Performance Tests and Electronic Alignment

Performance tests should be performed at regularly scheduled intervals (every 150 hours or 1 month periods) to ensure the recorder is performing within specifications. These tests should also be performed whenever the recorder appears to be malfunctioning and following repairs to the equipment that may affect performance. If the performance test is not successful, proceed to the applicable electronic alignment procedure. It is important that clean and demagnetize the head and tape guiding components before performing the following steps.

3-1 TEST EQUIPMENT↑ TOP

The test equipment listed in Table 1-1 is required for completion of the performance and alignment procedures.

3-2 TEST TAPES↑ TOP

The test tapes are precisely recorded under controlled conditions and must be correctly handled and stored to retain their accuracy. The following requirements should be followed:

1. Clean and demagnetize the heads and tape guiding components before installing the test tape.
2. Never store test tapes in areas where there are temperature or humidity extremes.
3. Remove test tapes from equipment only after a normal play run (never after a fast-winding mode). This is further explained below.

During the alignment procedure, the rewind and fast forward modes should not be used. After alignment, wind the tape completely on the takeup reel, interchange reels, thread the tape, and place the equipment in the play mode to wind the tape back on its original reel.

All tones on an Ampex 15 in/s standard alignment tape are recorded at operating level. On slower speed tapes, all tones are recorded 10 dB below operating level except for the last tone. After extensive use, high frequency tones may drop as much as 2 dB. In addition, flutter indications may rise even though actual flutter remains unchanged. Flutter increase is caused by : demagnetization of the recorded signal from repeated plays; tape deformation due to tape tension, changes in temperature and humidity; and increased dropouts resulting from tape wear.

3-3 TEST CONDITIONS↑ TOP

The test conditions specified in the following steps are to be used prior to performing the tests. After these test conditions are set up, continue with the procedures that follow for checking overall signal-to-noise, overall distortion, crosstalk, and flutter.

1. Clean and demagnetize the heads.
2. Use high quality low-noise tape such as Ampex 406, 407, 456 or Scotch 206, 207, 250, or equivalent. Bulk erase the blank tape.
3. Turn power on and allow unit to warm up for 20 minutes.
4. Be sure head cover is installed for all tests.

3-4 PERFORMANCE TESTS↑ TOP

Before making performance test, SRL check, reproduce frequency response check, record level check, monitor level check, overall frequency response check, and SEL/REP level check are necessary. Refer to 3-5 ELECTRONIC ALIGNMENT in this section for checking procedures.

For performance tests, preliminary proceed as follows.

Demagnetize and clean heads and guiding compornents. [sic]

1. Set REEL switch to appropriate position, and set EDIT switch to "out" non edit position.
2. Set LINE OUT switch to H, set each RECORD switch to "in" record position, set each SEL/REP switch to "out" position, and set each MONITOR switch to "out" SOURCE position.
3. Thread a reel of bulk-erased tape onto the transport, set SRL switch to SRL position, and push PITCH CONTROL knob to place fix position.

3-4-(1) OVERALL SIGNAL-TO-NOISE↑ TOP

The overall signal-to-noise test requires an ASA "A" weighted filter to attenuate noise outside of the audible frequency band. The filter is shown in Fig. 3-1 and may be built into a small alumimum box as shown in Fig. 3-1. [sic]

Signal-to-noise depends on SRL calibration, reproduce equalization, bias calibration, and record equalization. Proceed as follows:

1. Connect filter to CH-1 LINE OUT and connect VTVM to the output of filter.

2. Hold TEST OSC pushbutton depressed and adjust CH-1 INPUT LINE control for 0 VU indication on the VU meter.

   (On model MX-5050 2SD2, set reproduce head selector switch at the rear of the head assembly to 2T position.)

   Note VTVM indication, VTVM does not read +4 dBm due to insertion loss of filter.

3. Depress CH-1 MONITOR switch to "in" TAPE position, set CH-1 INPUT LINE and CH-1 INPUT MIC controls to full counterclockwise position. Reset TAPE TIMER to "0000".

