Oct. 7, 1952 c. F. oTls ET Al. 2,613,334 ELECTRICAL SYSTEM Filed Jan. 18, 1952 Vf lNvENToRs CH/IRLâS E 07/5 BY ¿Ul/)5mn H. .STH/9K5 MMV.: ATTOR Patented Oct. 7, 19‘52 ` Charles F._ t Philadelphia, Pa., assígnorsto,` Philco Corpora- - i »_i f tion, Philadelphia, Pa., a corporation o'i’ Remb“U ‘ A Sylvania. nppiieationianuaryis,1952,seria1n0.2s7,i4s‘ ' `s claims. (ci. 31a-27).» t This invention relatesïto electrical systems and yoke'duringA theVscan'ning cycle may 'bèfdissi more particularly, to< _improved `electromagnetic pated to a greater or lesser extentby means of "a systems of the type `commonly’used4 for deilecting suitably poled damping tube. Preferably; this Y the beam of av catliode•rayïtubeadapted to prof energy is‘rec‘ove'red, foi-example, by >~means` of‘a duce a television image. "j ' j j ¿ì , ` l so-called “boost"‘circuit`~which converts-'the mag- ‘ In their‘usual form;A electromagnetic deflection netic field energy into additional Supply` energy systems for the beam of a cathode-ray tube com-­ for the source. -Sucha boost circuit may take the;l prise a scanning' yoke‘induçtor‘whichsurrounds a“ form of acapacitor coupled in series "with'a‘vrecti portion of the tube`­ infc'ooperative relationship ñer- whichusually isf the damper tubeabove re with >the cathddeH-‘ray beam,'a source ofa deflec 10 ferred to.` This series combination is "connected tion signal forenergizing?the yoke, and a cou in shunt with thel yoke insofar as'yoke currents pling systemby which’the source is coupled to are concerned,` and in series vWith‘the anode sup- " the yoke in proneA ¿impedance matching rela ply‘of the source tube insofar as direct-»voltages tionship. " ` ’ ` ‘ ' ` are concerned. The energy source for the electromagnetic de- ‘ Because of the leakage inductancereferred td' nection system`> generallyv comprises a _ìmultigrid above, the boost circuit -is ‘tunable to recoverall of'v electron discharge tube of thebeam tetrode or the energy stored in the' deflection system at the pentode type, such-"tubesibeing used because of end of the deflection cycle'.l y This unrecovered en their large power sensitivity; Tubes of these ergy hasbeen' found ‘to Produce spuriousoscil types are characterized by relatively `high plate lations or` ringing currents in ythe‘trans‘formerV resistance values. _Whereasin Iits usual form, the windingsfÜTh'ese' spurious‘oscillations are un scanning yoke `thas" an impedance which is’rela desirable from twostan’dp'oints.’ `First, they may , tively small., Iri vvorder to‘achieve a satisfactory` be radiatedfi‘om the "circuits in which they ap? impedance match, the _coupling ¿element between pean‘f causinglfi interference in Äthe' nearby radio , source and yokejis 'thusjnecessarily a step-down and television equipment. Secondly, 4tlieserlng i coupling element. Thefcoupling element generf ing currents: are` coupled toptheïlanode ­'of the ally takesjthe form‘gof aÄítransformer the input tube constituting~~the source, and vvary tlie‘anode` and output windings of vvvhic‘zh are appropriately potential duringthe Vflybaclr period. In practice, related as to their numbers of `turns, to produce these spurious oscillations may have ysufll‘cie‘nt the desired impedance ratio. `In one form, the 30 4amplitude to cause theanode toîassume periodi transformer maybe an autotransformer having a ` callyl a. considerablyfnegative potential "with `:re- ' single winding `With appropriate taps, to which spect to,` theY screen grid of Vthe tube,` and mayk taps the source vandthe yoke are connected. even cause the anode; »to assume a negative `po-` Most‘efficient energy transfer occurs when the tential `with respect tothe cathode `of the tube» s coupling between‘the ‘sourcejandyoke is unity.` It hasloeen >found thatfwhen theïpotentîal of' Howeven‘in view ofv the different numbers of the anode of a beam tetrode or pentode undergoes i turnsof the input .and output windings, unity variations ofthe above type, -the negative 'voltage « coupling cannot be fully achieved. The departure gradient between thegscreen grid V,and the `anode from unity coupling >manifests itself as a leak.; may -bringgabout furtherspurious oscillations of . age inductance effect, vthe magnitude of which is primarily determined bythe geometry of `the 40 thetype known as transit-timeoscillations, and more especially, asÍBarkhausen-Kurz ¿or Gillê-v y windings.` Y ` ` ` “ , Morrell ,v oscillations. ~ l These oscîllational whoseÁ In the normal scanning cycle of the cathode frequencyisa function o_f thegeometry of.' the ray beam, the beam, starting from a given posi tube, the tube electrodepotentialsand the exter tion, is advanced in ‘one direction at a fairly uni 45 nal circuitry associated with the tube, may occur ` form predetermined velocity and, at the vend of over a wide range of frequencies-.fof theorder of4 ¿ the scanning cycle, is returned to its initial posi- ` fifty tothousands of ina/sec. „Such highire. tion. These movements of the beam maybe pro quency 'currents have associatedwith them elec duced by applying a signal of suitable Waveform 4tromagn'etic,Waves which `are ,readily radiated to the source, e. g., a sawtooth signal which,­ at 50 bythe tube4 and `its associated .circuits to sur the end of the Scanning period. cuts off the source . rounding circuits of the-cathode-ray'tube, e. gl. , for atleast a part of the flyback period and causes , a collapse of the magneticfleld in the coupling te the videdcircuits‘of the receiver. Unless ­spe-, cial precautions are taken;y these'radiatio'ns may ` transformer and the. deflection yoke.