Figure 1-7 Fixture in place on top of crowbar assembly Figure 1-8 Ground Lead connection for test fixture Rev. B: : Disconnect primary power prior to servicing.

14 BE SURE TO USE THE GROUNDING STICK TO DISCHARGE THE CONNECTION POINT IN THE NEXT STEP BEFORE CONNECT- ING THE TEST FIXTURE LEAD, ALONG WITH ANY OTHER POINTS THAT MAY BE TOUCHED WHILE CONNECTING THE LEAD. Step 6. Connect the second HV lead (the one attached to the piston) to the outer end of the resistors on the left side of the Crowbar assembly as shown in Figure 1-9. This is the 36kV cathode connection for the IOT or Klystrode. Step 7. Step 8. Remove the grounding stick from the circuit and secure in its holder. Route the foot pump out of the cabinet and re-install the door, keeping the hose near the bottom of the door, see Figure The hose for the pump is fairly thick and will not be harmed if reasonable care is taken when installing the door. CAUTION DO NOT SCREW THE DOOR DOWN TOO TIGHT AT THE BOTTOM TO KEEP THE HOSE FROM BECOMING COMPLETELY COM- PRESSED. Figure 1-9 Test fixture connection to -36kV Figure 1-10 Proper routing of air tubing outside of the cabinet Rev. B: : Disconnect primary power prior to servicing.

15 Step 9. Disengage the amplifier cabinet isolation switch, restore power to the transmitter via the line control cabinet breakers and turn it on. Step 10. Now that the transmitter is operational, it is time to test the crowbar. Remember to step firmly on the foot pump and be ready for the noise that could follow. IT IS RECOMMENDED THAT HEARING PROTECTION BE WORN IN CASE THE FUSE WIRE IS BURNT OPEN AS THIS CAUSES A VERY LOUD BANG ROUGHLY EQUIVALENT TO A SHOTGUN BLAST. DO NOT LOOK DIRECTLY AT THE FIXTURE, ESPECIALLY THE FUSE WIRE, DURING THE TEST. IF THE FUSE WIRE OPENS, A FLASH OF LIGHT EQUIVALENT TO AN ARC WELDER WILL OCCUR. THIS WILL BE INDIRECTLY VISIBLE THROUGH THE SHORTING SWITCH WINDOW WITHOUT LOOKING DIRECTLY AT THE FIXTURE Test Results This is an extreme case of a pass/fail test. The following is a description of the 2 possible outcomes. a. If the crowbar operates properly, the transmitter and supplies will shut off momentarily and then the transmitter should come back on. You should have Crowbar fired LED and possibly a Body Current LED on the front panel. Most importantly, the fuse wire on the test fixture should be intact (no loud BANG ). b. If the crowbar is not operating properly, a very loud BANG will be heard as the fuse wire vaporizes. The supplies and the transmitter will also shut off momentarily before coming back on. This means that the crowbar either did not operate at all, or it did not react fast enough. In either case, you will need to refer to the Transmitter technical manual for further troubleshooting of the crowbar circuit. 1.7 Removing the Test Fixture BE SURE TO REMOVE ALL POWER, PLACE THE AMPLIFIER CABINET-ISOLATION SWITCH IN THE EARTH (GROUNDED) PO- SITION AND THEN USE THE GROUND STICK TO MAKE SURE NO VOLTAGE IS PRESENT BEFORE ATTEMPTING TO INSTALL OR REMOVE THIS TEST FIXTURE. Step 1. Step 2. Step 3. Step 4. Step 5. Shut the transmitter off and remove all power from the transmitter by disengaging the breakers on the line control cabinet. Also lockout the line control cabinet and remove the key. Place the Isolation Switch, on the rear of the amplifier cabinet, in the EARTH (grounded) position. Remove the lower right-hand door (when viewing from the back) from the rear of the amplifier cabinet. Use the grounding stick to ground all exposed areas where voltage could be present. If in doubt, short it out! Leave the ground stick hanging on the high voltage side of the crowbar unit as shown in Figure 1-6. Disconnect the fixture clip-leads, remove the fixture from the transmitter and remove the grounding stick. If the test passed and the wire is still intact, re-install the back door and the transmitter is ready to be put back into service. If the test failed, the wire has been burnt open and the fixture will need to be thoroughly cleaned before its next use. This includes the fixture base and the clear shield over the wire. Once cleaned, install a new piece of wire and replace and secure all shields. The fixture is now ready for another test after the failure in the crowbar circuit is repaired. Rev. B: : Disconnect primary power prior to servicing.

