Heath Company Heathkit SB-220 Assembly Manual Download Page 116

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Summary of Contents for Heathkit SB-220

Page 1: ...LINEAR AMPLIFIER MODEL SB 220...

Page 2: ......

Page 3: ...Assembly and Operation of the LINEAR AMPLIFIER MODEL SB 220 HEATH COMPANY BENTON HARBOR MICHIGAN 49022...

Page 4: ...tion 58 Knob Installation 59 TEST AND FINALASSEMBLY 61 INSTALLATION 65 OPERATION Controls Connectors And Meters 69 General 70 Tune up 71 Periodic Maintenance 74 IN CASE OF DIFFICULTY 75 Troubleshootin...

Page 5: ...ted by exciter relay contacts to place the Amplifier in the transmit mode The Amplifier can be operated from either 120VAC or 240 VAC 50 60 Hz lines and can be easily changed from one to the other Ope...

Page 6: ...PARTS PICTORIAL B R O W N u continued on fold out from Page 7...

Page 7: ......

Page 8: ...ON No No Per Kit KEY PART PARTS DESCRIPTION No No Per Kit RESISTORS CAPACITORS 112 Watt 1 1 9 1 44 1 18 1 22 1 23 1 24 1 25 1 26 Other Resistors 2 1 8 1 1 38 1 1000S 2 brown black red 2200 S2 red red...

Page 9: ...ssembled in bag 39 73 4 1 5116 grommet 73 3 4 112 grommet 73 2 1 314 grommet 40 75 123 1 Line cord strain relief 75 124 1 6 x 4 112 fish paper insulator 41 75 125 8 Capacitor mounting insulator 42 255...

Page 10: ...screw 832 nut 8 lockwasher 8 32 x 1 318 spacer 8 solder lug 10 24x 1 round head screw 10 24riut 10 24wing nut 10 lockwasher Cable damp 440 x 5 16 screw 440 nut Control nut Speednut Control flat washe...

Page 11: ...PARTS PICTORIAL cont d...

Page 12: ...Page 8 p r e b l g...

Page 13: ...e to sethe actual positions of wires and components Lockwashers and nuts will be used with most screws when mounting parts unless the assembly steps state otherwise Consequently the applicable stepswi...

Page 14: ...TE D I O D E S M A Y BE S U P P L I E D I N A N Y OF THE F O L L O W I N G SHAPES THE CATHODE E N D OF THE D I O D E I S M A R K E D W l T H A B A N D OR 2 A N D S A L W A Y S P O S I T I O N T H I S...

Page 15: ...ck hookupwire to hole B on the circuit board 6 1 Preparethe following lengthsof hookupwire L 5 11 4 red 3 314 black 6 112 black 17 112 small black strandedwire 7 112 orange 6 112 yellow 9 112 heavy bl...

Page 16: ...ompletes the prewiring of the circuit board Set it aside until called for later Proceed with the Input Coil Assembly section INPUT COIL ASSEMBLY Refer to Pictorial2 1 for the following steps Refer to...

Page 17: ...ounting ears snap out to holdthe coil in placeas shown in Detail 2 1C Detail2 1B d lnstall the 2ameter mil 40965 at CV See Detail 2 1C Installthree 6 solder lugson the coil mountingshield 4 Installa 1...

Page 18: ...lug CL 3 NS d Connect a 115 pF mica capacitor from lug 1 of coil CY NS to ground lug CL 2 NS 4 Refer to the inset drawing on Detail 2 ID and twist together the leads of t w o 22 pF mica capacitors a s...

Page 19: ...pF and a 680 pF mica capacitor together Connect one pair of leads to lug 2 of coil CS NS and the other pair of leads to ground lug CL 1 6 5 y Connect a 470 pF mica capacitor from lug 1 of coil CT NS...

Page 20: ...witch lug at the same position it will count asthreewires 6 3 in the solder instructions 2 114 Connect the prepared hookup wires from the coils to wafer 1 of switch CZ as follows Connect to Wire Conne...

