TEAC V-700 (01) PDF MANUAL

1. Improvements may result in changes in specifications and service data.

2. 0 dB is referenced to 0.775 V in this manual.

Parts marked with a triangle sign are safety critical components. They must always be replaced with identical components. Refer to the appropriate parts list and ensure exact replacement.

Before returning the appliance to the customer, make leakage-current or resistance measurements to determine that exposed parts are acceptably insulated from the supply circuit.

External components should be disassembled in the number-order as indicated in Fig. 2-1 of the service manual. The general order is typically:

1. Top cover

2. Cassette door assembly

3. Power transformer related brackets/screws

4. Front panel assembly

5. Rear panel mounted components (e.g., power switch, connectors)

6. Bottom cover

(Note: This is a general interpretation from the diagram; refer to the specific numbered items in Fig. 2-1 for exact order.)

1. While pushing up the cassette-in sensor arm with the cassette holder shut (Fig. 3-2), activate the play mode. Keep the sensor arm pushed up during measurement.

2. Hook a spring scale to the small opening on the pinch roller arm.

3. Pull the scale downwards until there is sufficient force to separate the pinch roller from the capstan shaft, and then allow the pinch roller to just touch the capstan shaft again.

4. Read the scale when the pinch roller just starts to rotate. The readings should be as specified below.

Specifications:

V-900X: 330 g ~ 470 g (11.6 oz ~ 16.6 oz)

V-800X/V-700: 380 g ~ 520 g (13.4 oz ~ 18.3 oz)

1. Load the cassette torque meter on the deck and read the pointer indication on the dial scale for each tape transport operation. The measured torque should be within the following specified values:

Specifications:

Take-up: 30 ~ 60 g-cm (0.42 ~ 0.83 oz-inch)

Supply: 2 ~ 6 g-cm (0.028 ~ 0.083 oz-inch)

F.F./REW: 110 ~ 170 g-cm (1.5 ~ 2.4 oz-inch)

1. Adjust the position of holder guide plate so that it is parallel with the cassette holder as shown in Fig. 4-2 when a cassette tape (MTT-551, etc.) is loaded. Use the adjusting screw on the holder guide plate to achieve this parallel condition.

1. Load a C-60 tape (MTT-5061, etc.) and close the cassette holder.

2. Turn the air adj. screw so that after pushing the EJECT button, the cassette holder opens smoothly and completely.

Note: Be careful not to turn the screw beyond the permissible adjustment limit (1mm to 8mm range as shown in Fig. 4-3).

1. When remounting SW PCB L ass’y* or SW PCB R ass’y* is required, push it (them) as far upward (as shown by the arrows in Fig. 4-4) as possible. Afterwards, check that each of PCB-mounted leaf switch shape is normal (satisfactory shape as in Fig. 4-4’s A), then proceed to the next steps.

* SW PCB L ass’y: Record safety switch, EQ 70 µsec detection switch (CrO2, METAL) mounted

* SW PCB R ass’y: METAL position switch, cassette-in switch mounted

2. Load a NORMAL tape, then a METAL tape, with their record protection tabs in place, and check that the NORMAL indicator and then the METAL indicators on the front panel light respectively.

3. Load a METAL tape without its record protection tab, then check that when the EJECT button is depressed, the cassette holder properly opens.

4. Load a CrO2 tape with its record protection tab in place, and check that the CrO2 indicator lights.

1. Temporarily set resistance values of R10 and R11 on MECHA PCB at approx. the mid point of their respective variable ranges.

2. Load an empty cassette (without tape) or activate the cassette-in switch to the on position with your finger.

3. Push the PAUSE button, then adjust R11 so that the hole of marker PA coincides with the reference line of the reel motor mounting plate (See Fig. 4-6).

4. Rotate in both directions the control cam by hand several times to check the points where the reel motor starts to vibrate. If necessary, readjust R11 so that the distances from CW to the hole and CCW to the hole on the PA marker are nearly equal when the reel motor starts to vibrate.

