RCA-21-S-348-Sams-24.. - Early Television Foundation

1U 21-3-362U, MODELS 21-S-348U THRU 21-S-369U)ully clockwise. Models 21-S-348U thru 21-S-369U incorporatetheir A numbers Is shown in Fig. 6.NECT:>PElfto point^^o chassis.ADJUSTA5A6REMARKSAttenuate generator output to maintain -3volts at VTVM. Adjust for maximumef lection.ALIGNMENT INSTRUCTIONS (cont)14.KHK29B TUNER ALIGNMENT (MODE)An RF unit which is operative and requires only minor touch-us necessary make the following adjustments.Jre-set A14 all the way out. Set channel 7 to 13 oscillator slugsrom terminals "A" and"B" of L27 (first video IF trans) and te:["uner alignment as outlined below requires the use of a heteroiConnect the synchronized sweep voltage from the sweep genera'he sweep generator output lead should be terminated with Its cDUMMYANTENNADirectSWEEPGENERATORCOUPLINGHigh side to point .Low side to chassis.SWEEPGENERATORFREQUENCYNot usedMARKERGENERATORFREQUENCY43. SMC(400%Mod)). thrurig.1) toe) of firstmp. Lowissis.>. to pointw side to7A810, All9Ise sufficient generator output to produce3 volts at VTVM. Adjust for MINIMUMdeflection.Connect 330(2 carbon resistors across primariesof third and fourth video IF transormers.Preset A9 to MINIMUM capacity.Connect 180S2 carbon resistor across primaryof second video IF transformer. Couplesecond signal generator loosely to detectorrobe (Fig.l) to furnish markers,, Attenuateweep output to maintain 0.3 volts peak toteak for final adjustments. Adjust A10 and Allor maximum gain with 45.75MC marker at5%. Adjust A9 to place 420 BMC marker at0% on response curve as shown in Fig. 30lemove detector probe , the 1800 and thewo 300 resistors.Adjust sweep generator output for 3 volts peako peak on scope. Couple the marker genertorloosely to grid of first video IF ampliier.Retouch A5, A6 and A7 to obtain reponsecurve similar to Fig. 4.F IG.4F IG.51ST VIDEO IFAMP2ND VIDEO IFAMP3RD VIDEO IFAMP15.16.RF Input of heterodynefrequency meter to endof Insulated wire insertedin hole provided foradjustment of A17.Set freq.meter to227MCNOTE : If channel 8 oscillator frequency cannot be reached bythen switch to channel 12 and adjust A20 for channel 12 osclllatproper oscillator frequency on each channel. Also, on channelthen switch back to channel 8 and adjust A18 again.Two 130CCarbonResistorsAcross antenna terminalswith 130(2 ineach lead.183MC(10MC Swp)181.25MC185.75MCp. thru A12, A13Fig.l) toE 180H re-. .0015MFDat pointee remarksto tunerp. to point>w side toip. to point,ow side toSet UHF changeover switch to UHF position.Connect a . 0015MFD capacitor iiuseries with,8011 carbon resistor from point^f/tochassis with the capacitor end connected topointoy . Couple second signal generator toletectOT probe (Fig.l) to furnish markers.Connect the potentiometer arm of a second>las supply to the tuner AGC terminal. Connectpositive side to chassis. Adjust for -3volts at tuner AGC terminal. Attenuatesweep generator output to produce 0,3 voltjeak to peak on scope. Adjust A12 and A13or maximum gain with video and soundmarkers not lower than 90% or responsecurve as in Fig. 5. Remove resistor,capacitor and detector probe from point \fy .Attenuate sweep generator output to main-:aln 3 volts peak to peak on scope. Ifnecessary, retouch A12 and A13 only toobtain response similar to Fig. 5.Couple marker generator loosely to gridof first video IF amplifier , Leave theAGC bias at -3 volts and the IF bias at-5 volts. Check all channels for responsesimilar to Fig. 4. If necessary, SLIGHTLYretouch A5 and A6 to correct any overalltilt that is essentially the same on allchannels.FIG.6VIDEO DET17.18.19.20.21.Connect the DC probe of VTVM to point