16 1.8 Sigma Classic Test Fixture Installation This section is for the older Sigma transmitters designated as the Classic model. The classic in this case can be easily recognized as the crowbar assembly is mounted to the cabinet floor in an upright position. In later models, the crowbar assembly is mounted horizontally as shown in the pictures of the previous section. However, the basic connection points for the fixture are the same. The following is a step by step procedure for installing and operating the test fixture in the transmitter. Please read and understand the entire procedure before proceeding. THIS TEST FIXTURE IS USED TO SHORT THE 36kV POWER SUPPLY TO GROUND IN ORDER TO TEST THE OPERATION OF THE CROWBAR ASSEMBLY IN THE SIGMA SERIES TRANSMIT- TERS. BE SURE TO REMOVE ALL POWER, PLACE THE AMPLI- FIER CABINET-ISOLATION SWITCH IN THE SHORT TO EARTH (GROUNDED) POSITION AND THEN USE THE GROUND STICK TO MAKE SURE NO VOLTAGE IS PRESENT BEFORE ATTEMPT- ING TO INSTALL OR REMOVE THIS TEST FIXTURE. Step 1. Step 2. Step 3. Step 4. Step 5. Shut the transmitter off and remove all power from the transmitter by disengaging the breakers on the line control cabinet. Also lockout the line control cabinet and remove the key. Place the Isolation Switch, on the rear of the amplifier cabinet, in the SHORT TO EARTH (grounded) position. Remove the 2 lower left-hand doors (when viewing from the back) from the rear of the amplifier cabinet. Use the grounding stick to ground all exposed areas where voltage could be present. If in doubt, short it out! Place the test fixture in between the two transformers asshowninfigure1-11. Connect the HV lead attached to the lower end of the fuse wire to the ground strap running along the floor of the cabinet as shown in Figure Figure 1-11 Test Fixture Location and Ground Lead Connection Rev. B: : Disconnect primary power prior to servicing.

17 BE SURE TO USE THE GROUNDING STICK TO DISCHARGE THE CONNECTION POINT IN THE NEXT STEP BEFORE CONNECT- ING THE TEST FIXTURE LEAD, ALONG WITH ANY OTHER POINTS THAT MAY BE TOUCHED WHILE CONNECTING THE LEAD. Step 6. Step 7. Connect the second HV lead (the one attached to the piston) to the Top of the resistors on the left hand side of the crowbar assembly as shown in Figure Remove the grounding stick from the circuit and secure in its holder. Step 8. Route the foot pump out of the cabinet and re-install the door, keeping the hose near the bottom of the door. The hose for the pump is fairly thick and will not be harmed if reasonable care is taken when installing the door. CAUTION DO NOT SCREW THE DOOR DOWN TOO TIGHT AT THE BOTTOM TO KEEP THE HOSE FROM BECOMING COMPLETELY COM- PRESSED. Figure 1-12 Test fixture connection to -36kV Rev. B: : Disconnect primary power prior to servicing.