5. Place the deck in STOP mode and adjust R10 as explained above for R11, this time referring to the center ST hole.

6. Repeat steps 3 – 5 until PA and ST position adjustments are satisfied.

1. Connect a frequency counter to the deck as shown in Fig. 4-7.

2. On the V-800X/V-700, depress POWER switch to “on” in order to warm up the capstan motor for at least one minute.

3. Playing the mid portion of an MTT-111 test tape, adjust the trimmers below so that tape speed becomes 3,000 Hz ±5 Hz (on V-800X/V-700: 3015~3025 Hz if more than 5 minutes after its motor rotation starts). An insulated and non-metallic flat-head screwdriver should be used for this adjustment.

Adjustor:

V-900X: Semi-fixed resistor on DC capstan motor assembly’s PCB (Fig. 3-3)

V-800X/V-700: Semi-fixed resistor on the capstan motor (Fig. 3-4)

4. Make sure the following values are obtained at the beginning and at the end of the tape.

Deviation:

3,000 Hz ±45 Hz (V-900X)

3,000 Hz ±60 Hz (V-800X/V-700)

Width of deviation:

Within 45 Hz (V-900X)

Within 60 Hz (V-800X/V-700)

Note: These measurements should be made at the beginning, middle and the end of the tape.

4-8-1 PLAYBACK METHOD

1. Connect a wow and flutter meter to the deck as shown in Fig. 4-7.

2. Load and play a TEAC MTT-111 test tape or equivalent.

3. Measure the wow and flutter value.

Specification: 0.06% WRMS

4-8-2 RECORD/PLAYBACK METHOD

Note: When measuring with this method, the recorded section should be played back repeatedly to obtain an average value. Be careful not to read the meter for those parts of the tape in which wow and flutter components in recording and playback cancel each other.

4. Load a blank TEAC MTT-552 test tape or equivalent and record a 3,000 Hz signal.

5. Rewind the tape to the beginning of the recorded section, and play it.

6. The wow and flutter should not be more than specified.

Specifications:

0.20% RMS (V-900X)

0.25% RMS (V-800X/V-700)

1. Turn the azimuth adj. screw so that observing by eye the REC.PLAY head becomes parallel with the mechanism chassis as far as possible.

2. Press the EJECT button to open the cassette holder. Insert the head check jig A into the cassette holder. Close the holder then push the jig in firmly.

Notes:

• Head check jig A should be inserted with its edge set on the stoppers at the bottom of the cassette holder (Fig. 4-9).

• Be careful for the head check jig A not move off the stoppers of the cassette holder when closing the cassette holder.

3. Making sure that in play mode the head check jig B touches the surface of the REC.PLAY head, adjust head position so that the slanted edge of the head check jig B comes to rest approximately in the middle between the two line markers on the head check jig A. For adjusting, loosen the head position adj. screw, then adjust head position, and complete by tightening the screw.

4. Set the head check jig B as shown in Fig. 4-11 so that the head check jig B can just pass through smoothly between the tape guides. If head height is too low, add the head spacer*. If it is too high, remove the head spacer. Height adjustment should be satisfied together with parallel adjustment mentioned in step 1.

* Head spacer: TEAC P/N 5800468900, thickness 0.15 mm

5. In the same way as above, check the erase head height using the head check jig B. If needed, adjust it by turning the adj. nut.

6. Play a C-90 type mirror tape (MTT-902T, etc.) and check the following contents.

• The head core (silver) of the REC.PLAY head should not be visible from the tape edge.

• Any noticeable tape curling should not occur on the sides of the REC.PLAY head guide.

• Moving tape should touch the erase head’s upper guide.

7. In play mode, check the following contents.

• The clearance between erase head plate/head stopper: more than 0.3 mm (Adjust by bending the stopper)

• There should be a gap between head cover (B)/head stopper.

Lubrication is only required when parts are replaced. For this purpose, use the oil and grease specified below.

