[R-390] R390_Inspection_List_Part_4A

[Roger Ruszkowski]

Q IF And Audio Module Tube Optimizing
Optimizing the vacuum tube lineup in the signal path isanother technique to maximize performance. Start with the tubes in the IFstrip. These are the 5749W's IF amps, V-501, V-502 and V-503. The 6AK6 4th IFamp V-504 and the detector, V-506, a 5814A. Continue with the Audio moduletubes. Then do the RF module tubes last. The tubes can be optimized before anyalignment is conducted. But the usual procedure is to do a signal alignment,conduct the tube optimization and then do another complete signal alignment.Normal procedure is to conduct the signal alignment and tube optimizationtogether in module by module stages IF and Audio modules, then RF and oscillatormodules. Watch the noise level of each tube with the modulation off. The metershould lie quietly. If the meter needle is bouncing then consider this asadditional noise from the tube. It may take several passes in a poor receiverto grade other noisy tubes out of the receiver and reach acceptable levels ofperformance. Use the best tubes on hand and place them in the optimumperformance order. New tubes may not be better than existing tubes. When newtubes are received, grade them against all like tubes on hand. Keep track ofthe spares and their values. If the signal to noise ratios are good some meterbounce is expected. If you reach the point where you believe you have goodtubes through the receiver and the meter just will not lie quietly, then youhave to start looking for, leaky caps, poor resistors, bad solder joints, dirtytube sockets, dirty connector pins, loose or corroded tie lugs.
 
___ 01 Set the Line Meter OFF
___ 02 Set the Line gain to 0
___ 03 Set the ANT Trim to 0
___ 04 Set the AGC to MED
___ 05 Set the LIMITER to OFF
___ 06 Set the Band Width to 2KHz
___ 07 Set the BFO Pitch to 0
___ 08 Set the Audio Response to WIDE
___ 09 Set the Breakin OFF
___ 10 Set the Function Switch to MGC
___ 11 Set the BFO to OFF
___ 12 Release the Zero Adjust
___ 13 Release the Dial Lock
___ 14 Set the Local Audio to max
___ 15 Set the RF to max
___ 16 Remove P114 from J514
___ 17 Remove P213 from J513
___ 18 Remove P218 from J518
___ 19 Remove J116 adapter from the back panel if necessary
___ 20 Couple P114 to J513
___ 21 Couple P116 to J116
___ 22 Couple J116 to the signal generator RF output
___ 22 Adjust signal generator for 455 KHz output frequency
___ 24 Adjust signal generator for 150 micro volt RF output 
___ 25 Adjust signal generator for 30 % audio tonemodulation (400 Hz)
___ 26 Meter diode load output for –7 volts DC
___ 27 Place a 600 ohm load across the local audio output
___ 28 Meter local audio output for 450 milliwatts, 27 db,or 17.3 Volts AC
___ 29 In pass one gather all the spare 5749’s
___ 30 Pull the BFO and VFO 5759 tubes (V505, V701)
___ 31 Pull the AGC IF AMP (V508)
___ 32 Remember the goal is best signal to noise ratio oreach tube
___ 33 Set the signal generator modulation on and record theaudio output
___ 34 Set the signal generator modulation off and recordthe audio output
___ 35 The difference in these two values is the merit ofthe tube in V501
___ 36 Place each spare 5759 into V501 to find a merit valuefor the tube
___ 37 Grade the spare 5749’s from worse to best
___ 38 Place the worse tube in V503
___ 39 Place the second poorest tube in V502
___ 40 Start over and re-grade the 5749’s in V501 (32, 33,34)
___ 41 Select the very best signal to noise 5749 for theV701 (VFO)
___ 42 Place the second best 5749 in V501
___ 43 Place the third best 5749 in V502
___ 44 Place the fourth best 5749 in V503
___ 45 Place the fifth best 5749 in V505 (BFO)
___ 46 Place the sixth best 5749 in V508 (AGC IF AMP)
___ 47 In pass two gather all the spare 6AK6’s
___ 48 Remove V604 Line Audio
___ 49 Set the signal generator modulation on and record theaudio output
___ 50 Set the signal generator modulation off and recordthe audio output
___ 51 The difference in these two values is the merit ofthe tube in V504
___ 52 Place each spare 6AK6 into V504 to find a merit valuefor the tube
___ 53 Place the worse tube in V603 Local Audio
___ 54 Start over and re-grade the 6AK6’s in V504 (49, 50,51)
___ 55 Place the best 6AK6 in V504 (4th IF Stage)
___ 56 Place the second best 6AK6 in V603 Local Audio
___ 57 Place the third best 6AK6 in V604 Line Audio
___ 58 In pass three gather all the spare 5814’s
___ 59 Remove V507, V509, V205, V206
___ 60 Set the signal generator modulation on and record theaudio output
___ 61 Set the signal generator modulation off and recordthe audio output
___ 62 The difference in these two values is the merit ofthe tube in V601
___ 63 Place each spare 5814 into V601 to find a merit valuefor the tube
___ 64 Place the worse tube in V602
___ 65 Place the second worse tube in V506
___ 66 Start over and re-grade the 5814’s in V601 (60, 61,62)
___ 67 Place the best 5814 in V506 Detector
___ 68 Place the 2nd best 5814 in V601 1stAF AMP and Follower
___ 69 Place the 3rd best 5814 in V602 Local AFAMP
___ 70 Place the 4th best 5814 in V507 Limiter
___ 71 Place the 5th best 5814 in V205Calibration Oscillator
___ 72 Place the 6th best 5814 in V206 100 KCMultivibrator
___ 73 Place the 7th best 5814 in V509 AGCRectifier
___ 74 Adjust signal generator for 455 KHz output frequency
___ 75 Adjust signal generator for 150 micro volt RF output 
___ 76 Adjust signal generator for 30 % audio tonemodulation (400 Hz)
___ 77 Meter diode load output for –7 volts DC
___ 78 Set the Band Width to 2 KHz
___ 79 Adjust the IF gain R519 for –7 V DC on the diode load
___ 80 Meter local audio output for 450 milliwatts, 27 db,or 17.3 Volts AC
___ 81 Set the signal generator modulation on and record theaudio output
___ 82 Set the signal generator modulation off and recordthe audio output
___ 83 Meter local audio output for 1 milliwatt, 0 db, or.775 Volts AC
___ 84 If the difference must be greater than 27 db. (30likely)
___ 85 Remove all test equipment
___ 86 Return the receiver connections to their originalconfigurations
 
