Contents 1 2 3 4 5 6 7 General Mechanical Description 2.1 Mechanical checks and adjustments 2.1.1 Tape path 2.1.2 Brakes 2.1.3 Tape tension 2.1.4 Pinch roller 2.1.5 End of tape switch 2.1.6 Wow and flutter 2.1.7 Tape speed 2.2 Routine maintenance 2.2.1 Cleaning 2.2.2 Lubrication 2.2.3 Servicing of solenoids 2.2.4 Servicing of push button assembly 2.3 Removal of capstan assembly Electronic Description 3.1 Circuit checks and adjustments 3.1.1 Measuring instruments 3.1.2 De-magnetising 3.1.
1 General The REVOX Series 36 has been constantly improved and kept up to date, since it was first introduced in 1956. However, the present G still bears the same basic layout and conception as did the original A recorder. Compared with the preceding models, the following major innovations have been incorporated in the REVOX G 36 recorder : Hysteresis-Synchronous Capstan motor, VU-meters for record level control and a tape-tension switch to permit the use of all reels from 7 inch up to 10 1/2 inch diameter.
arm carries the shield for the playback-head and the tape-lift mechanism for the rewind function. The brakes are mechanical in nature but are electrically operated. This is achieved by the action of the brake solenoid which pulls the brakes off during all operating functions. When the stop button is pressed however, or when the current fails for any reason, the solenoid is de-energized, and the brakes automatically come on, with the higher braking force always on the trailing spindle.
great care in tightening the turntable screws uniformly to prevent them from wobbling. For best results, they may have to be rotated by 120°. 2.1.1 Tape path The tape path level is determined by the left and right hand tape guides (3 in fig. 1) and by a small guide (4) positioned between the playback head and the capstan. We do not recommend that these guides should be interfered with in any way.
It is important to check that the brake band (6) is running flat on the brake lining and not biting on the upper or lower edge. Adjust alignment of brake band by slightly pivoting it in the rivets if required. Correct tension for spring 7 is obtained when 160-220 grams applied as a tangent force to a 10 cm diam (spool and tape) causes the spool to move. See fig. 3. Brake tension may be altered by resetting the brake return spring (7) into any of the three holes on the end-brackets (5 and 9).
2.1.4 Pinch roller The pressure of the pinch roller can be measured by a gauge fixed to the pinch roller arm as close as possible to the spindle of the pinch roller (fig. 4). A constant tone tape should be played and the pinch roller withdrawn by the gauge until the note is heard to change. A reading in the region of 1.7 kg should be obtained. Adjustment to this value can usually be obtained by turning nut no 13 in fig. 5.
To de-energize the solenoid and to restore the nonconducting condition, the supply voltage has to be interrupted. B. Mechanical end-of-tape switch. This switch and its associate operating levers must be thoroughly clean to function correctly. On G-36 recorders up to serial number 36 500, the tape sensing lever operates a snap-action switch (SE schematic A) which is closed with tape tension applied. The right position of the switch assembly is essential for correct operation to be obtained.
Accurate and useful measurement of wow and flutter can only be made with an appropriate instrument. The recorder is calibrated using the EMT Model 420. Possible causes of flutter may well lie with the capstan, capstan motor. Wow can usually be seen as associated with the pinch roller speed and in some cases a faulty pinch roller may be the cause, and in others too much back tension or insufficient pinch roller pressure. For all wow and flutter investigations the transport mechanism must be completely clean.
once their supply of lubricant has been used up. Felt linings are to be saturated with Teresso 43 (Esso). If signs of wear become visible on the capstan shaft, the whole bearing plate complete with shaft should be replaced (see sect 2.3). Lubrication of the capstan bearings is not anticipated. However, where this can not be avoided, Teresso 43 (Esso) only must be used. 2.2.
3 Electronic Description Access to the majority of the electronics of. the recorder can be obtained by removing the base of the recorder. The REVOX G-36 has two identical record- and replaychannels. The common bias and erase Oscillator can be switched onto either one or both channels, thus allowing stereophonic recordings, two-track sound with sound and monophonic recordings. Each channel is equipped with pre-amplifier stages to accept low-level signals from linear high-impedance sources.
schematic G-36) provided that the residual RF-signal is at least 35 db below peak record level (3 % distortion). A wow- and flutter meter may be required in rare instances only. 3.1.2 De-magnetising From time to time the ferrous parts in contact with the tape may become magnetised. When this occurs, especially with head magnetisation, an increase in background noise will be evident and in serious instances, partial erasure of the tape may come about.
Good high frequency response is possible only when the gaps of the record- and playback heads are parallel to each other. Where recordings are to be exchanged for replaying on other machines, it is furthermore essential that the head gaps are accurately aligned to an angle of 90° against the direction of tape travel.
Adjustment of four track heads This is a highly delicate operation as with a track separation of only 3/16", slight inaccuracies in head alignment cause a track overlap and lead to the very annoying “dead channel” cross-talk. Where a four track recorder is under examination, it is advisable to obtain the REVOX four track alignment tape. Relevant instructions are included with the tape. 3.1.
