5.36 Regulated B+ Supply VOLTS CLOSE SWITCH VOLTS CLOSE SWITCH 10 D-17, L-3, L-4 140 B-17, L-4 20 D-17, E-17, L-4 150 B-17, E-17 30 D-17, L-4 160 B-17 40 D-17, E-17 170 L-2, L-3, L-4 50 D-17 180 L-2, E-17, L-4 60 C-17, E-17, L-3, L-4 190 L-2, L-4 70 C-17, L-3, L-4 200 L-2, E-17 80 C-17, E-17, L-4 210 L-2 90 C-17, L-4 220 L-3, L-4 100 C-17, E-17 230 E-17, L-4 110 C-17 240 L-4 120 B-17, L-3, L-4 250 E-17 130 B-17, E-17, L-4 260 None C. Amplifier Tube Test Circuit Programming 5.42 With the help of a tube manual as published by tube manufacturers the following in- structions will enable establishment of a desired test circuit for an amplifier tube. Wiring dia- grams, Sheet 2 of 4, Sheet 3 of 4 and Sheet 4 of 4 at the back of this book should be studied be- fore any circuits are begun. 5.43 Test Socket Pin Connections. The pins of the various test sockets are wired in par- allel according to the standard EIA designation. See Wiring Diagram Sheet 4 of 4. It will be noticed that the top cap connector is identified as pin 10. The following table may be used to connect the supply voltages to the desired tube socket pins. Note also that the letter "I" is omitted. Socket Pin Cardmatic Switch Number Column Letter 1 A 2 B 3 C 4 D 5 E 6 F 7 G 8 H 9 J CAP K 5.44 The Cardmatic switch rows 1 and 2 are the filament (or heater) supply lines. Row 1 is the filament plus (+) supply and Row 2 is the filament minus (-) supply. One letter of each of these rows must be chosen to connect the desired pins to the filament voltage. If a heater is desired to be connected in parallel then two letters of one of these rows must be used with one of the other row. Never close the same switch letters on Rows I and 2 as the filament voltage source will be shorted; that is, never close A-1, A-2; B-1, B-2; C-1, C-2, etc. Some common heater pins are: 2 and 7 - close B-1 and G-2; 3 and 4 - close C-1 and D-2, 4 and 5 - close D-1 and E-2. An example of a 12AU7 heater in parallel would be: close D-1, E-1 and J-2 or J-1, D-2 and E-2. 5.45 The cardmatic switch row 3 is the control grid line. A negative or a positive bias voltage may be applied to this line with or without the 0.222 volt signal. An example of con- necting test socket pin 4 to this line would be to close D-3. 5.46 The Cardmatic switch row 4 is the cathode line. The line may be connected to the "0" volts floating ground; it may be by-passed with a 1000 microfarad capacitor to the "0" volts line; it may be connected to the suppressor line; it may be connected to the decade resistors which act as a load, a grid bias divider, or a self bias resistor; and it may be by-passed by a 4 microfarad capacitor to the opposite end of the decade resistors. An example of connecting test socket pin 8 to this line would be to close H-4. 5.47 The Cardmatic switch row 5 is the screen line. This line may be connected to the regulated B+ source, to the "bottom" of the Gm bridge, to the "top" of the Gm bridge, to one end of a 500 volt AC center-tapped transformer winding or to an auxiliary B+ (0 to 300 VDC knob controlled) supply. An example of connecting test socket pin 6 to this line would be to close F-5. 5.48 The Cardmatic switch row 6 is the suppressor line and four possible connections may provide different voltages to it. By closing L-16 the suppressor is tied directly to the cathode, by closing K-16 the suppressor is returned to the "0" volts or floating ground reference point, by closing J-16 the suppressor is connected to a high negative bias (approximately 50 VDC when C-16 is also closed) which is useful in twin tetrode tests, and by closing H-16 the same bias maybe applied to the suppressor grid as the control grid except without the signal. An example of connecting test socket pin 7 to this line would be to close G-6. 5.49 The Cardmatic switch row 7 is the plate line. Switch J-17 places the negative ter- minal of the meter to this line for DC current measurements, switch K-17 connects the "top" of the Gm bridge to this line and switch L-17 connects the remaining end (see para. 5.47) of the 500 volt AC center-tapped transformer winding for rectifier tests. 