Page 21: ...ws Prepare the following lengths of black hookup wire Connect to Wires are listed in the order in which they will be used Wire Connect From Wafer 1of Length Lug 2 of Switch CZ 2 112 04 2 112 Coil CY 6...

Page 22: ...THE INNER I N S U L A T I O N AND STRETCH OUT to solder lug DF NS THE S H I E L D A P P L Y A S M A L L AMOUNT OF SOLDER TO THE END OF THE SHIELD AND THE INNER L E A D U S E I cut each lead of a 500 v...

Page 23: ...A F T END Detail 2 66 Refer to Detail 2 68 for the following steps I fStan two 6 32 x 3 16 screws into the tapped holesof the shaft coupler 456 16 Then slide half the length of the shaft coupler onto...

Page 24: ...ail 3 1A INSET P U S H O N C O N T R O L N U T C O N T R O L FLAT W A S H E R Detail 3 1B J dRefer to Detail 3 16 and install the 3 position rotary switch 63 47 at EU Use a control lockwasher a contro...

Page 25: ...to Detail 3 ID and install the plate meter 407 145 at EA Use the hardware supplied with the meter Install a 3 lug terminal strip at EB Note the lockwashers used CAUTION Do not overtighten the meter h...

Page 26: ...Cut the leads of two 02 pF disc capacitorsto a length of 112 These capacitors will be used in the next two steps Connect the black pilot lamp lead coming from meter ECto lug 1of terminal strip EB NS 4...

Page 27: ...6 4 dConnect an 18 length of brown wire to lug 1 of terminal strip EB 6 4 4 Connect a 30 length of green wire to lug 3 of control ET S I dRemove an additional ID of insulation from one end r r Gather...

Page 28: ...larly mount a DPDT rocker switch 61 15 at on the rear apron AN on the chassisfront apron 4 Refer to Detail 4 1B and mount a phono socket a t u NOTE Discard any loose metal clips you ind in the tube on...

Page 29: ...D E R L U G 8 6 3 2 x 114 S C R E W Detail 4 1F Refer to Detail 4 IF and mount a 3 lug terminal strip at P Use 6 32 x 114 hardware Refer to Detail 4 1G and mount a long solder lug at R Use 6 32 x 114...

Page 30: ...ition the relay with its lugs to the left Unsolder and discard the black insulatedwire between lug 9 and the movable arm Replace the wire discarded in the previousstep with a 4 length of small metal b...

Page 31: ...citor from lug6 of terminal strip BE NS to solder lug BF S 3 Refer to Part Bof the Pictorialfor the next eight steps J Prepare a 10 lengthof orangehookupwire and a 17 length of yellow hookupwire dConn...

Page 32: ...K F PICTORIAL 4 1 w rC 0 0 n 0 e 3 LUG 0 0 0 0 0 0 0 0 0...

Page 33: ...PICTORIAL 4 5...

Page 34: ...R A S S S P R I N G J 6 LOCKWASHER 6 32 N U T SOLDER LUG 4 Refer to Detail 4 38 and mount the brass spring 258 115 at CD and CE on the RF shield Use6 32 x 318 flat head hardware with a 6 solder lug at...

Page 35: ...MMFD Use a 6 32 x 1 4 flat head screw with a 8 lockwasher between the capacitor and the RF shield STEEL A Install a 6 solder lug on the other terminal of the capacitor with a 6 32 x 3 16 screw Positio...

Page 36: ...Page 30 6 SOLDER LUG 6 x 318 SHEET M E T A L SCREW SHEET M E T A L PICTORIAL 4 4 S H I E L D r l...

Page 37: ...l 4 5B for the next two steps tfl From the bottom of the chassis install 6 sheet metal 4 Install two 1 118 tapped spacers on the 80120 plate screws at CH and CJ into the coil mountingshield coil 40 59...

Page 38: ...it is soldered in place The end of each wire going through the switch lugs must first be flattened as shown in the inset drawing of Detail 4 5E DO NOT use the switch lugs to hold one end of the wire...

