Heathkit GD-125 Assembly Manual Download | Manualshive

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Summary of Contents for GD-125

Page 1: ...P I r3 E A Tr3 K I T Q MUL TIPLIE MODEL GD 125 ...

Page 2: ...p CO L L ECT OR TR ANSISTOR c BASE EM I TT ER C OLLE CTOR B NPN EM ITTER NEON BULB FUSE ILLUMINAT 5 9NG BULB h I I SPST SWITCH TOGGLE r r _ DPDT B METER W RECTI FIE DIODE Y CONDUCTORS r NOT CONNECTED SHIELDED CONNECTED PHONE JACK EARTH GROUND PHO NO o JACK CROPHO CHASSIS GROUND VARIABLE CAPACITOR 1t riI RECEPTACL E T wt 1 LOOP B INDING POST TRANSFORMER ADJUSTABLE POWDERED IRON CORE ARROW t INDICA ...

Page 3: ...TABLE OF CONTENTS Introduction 2 Par ts List 3 Step By Step Assembly Chas s is As s embly 4 Function Switch Wiring 6 Installation 12 Alignment 13 Oper ation 15 In Cas e Of Difficulty 16 Specifications 16 Cir cuit Descr iption 17 Sche matic fold out from page 19 Ccpyri ghl r 965 Heath Compa ny ill I IJ ru tr 12 17 65 ...

Page 4: ...ignal and the Q Multiplier used to null an adjacent signal When properly connected and adjusted the Q Multiplier will not decrease receiver sensitivity In the peak function an audible gain will be noted on CW signals and a carrier gain will be noted on the S meter for phone signals However the audio will be attenuated slightly due to narrowing of the received sidebands The reduced sideband recepti...

Page 5: ...ge 343 2 1 Coaxial cable 344 59 1 Hookup wire V 346 1 1 Sleeving V MISCELLANEOUS C APAC ITORS 510 JlJlf mica J 26 57 27 1 j Silicon diod 750 rna 3 20 42 1 20 53 1 0011 ufd mica 1100 Jluf 5 0 PIV 20 54 1 0033 ufd mic 330 fJ Jlf 27 75 24 1 Lme cord stram relIefl 005 ufd disc 28 205 254 1 Alignment tool blade 4 21 27 4 5 25 80 1 20 20 Jlfd electrolytic 261 4 4 Rubber feet 6 26 28 1 100 u uf variable ...

Page 6: ...PARTS PICTORIAL CD CD I l 4I IID Y CD y Q g r 0 0 C j f a 4f J ...

Page 7: ...o o o o a o o PICTORIAL 5 ...

Page 8: ...er to Detail lA and mount the 9 pin tube socket at VI with 4 40 x 1 4 screws 4 lockwashers and 4 40 nuts Position the blank space as shown by the arrow on Pictorial 1 4 40 NUT 4 LOCKWASHER 1 1 J J PICTORIAL 1 4 40xl 4 SCREW Detail lA Locate the 100 L Lf variable capacitor and clip off lug 2 as shown in Detail lB I v Refer to Detail 1B and mount the 100 L Lf variable capacitor at C with four 4 40 x...

Page 9: ...o lug 1 of tube socket VI N8 Place a 1 1 4 length of sleeving over one lead of a 005 fJ fd capacitor Connect this lead to lug 2 of co il D N8 Leave the other lead free It will be connected later Connect a 1 1 2 wire from lug 6 of tube socket VI 8 1 to lug 1 of variable ca pacitor C N8 1500 2 2 MEG PICTORIAL 2 V Connect a 1 1 2 wire from lug 1 of var iable capacitor C 8 2 to lug 1 of coil A 8 2 Con...

Page 10: ...ct the lead extending from the pr e pared end of the combination to lug 9 of the s witch 8 1 Leave the other leads free They will be connected later 0 Connect a 1 1 4 wir e between lugs 6 8 1 and 4 N8 of the switch 0 Connect one end of a 2 3 4 wire to lug 4 of the s witch 8 2 Leave the other end free It will be connected later Connect one end of a 3 wir e to lug 5 of the switch 8 1 Leave the other...

Page 11: ...VI 8 2 v Connect the free capacitor lead of this combination to lug 2 of tube socket VI 8 2 Use sleeving on the capacitor lead Connect one end of a 3 wire to ground lug D on tube socket VI 8 1 Leave the other end free It will be connected later set the chassis aside temporarily PUSH ON SPEEDNUT Detail SA Refer to Pictorial 5 for the following steps Position the cabinet base as shown in Pic torial ...

Page 12: ... 32 nuts as shown in Detail 5D Position the power transformer so the leads are as shown in Pictorial 5 Detail5D REB ENO CO N T RO L Iir y Detail SE 0 Place a contr ol solder lug on the bushing of a 5000 Q contr ol Rebend th e solder lug so that it touches lug 3 of th e contr ol See Deta il 5E Refer to Detail 5E and mount th e 5000 Q control at G with the contr ol solder lug contr ol flat washer an...