4. Start record mode and record for one minute. Rewind the tape to "0000" indication on the timer.

5. Reproduce the recorded portion and read noise level on VTVM.

6. Signal-to-noise retio [sic] is determined by calculating the difference in readings obtained in step 2 and step 5 plus 9 dB (peak recording level—520 nWb/m—is 9 dB above SRL—185 nWb/m)

7. Repeat step 1 through 6 for the other channels as required, change tape speed to other and check signal-to-noise retio. [sic]

Table 3-1. Signal-to-noise specifications (ASA weighted)

Models	2S or 2SD	4S or 4SD
15 or 7½	68dB	65dB
3¾	67dB	64dB

If signal-to-noise specifications are not obtained, check and adjust following items.

1. SRL caliblation [sic] is incorrect.
2. BIAS/CAL adjustment is incorrect.
3. Reproduce equalization is incorrect.
4. Record equalization is incorrect.
5. Bias buffer adjustment is incorrect.
6. Record and/or reproduce electronics is defective.
7. Head is magnetized
8. Affected with magnetic flux of a motor, a soldering iron or a transformer near the recorder.

⤢ zoomFig. 3-1 ASA "A" Weighted Filter · Redrawn as vector — zooms cleanly · view the original scan

3-4-(2) OVERALL DISTORTION TEST↑ TOP

For accurately checking distortion it is necessary to use an audio oscillator with less than 0.1% distortion and a wave analyzer with an adjustable bandwidth capability. A wave analyzer with too narrow a bandwidth may make it difficult to measure harmonics due to flutter components within the transport. Instruments that measure total harmonic distortion will be affected by tape and modulation noise in addition to harmonic distortion. To measure overall harmonic distortion proceed as follows:

1. Connect wave analyzer to CH-1 LINE OUTPUT and connect audio oscillator to CH-1 LINE INPUT.
2. Set MONITOR switches to "in" TAPE position, set audio oscillator frequency to 1000 Hz.
3. Set wave analyzer frequency to 1000 Hz, bandwidth to 100 Hz, and mode selector switch to AFC.
4. Start Record mode and adjust CH-1 INPUT LINE control for O VU [sic] on the VU meter.
5. Adjust fine tuning control on the wave analyzer and adjust analyzer input level control for full scale reading of 100%.
6. Change wave analyzer tuning control to 2000 Hz and measure second harmonic content. The second harmonic content should not exceed 0.5%.
7. Change wave analyzer tuning control to 3000 Hz and measure third harmonic content. The third harmonic distortion is dependent upon the type of tape used, accuracy of the BIAS/CAL setting. Typical reading for low noise high output tape is 0.5%: Typical reading for standard output professional grade tape is 0.8%.
8. Repeat step 1 through 7 for channel 2.

If distortion specification is not obtained, check and adjust the following items.

1. SRL caliblation [sic] is incorrect.
2. BIAS/CAL adjustment is incorrect.
3. Head is magnetized.
4. Record and/or reproduce electronics is defective.

3-4-(3) CROSSTALK TEST↑ TOP

It is important that blank bulk-erased tape is used for crosstalk test. To measure crosstalk between channels proceed as follows:

1. Follow the procedure for Overall Distortion Test, steps 1 through 5.

2. Connect wave analyzer from the output of CH-1 to CH-2 LINE OUTPUT.

3. Measure the crosstalk in dB.

   Crosstalk should not exceed Table 3-2. If crosstalk specification is not obtained, record and/or reproduce head alignment (height and tape contact) is incorrect or record or reproduce head is detective. [sic]

Table 3-2. Crosstalk specifications (Between adjacent channels)

2S or 2SD	4S or 4SD
60 dB	55 dB

3-4-(4) ERASURE TEST↑ TOP

It is important that blank bulk-erased tape is used in erasure test. To measure erasing effect proceed as follows.

1. Follow the procedure for Overall Distortion Test step 1 through 5. A 1000 Hz signal is being recorded at SRL.

2. Set SRL switch to off position and adjust OUTPUT control for -10 VU on VU meter.

3. Adjust INPUT LINE control for O VU [sic] on VU meter and 1000 Hz signal is being recorded at 10 dB above SRL. Continue recording for a few minutes.