Page 39: ...B R A C K E T and a 6 32 nut on the third made bolt Bendthe two indicated solder lugs straight down before installing the capacitor Refer to Detail 4 5G and mount variable capacitor 26 131 at holes BA...

Page 40: ...butt snugly against it AConnect the tab on the coil to hole DA in the plate coil bracket Use 6 32 x 114 hardware 1 Solder the coil tubing and the wire lead from the switch wafer to lug 1 of the 80120...

Page 41: ...tenthe screw as the threads in the ceramic choke form can be damaged Position the choke so solder lug DC pointstoward spacer DD Refer to the Pictorial for the next two steps Install a 6 solder lug on...

Page 42: ...PICTORIAL 4 6...

Page 43: ...ake sure the fish paper clears the zener diode and the sheet metal screw at CG Rubthe paper firmly into place d Refer to Detail 4 68 and mount the filament and bias transformer 54 238 on the top of th...

Page 44: ...unt the front panel Replace the control flat washer and the control nut on assembly on the front of the chassis Insertthe twisted switch CZ hookup wires two brown and one green down through grommet AL...

Page 45: ...e 1 Adjust the position of the filament and bias Refer to Detail 4 6D and install the left side panel 203 6461 Use 6 32 x 318 phillipshardwareat EF between the transformer end bell and any connections...

Page 46: ...the red and the against the rear panel check the two offcenter holes redlyellow leads down through grommet Y Use an FK and FJ which if viewed a s shown in the Detail 8 32 x 318 screw a 112 flat washer...

Page 47: ...t I I 4 Rkfer to Detail 4 6H and installthe fan blade assembly 266 296 on the fan motor shaft Position the fan m m r and the blade assembly as shown and apply I I firm downward pressurewith both thumb...

Page 48: ...32 x 318 flat head screws Note that the diodes and the phenolic spacers are along the lower edge of L l the circuit board Refer to Detail 4 78 and mount the capacitor bank bracket with one spade bolt...

Page 49: ...on into the vacated space in the bracket Part D Align the capacitor lugs and the polarity markings as shown Then push the capacitors snugly against the fish paper and tighten the spade bolt nuts on th...

Page 50: ...t end of one of the 1 518 bare wires t o the negative lug of capacitor 3 NS and the straight end t o the positive lug o f capacitor 4 NS J Place a 314 length of slewing on one lead of a 30 kS2 resisto...

Page 51: ...f PICTORIAL 4 7...

Page 52: ...lead of a 001 eF 6 kV capacitor through J Black C solder lug CF 6 21 to hole K in the circuit board J Red S 1 Connect the other lead of this capacitor to A Lug2 of plate meter S 2 Lug 1of plate meter...

Page 53: ...M J Page 45 H I G H VOLTAGE DANGER I C A P A C I T O R B R A C K E T PICTORIAL 4 8...

Page 54: ...5 314 J1 At grommet AK cut the transformer leadsas follows One red 4 112 Other red 4 Black Red 3 314 Black Yellow 3 314 Black 3 112 Black Green Do not cut i i1 NOTE When you remove insulationfrom tra...

Page 55: ...ER 6 Connect a 02 pF disc capacitor from lug 1 NSIto lug 2 NS of terminal strip P Connect a 02 uF disc capacitor from lug 3 NS to lug 2 S 2 of terminal strip P Connect the green wire from grommet AL t...

Page 56: ...ceding step onto lug 3 of switch Z Connect the other end of this wire to double lug AW NS Connect the black lead from grommet AK to double lug AW NS f I Connect the black lead from grommet Y to double...

Page 57: ...ip BT other 13 112 wire onto lug2 4Connect the black stranded wire coming from J Prepare a 12 112 length of black strandedwire grommet AL to lug 5 of relay F S 1 4 Connect a 3 red hookup wire from lug...

Page 58: ...PICTORIAL 4 10...

Page 59: ...PICTORIAL 4 11...

Page 60: ...W PICTORIAL 4 13...

Page 61: ......

Page 62: ...ug M2 S 2 4 Connect a 02 uF disc capacitor from lug 1 NS to lug 2 NS of terminal strip B 4 Connect one lead of a 1000 G brown black red resistor to lug 2 6 2 and the other lead to lug 3 NS of terminal...