Connect an audio generator across the resistor and adjust output at 1 kc/s to give 70 mV at the cathode follower. The frequency response obtained should coincide with the graph shown on the back of the respective circuit diagram. Where a considerable deviance exists, checks should be made on the voltage values obtained within the circuit with special regard to the negative feedback loop which is frequency conscious. 3.1.5 Bias adjustment The procedure is described for one channel only.
The generator signal level should then be reduced by 20 db and the output level noted. After changing the frequency to 10 kc/s, bias should be adjusted to an output identical to that at 1 kc/s. 3.1.6 Measurement of overall frequency response Before any attempt is made to verify the overall response, it is advisable to see that all tests described in the preceding paragraphs have been properly observed and that the settings arrived at have been left undisturbed.
3.1.7 VU-Meter adjustment Peak record level is defined as the level at which the signal contains 3 % of third harmonic due to tape distortion. This should correspond to an output level approx. 3 db above the reference level of the calibration tape.
3.1.8 Adjustment of head shielding This may sometimes be necessary in order to keep the operating hum levels at a minimum. It should be noted also that since hum can be picked up by the electronics on the underside of the recorder, care must be taken to screen the base when the chassis is removed from its case, whether on the service bench for attention, or when built into a cabinet.
3.2 Tuning the bias traps The following procedure is suggested for tuning the filters L l/T 855 and L 2/T 855 (see schematic G 36, 6) on the output of the stages V 5. 1 and V 5.2 : The record circuits of both channels should be switched on by depressing the buttons “record” and channels I + II (stereo), causing the oscillator (V 12) to generate 70 kc/s. The record level controls P 3 and P 4 remain closed.
4 Troubleshooting 4.1 Mechanical troubleshooting Trouble Capstan motor does not run at either speed Noisy capstan Tape speed too low Capstan runs at 3 3/4 but not at 7 1/2 ips Pinch roller arm does not operate Brakes do not release Push-button will not remain in pressed position End of tape switch does not operate Cause How to repair Switch to 3 3/4 or 7 1/2 speed Replace wafer Speed switch defective Clean and lubricate Jamming motor bearings (2.2.2.
Wow and flutter Damaged or dirty pinch roller, pinch roller pressure insufficient, left side brake maladjusted, jammed turntable motor. Fast rewind or forward too slow Brake maladjusted Dirty brake solenoid Open-circuit winding in the Turn-table-motor Defective motor-condenser Replace pinch roller. Clean capstan and pinch roller, adjust pinch roller arm (2.1.4.) adjust brake (2.1.2.) clean and lubricate motor-bearings Adjust brakes (2.1.2.) Clean solenoid (2.2.3.
5 Technical Data Tape Speed: Wow and flutter: Tape speed deviation: Max.
Case dimensions: Chassis dimensions: (with 10 ½” reels) Colour: 19 x 13 ½ x 12” 21 ¾ x 15 ½ x 10 ¾” grey All data are valid for the 2-track as well as for the 4-track recorder unless specified otherwise.
6 Circuit Diagram
Modifications effective from serial number: 48401 (Motor-control circuit) onwards 48701 (Transmission response of record amplifier) Motor - control circuit Changes in the circuit of the spooling motors were effected in order to improve the performance during the start-mode under extreme ratios of the supply and feed loads. The relay R. St. mentioned on page 3 which operates with a delayed release time, now supplies the higher voltage during the start-mode to the right hand spooling motor only.
REVOX G 36 recorders not containing these modifications can easily be adapted to the new response characteristic by replacing and/or adding the above mentioned components.
7 SPARE PARTS LIST - ISSUE IV This Issue of the Spare Parts List has been augmented in all sections and exploded views are included for the more complicated sub-assemblies. The tabulations are divided into the following columns: INDEX ORDER NUMBER PART DESCRIPTION SERIES QUANTITY INDEX III Index numbers are identical with the tracer numbers shown in the drawings and photographs. This number must be used when ordering spare parts.
INDEX ORDER N° PART DESCRIPTION SERIES I II III x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x Qu Ind III Carrying Case 1.736.825 1.736.828-01 1.736.828-03 21.01.0458 23.01.1043 1.736.830 1.736.850-02 1.736.832 1.736.836 1.736.837 1.736.832-05 1.736.834 20.22.7306 1.736.832-04 1.736.832-08 33.03.0101 28.99.0106 1.736.501-04 33.03.0102 21.01.
INDEX ORDER N° 03 03 04 05 06 07 SERIES I II x x Qu Ind III III Push Button Assembly A 01 01 02 PART DESCRIPTION 1.736.550 1.736.550 20.21.7203 1.736.578-02 1.736.578-02 25.16.1211 54.04.0118 50.04.0128 1.736.587 1.736.592 1.736.591 1.736.588 1.014.300 1.014.910-01 1.736.551-05 1.736.551-11 1.736.551-07 1.736.150 1.736.
1.736.150-05 1.736.150-10 1.736.150-06 1.736.170 1.736.170-03 1.736.