4. Remove the audio oscillator.

5. Rewind and reproduce the recorded position.

   VU meter reading should be O VU. [sic]

   Check wave analyzer and readjust as necessary.

6. Press RECORD pushbutton to place recorder in record mode.

   As the tape is being erased, adjust the percent scale on the wave analyzer to read the residual 1000 Hz tone.

7. Repeat the same procedure for other channels.

8. Erasure effect should be more than 65 dB.

If erasure specification is not obtained, check and adjust following items.

1. Erase and/or record head alignment is incorrect. (height, tape contact)
2. Erase head is worn.
3. Erase head surface is dirty.
4. Bias oscillator is detective. [sic]

3-4-(5) TAPE SPEED MEASUREMENT↑ TOP

A flutter test tape is used for measuring tape speed.

Since tape tension affects the tape speed, it is important for accurate measurement that flutter test tape is used to be attached to end of full winded blank tape as Fig. 3-2 and is used with REEL pushbutton to appropriate reel size to be used.

Proceed as follows:

1. Place PITCH CONTROL to fix position and set all RECORD switch to off "out" position.

2. Connect frequency counter to LINE OUT and set MONITOR switch to TAPE position.

3. Set SPEED switch to HI and use test tape to appropriate tape speed.

4. Attach test tape to 10½ inch NAB reel as Fig. 3-2, place test tape onto supply reel table, thread the tape, and set REEL switch to L position.

5. Place recorder in play mode and note reading on frequency counter.

   Reading should be 2994 ~ 3006 Hz (3000Hz ± 0.2%).

6. Repeat procedure for at a point towards the end of the reel, for at 7 inch EIA reel and for at low tape speed.

If speed accuracy is not within ± 0.2%, check and adjust following items.

1. Capstan servo control is incorrect (on 2SD or 4SD).

   Capstan belt is dirty or worn (on 2S or 4S).

2. Capstan motor is defective.

3. Pinch roller tire is worn, or has insufficient pressure.

4. Brakeshoe is contacting brake drum.

5. Tape tensions are incorrect.

6. Power requirement is incorrect.

⤢ zoomFig. 3-2 Using Test Tape · Redrawn as vector — zooms cleanly · view the original scan

3-4-(6) FLUTTER AND WOW TEST↑ TOP

It is recommended that these checks be made with standard flutter test tapes (See Table 1-2) which are recorded on pricise [sic] equipment to produce less than 0.03% rms flutter. If flutter tapes are not available it is possible to record a 3000 Hz or 3150 Hz signal to be used for a flutter measurement. After recording a section of tape, rewind to the begining [sic] and start the tape in the reproduce mode. Since it is possible for the record mode flutter to either add or subtract from the reproduce mode flutter depending upon the phase relationship, it is necessary to make several passes over the recorded section of tape and average the flutter meter readings.

Flutter meters are sensitive to amplitude modulation that results from poor head-to-tape contact or from signal dropouts. Therefore, clean the heads before making flutter tests.

Test tape method is as follows:

It is important that flutter test tape is used to be attached to end of full winded blank tape as Fig. 3-2, and is used with REEL pushbutton to appropriate reel size to be used.

1. Set all RECORD switch to off "out" position, and on 2SD or 4SD, place PITCH CONTROL to fix psition. [sic]
2. Connect flutter meter to LINE OUT of CH-2 and set the channel MONITOR switch to TAPE position.
3. Set selector switch of flutter meter to NAB weighted position, set SPEED switch to HI and use test tape of appropriate tape speeds.
4. Attach test tape to 10½ inch NAB reel as Fig. 3-2, place test tape onto supply reel table, thread the tape, and set REEL switch to L position.
5. Place recorder in play mode and note reading on flutter meter. Reading should be Table 3-3.
6. Repeat procedure for at a point towards the end of the reel, for at 7 inch EIA reel and for at low tape speed.

