DEPARTMENT OF THE ARMY TECHNICAL MANUAL TM 11-5820-256-20 .

DEPARTMENT OF THE ARMY TECHNICAL MANUALDEPARTMENT OF THE AIR FORCE TECHNICAL ORDERTM 11-5820-256-20TO 31R2-2GRC26-132ORGANIZATIONALMAINTENANCE MANUALRADIO SET AN/GRC-26DThis copy is a reprint which includes current pages fromChanges 1 through 5.DEPARTMENTS OF THE ARMY AND THE AIR FORCE5 JANUARY 1962

WARNINGDANGEROUS VOLTAGES EXIST IN THIS EQUIPMENTBe careful when working on the power supply circuits, the 115-volt ac line connections, or the240-volt plate circuits in Receiver, Radio R-390(*)/URR. Turn off power when working on thetransmitting antenna or the transmitting antenna terminals; high radio frequency voltages existat these points.DON'T TAKE CHANCES!EXTREMELY DANGEROUS VOLTAGESEXIST IN THE FOLLOWING UNITS:TRANSMITTER, RADIO T-368(*)/URTCONVERTER, FREQUENCY SHIFT CV-116(*)/URR2,400-volt circuits620-volt circuitsWARNINGVENTILATIONThe shelter must be ventilated when occupied. Be sure to open the vents, window shutters, ordoor when the equipment is operated.Keep the shelter air intake fan closed duringtransportation. The truck exhaust stack is near the air intake vent and danger from carbonmonoxide poisoning exists. When the vehicle is moving, adequate air circulation exists throughthe shelter windows.

Changes in force: C 1, C 2, C 3, C 4. and C 5TM 11-5820-256-20C5CHANGENo.5HEADQUARTERSDEPARTMENT OF THE ARMYWashington, D.C., 6 June 1975}Organizational Maintenance ManualRADIO SET AN/GRC-2TM 11-5820-356-20, 5 January 1962, is changed as follows:General.Change the words “second echelon”wherever they appear in the technical manual to“organizational”.Page 1. Paragraph 1a. Delete paragraph designation“a”.Paragraph 1b and c are superseded as follows:NOTEFor applicable forms and records,see paragraph 2, TM 11-5820-256-10Page 11. Paragraph 11d(1) change PU-294/G to read“PU-474/M or PU-619/M.”Paragraph 12a.Step 1, corrective measurementscolumn, change to read, “Refer to TM 11-6115-230-15or TM 11-6115 275-15”Page 15.Paragraph 12d.Step 1, Correctivemeasures column, change to read, “Refer to TM 116115-230-15 or TM 11-6115-275-15.”Page 24. Add the following references in propernumerical order.TM 5-2805-259-14Operator’s Organizational, DirectSupport,GeneralSupportMaintenance Manual: Engine,Gasoline, 20HP; Military StandardModels (Model 4A084-2) FSN2805-985-3926 (Model 4A084-3)FSN 2805-872-5972TM 5-6115-275-15Operator’s Organizational, DirectSupport, General Support, andDepotMaintenanceManual:Generator Set, Gasoline Engine10KW, AC, 120/208 V, 3 Phase,60HZSkidMounted(LessEngine).Page 25. Delete the last itemPage 30. Section II, Part or Component column,second item, change Generator PU-294/G to read”Generator PU-474/M or PU-619/M.”1.1. Indexes of Publicationsa. Refer to latest issue of DA Pam 310-4 todetermine whether there are new editions, changes, oradditional publications pertaining to the equipment.b. Refer to DA Pam 310-7 to determine whetherthere are modification work orders (MWO’s) pertainingto the equipment.1.2.Reporting of Equipment Publications ImprovementsThe reporting of errors omissions, and recommendations for improving this publication by the individualuser is encouraged. Reports should be submitted on DAForm 2028 (Recommended Changes to Publicationsand Blank Forms) and forwarded direct to Commander,US Army Electronics Command, ATTN: -AMSEL-MA-Q,Fort Monmouth, NJ 07703.1