Page 63: ...is first removed from end A and that the center conductor and inner insulation are then cut U Detail4 12E END A d Refer to Detail 4 1 2E and form and fit a 5 314 length of silver plated strip as shown...

Page 64: ...g8 6 21 and the 1 lead to lug 2 6 31 of relay F as shownin inset drawing 2 of the Pictorial Refer to Pictorial 4 13 Wd out from Page 501 for the following steps Refer to Detail4 13A for the followingt...

Page 65: ...in relief on the terminal strip AE S 1 to lug 2 of circuit breaker AA line cord just beyond the split portion of the cord as NS shown Use a pair of gas pliers to compress the strain relief and then in...

Page 66: ...r the green lead to the wire loop and the wire loop to the solder lug but be to keep the other wire loopfree of solder Also solder the lead from the 02 uF disc capacitor and the brown wire to lug 1at...

Page 67: ...tail 4 148 and pass a cable tie 354 5 around all of the wires a t each of the six points shown in the Pictorial to form a neat cable Equalize any slack in each wire between the ends of the wire Then p...

Page 68: ...y PICTORIAL 4 14...

Page 69: ...I2 x S C R PICTORIAL 4 20...

Page 70: ...eps 1 Install a 6 solder lug on the top end of each plate connector 260 12 Use a 6 32 x 3 16 screw but leave it loose Start a 6 32 x 3 16 screw into the side of each plate connector 41 Place each plat...

Page 71: ...e at DK S 3 Push the other end over the solder lugon the capacitor at DN S I Detail 4 15B NOTE When you install parasitic chokes in the following steps center the chokes betweenthe solder lugs Y P E N...

Page 72: ...ur exciter Refer to Pictorial 4 16 or Pictorial 4 17 as appropriate I P R E P A R E ONE END A S SHOWN I T A K I N G C A R E NOT TO N I C K THE OUTER S H I E L D OF W I R E S R E M O V E THE OUTER I N...

Page 73: ...rews into each of the three large knobs Start a single setscrew into each of the two small knobs 1 Turn the shafts of the Tune and Load capacitors so the platesof each are fully meshed 1 Turn the thre...

Page 74: ......

Page 75: ...ot between the brass spring and the metal spacer If you fail to do this the high voltage circuit will be short circuited you will be unable to obtain a plate connector resistance reading and damage wi...

Page 76: ...ringwhich protrudesbeyondthe metal spacer NOTE If at any time during the testing and operation the Linear Amplifier does not perform as described unplugthe d Refer to Detail 4 198 and install a 6 32 X...

Page 77: ...imately 3000volts TESTS J 1 Pushthe POWER switch to ON NOTE There should be no indicationon either panel meter except when the METER SWITCH is at the HV position Check to see that the tube filaments a...

Page 78: ...ave the amplifier cabinet sit level install a rubber foot at each corner of the cabinet Use 6 32 x 11116 screws If you wish the front of the cabinet to be elevated install a rubber foot on each rear c...

Page 79: ...ving 10gauge conductorsand 20 ampere fuses DO NOT use this Amplifier at its full ratings on a regular house wiring circuit as the ratings of the wire will almost certainly be exceeded Avoid excessivel...

Page 80: ...is not available this function must be provided by other means If a separate coaxial send receive relay is used in your station it may have external contacts available A separate switch can also be u...

Page 81: ...Page 67 I R F H P S E R I E S A LC S B 1 0 1 T R A N S C E I V E R O U T P O W E R S U P P L Y RELAY ALC Figure 2 1 C A P P O W E R C A B L E PICTORIAL 5...

Page 82: ...H W 1 0 0 T R A N S C E I V E R ANTENNA FIGURE 2 2 8 0 4 0 OR 20 METER S I N G L E B A N D T R A N S C E I V E R H P S E R I E S POWER S U P P L Y 5 8 2 2 0 A M P L I F I E R FIGURE 2 4...