R. Adjust T208, C520, L503, and Zero BFO
___ 01 Set the Line Meter OFF
___ 02 Set the Line gain to 0
___ 03 Set the ANT Trim to 0
___ 04 Set the AGC to MED
___ 05 Set the LIMITER to OFF
___ 06 Set the Band Width to 2KHz
___ 07 Set the BFO Pitch to 0
___ 08 Set the Audio Response to wide
___ 09 Set the Breakin OFF
___ 10 Set the Function to MGC
___ 11 Set the BFO OFF
___ 12 Release the Zero Adjust
___ 13 Release the Dial Lock
___ 14 Set the Local Audio to max
___ 15 Set the RF to max
___ 16 Adjust signal generator for 455 KHz output frequency
___ 17 Adjust signal generator for 75 micro volt RF output
___ 18 Adjust signal generator for 30 % audio tonemodulation (400 Hz)
___ 19 Meter diode load output for –7 volts DC
___ 20 Place a 600 ohm load across the local audio output
___ 21 Meter local audio output for 450 milliwatts, 27 db,or 17.3 Volts AC
___ 22 Connect the signal generator to E211 through acapacitor.
___ 23 Adjust signal generator for diode load output of –7volts DC
___ 24 Adjust T208 for peak (This adjustment is broad)
___ 25 Adjust signal generator for diode load output of –7volts DC
___ 26 The signal level should be less than 75 micro volt RFoutput (50)
___ 27 The signal with 30% modulation should output 450milliwatts audio
___ 28 Set the signal generator modulation on and record theaudio output
___ 29 Meter local audio output for 450 milliwatts 27 db,ormore
___ 30 Set the signal generator modulation off and recordthe audio output
___ 31 Meter local audio output for 1 milliwatt, 0 db, orless
___ 32 Set the Band Width to .1 KHz
___ 33 Rock the signal generator for maximum diode loadoutput
___ 34 Adjust signal generator for diode load output of –7volts DC
___ 35 Record the signal generator output level
___ 36 The following steps should produce six marks aroundC520
___ 37 Switch the generator output up 60 db (two switchsteps on URM 25)
___ 38 Increase the generator frequency until output dropsto –7 volts DC
___ 39 Adjust C520 for a dip in the diode load voltage
___ 40 Mark the can and label this H (5 o’clock)
___ 41 Adjust C520 for the other side dip in the diode loadvoltage 
___ 42 Mark the can and label this H (7 o’clock)
___ 43 Decrease the generator frequency until output dropsto –7 volts DC
___ 44 Adjust C520 for a dip in the diode load voltage
___ 45 Mark the can and label this L (4 o’clock)
___ 46 Adjust C520 for the other side dip in the diode loadvoltage 
___ 47 Mark the can and label this L (8 o’clock)
___ 48 Divide each pair of dips and mark the can C
___ 49 Set C520 to the C mark (either 4:30 or 7:30)
___ 50 Rock the signal generator (to 455) for maximum diodeload output
___ 51 Adjust signal generator for diode load output of –7volts DC
___ 52 Set the Band Width to 1 KHz
___ 53 Adjust L503 for peak output
___ 54 Set the BFO switch ON
___ 55 Loosen the clamp on the BFO shaft extension
___ 56 Zero the BFO knob
___ 57 Zero the BFO against the signal
___ 55 Tighen the clamp on the BFO shaft extension
___ 56 Set the BFO switch OFF
___ 57 Disconnect the generator