By Order of the Secretary of the Army:FRED C. WEYANDGeneral, United States ArmyChief of StaffOfficial:VERNE L BOWERSMajor General, United States ArmyThe Adjutant GeneralDistribution:To be distributed in accordance with accordance with DA form 12-51, (qty rqr block no. 98) Organizational maintenancerequirements for AN/GRC-262

Changes in force: C 1, C 2, C 3, and C 4TM 11-5820-256-20C4CHANGENO. 4HEADQUARTERSDEPARTMENT OF THE ARMYWASHINGTON, DC, 9 April 1975}Organizational Maintenance ManualRADIO SET AN/GRC-26DTM 11-5820-25620, 5 January 1962, is changed as follows:Inside front cover. Radiation warning is added after existing notices.1

WARNINGRADIATION HAZARDRADIOACTIVE MATERIALCONTROLLED DISPOSAL REQUIREDACCOUNTABILITY NOT REQUIREDSTD RW-2Audio level meter.Ra 226 .0.69uCi . 6625-00-669-0769Audio level meter.Ra 226 .0.40uCi . 6625-00-669-0770Electron Tube CC3W . 5960-00-188-0968Sylvania.Co 60 .1.0uCiElectron Tube OA2WA. 5960-00-503-4880EEVC.U 238 .0.1uCiCBS Hytron.Ni 63 .0.5uCiRaytheon .Co 60 .0.2uCiElection Tube OA2WAEEVC.U 238 .0.1uCiCBS Hytron.Ni 62 .0.5uCiRaytheon .Co 60 .0.2uCiRadiation Hazard Information: The following radiation hazard information must be read and understood by allpersonnel before operating or repairing Radio Set AN/GRC-26D. Hazardous radioactive materials are present inthe above listed components of the MD-239A/GR, R-390/URR, C-632/GRC-10, R-125/GRC-10, and T-235/GRC10.The components are potentially hazardous when broken. See qualified medical personnel and the localRadiological Protection Officer (RPO) immediately, if you are expose to or cut by broken components. First aidinstructions are contained in TB 43-0116, TB 43-0122, and AR 755-15.NEVER place radioactive components in your pocket.Use extreme care NOT to break radioactive components while handling them. NEVER remove radioactivecomponents from cartons until you are ready to use them.2

If any of these components are broken, notify the local RPO immediately. The RPO will survey the immediatearea for radiological contamination and will supervise the removal of broken components. The above listedradioactive components will not be repaired or disassembled.Disposal of broken, unserviceable, or unwanted radioactive components will be accomplished in accordance withthe instructions in AR 755-15.By Order of the Secretary of the Army:FRED C. WEYHANDGeneral, United States ArmyChief of StaffOfficial:VERNE L. BOWERSMajor General, United States ArmyThe Adjutant GeneralDistribution:To be distributed in accordance with DA Form 12-51, (qty block No. 98). Organizational maintenance requirements forAN/GRC-26.3