Page 83: ...FIGURE 2 3 C O A X I A L A N T E N N A RE LAY r f 1 TO R E C E I V E R C O A X I A L R E L A Y E X T E R N A L C O N T A C T S FIGURE 2 5...

Page 84: ...Shows plate current to Shows hlgh voltage In kV g r d current In mA 2 K W L I N E A R A M P L I F I E R ON CW TUNE I 1 FIGURE 3 1 I iI I 11 II I I ANT RELAY ALC RF INPUT RF OUTPUT I I Figure 3 2...

Page 85: ...Page 68...

Page 86: ...ampere Notethat by adding the proper number of zeros and dropping the decimal point each scale number may be read as milliamperes Thus 5 amperes would become 500 milliamperes Multi Meter Read the Mult...

Page 87: ...proximately 100 watts of RF output An exciter of lower power output may be used a s a driver but the Amplifier s output will be less If you use an exciter that deliversmore than 100 watts carefully ad...

Page 88: ...wing procedure for tuning the Amplifier should a s the Heathkit Cantenna or an appropriate antenna take only a few seconds after you go through it afew times connectedto the Amplifier output Note the...

Page 89: ...nal trapezoid display pattern is more easily interpreted for voice patterns CAUTION While actually transmitting DO NOT switch betweenCW TUNEand SSB modes SSB PROCEDURE Jl Tune up the exciter and Ampli...

Page 90: ...on the oscilloscope pattern They are sharp indicating a clean signal and they will attain a height greater than the single tone pattern of Figure 3 5 indicating maximum power input Figure3 6 Oscillosc...

Page 91: ...ver of the Amplifier and remove the dust While the top cwer is removed add onedrop of light at least once a year This can be done by using the blower machineoil to each fan bearing connection on a vac...

Page 92: ...wired into the circuit as shown in the 2 The majority of the kits that are returned for repair Pictorial Diagrams and as called out in the wiring do not function properly due to poor connectionsand in...

Page 93: ...USE A Circuit breakersopen B Jumpers missingon terminal strip AE C Terminal strip AE wired wrong A Resistor R1 R3 B D17 R25 R24 C54 R26 C R6 R7 R8 R9 D Meter switch A Meter jumper wire not removed B R...

Page 94: ...al invoiceor sales slip it will be returned to you If it is not convenient to deliver your kit to a Heathkit Electronic Center please ship it to the factory at Benton Harbor Michigan and observe the f...

Page 95: ...is packed in the Model 220 Service Pack Due to the weight The deposit for the Service Pack will be credited against any of the transformers shipment without special packagingwill service charges or wi...

Page 96: ...0watts RTTY 1000watts SSB continuousvoice modulation CW Continuous maximum key down 10 minutes RTTY 50 maximumtransmit time 10 minutes C 30dB or better 52 51unbalanced 5052unbalanced SWR 2 l or less T...

Page 97: ...160 Hz at 10 amperesmaximum Cabinet Size 14 718 wide 8 114 high 14 112 deep NetWeight 50 Ibs The Heath Company reserves the right to discontinue instruments and to change specifications at any time wi...

Page 98: ...The red yellow transformer lead is connected to the C2 junction of capacitors C13 and C14 During the half cycle when this lead is positive capacitors C14 through C17 are charged During the other half...

Page 99: ...ansmit mode the center tapof the filamentwinding is connectedto ground through lugs 8 and 5 of the relay the 5 1 volt zener diode ZDI and R3 The plate current through the zener develops 5 1 VDC operat...

Page 100: ...55 loading capacitors C56and C57 and coils L6 and L7 Band switch wafer 2 progressively shorts out the unused portions of coils L6 and L7 The coil turns in useare tuned to resonance by Tune capacitor C...

Page 101: ...nsitivity control R26 to the Multi Meter The Sensitivity control adjuststhe Multi Meter for the desired reading To read grid current the Multi Meter is switched in parallel HighVoltage Figure4 4 with...

Page 102: ...CIRCUIT BOARD X RAY VIEW VIEWED FROM FOIL SIDE...