5.50 The Cardmatic switch row 8 is used for special circuits where two tube pins may be connected without a short test voltage or any other voltage directly applied. This line may be returned to the "0" volts reference point without the transient effect of button No. 2. Also, in twin diode and triode testing, this line may function as the cathode line when button No. 4 inter- changes rows 4 and 8. 5.51 Twin Tube Section Circuitry. For a twin triode such as a 12AU7 the first section (pins 6, 7, 8) should be treated as a single triode where row 7 is to be used for the plate, row 3 is to be used for the grid and row 4 is to be used for the cathode. Since Button No. 4 inter- changes plate and screen (row 7 and row 5), grid and suppressor (row 3 and row 6) and cathode and row 8 (row 4 and row 8), the second triode elements must be connected as follows: the plate is connected to row 5, the grid is connected to row 6 and the cathode is connected to row 8. See Figure ii. For this dual testing the lamp next to Button No. 4 should be lighted. Close J-8. To establish the function of row 8 as a cathode close K-8. If switch J-15 is used the regu- lated B+ voltage will be on the second section plate. Therefore consideration must be given to the suppressor supply (second section grid). When switch C-16 and the associated circuitry for the negative grid bias is used (see paragraph 5.57) switch J-16 will provide about 50 VDC negative on the suppressor row 6. This voltage may be used for cutting off plate current in the untested section in case the respective cathode is returned to the "zero volts" or floating ground point. One such case may be when a 6J6, which has a common cathode, is desired to be tested one section independent of the other. When the same cathode pin is to be used on the second section test close the switch in row 8 that is in the same column as that in row 4. In the case of the 6J6 basing close G-4 and G-8. If it is desired to bias off the untested section of a twin triode such as the 6J6 while the section under test is in a self-bias circuit, then switch C-16 must be closed to be assured of 50 volts and not 150 volts negative through switch J-16 to the suppressor row 6. Switch C-15 will provide the "ground" end connection of the self-bias resistance through switch A-16. 5.52 Heater Voltages. The AC heater or filament voltages are obtained from the sum of three decade steps: tens of volts, units of volts and tenths of volts. The voltage chosen is ap- plied to row 1 and row 2 to pins of a tube when switches A-12 and B-15 are closed. One switch of each of the three decades must be closed for the desired voltage. Volts Switch Volts Switch Volts Switch 0: A-9 0: A-10 0.0: A-11 10: B-9 1: B-10 0.1: B-11 20: C-9 2: C-10 0.2: C-11 30: D-9 3: D-10 0.3: D-11 40: E-9 4: E-10 0.4: E-11 50: F-9 5: F-10 0.5: F-11 60: G-9 6: G-10 0.6: G-11 70: H-9 7: H-10 0.7: H-11 80: J-9 8: J-10 0.8: J-11 90: K-9 9: K-10 0.9: K-11 100: L-9 110: L-10 For DC filament voltages A-12 and B-15 must be open, with K-1 and K-2 closed. Since the voltage drop across the silicon full-wave bridge rectifier is proportional to the load current and since this drop is an appreciable percentage of the desired output voltage it becomes simpler to meter the DC voltage across the filament pins of a tube while adjusting the AC winding taps. The silicon diodes are rated at 0.5 ampere and the circuit is fused for 1 ampere. To properly tie in the filament to the cathode line the same column lettered switch in row 4 should be closed as is closed in row 2. This will short the 50 ohms that is used at other times in reaching the electrical center of AC heated tubes. This short will also appear as a hearer-cathode short on the meter scale and therefore switch G-17 must be closed to eliminate the DC heater-cathode leakage test voltage. 