Page 13: ...itor so it does not extend past lug 2 of terminal strip L as shown in Pictorial 6 Place a 1 2 length of sleeving on one positive lead and a 1 length of sleeving on the other positive lead Connect the lead with 1 2 of sleeving to lug 2 S 3 and the other lead to lug 1 NS of ter minal strip L oJ Connect the negative lead of this capac itor to lug 4 of terminal strip L NS V Connect either neon lamp le...

Page 14: ...o o c PICTORIAL 6 ...

Page 15: ...PICTORIAL 8 ...

Page 16: ...gs of Pictorial 7 and install the chassis in the cabinet base Secure switch E with a control flat washer and a control nut Refer to Pictorial 8 for the following steps I Connect the free end of the wire extending from lug 4 of switch E to lug 1 of ter minal strip J 8 2 Connect the free end of the wire extending from lug 5 of switch E to lug 2 of ter minal strip J 8 2 o CONTROL FLAT X Ir i WASHER C...

Page 17: ...I Wrap the long line cord lead and the remain ing black transformer lead together Con nect the line cord lead to lug 12 S I and the black transformer lead to lug 13 S I of switch E DetaiI8A r Refer to Detail 8A and install the line cord strain relief at N rnstall the 12AX7 tube in tube socket VI Refer to Pictorial 9 for the following steps Turn the variable capacitor shaft until the plates of the ...

Page 18: ... E C T O R T R I M 1 R E MO VE E XCE SS I C U T S H I E L D O FF L EV ENLY AR OUND PHONO C O N N ECT O R Figure lA B ICOMMUNICATIONS RECE IVER I Figure 1 The connection from the mixer plate to th e inner lead of th e co axial cable should be as short as possibl e and isol ated from other r eceiver cir cuits If shielded wire is used for the connection between th e coaxial cable and th e mixer plate...

Page 19: ...h the Function s witch in the OFF position tune in a steady phone signal or possibly a broadcast stati on Be sure that the signal is centered in the IF bandpass This can be noted by the greatest S meter reading maximum audio signal or by a maximum reading on the voltmeter AVe voltage in the receiver Refer to Figure 3 for the location of the align ment points P la ce the cabinet top shell upside do...

Page 20: ...will be extremely sharp With a 455 kc IF it will occur when the coil screw is between 1 8 and 1 4 above the coil mounting frame Rock the adjustment back and forth over this point several times to make sure that the best null reading is obtained This completes the Alignment Refer to Pictorial 10 for the following steps Install a rubber foot in each corner of the cabinet base CA B I N E T T O P SHEL...

Page 21: ... is reached just below the point of oscillation Phone signals may lose some volume due to the loss of high frequency audio response With the Q Multip ier peaked the TUNING setting can be changed to accentuate any signal within the receiver IF bandpass and attenuate all others Th is is the main advantage that the Q Multiplier has over a filter As the receiver does not have to be tuned to peak any p...

Page 22: ...of the component parts Be sure that the proper part has been wired into the circuit as shown in the pictorial diagrams and as called out in the wiring instructions 6 Check for bits of solder wire ends or other foreign matter which may be lodged in the wiring 7 If after careful checks the trouble is still not located and a voltmeter is available check voltage readings against those found on the Sch...

Page 23: ... adjacent to the desired signal can be dropped into the notch null point and eliminated CIRCUIT OPERA TION The Q Multiplier circuit is centered around coil L2 in the plate circuit of tube V1B which has a Q of 200 or more The Q of this coil is ampli fied to approximately 4000 by the positive feed back that is coupled back to the grid of tube V1B through capacitor C9 The resonant fre quency of the c...

Page 24: ...OF c g OR NUL L 6 VI8 1 21 2 A X 7 PEA K A D JUST R 2 2 2MEG 510 I 2 3 4 5 WAF ER R 27K R4 2 2MEG THE C2 1 LI 1 5 3 MH Ell HEATHKIT 6 3VAC V I 12AX7 MODEL GD 125 9 I AL L RESISTORS ARE 1 2 WATT UNLESS MARKED OTHERWISE 2 CA PACITOR VA LUES LESS THAN 1 ARE IN IJ fd AND ABOVE I ARE IN iJ ut UNLESS MARKED OTHERWISE 3 FUNCTION SWITCH SHOWN IN OFF POSITION 4 VOLTAGE READINGS MAY VARY 10 S AL L DC VOL TA...

Page 25: ...O Y THE WO R LD S FINEST ELECTRONIC EQUIPMENT IN KIT FORM LITHO IN 5 95 775 ...

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