Oil: TEAC TZ-255A motor oil (from TEAC TZ-255 oil kit), Mobil D.T.E. Oil Light, or equivalent

Grease: ORE-LUBE G1/3 or equivalent

1. Apply a drop of oil with an oil applicator to a point about 1/3 the way down the shaft (from the free end) of the flywheel, then insert the shaft into the capstan housing.

2. Apply a suitable amount of light grease to the well of the flywheel bearing.

If the RC-203 remote control unit (optional) is used to operate the deck, the following adjustment procedure is needed.

1. Connect the remote control unit to the REMOTE socket.

2. Connect the digital-type DC voltmeter to TP. 1 on the POWER/CONTROL PCB (See Fig. 4-14).

3. Temporarily adjust RV902 so that voltage at TP. 1 becomes +1.32 V.

4. Even though the number on the CPS display is increased by one each time the CPS button on the remote control unit is pressed, adjust RV902 until its number is not increased.

5. Adjust RV902 while pressing the CPS button on the remote control unit so as to find the beginning point at which the CPS display’s number is increased when the CPS button is pressed.

6. Adjust RV902 so that voltage at TP. 1 goes into +0.04 V than the value at the above beginning point.

ALWAYS DISCONNECT THE POWER LINE CORD BEFORE MAKING THESE CHANGES.

1. Locate the voltage selector on the rear panel as shown in the illustration (Fig. 4-15).

2. Using a regular (slot blade) screwdriver, turn the selector so that the desired voltage indication aligns with the arrow mark.

1. Since this deck has an automatic tape selector, be sure to use test tapes that have tape position detecting holes.

2. Before performing adjustments and checks, clean and demagnetize the entire tape path.

3. Make sure the deck is properly set for the voltage in your locality.

4. In general, adjustments and checks are made in the order of L-ch then R-ch. A note for alphanumeric codes with “L/R” suffixed in parenthesis; RV901(L/R), for example, means RV901L and RV901R, where L indicates left channel and R, right channel. For the double test point designations with a slash between, such as TP.1/TP.2, they also indicate the test points of left and right channels respectively.

5. 0 dB is referenced to 0.775 V. If an AC voltmeter that references 0 dB to 1 V is used, appropriate compensation should be made.

6. The AC voltmeter used in the procedures must have an input impedance of 1MΩ or more.

Initial switch settings (Table 1):

TEAC test tapes mentioned:

MTT-150: For Dolby level calibration

MTT-256: For playback frequency response check for NORMAL

MTT-356: For playback frequency response check for CrO2, METAL

MTT-551: For S/N check with NORMAL

Setting: Connection as per Fig. 5-2, Settings as per Table 1.

1. Initial Check:

Input Signal: MTT-150.

Adjust (or CHECK): Check.

Measuring Point: Result: OUTPUT: Phase: within 45°.

Remarks: Refer to Fig. 5-4.

2. Adjustment:

Input Signal: MTT-356 (12.5 kHz).

Adjust (or CHECK): Azimuth screw of R.P head (Fig. 5-3).

Measuring Point: Result: OUTPUT: Max. output at L-& R-ch’s (on VTVM).

Setting: Same as REC PLAY head azimuth check. Connection: Fig. 5-5, but do not connect LINE IN (L/R). (For main output: Connection Fig. 5-1)

Input Signal: MTT-150.

Adjust (or CHECK): RV601 (L/R) (for internal test point check), Check (for main output check).

Measuring Point: Result:

TP.1/TP.2 (R/P AMPL. PCB): 580mV (-2.5 dB).

OUTPUT: 490 mV (-4 dB) ± 1 dB (436 mV to 548 mV).

Setting: Same as REC PLAY head azimuth check. Connection: Fig. 5-6.

Input Signal: MTT-150.

Adjust (or CHECK): Check.

Measuring Point: Result: PHONES: 250 mV (-9.8 dB) ±3 dB (177 mV to 353 mV).

Remarks: 8 Ω load.

Setting: Same as REC PLAY head azimuth check. Connection: Fig. 5-1.

Input Signal: MTT-256 (for NORMAL), MTT-356 (for CrO2, METAL).

Adjust (or CHECK): Check.