5.53 Heater-Cathode Leakage Meter Sensitivities. Whenever G-17 is open, Cardimatic switch rows 1 and 2 are used for a heater and row 4 is used for a cathode, a hearer-cathode leakage test is being applied which consists of 100 VDC in series with a microammeter. At rejection (10% of full scale) the following meter values are obtained: A-14, B-14, C-14 each open 10 microamperes A-14 only closed 20 microamperes B-14 only closed 50 microamperes A-14, B-14 each closed 70 microamperes C-14 only closed 100 microamperes B-14, C-14 each closed 150 microamperes 5.54 Regulated B+ Supply. Refer to paragraph 5.36 to set the regulated B+ supply from 10 volts to 260 volts at any 10 volt level. The minimum allowable output current of this supply de- pends upon three conditions: (1) maximum plate dissipation of the passing tube, (2) character- stics of the passing tube under low line voltage and (3) maximum available voltage in the tes- ter. Refer to the following tabulation for maximum allowable currents: Regulated B+ Maximum Regulated B+ Maximum Supply Volts Current (MA) Supply Volts Current (MA) 10 69 140 140 20 72 150 140 30 75 160 129 40 76 170 120 50 80 180 110 60 82 190 102 70 86 200 94 80 90 210 85 90 95 220 77 100 100 230 68 110 110 240 60 120 119 250 50 130 129 260 42 These regulated B+ voltages are available to be used on the screen (row 5) and/or plate (row 7) for plate current or mutual conductance tests. To connect the regulated B+ to the screen line (row 5) close J-15. To connect the B+ to one end of the Gm bridge close J-15 and H-15 and to complete the Gm bridge circuit to the plate (row 7) close K-17, A-13, B-13 and H-13. 5.55 Micromhos Full Scale Meter Sensitivities. Switches L-7, L-12, C-12, D-12, E-12, F-12, G-12, H-12, J-12, and K-12 determine the full scale micromho value of the meter. Since there are over 500 ranges of micromhos only some of the more useful values are tabulated in the following: Full Scale Full Scale Micromhos Close Micromhos Close 500 L-12 4500 F, H, L-12 600 C, L-12 5000 C, E, F, H, L-12 700 D, L-12 6000 C, D, E, G, H, L-12 800 C, D, L-12 7000 C, J, L-12 900 E, L-12 8000 C, D, F, I, L-12 1000 C, E, L-12 9000 C, E, G, J, L-12 1200 C, D, E, L-12 10,000 C, D, E, F, G, J, L-12 1500 D, F, L-12 12,000 C, D, G, H, J, L-12 1800 C, E, F, L-12 15,000 C, G, L, L-12 2000 C, D, E, F, L-12 20,000 C, D, J, K, L-12 2500 E, G, L-12 25,000 C, E, G, H, J, K, L-12 3000 C, F, G, L-12 40,000 C, D, E, F, J, L-7 3500 D, E, F, G, L-12 60,000 C, D, E, G, H, J, L-7 4000 C, D, H, L-12 100,000 C, D, E, J, K, L-7 The full scale value in micromhos may also be determined from the following when switch L-12 is closed: Gm = 500 plus 100 times the choice number and Choice No. = Gm less 500 divided by 100. A choice number is an arbitrary assignment of a number to a meter shunt resistance so that a convenient mathematical relationship exists for the series of combinations. When a de- sired meter shunt resistance Is one of the eight resistors the choice number is identified as "primary". A "secondary" choice number is then one that is made up of primary choice num- bers. The primary choice numbers are related to the meter shunt resistors according to the binary system: Primary Meter Shunt Switch Closed Choice No. Resistor (with L-12) 1 A (1280 ohm) C-12 2 B (640 ohm) D-12 4 C (320 ohm) E-12 8 D (160 ohm) F-12 16 E (80 ohm) G-12 32 F (40 ohm) H-12 64 G (20 ohm) J-12 128 H (l0 ohm) K-12 Choice No. zero is obtained when no meter shunt resistor Is used. The primary choice numbers may be added to form secondary choice numbers. Secondary Choice No, 31, for ex- ample, consists of the summation of primary choice Nos. 1, 2, 4, 8 and 16. Secondary choice numbers consist of combinations of only single primary choice numbers. A primary choice number cannot be used twice, as inspection of switching will reveal, To determine the primary choice numbers for a given secondary choice number begin with the highest possible primary choice number and subtract, repeating this procedure until all the primary choice numbers are found. For example, the primary choice numbers for choice number 51 are desired. Since 51 is between 32 and 64, subtract 32 (use Resistor "F", switch H-12) which leaves 19. This number is between 16 and 32: subtract 16 (use resistor "E", switch G-12) which leaves 3. This number is between 2 and 4: subtract 2 (use resistor "B", switch D-12) which leaves I (use re- sistor "A", switch C-12). Choice number 51 is then made up of 1, 2, 16 and 32, and corres- ponds with the use of meter shunts "A" - l280 ohm, "B" - 640 ohm "E" - 80 ohm and "F" - 40 ohm The full scale value in micromhos for choice number 51 is then: Gm 500 + l00 x 51 = 500 + 5100 = 5600 Reversing the order, for a full scale of 5600: Choice No. = (5600 - 500) 100 = 5100 100 = 51 Observing this series it will be noted that: 1. Full scale Gm values begin at 500. 