Page 103: ...C H A S S I S PHOTOGRAPHS M O D E POWER SWITCH SWITCH...

Page 104: ...Page 87...

Page 105: ...T H A N 1 ARE I N pF VALUES OF 1 AND ABOVE ARE I N pF UNLESS M A R K E D OTHERWISE 3 THE B A N D S W I T C H I S I N THE 8 0 METER P O S I T I O N ARROWS I N D I C A T E THE D I R E C T I O N OF R O T...

Page 106: ...Page 88 MULTI METER PLATE METER METER SENSlTlVllTY C24 C25 SWITCH CONTROL EU ET...

Page 107: ...c J i j Page 89 40 1012 40 965 40 964 LUG 1...

Page 108: ...Form is not available refer to are available from your local Heathkit source and will reflect Replacement Parts in the Kit Builders Guide PART PRICE Each No RESISTORS 112Watt 1 9 1 44 1 18 1 22 1 23...

Page 109: ...45 34 00 3 5002tube PART PRICE DESCRIPTION No Each INSULATORS GROMMETS TERMINAL STRIPS CONNECTORS Ceramic feedthrough insulator 5116 grommet 112 grommet 314 grommet Linecord strain relief 6 x 4 112 fi...

Page 110: ...rew 8 32x 318 screw 8 32nut 8 lockwasher 8 32x 1 318 spacer 8 solder lug 10 24x 1 round head screw 10 24nut 10 24 wing nut I0 lockwasher 4 40x 5 16 screw 4 40nut Control nut Speednut Control flat wash...

Page 111: ......

Page 112: ......

Page 113: ...nnections for the surge protection circuit matic with a standard relay coil and a current limiting resistor Therefore the high cost plus purchase time and final alteration of a time delay relay can be...

Page 114: ...rom the componentside Next a Solder each padwith its three wires b Clipcomponent pigtailsas you go c Clean boardto removeflux d Ohmmetercheck note highswill be 470 k 9 Connect board to SB 220 using th...

Page 115: ...few seconds of dead silence This delay time is controlled by the value of the limit ing resistors During this period the plate voltage meter can be observed to slowly increase from zero to about 1500...

Page 116: ...the rig into a dummy load on the same table with my plastic encased television set You may have to scrape some paint off the mating metallic surfaces of the FT 7B enclosure if you live in a weak TV si...

Page 117: ...gh switched broadband pi same The new version contained a sealed filter section matching networks The amplifier in in the excitation line to prevent 27 or 28 MHz put impedance is approximately 50 ohms...

Page 118: ...Editor I 41 41 4b C21 Y FROM FILAMENT HV BAND SWITCH B A TERMINAL 7 Fig 1 Part o f the SB 220VHF parasiticoscillation cure A consists o f installing Qdamping resistors RIA R2A in the amplifier cathode...

Page 119: ...dn t test it because I didn t have a mate for its power connector Here s one Fig 1 K8SS SB 220 modification lowers the voltage at the ANT RLY jack J1 from 125 at A to approximately 12 at B Short circu...

Page 120: ...ableaccessory or ignitioncircuitnot powered duringcranking C Cometions for multiple transceivers and receivers If multiple transceivers or receivm are installed in the vehicle install heavy power cond...

Page 121: ...sed the desire for a color top inner shield of the case and the plate that would match equipment other than P 0 BOX 2234 Stamford CT 06906 connections on the tubes A STANDBY Heathkit As none of these...

Page 122: ...ting location of the surge protection resistor If the specified resistor is used it can be mounted on existing screws off paddle switch was mounted on the front panel in a position on line with the tw...

Page 123: ...the primary Two leads are now connected between the contacts of the time delay relay and one end of the resistor and terminal AW One side of the relay coil is connected to terminal block AE terminal n...

Page 124: ...as a comparable non doubling supply which yields a more efficient trans former design Here s why One layer of insulating paper is required between each layer of wires so fewer turns means fewer layer...

Page 125: ...the only HV negative path to chassis The peak discharge current can be substantial and damage to the meter shunt and movement can occur For example if the filter capacitors are at the 100 Vlevel when...