Record-playback method is as follows:

1. Connect oscillator signal output of the flutter meter to CH-2 LINE INPUT of the recorder.

2. Connect the LINE OUTPUT of the recorder to the signal input of the flutter meter

3. Set SPEED switch to HI, set SRL switch to SRL position set MONITOR switch to TAPE position, start record mode, and adjust appropriate INPUT LINE control

4. Rewind and reproduce recorded portion, note the flutter and wow on the flutter meter.

5. Check flutter and wow at low tape speed and check at a point towards the end of the reel.

Table 3-3 Flutter and wow specifications

Tape speed	Flutter and wow
15 ips	0.05 %
7.5 ips	0.06 %
3¾ ips	0.15 %

Flutter and wow can be caused by any element in the tape path. Excessive flutter and wow may be traced by observing the flutter component on an oscilloscope screen connected to the demodulator output of the flutter meter. If the fluctuation rate observed on the oscilloscope coincides with the rotation elements, such as the supply or takeup reel, capstan or pinch roller, the problem source may be easily traced. Other sources of excessive flutter and wow are:

1. Capstan servo control is defective (on D type).
2. Capstan motor is damaged.
3. Capstan needs lubrication (dry bearing).
4. Tape tensions are incorrect.
5. Brakeshoe is contacting brake drum.
6. Tape reels or tape is defective.
7. Pinch roller tire is worn, has insufficient pressure, or pinch roller solenoid is not bottomed.
8. Pinch roller and capstan are dirty.

3-5 ELECTRONIC ALIGNMENT↑ TOP

If the previous performance tests were not successful, perform the following applicable reproduce and record alignment procedure.

Access to electromic [sic] assembly is as follows: The record/reproduce electronic circuitry is contained on three printed circuit board assemblies (PCB). Access to these PCB may be obtained by removing the base of the cabinet (four screws). Fig. 3-4 shows the location of the various circuits contained on the PCBs.

⤢ zoomFig. 3-3 Access to Electronic Assembly · Redrawn as vector — zooms cleanly · view the original scan

3-5-(1) REPRODUCE ALIGNMENT↑ TOP

Reproduce adjustment consists of reproduce head azimuth adjustment, reproduce equalization adjustment, maximum reproduce level caliblation [sic] (MRL), and standard reference level (SRL) calibration. Location of each calibration potentiometer control is shown in Fig. 3-4. To adjust the reproduce system, proceed as follows:

1. Lift head cover and demagnetize and clean heads and guides.
2. Set LINE OUT switch to HIGH, set SRL switch to "off" variable position. Set REEL switch to appropriate position, and set EDIT switch to "out" (non edit) position. Set reproduce head selector switch to 2T position for models 2S or 2SD, to 4T position for mosels [sic] 4S or 4SD.
3. Set each RECORD switch to "out" (non record) position, set SEL/REP switches to "out" position, and set MONITOR switches to "out" SOURCE position.
4. Connect VTVM to LINE OUT.

⤢ zoomFig. 3-4 Adjusting Parts Location · Redrawn as vector — zooms cleanly · view the original scan

3-5-(2) VU METER CALIBLATION[sic]↑ TOP

1. Depress TEST OSC switch and adjust INPUT LINE CONTROL to obtain +4dBm reading on VTVM.
2. Adjust R86 (CH-1) and R186 (CH-2) to obtain OVU [sic] reading on VU meter.

3-5-(3) REPRODUCE HEAD AZIMUTH ADJUSTMENT↑ TOP

It is recommended that reproduce head azimuth adjustment is made at 7½ ips tape speed.

1. Set SPEED switch to appropriate position for 7½ ips and set MONITOR switches to "in" TAPE position.
2. Thread 7½ alignment test tape on the equipment.
3. Place equipment in play mode, first tone on test tape is refference [sic] level of 700 Hz. Adjust OUTPUT level control to obtain O dBm on the VTVM. Next tone is for azimuth adjustment (15 kHz).
4. Adjust the head azimuth screw (appropriate screw "A" in Fig.4-6) to obtain a maximum reading on the VTVM.

CAUTION

DO NOT ADJUST ANY OTHER SCREWS EXCEPT AZIMUTH ADJUSTMENT SCREW (LABELED "A" IN FIG. 4-6).

If a maximum reading cannot be achieved within one full turn of the azimuth screw, or a maximum reading on the VTVM is way below O dBm, a full head alignment may be required. Refer to section 4 of this manual.