2. Full scale Gm values progress in 100 micromho steps. 3. There are 256 full scale values of Gm available. 4. The maximum full scale Gm value is 26,000. An alternate system for determining the meter shunt resistors for desired full scale values of micromhos may be employed. With no meter shunt and with L-12 closed the full scale value is 500. Each meter shunt resistor then adds the following to the initial 500 micromhos. Added Full Scale Meter ShuntSwitch Closed Micromhos Resistor with L-12 100 A (1280 ohm) C-12 200 B (640 ohm) D-12 400 C (320 ohm) E-12 800 D (160 ohm) F-12 1600 E (80 ohm) G-12 3200 F (40 ohm) H-12 6400 G (20 ohm) J-12 12,800 H (10 ohm) K-12 The meter shunt resistors can be determined by subtracting 500 from the desired full scale value and from this remainder by subtracting the highest possible added full scale values. For example, 9300 micromhos full scale is desired. Subtract 500 which leaves 8800. From the table, 6400 (Resistor "G" - 20 ohm) is subtracted next which leaves 2400. Subtract 1600 (Re- sistor "E" - 80 ohm) which leaves 800 (Resistor "D" - 160 ohm). Therefore, resistors D, E, G will provide a 9300 micromho full scale range. 5.56 Extended Ranges of Full Scale Meter Micromhos. With switch L-12 closed and with all the meter shunt resistors used, the maximum full scale value is 26,000 micromhos. By leaving L-12 open and by closing L-7 the basic metering is extended and by repeating the same shunts across the extended meter a new set of micromho ranges is obtained. Although this set of ranges also begins at 500 micromhos its usefulness begins at 26,000 micromhos and it is recommended that full scale values from 26,000 to 128,000 micromhos only be used. For 500 to 26,000 micromhos the extended Gm ranges may inherently introduce plate circuit resistances which will result in readings deviating appreciably from the theoretical. With switch L-7 closed, use the "Choice No," system with the same meter shunt identifica- tion with the following; Gm = 500 (1 + Choice No. ) and Choice No. = Gm / 500 less 1 Examples: Choice No. 84 represents shunt resistors C, E and G (switches E-12, G-12 and J-12). Full Scale Gm = 500 (1 + 84) = 500 x 85 = 42,500. Desired: 80,000 micromhos full scale. Choice No. = 80,000 / 500 less 1 = 160 - 1 159. Choice No. 159 represents shunt resistors A, B, C, D, E and H or switches C, D, E, F, G, K-12 closed with L-7 closed and L-12 open. 5.57 Negative Grid Bias Voltages. The grid bias voltages are obtained according to the formula: Ec = 150R / (R + 15, 000). The following switches must be closed to apply a negative voltage from cathode (row 4) to grid (row 3): H-14 K-13 (without 0.222 V signal) L-14 L-13 (with 0.222 V signal) A-16 Never close both K-13 and L-13. C-16 Select resistance "R" according to the above formula by leaving one or more of the follow- ing switches open: 10 ohm: D-13 100 ohm: E-13 1000 ohm: F-13 10,000 ohm: G-13 20 ohm: D-14 200 ohm: E-14 2000 ohm: F-14 20,000 ohm: G-14 30 ohm: D-15 300 ohm: E-15 3000 ohm: F-15 30,000 ohm: G-15 40 ohm: D-16 400 ohm: E-16 4000 ohm: F-16 5.58 Self-bias Tests. If a triode or pentode is desired to be tested under self-bias the grid-cathode circuit must be arranged according to the following: Close H-14, K-14, A-16, C-15, K-13 (L-13 if the signal is desired instead of K-13) and all except the resistance desired of the following: 10 ohm: D-13 100 ohm: E-13 1000 ohm: F-13 10,000 ohm: G-13 20 ohm: D-14 200 ohm: E-14 2000 ohm: F-14 20,000 ohm: G-14 30 ohm: D-15 300 ohm: E-15 3000 ohm: F-15 30,000 ohm: G-15 40 ohm: D-16 400 ohm: E-16 4000 ohm: F-16 Note that a resistance may be made up of several combinations of these series resistors. A resistance of 50 ohms may consist of 10 and 40 or 20 and 30. A resistance of 1000 ohms may consist of 1000 ohms; 100, 200, 300, 400; or 10, 20, 30, 40, 200, 300 and 400. These decade resistors are within 1% of their indicated value. Also, 200 milliamperes may be passed through any resistor from 10 ohms up to and including the 1000 ohm resistor which is across F-13. The remaining individual resistors should never have in excess of 200 volts across them. 5.59 Plate Circuit Arrangement for Plate Current Measurements. In the event that a plate current test is desired using the regulated B+ source close J-15, K-15, A-13, C-13, J-17 and the suitable meter shunts C, D, E, F, G, H, J, K, L-12 and/or L-7. For pentodes the screen and plate voltage are the same for this circuit. 