INDEX ORDER N° SERIES Qu I II III x x x 1 x x x 1 x 1 x 1 Ind III Capstan Drive Assembly B 1.736.125 1.736.126 1.736.120 1.736.122 01 02 03 04 PART DESCRIPTION 22.01.8040 1.736.125-01 1.736.136 04 21.01.0355 1.736.125-02 05 1.736.134 05 1.736.135 06 07 08 09 09 1.736.128-07 37.01.0110 22.01.5060 1.736.138-02 1.736.140-02 10 10 10 10 10 10 11 12 1.060.060-01 1.736.141 1.736.140-01 1.736.142 1.736.140-05 1.736.141 1.060.052-01 21.01.
INDEX ORDER N° 1.736.128 1.736.129 1.736.128-02 1.736.129-02 1.736.120-02 1.736.122-02 1.736.128-08 1.736.128-06 1.736.130 1.062.351-03 1.736.128-04 1.736.125-03 1.736.128-03 37.02.0107 07 SERIES I II x x x x x x x x x x x x x x x x x Qu Ind III III Capstan Bearing Plate with Shaft C 01 01 01 01 02 03 04 05 06 06 PART DESCRIPTION 24.16.
INDEX ORDER N° PART DESCRIPTION SERIES I D Head Support Block II Qu III Ind III
1.736.227 1.736.228 1.736.229 01 02 02 03 04 05 06 07 08 09 10 10 11 12 13 13 14 14 15 16 1.736.226-01 1.736.226 1.736.224 17 18 19 20 21 22 23 24 21-24 25 26 27 28 29 29 29 1.736.225 1.736.226-02 1.736.226-05 1.736.226-04 22.01.8026 23.01.1032 37.01.0101 1.736.226-07 1.736.222-01 1.736.222-09 1.736.222-07 1.736.222-04 1.736.222-05 1.736.221 1.736.222-06 1.027.114 1.736.222-08 1.736.250 57.99.0132 1.736.222-03 24.16.1040 21.01.0456 22.01.8030 1.736.232-01 1.736.232-03 1.736.232-02 22.01.8020 1.736.232 1.
38 39 40 41 50.03.0210 50.03.0421 1.736.237-01 53.99.0114 51.99.0108 71 1.736.219 24.16.3032 1.736.220 24.16.3023 23.01.1032 1.736.150-08 21.01.0356 24.16.1030 1.736.500-05 1.736.500-06 1.736.793 21.01.0203 1.736.201 1.736.502-12 1.736.502-09 24.16.3032 1.736.200-04 1.736.205 1.736.200-03 1.736.501-06 1.736.200-02 1.736.275-01 21.59.6504 1.736.275-05 1.736.275-03 22.01.8040 1.736.275-02 1.736.275-04 1.014.910-02 1.014.910-01 1.736.375 (1.014.300 (1.736.378 22.01.8040 72 73 23.01.2043 1.736.
INDEX ORDER N° 04 04 05 06 07 08 09 10 11 12 SERIES Qu I II x x x x x x x x x x x x x x x x x x 2 6 2 2 2 2 2 x x x x x x x x x x x x x x x x x x 2 2 4 2 2 1 1 2 Ind III III Brakes – Spooling Motors E 01 02 03 PART DESCRIPTION 1.736.794 21.02.3355 1.736.794-01 1.736.794-02 1.736.794-03 1.736.360 1.736.358 1.736.360-01 1.736.351 1.736.502-10 24.16.3032 20.21.7153 1.736.502-07 1.736.502-14 1.736.502-02 1.736.502-05 1.736.
13 14 15 16 16 16 17 1.736.502-17 1.736.502-16 21.01.0455 1.736.103-02 1.736.002-03 1.736.103-01 1.736.515-01 1.736.520 1.736.521 1.736.378 59.15.4209 59.99.0154 59.15.4309 59.15.4359 1.736.002-08 1.736.502-15 1.736.502-15 1.736.851-07 31.99.0101 31.99.0106 1.736.365 1.736.500-12 1.736.500-12 1.094.001 1.093.002 1.093.004 56.04.
INDEX ORDER N° 59.12.0103 59.12.0106 70.01.0131 70.01.0102 70.01.0161 70.01.0121 1.736.648 1.736.654 1.736.650 1.736.660 1.736.680 1.736.682 1.736.681 1.736.689 1.736.683 12 61.01.0163 58.20.1104 59.16.0122 1.736.480 12 12 12 12 13 14 15 15 1.736.486 1.736.481 1.736.487 1.736.491 58.20.0504 58.20.0104 1.736.686 1.736.687 15 1.736.688 16 17 1.736.684 1.736.
G 01 02 03 04 05 06 07 1.736.880 1.736.400-03 1.736.400-02 1.736.770-02 1.736.770 1.736.501-04 20.21.7206 22.01.8040 20.21.7305 Outer Shaft Extension Complete Monitor Selector Inner Shaft Extension, Long Inner Shaft Extension, Short Loudspeaker AD 3800 M Loudspeaker Complete with Baffle Washer, Speaker Baffle Self Tapping Screw Hexagon Nut M 4 Self Tapping Screw, Upper to Lower Chassis x x x x x x x x x x x x x x x x x x x x x x x x x x x 2 3 1 1 1 4 2 2 4 7208 7209 7211 7193 22.16.2001 54.02.