Measuring Point: Result: OUTPUT: Standard: Fig. 5-9.

Setting: Same as REC PLAY head azimuth check. Connection: Fig. 5-1.

Input Signal: MTT-551.

Adjust (or CHECK): Check.

Measuring Point: Result: OUTPUT: S/N: 47 dB min.

Settings:

Mode: STOP

MONITOR switch: SYNC (V-900X), or SOURCE (V-800X/V-700)

OUTPUT Control: Max.

Connection: Fig. 5-5. RECORD cont.: Max.

Input Signal: LINE IN: 400Hz/86.9mV(-19dB).

Adjust (or CHECK): Check.

Measuring Point: Result:

TP.5/TP.6: 580mV (-2.5dB)±3dB (411 mV to 0.820 V).

If checking main output (Connection: Fig. 5-1): OUTPUT: 490mV(-4dB)±3dB (346mV to 690mV).

Settings: Same as Min. LINE input level check.

Input Signal: MIC: 400Hz/346μV(-67dB).

Adjust (or CHECK): Check.

Measuring Point: Result:

TP.5/TP.6: 580mV (-2.5dB)±3dB (411 mV to 0.820 V).

If checking main output (Connection: Fig. 5-1): OUTPUT: 490mV(-4dB)±3dB (346mV to 690mV).

Settings: Same as Min. LINE input level check.

Input Signal: LINE IN: 400 Hz/-9dB (275 mV).

Adjust (or CHECK): RECORD cont.* (for TP.5/TP.6), Check (for OUTPUT).

Measuring Point: Result:

TP.5/TP.6 (R/P AMPL. PCB): 580mV (-2.5dB).

If checking main output (Connection: Fig. 5-1): OUTPUT: 490mV(-4dB)±3dB (346mV to 690 mV).

Remarks: *After adjusting RECORD control, do not disturb (Specified position).

Settings: Same as Min. LINE input level check. RECORD cont.: Specified position.

Input Signal: LINE IN: 400Hz/-9dB (275 mV).

Adjust (or CHECK): RV603 (L/R).

Measuring Point: Result: PEAK PROGRAM LEVEL METER: 0 dB lit.

Mode: REC/PLAY (Unless otherwise specified)

MONITOR switch: SYNC (V-900X), or TAPE (V-800X/V-700)

RECORD control: Specified position (position set at item 8 of Monitor Performance)

OUTPUT control: Max.

TEAC test tapes:

MTT-5072: For METAL record test

MTT-5061: For CrO2 record test

MTT-551: For NORMAL record test

Setting: Connection: Fig. 5-7. Mode: REC/PAUSE.

Input Signal: None.

Adjust (or CHECK): OSC601.

Measuring Point: Result: Refer to Fig. 5-7: Bias osc. freq.: 100kHz ± 3 kHz.

Setting: Same as bias osc. frequency check. Connection: Fig. 5-8. Mode: REC/PAUSE.

Input Signal: None.

Adjust (or CHECK): L601 (L/R) for V-900X, L602 (L/R) for V-800X/V-700.

Measuring Point: Result: Refer to Fig. 5-8: Min. bias leakage.

Setting: Same as bias osc. frequency check. Connection: Fig. 5-5. Mode: REC/PLAY (with empty cassette loaded).

Input Signal: None.

Adjust (or CHECK): L601 (L/R).

Measuring Point: Result: TP.1/TP.2 (R/P AMPL. PCB): Min. bias leakage.

Note: After adjusting overall frequency response (item 14), re-do this item’s checks and adjustments.

1. Initial Level Check:

Setting: Same as bias osc. frequency check. Connection: Fig. 5-1. Mode: STOP.

Input Signal: LINE IN: 400 Hz/-34 dB (15.5 mV).

Adjust (or CHECK): Check.

Measuring Point: Result: OUTPUT: -29dB (27.5 mV)*. (*Give actually-measured level as ref. level (1)).

2. Record Level Adjustment (MTT-551):

Setting: Mode: REC/PLAY. Tape: MTT-551.

Input Signal: LINE IN: 400 Hz/-34 dB (15.5 mV).