3-5-(4) REPRODUCE EQUALIZATION ADJUSTMENT↑ TOP

This adjustment is performed at 7½ ips tape speed for both High speed models and Low speed models.

1. Reproduce the 10 kHz tone and adjust REP EQ potentiometer R60 (CH-1) and R161 [sic] (CH-2) so that VTVM indicate O dBm. If adjustment was required, recheck the 15 kHz tone and note if reading is O dBm ±2 dB.
2. Check response for the other tones on the alignment tape. Frequency response should be O dBm ± 2 dB.
3. Check frequency response for the other tape speed. Frequency response should be O dBm ±2 dB. It is unnecessary to readjust equalization for 15 ips or 3¾ ips, since adjustment has been done at the same time of 7½ ips.

NOTE

Many test tapes are recorded full track. When reproduced by a half-track or multi--track head, the fringing effect produces invalid response at frequencies below 700 Hz. This effect, which results in high indications in the lower frequencies, does not occur when tapes are recorded and reproduced with heads of the same configuration. Do not adjust the low frequency reproduce equalizers for flat response from a full track standard tape.

3-5-(5) MAXIMUM REPRODUCE LEVEL (MRL) CALIBLATION[sic]↑ TOP

This adjustment is performed at 7½ ips tape speed.

1. Set both OUTPUT controls to full clockwise position.
2. Reproduce a 7½ ips alignment test tape. When the first 700Hz tone is reached, adjust maximum reproduce level caliblation [sic] potentiometers R63 (CH-1) and R163 (CH-2) so that each VU meter indicates O VU.

NOTE

The first tone is a reference level which is recorded at 10 dB below operating level (185nWb/m).

3-5-(6) SRL ADJUSTMENT↑ TOP

This adjustment is made with the operating level 700 Hz signal of the standard alignment tape. It is important that this adjustment is accurate since it affects signal to noise ratio, distortion, and tape saturation level. On Ampex standard alignment tapes this level is 185 nWb/m and is the first tone for 15 ips the last tone for 7½ ips and 3¾ ips tapes. It is suggested that SRL be set at the speed at which the equipment will usually run. If used equally, set at 15 ips for high speed models, 7½ ips for low speed models.

Set SRL switch to SRL position. Reproduce the operating level tone and adjust SRL/CAL potentiometers R65 (CH-1) and R165 (CH-2) so that each VU meter indicates O VU or a +4 dBm or -10 dBm reading on the VTVM depending upon the LINE OUTPUT LEVEL selector.

NOTE

If high output extended dynamic range tapes are to be used exclusively such as Scotch 206, 207 or 250 or Ampex 406, 407 or 456 (or equivalent), the SRL/CAL and SEL/REP levels may be set lower than O VU. Consult Otari representative. Nominal setting for these tapes is -3 VU.

3-6 RECORD AND BIAS SYSTEM ADJUSTMENT↑ TOP

Record and bias system adjustment consists of bias calibration, record level calibration, record head azimuth adjustment, record equalization adjustment, and SEL/REP LEVEL adjustment. The record and bias system adjustment should be made after reproduce system adjustments are completed.

1. Connect VTVM to LINE OUT, connect audio oscillator to LINE IN, and thread blank bulk-erased tape onto the transport.
2. Push POWER switch to on, set SPEED switch to HI position, and set MONITOR switch to TAPE position, set LINE OUT LEVEL switch to HIGH position, and SRL switch to SRL position.

⤢ zoomFig. 3-4 Adjusting Parts Location · Redrawn as vector — zooms cleanly · view the original scan

3-6-(1) BIAS CALIBRATION↑ TOP

Bias adjustment should be made at 15 ips for high speed models and 7½ ips for low speed models. Record bias current affect signal-to-noise ratio, frequency response, distortion, and recording level. Then it is important to adjust bias current for the using tape in order to make perfect recording.

1. Connect 1 kHz tone of audio oscillator to LINE INPUT. (Built in TEST oscillator is also available.) Set MONITOR switch to TAPE position.
2. Start Record mode and adjust INPUT LINE control for O VU on the VU meter.
3. Adjust the BIAS/CAL potentiometers R38(CH-1) and R138(CH-2) so that each VU meter indicates maximum record output.