5.60 Meter Current Ranges. Since 50 on the 0-100 scale is the rejection point for most tubes, a convenient mathematical relationship was made to exist at half-scale for the current ranges. This tester has three sets of overlapping DC current ranges. With reference to the lettered resistors used for meter shunting in the "Choice Number" system for mutual conduct- ance ranges the following formulas are useful in setting desired meter ranges. With L-12 closed: I (half scale) = 50 + (Choice No. x 10) microamperes. Example: For Choice No. 200 (resistors D, G, H: switches F-12, J-12 and K-12 closed) I (at 50) = 50 / 200 x 10 = 50 + 2000 2050 microamperes or 2.05 milliamperes This value of 2.05 ma at 50 means 4. 1 milliampere full scale. With L-12 open and L-7 closed: I (half-scale) = 50 + (Choice No. x 50) microamperes. Example: For Choice No. 192 (resistors G, H: switches J-12 and K-12 closed) I (at 50) = 50 + (192 x 50) = 50 + 9600 = 9650 microampere. or 9.65 mIlliamperes This value of 9. 65 ma at 50 means 19.30 milliamperes full scale. With L-7 and L-12 open: I (half scale) = 0.05 + (Choice No. ) milliamperes Example: For Choice No. 96 (resistors F, G: switches H-12 and J-12 closed) I (at 50) = 0.05 + 96 = 96.05 milliamperes This value of 96.05 milliamperes means 192.1 ma full scale. With L-12 closed the maximum available full scale value is 5200 microamperes or 5.2 milliamperes, with L-7 closed the maximum available full scale value is 25.6 milliamperes and with L-7 and L-12 open the maximum available full scale value is 510.1 millIamperes. Examples of useful ranges are as follows: Full Scale Close L-12 Full Scale Microamperes and: Microamperes Close 100 L-12 alone 1000 C, E, F, H-12 200 C, E-12 2000 C, D, E, F, G, J-12 500 E, G-12 5000 C, E, G, H, J, K-12 Full Scale Close L-7 Full Scale Close L-7 Milliamperes and: Milliamperes and: 6 C, D, F, G, H-12 12 C, D, E,G, H, J-12 8 C, D, E, F, J-l2 15 C, E, G, K-12 10 C, D, H, J-12 20 C, D, E, J, K-12 Full Scale (L-7 and L-12 Open) Full Scale (L-7 and L-12 Open) Milliamperes Close Milliamperes Close 30 C, D, E, F-12 200 E, H, J-12 50 C, F, G-12 300 D, E, G, K-12 100 D, G, H-12 500 D, F, G, H, J, K-12 5.61 Miscellaneous Switches. For filamentary tubes switch L-11 places a 100 ohm center- tapped resistor across the filament to reach the electrical center. One end of this resistor is permanently connected to row 2 or the filament minus (-) supply and the center-Lap becomes connected to the cathode supply after the quality button (No. 2 button) is depressed. Do not close L-11 when the filament or heater voltage is greater than 12. 6 volts. Switch G-17 is closed for filamentary amplifier tubes to prevent a meter deflection for normal tubes on the heater-cathode leakage test. For all filamentary tube types close switches A-12, B-14 and C-14. If these switches are open and a plate or screen to filament short is present the meter will deflect to the left with appreciable force although no damage will be done. Since this deflection is not intended to iden- tity the short, the meter sensitivity may be reduced by using the three heater-cathode leakage parallel resistors across the meter. D. Diode and Rectifier Tube Test Circuit Programming 5.62 The filaments and heaters of diodes and rectifiers should be treated the same as those for amplifier tubes. For filamentary types it will be sufficient to close L-11 only and it will not be necessary to close the switch in row 4 that corresponds to the switch dosed in row 2. Also, it will not be necessary to close G-17 for diodes and rectifiers. 