Page 126: ...s the useful emission life of the two 3 5002sto only a few percent of what could have been realized if the tubes had been operated near the low end of the recom mended filament voltage range Although...

Page 127: ...immediately when this noise is heard Here s why In a full wave voltage doubler rectifier circuit there are two series connected filter capacitors ll One capacitor charges during the positive half of...

Page 128: ...ost serious design weakness in the to decreasethe values of the grid to ground 5 T 2 a SB 220is its tendency to support an inter capacitors from 200 pF to 115 pF Three grade motor oil can also be used...

Page 129: ...estringfor forwardbias not reverse bias likea Zener diode Thereplacementcircuitisshown hFig 5 The voltage can be controlled in 0 8 V steps by addingor subtractingdiodes T h i s allows you to easily se...

Page 130: ...QSK And Other Circuit Improvements For The Trio Kenwood TL 922Amplifier Plus QSK for the Heath SB 220 SB 221 and HL 22OO by hard L a Jl563C...

Page 131: ...e in the same room This is not practical When driven by a voltage limited current source a relay can be made to switch faster without the risk of coil insulation damage A voltage limited current sourc...

Page 132: ...el that causes a decrease in output power A 9 decrease in filament voltage can increase the useful emission life by 2 cubed or times Reducing filament voltage to achieve maximum power grid tube life i...

Page 133: ...tent parasitic oscillation occasionally causes the bandswitch to arc over The arcing can melt the contacts on the output sections of the b a n d w i t c h If a full blown parasitic oscillation occurs...

Page 134: ...should not be used for grid fuse resistors because they are too hardto burn out DC negative feedback per grid under maximum signal condition This helps to equalize the currents in two 3 5002s that are...

Page 135: ...le stock is bolted to the bottom of the rectangle to form a mounting bracket A self clinching nut is pressed into a hole in the angle stock The fastening is done from the top side of the chassis with...

Page 136: ...it from an external amplifier The conventional relay in the transceiver causes a needless and often excessive time delay in the operation of the QSK relays in the amplifier In some cases this delay ma...

Page 137: ...he manual and deposit it on Bandini Mountain The amplifier can be tuned up more gently by using an electronic keyer to key the transceiver on CW mode sending dits a t 50wpm Since standard Internationa...

Page 138: ...bout 17A a t 28MHz or even more current at lower frequencies The DC contact rating is 45A 17A of RF in a 50Q circuit translates to 1 7 x 50Q 14 4kW The rms voltage at this power level is 50Q x 17A 850...

Page 139: ...shown in diagram or PS2505 1 An TH1 ECG 3044 may be used except that the output pins are 5 C and 4 E TH2 Unspecified diodes are 1A 2200piv silicon rectifiers 1459 F 63 thermal cutout switch Unspecifi...

Page 140: ...ted to the two 10A circuit breakers Each pair of wires is connected in series with each circuit breaker A l2VDC coil relay may be used if a fullwave voltage doubler rectifier circuit is powered by the...

Page 141: ...am or PS2505 1 input capacitor I pF 16Vto protected I I NOTE The current i amws show the flow of negative i electron current An ECG 3044 may be used except that 35v the output pins are 5 Cand 4 E Unsp...

Page 142: ...onics is not needed Anyone who can build a Heathkip can install a suppressor retrofit kit And if you have a problem you can call me on the telephone If you would rather have low VHF Q parasitic suppre...

Page 143: ...or prevents contact pitting in the transceiver s amplifier control relay 1 25 each postage paid These articles can NOT be prints 3in any ham magazine that carries Trio Kenwood advertising Silver Condu...

Page 144: ...n t e ous anodevoltage is swinging to its lowest point about 250 V and the total cathode current is 3 4 A I8Thus the driv ing resistanceat this point R is 117V 3 4 A 34 5 Qand incredibly P 117 V x 3...

Page 145: ...k during tuning It s also advisable to wrap some 1 inch 25 mm plastic electrical tape around the nuts on the HV feed throughinsulatorbeforeplug ging in the amplifier If you would prefer not towork aro...

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