- The energy overload the video-signal systemof `the receiver,` which has been stored in the transformer and Oi Ul and degrade the image seen upon the screen of ' > 2,613,334 the cathode-ray tube. I In some instances, thel ringing currents and lhas la high impedance at -presence of vthese oscillations are manifested by the scanning frequency. ­ 1 irregular~ black lines onzthe screen of the cath- ,Y The invention will be described in greater de - 1^ode-rayftube, which lines are substantially per- ~ tail with reference to the appended ldrawing ,pendicular to the :direction of scanning, and forming part of the specification, the single' iigure „ points of which lines usually occur‘near the start of which is a schematic diagram of a magnetic denection system `embodying­ ythe invention. of_1t the nasfbeenfproposodtoï'euminate scanninglines;l - tnësetìansitr ,Referring .tothe drawing,V the ldeflection sys „ `time oscillations by modifying the structure' of ‘ tern there shown comprises a source tube I0, an . the tube» serving asy the scanning signal source.` ioy autotransformer I2,'and ya yoke 32. -Tube I6 ~ i' Such a procedure, however, considerably increases comprise‘sl'fa cathode I4, a control grid I6, a screen v '_the cost of the tube and has been found to be not grid'IIB and an anode 20. (Although tube l0 is specîiicallyV shown as a beam tetrode, it is ap effective forall circuit arrangements: _ »v j . y' 1 ,',Another proposalV has 'beenâ to >shieldv `,c_iarefully L'parentithat'the source tube'rnay be a pentode or ' Athe ' circuits in lwhich the transit-time »oscillations Vother.,multi-’element tube.) The control grid I6 are likely to arise. While shielding may' reduce , is energized by .a vsuitableA sourceof scanning po l image degradation by attenuating the radiated. tentiall (not shown), said source Vproviding a ' scanning signal of generally sawtooth waveform „ . ­ Waves, itis an expensive expedient, particularly Ap ' »y in assembly -lineÃproçïluction~ Furthermore; since . ­in accordance with Well-known practice. ` shieldingI does nothing to eliminate the transit proximate operating potentials are .applied` to time. oscillations themselves,_ the loss. of , energy> the control grid _I6 and the screen grid I8 from a n repreysen'ßfëíl''therebyV reduces the efficiency ofthe Í sourcel_.(notshown).`V> f . ,. o . 'I‘heautotransformer I 2 comprises three> wind-` v scanningacircuit. o , . Ü ‘j p ` v , ~ -f w , v y l,It hasalso beenïvproposed ,to preventthese os ing sections, 22, 24 and 426, connected in series. V „ cillationsbyreducing the screen-'grid yoltag'e of The anode ¿Ill of vacuum tubevr I0 is connected the source Ytube during the ñybaclc Vperiod._ How-_ to the -junction 30 of _sections 22 and 24, whereby . ever,¿this' ymethod requires A'auxiliary equipment, the windingI sections 24 and 26 together serve .thefëoperationrof which.` must be carefully syn. as an output coupling impedance for the tube I0, ' . c_hroni'zed-çin order, that` the screen grid potential whereas theyoke 3_2 is connected to the junction is,reducedto-the‘çproper .value at‘tlie proper time. 30 64 of_..sections y24 and 26, whereby the 'yoke is .. It is'anobject of the inventionto provide an coupled to the winding 2,6.~> In accordance with well-known practice, the turns ratio of the wind’- . ing sections 24 and 26 is so selected that­ a desired ‘ ' ­nother object of the invention'_isîçtofprovide impedance match between the tube I0 and the yoke >32 is eil‘ected. ` _ an- improved magnetic deflectionA scanning‘cir Winding'section 22 ...is the usual high voltage rcuitq-ini-Iwhich spurioussignals >are reducedv to a winding lhaving a terminal 28 which may be con­` tolerable­ value A«or‘ eliminated. ' ' nectedl't'o la suitablerectiñersystem (not shown) ' `A> further i obj ect ofthe inventionïislto provide ~ anj improved„magnetic` deflection scanning cir for supplyingan accelerating potential for the 40 beam'of the cathode-ray tube. cuitf-injuwhich radiationoi .spurious signals is The ‘anode 20 of tube I0 is supplied from ka `reduced -».to.¿a;­ .tolerable f ,value or eliminated.V - suitab1e.D.`C. source. 4(not shown), introduced at . A f specific: -object of :the inventionY is -.„to pro-' Br'terminal V44, and connected through a voltage vide an; ~,.improved> magnetic fîdeflection »scanning boost circuit comprising a diode 36 and a boost circuit which is, substantially'éffreeï from transit capacitor 46. Diode 36 has .itscathode 38 con time"-cscillatio~ns».«jl . - 1 nected vto' the junction 34 and its anode 42 con g A2 still further vobject oftheinventionis’to pro nected to'thef'Btjterminal 44.