Adjust (or CHECK): RV603 (L/R).

Measuring Point: Result: OUTPUT: Difference against ref. level (1): 0 dB.

3. Record Level Check (MTT-5072, MTT-5061):

Setting: Mode: REC/PLAY. Tape: MTT-5072 then MTT-5061.

Input Signal: LINE IN: 400 Hz/-34 dB (15.5 mV).

Adjust (or CHECK): Check.

Measuring Point: Result: OUTPUT: Difference against ref. level (1): ± 1 dB.

Adjust in the order of (1) NORMAL, (2) METAL, (3) CrO2 tape. Since record level varies after making this item instruction adjustments, re-do checks and adjustments shown in items 13 (Record Level V-900X) and 14 (Overall Frequency Response V-900X).

(1) NORMAL Tape (MTT-551):

Setting: Same as initial recording settings. Tape: MTT-551.

Input Signal: LINE IN: 400 Hz & 16 kHz alternately/-34 dB (15.5 mV).

Adjust (or CHECK): RV604 (L/R).

Measuring Point: Result: OUTPUT: 16kHz output against that of 400Hz: ±1 dB.

(2) METAL Tape (MTT-5072):

Setting: Same as initial recording settings. Tape: MTT-5072.

Input Signal: LINE IN: 400 Hz & 16 kHz alternately/-34 dB (15.5 mV).

Adjust (or CHECK): RV606 (common to L,R).

Measuring Point: Result: OUTPUT: 16kHz output against that of 400 Hz: ±2 dB.

(3) CrO2 Tape (MTT-5061):

Setting: Same as initial recording settings. Tape: MTT-5061.

Input Signal: LINE IN: 400 Hz & 16 kHz alternately/-34 dB (15.5 mV).

Adjust (or CHECK): RV605 (common to L,R).

Measuring Point: Result: OUTPUT: 16kHz output against that of 400 Hz: ±2 dB.

Remarks: Standard frequency response curves as per Fig. 5-10.

Note: After adjusting overall frequency response (item 16), re-do this item’s checks and adjustments.

1. Initial Level Check:

Setting: Same as initial recording settings. Connection: Fig. 5-1. MONITOR sw: SOURCE.

Input Signal: LINE IN: 400Hz/-34 dB (15.5 mV).

Adjust (or CHECK): Check.

Measuring Point: Result: OUTPUT: -29 dB (27.5 mV)*. (*Give actually-measured level as ref. level (2)).

2. Record Level Adjustment (MTT-5072 – METAL):

Setting: MONITOR sw: TAPE. Mode: REC/PLAY. Tape: MTT-5072.

Input Signal: LINE IN: 400Hz/-34 dB (15.5 mV).

Adjust (or CHECK): RV602 (L/R).

Measuring Point: Result: OUTPUT: Difference against ref. level (2): 0 dB.

3. Record Level Check (MTT-5061 – CrO2, MTT-551 – NORMAL):

Setting: MONITOR sw: TAPE. Mode: REC/PLAY. Tape: MTT-5061 then MTT-551.

Input Signal: LINE IN: 400Hz/-34 dB (15.5 mV).

Adjust (or CHECK): Check.

Measuring Point: Result: OUTPUT: Difference against ref. level (2): ±1 dB.

Adjust in the order of (1) METAL, (2) CrO2, (3) NORMAL tape. Since record level varies after making this item instruction adjustment, re-do checks and adjustments shown in items 15 (Record Level V-800X/V-700) and 16 (Overall Frequency Response V-800X/V-700).

(1) METAL Tape (MTT-5072):

Setting: Same as initial recording settings. Tape: MTT-5072.

Input Signal: LINE IN: 400Hz & 16 kHz alternately/-34 dB (15.5 mV).

Adjust (or CHECK): RV604 (L/R).

Measuring Point: Result: OUTPUT: 16 kHz output against that of 400Hz: ±1 dB.

(2) CrO2 Tape (MTT-5061):

Setting: Same as initial recording settings. Tape: MTT-5061.