5.63 Heater - Cathode Leakage Consideration for Diodes and Rectifiers. For detector- type diodes wherein signals to be amplified are involved, a lower value of rejection may be set. A value of 20 microamperes is generally satisfactory. For power rectifiers a higher level of leakage is acceptable and 150 microamperes is suitable for most tubes such as the 6X4. Damper diodes used in horizontal deflection circuits for cathode ray tubes are made to withstand high- er heater-cathode voltages than other types of rectifiers. Therefore a lower level of leakage is an inherent feature of this tube. Rejection at 10 microamperes is desired for damper diodes. For filamentary diodes or rectifiers use switches A-14, B-14, and C-14 for the reason stated in paragraph 5. 61, Miscellaneous Switches. 5.64 Plate-Cathode Circuit Configurations. a. The simplest of diode test circuits is one wherein the diode is treated as a triode without the grid-cathode circuit consideration. With L-14 closed and the rest of the plate circuit arranged per paragraph 5.58 a plate current test is readily pro- vided. For DC currents up to 30 milliamperes the manually controlled Auxiliary B+ supply may be used by opening J-15 (and K-5) and by closing L-5. The 0-100 scale indication X3 will be the applied DC voltage when monitored by depressing the Aux. B+ button in the Auxiliary Control Compartment. If current limiting resistance is desired in the plate-cathode circuit open L-14, close H-14 A-16, C-15 and open the switches across the desired decade resistors described in paragraph 5.57. Because of the current delivering capability of the regulated DC supplies, the meter ranges available and the resistances attainable the des- cribed circuit is suitable for plate current tests on high voltage diodes and high and low perveance diodes. b. Half-wave power rectifiers intended for use with a 117 VAC line may be tested in a circuit that subjects the tube to its rated inverse voltage at the same time that it is delivering rated DC current. The plate of such a tube should be con- nected to the proper switch on row 7 (see paragraph 5.49) and switch L-17 should be closed. Switch L-17 provides 250 VAC (350 V peak) to be applied between the floating ground and the plate of the tube. The cathode to ground circuit is com- pleted by the following switches: H-14, the desired decade resistors for a load, B-16, C-13, A-13, the desired meter range, and J-13. For a half-wave recti- fier with a maximum 330 volt inverse rating do not close J-14. It is recommend- ed that the meter sensitivity be set so that 63 on the 0-100 scale represents the value of rated current for the tube. Then, starting with the highest value for the load resistance, the decade resistance should be decreased until the meter reads 63. A reading of 63 for rectifiers will provide the acceptable 80% of aver- age rejection factor for output current when rejection is to be regarded at 50. c. Full-wave power rectifiers may be treated the same as half-wave power recti- tiers except the second plate must be connected to the "screen" row 5 and switch L-15 must be closed. Switches L-15 and L-17 provide 500 VAC plate to plate with the center of this transformer winding connected to the floating ground. Close switch J-14 to place a 4 microfarad capacitor across the load resistance, The maximum current that may be passed through a rectifier tube is limited by the rating of the resistors that are used as a load in the tester. See paragraph 5.57 for these ratings. d. Damper diodes such as the 6AX4 may be tested in a half-wave circuit that sub- jects the tube to an inverse voltage of about 1200 volts. Connect the cathode pin to row 4 and close switches H-14, J-14, open the switches across the desired load resistances (decades), close B-16, C-13, A-13, the switches for the de- sired meter sensitivity, J-17 and L-17. The plate of the damper diode must be connected to the screen row 5 and L-15 must be closed. If the rated current is attempted to be drawn through this type of tube the load reflected to the primary of the transformer will cause a fuse to open. Therefore, it is recommended that 92 milliamperes maximum be drawn through any damper diode. The decade resistances will be near 5500 ohms for this condition.