18 Step 9. Disengage the amplifier cabinet isolation switch, restore power to the transmitter via the line control cabinet breakers and turn the transmitter on. Step 10. Now that the transmitter is operational, it is time to test the crowbar. Remember to step firmly on the foot pump and be ready for the noise that could follow. IT IS RECOMMENDED THAT HEARING PROTECTION BE WORN IN CASE THE FUSE WIRE IS BURNT OPEN AS THIS CAUSES A VERY LOUD BANG ROUGHLY EQUIVALENT TO A SHOTGUN BLAST. DO NOT LOOK DIRECTLY AT THE FIXTURE, ESPECIALLY THE FUSE WIRE, DURING THE TEST. IF THE FUSE WIRE OPENS, A FLASH OF LIGHT EQUIVALENT TO AN ARC WELDER WILL OCCUR. THIS WILL BE INDIRECTLY VISIBLE THROUGH THE SHORTING SWITCH WINDOW WITHOUT LOOKING DIRECTLY AT THE FIXTURE Test Results This is an extreme case of a pass/fail test. The following is a description of the 2 possible outcomes. a. If the crowbar operates properly, the transmitter and supplies will shut off momentarily and then the transmitter should come back on. You should have Crowbar fired LED and possibly a Body Current LED on the front panel. Most importantly, the fuse wire on the test fixture should be intact (no loud BANG ). b. If the crowbar is not operating properly, a very loud BANG will be heard as the fuse wire vaporizes. The supplies and the transmitter will also shut off momentarily before coming back on. This means that the crowbar either did not operate at all, or it did not react fast enough. In either case, you will need to refer to the Transmitter technical manual for further troubleshooting of the crowbar circuit. 1.9 Removing the Test Fixture BE SURE TO REMOVE ALL POWER, PLACE THE AMPLIFIER CABINET-ISOLATION SWITCH IN THE SHORT TO EARTH (GROUNDED) POSITION AND THEN USE THE GROUND STICK TO MAKE SURE NO VOLTAGE IS PRESENT BEFORE ATTEMPT- ING TO INSTALL OR REMOVE THIS TEST FIXTURE. Step 1. Step 2. Step 3. Step 4. Step 5. Shut the transmitter off and remove all power from the transmitter by disengaging the breakers on the line control cabinet. Also lockout the line control cabinet and remove the key. Place the Isolation Switch, on the rear of the amplifier cabinet, in the SHORT TO EARTH (grounded) position. Remove the 2 lower left-hand doors (when viewing from the back) from the rear of the amplifier cabinet. Use the grounding stick to ground all exposed areas where voltage could be present. If in doubt, short it out! Disconnect the fixture clip-leads, remove the fixture from the transmitter and remove the grounding stick. If the test passed and the wire is still intact, re-install the back door and the transmitter is ready to be put back into service. If the test failed, the wire has been burnt open and the fixture will need to be thoroughly cleaned before its next use. This includes the fixture base and the clear shield over the wire. Once cleaned, install a new piece of wire and replace and secure all shields. The fixture is now ready for another test after the failure in the crowbar circuit is repaired Rev. B: : Disconnect primary power prior to servicing.

19 Section II Parts List Table 2-1. KIT, CROWBAR TEST HARRIS P/N DESCRIPTION QTY/UM REF. SYMBOLS/EXPLANATIONS PUMP, FOOT PEDAL 1.0 EA WIRE, BARE COPPER, 36 AWG 1.0 RL SCR, X 1-1/2 1.0 EA SCR, X EA NUT CAP BRASS 2.0 EA NUT, HEX EA NUT, STOP EA WASHER FLAT EA WASHER, INT LOCK EA WASHER, SPLIT-LOCK EA SCREW THD CUT 6-32 X 3/8 1.0 EA CABLE CLAMP 3/16 D 1.0 EA NUT HEX NYLON 7.0 EA SCREW X.75 BHMS 6.0 EA ELBOW 90 DEG, 5/16 OD TUBE 1.0 EA GROMMET 5/16 MTG DIA 4.0 EA ASSY DWG, 0.0 EA CABLE PKG, CROWBAR TEST CABLE 1.0 EA CYLINDER 1.0 EA COVER, SAFETY, CONTACT SIDE 1.0 EA COVER, SAFETY, WIRE SIDE 1.0 EA ASSY, MOUNTING STAND 1.0 EA ASSY, PISTON/CAP 1.0 EA Table 2-2. CABLE PKG, CROWBAR TEST CABLE HARRIS P/N DESCRIPTION QTY/UM REF. SYMBOLS/EXPLANATIONS COND, FLEX.084 OD 0.80 FT WIRE, TURBO 18AWG RED 6.0 FT TUBING, SHRINK 3/8 WHITE 0.30 FT LUG 6 RING 1.0 EA LUG #10 RING YEL 12-10AWG 2.0 EA CLIP, ALLIGATOR 60S 2.0 EA INSULATOR RED VINYL 2.0 EA CADS, CROWBAR TEST CABLE 0.0 EA 5/8/ : Disconnect primary power prior to servicing.

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