3-6-(2) RECORD HEAD AZIMUTH ADJUSTMENT↑ TOP

This adjustment should be made at 7½ ips tape speed and at least 10 dB below SRL.

1. Set audio oscillator frequency to 15 kHz.
2. Start record mode and adjust INPUT LINE control for -10 dBm on VTVM (14 dB below SRL).
3. Adjust record head azimuth adjustment screw (labeled "A" in Fig. 4-6) for maximum reading on VTVM.
4. If a peak reading cannot be achieved within one full turn of the azimuth screw, a full head alizument [sic] may be required. Refer to Section 4 of this manual.

3-6-(3) RECORD LEVEL CALIBLATION[sic]↑ TOP

This adjustment should be made at 15 ips for high speed models and 7½ ips for low speed models.

1. Set audio oscillator frequency to 1 kHz, set SRL switch to SRL position, and set MONITOR switches to TAPE position.
2. Start record mode and adjust input LINE controls so that each VU meter indicates O VU.
3. Set MONITOR switches to SOURCE position and adjust REC. CAL. potentiometers R30 (CH-1) and R130 (CH-2) so that each VU meter indicates 0 VU.

3-6-(4) RECORD EQUALIZATION ADJUSTMENT↑ TOP

This adjustment should be performed at SRL position for 15 ips tape speed and at least 10 dB below SRL for 7½ ips or 3 ¾ ips tape speed. Since overall frequency response is affected with bias current, bias calibration may be performed before making this adjustment.

ADJUSTMENT FOR 15 ips

1. Set SRL switch to SRL position, and set MONITOR switches to TAPE position.
2. Place recorder in record mode, set audio oscillator frequency to 1 kHz and adjust INPUT LINE controls for O VU on VU meters.
3. Change frequency to 18 kHz and adjust REC/EQ potentiometers R29 (CH-1) and R129 (CH-2) so that each VU meter indicates O VU.
4. Sweep oscillator frequency from 35 to 22 kHz. Check that the overall frequency response is within ±2 dB. Readjust REC/EQ potentiometers R29 (CH-1) and R129 (CH-2) as necessary.

ADJUSTMENT FOR 7½ ips

1. Set SRL switch to "off" or "variable" position and set OUTPUT controls to full clockwise position.
2. Place recorder in record mode. Set audio oscillator frequency to 1 kHz and adjust INPU [sic] LINE controls for O VU on VU meters (recording is made at 10 dB below SRL).
3. Change frequency to 15 kHz and adjust REC/EQ potentiometers R28 (CH-1) and R128 (CH-2) on high speed models or R29 (CH-1) and R129 (CH-2) on low speed models, so that each VU meter indicates O VU.
4. Sweep oscillator frequency from 30 to 18 kHz and check that the over all frequency response is within ±2 dB. Readjust appropriate REC/EQ potentiometer as necessary.

ADJUSTMENT FOR 3 ¾ ips

1. Set SRL switch to "off" or "variable" position and set OUTPUT controls to full clockwise position.
2. Place recorder in record mode. Set audio oscillator frequency to 1 kHz and adjust INPUT LINE controls for O VU on VU meter (recording is made at 10 dB below SRL).
3. Change frequency to 10 kHz and adjust REC/EQ potentiometers R28 (CH-1) and R128 (CH-2) so that each VU meter indicates O VU.
4. Sweep oscillator frequency from 30 to 12 kHz and check that the over all frequency responce [sic] is within ±2 dB. Readjust appropriate REC/EQ potentiometer as necessary.

3-6-(5) SEL/REP LEVEL ADJUSTMENT↑ TOP

1. Record 1 kHz signal at SRL for about one minute for both channels.
2. Rewind and reproduce the recorded position in the step, and check both VU meters should indicate O VU.
3. Depress SEL/REP switch and adjust SEL. REP LEVEL potentiometers R367 (CH-1) and R387 (CH-2) so that each VU meter indicates O VU.

NOTE

If this adjustment is made by using standard alignment test tapes which are full track recorded, there will be a little error on acount [sic] of fringing effect.