Input Signal: LINE IN: 400Hz & 16 kHz alternately/-34 dB (15.5 mV).

Adjust (or CHECK): R655 (RV605) (common to L, R).

Measuring Point: Result: OUTPUT: 16 kHz output against that of 400Hz: ±2 dB.

(3) NORMAL Tape (MTT-551):

Setting: Same as initial recording settings. Tape: MTT-551.

Input Signal: LINE IN: 400Hz & 16 kHz alternately/-34 dB (15.5 mV).

Adjust (or CHECK): R658 (RV606) (common to L, R).

Measuring Point: Result: OUTPUT: 16 kHz output against that of 400Hz: ±2 dB.

Remarks: Standard frequency response curves as per Fig. 5-10.

Setting: Same as initial recording settings. Tapes: MTT-551, MTT-5061, MTT-5072.

Input Signal: LINE IN: 400 Hz/-9 dB (275 mV).

Adjust (or CHECK): Check.

Measuring Point: Result: OUTPUT: 2.5% or less for all tape positions.

Setting: Same as initial recording settings.

Input Signal: LINE IN: 400 Hz/-9 dB (275 mV), then no signal.

Adjust (or CHECK): Check.

Measuring Point: Result: OUTPUT:

NORMAL 45 dB min.

CrO2 46 dB min.

METAL 46 dB min.

When NR SYSTEM is set to dbx, 65 dB min. for all tape positions.

Setting: Connection is same as in Fig. 5-1, but engage 1-kHz filter. Record a 1-kHz signal. Rewind tape to midpoint of recorded portion. Record a “no signal” portion. Find the difference between the 1-kHz portion and the “no signal” portion. Tapes: MTT-551, MTT-5061, MTT-5072.

Input Signal: LINE IN: 1 kHz/+1 dB (0.869 V), then no signal.

Adjust (or CHECK): Check.

Measuring Point: Result: OUTPUT: 65 dB min. ratio.

Setting: Connection: Fig. 5-1, but do not connect LINE IN (R), and engage 1-kHz filter. Set the deck to record mode. Find the difference between the 1-kHz recorded portion (L-ch) and the “no-signal” portion (R-ch). Then change the connection and check reverse operation. Tape: MTT-551.

Input Signal: LINE IN: L-ch 1 kHz/-9 dB (275 mV), R-ch No signal.

Adjust (or CHECK): Check.

Measuring Point: Result: OUTPUT: 30 dB min. ratio.

Setting: Connection: Fig. 5-1, but do not connect LINE IN (L) and OUTPUT (L). Record a 125-Hz signal on R-ch and note output level. Invert tape and play R-ch track. Check leakage level against the output reference of previously recorded portion. Tape: MTT-551.

Input Signal: LINE IN: L-ch No signal, R-ch 125 Hz/-9 dB (275 mV).

Adjust (or CHECK): Check.

Measuring Point: Result: OUTPUT: 40 dB min. ratio.

Setting: Connection: Fig. 5-1, but engage 1-kHz filter. Record a 1-kHz signal. Push REC MUTE button for several seconds. (At this time, make sure LED on the button lights). Rewind and play the tape. Find the difference between the 1-kHz portion and the “no-signal” portion. Tapes: MTT-551, MTT-5061, MTT-5072.

Input Signal: LINE IN: 1 kHz/+1 dB (0.869 V), then no signal.

Adjust (or CHECK): Check.

Measuring Point: Result: OUTPUT: 65 dB min. ratio.

Setting: Record a 1-kHz signal with NR SYSTEM switch OUT. Play this portion with NR SYSTEM switch set first to OUT, then to B. Obtain the difference in output level between OUT and B positions. Repeat the above process using a 10-kHz signal. Tape: MTT-5061.

1. For 1 kHz signal:

Input Signal: LINE IN: 1 kHz/-29 dB (27.5 mV).

Adjust (or CHECK): Check.

Measuring Point: Result: OUTPUT: Variation 3 dB ~ 8 dB.