Changes in force: C 1, C 2, C 3TM 11-5820-256-20C3CHANGENo. 3HEADQUARTERSDEPARTMENT OF THE ARMYWashington, D.C., 4 June 1969}Organizational Maintenance ManualRADIO SET AN/GRC-26DTM 11-5820-256-20, 5 January 1962 Is changed as follows:Page 4, figure 1. On the left side of the illustration,delete callout "WIRE W-128" and substitute: WIRE W146.Note. The parenthetical reference to previous change(example: "page 1 of C 1") indicates that pertinentmaterial was published In that change.Page 11, paragraph 11d(1), line 2. After "PU-294/G"add: or Generator Set, Gasoline Engine, TrailerMounted PU-474/M.Paragraph 12c, chart, step 1, Corrective measurescolumn. Delete "Refer to TM 11-940A" and substitute:Refer to TM 11-6115-204-10 or TM 11-6115-230-15.Page 2, paragraph 1. Delete subparagraph b (page 1of C 2) and substitute:b. The reporting of errors, omissions and recommendations for improving this manual by the individualuser is encouraged. Reports should be submitted on DAForm 2028 (Recommended Changes to DAPublications) and forwarded direct to CommandingGeneral, U.S. Army Electronics Command, ATTN:AMSEL-ME-NMP-AD, Fort Monmouth, N. J. 07703.Delete subparagraph c (page 1 of C 1) and substitute:c. Refer to the latest issue of DA Pam 310-4 todetermine whether there are new editions, changes, oradditional publications pertaining to the equipment.Refer to DA Pam 310-7 to determine whether there aremodification work orders (MWO's) pertaining to theequipment.Paragraph 2, line 5. After "components" add: and theaddition of cryptographic equipment.Page 3, paragraph 5e, line 1. Delete "W-128" andsubstitute: W-126.Page 13, step 9, Corrective measures column, line 19.Delete "W-128" and substitute: W-146.Lines 32 and 33. Delete "CX-1200/U and CX-1201/U"and substitute: CX-11411/U and CX-9996A/U.Page 14, step 10, Corrective measures column, lasttwo lines.Delete "Refer to TM 11-2225" and substitute: Refer toTM 11-5815-238-12.Step 12, Corrective measures column, line 8. Delete"Refer to TM 11-2225" and substitute: Refer to TM 115815-238-12.Page 20, paragraph 18. After subparagraph a(1), add(1.1):1

(1.1) When fsk operation is used in a Radio SetAN/GRC-26D which has been modified to use securityequipment, signals are routed to Electronic Switch SA1253/GRC through Junction Box J-2597/GRC and thento Control, Radio Set C-1123/GRC. From Control,Radio Set C-1123/GRC, signals follow the same path asa plain text transmission, except that the signals passthrough Polar Relay F-1084/GRC before being appliedto Modulator, Radio MD239(*)/GR.Delete subparagraph b, and substitute:b. Remote Control Unit.Control, RemoteSwitching C-1474/GRC, together with InterconnectingBoxes J-2623/GRC and J2624/GRC, provides routingfacilities from a remote location. All signals initiated bythe remote equipment are routed through interconnecting boxes to Control, Radio Set C-1123/GRC.Page 24, appendix I (page 1 of C 2).Delete appendix I and substitute:APPENDIX IREFERENCESFollowing is a list of applicable references available to organizational maintenance personnel of Radio Set AN/GRC-26D.AR 380 5D-A Pam 310-4DA Pam 310-7SB 38-100TB 746-10TM 9-213TM 11-337TM 11-809-20TM 11-2155TM 11-2241TM 11-3895-201-13PTM 11-4140-200-20PTM 11-5410-200-12PTM 11-5805-201-12Military Security.Index of Technical Manuals, Technical Bulletins, Supply Manuals (types 7, 8, and 9),Supply Bulletins, and Lubrication Orders.U.S. Army Equipment Index of Modification Work Orders.Preservation, Packaging and Packing Materials, Supplies, and Equipment Used by theArmy.Field Instructions for Painting and Preserving and Electronics Command Equipment.Painting Instructions for Field Use.Telephone Sets TA-43/PT and TA-263/PT.Organizational Maintenance; Radio Transmitters T-368/URT, T-368A/URT, T-368B/URT,T-368C/URT, T-368D/URT, and T-368E/URT; Antenna Tuning Unit BC-939-B; RadioFrequency Tuner TN-399/GR; and Standing Wave Ratio-Power Meter ME-165/G.Telephone Set TA-312/PT.Frequency Shift Converters CV-116/URR, CV-116A/URR, CV-116B/URR and CV116C/URR.Operator, Organizational, and Field (Third Echelon) Maintenance Repair Parts andSpecial Tool Lists and Maintenance Allocation Chart: Axles RL-27-B, RL-27-C, andRL-27-D.Organizational Maintenance Repair Parts and Special Tools List and MaintenanceAllocation Chart: Blower Assembly, Electrical HD-223/G.Operator's and Organizational Maintenance Repair Parts and Special Tools List andMaintenance Allocation Chart for Shelters S-56/G and S-56A/G.Organizational Maintenance Manual: Telephone Set TA-312/PT.2