2. For 10 kHz signal:

Input Signal: LINE IN: 10 kHz/-39 dB (8.69 mV).

Adjust (or CHECK): Check.

Measuring Point: Result: OUTPUT: Variation 8 dB ~ 10 dB.

Setting: Repeat the same procedure as for B-type, only see that the NR SYSTEM switch is set to C. Tape: MTT-5061.

1. For 1 kHz signal:

Input Signal: LINE IN: 1 kHz/-39 dB (8.69 mV).

Adjust (or CHECK): Check.

Measuring Point: Result: OUTPUT: Variation 16 dB ~ 20 dB.

2. For 10 kHz signal:

Input Signal: LINE IN: 10 kHz/-49 dB (2.75 mV).

Adjust (or CHECK): Check.

Measuring Point: Result: OUTPUT: Variation 16 dB ~ 20 dB.

1. 400Hz Oscillation Waveform:

Setting: Same as Dolby NR effect check. Connection: Fig. 5-13. Mode: STOP.

Input Signal: None.

Adjust (or CHECK): RV601.

Measuring Point: Result: U602-1: Adjust to get 400Hz oscillation waveform shown in Fig. 5-13.

2. 400Hz Level:

Setting: Same as Dolby NR effect check. Connection: Fig. 5-14. Mode: STOP.

Input Signal: None.

Adjust (or CHECK): RV602.

Measuring Point: Result: U606-1: 400Hz level: 5 mV.

Temporary Setting:

Setting: Connection: Fig. 5-1. Mode: STOP. Tape: MTT-551. RV607(L/R): Set temporarily as shown (approx. 15° from an edge, viewed from top of deck).

Procedure:

1. Press AUTO CAL switch.

2. Deck does the auto calibration process (AUTO indicator blinks).

3. After completing auto calibration (AUTO indicator remains lit), deck enters the REC/PAUSE mode.

Adjustment:

Setting: Mode: REC/PAUSE (after auto calibration) then REC/PLAY.

Adjust (or CHECK): RV607 (L/R).

Measuring Point: Result: OUTPUT: Adjust for output in REC/PLAY mode (“off-the-tape” signal monitored) to become almost the same level* as one in REC/PAUSE mode (the source signal monitored). *-29 dB ± 0.5 dB (25.9 mV to 29.1 mV).

NOTE: If temporary setting is not done, deck may invite error calibration. In this case, after completing auto calibration, deck enters the STOP mode and REF indicator lights.

Note:

1. Since the dbx NR PCB assembly has been precisely adjusted at the factory, this adjustment is not usually needed unless any of the trimmers have been changed, or any components on the PCB have sustained damage.

2. As a necessary procedure for the ENCODING ADJUSTMENT only, disconnect either end of each jumper of J45 and J46 on the R/P AMPL. PCB. (For their location see Fig. 5-21.)

3. Make the following initial settings:

• POWER switch: ON

• NR SYSTEM switch: OUT

• All other front panel switches and controls have no effect on this adjustment.

Before returning the appliance to the customer, make leakage-current or resistance measurements to determine that exposed parts are acceptably insulated from the supply circuit.

Parts marked with a safety critical sign must always be replaced with identical components. Refer to the appropriate parts list and ensure exact replacement.

Chip resistors have a three-digit number which represents the value of resistance. The first two digits indicate the significant numeric value of resistance. The third digit or multiplier indicates the number of zeros after the first two digits. Please follow the examples below:

Chip transistors can be identified by a two-letter code. Use of the schematic diagram, parts list, and parts layout diagram should provide adequate identification for service. For example:

Handling Chip Devices:

The chip devices are not heatproof or shockproof. The devices are made of ceramic and plastic moldings so they cannot stand a direct shock to them.

Soldering Chip Devices:

(A) Set the device flat on the printed circuit board.

(B) Sometimes when one terminal is soldered, the other unsoldered terminal is slightly raised. In such a case, do not try to push down the end of the device.

Also, try to keep prolonged heat away from the area of the device and avoid an excess of solder as this might result in a short. Do not mount the chip devices incorrectly.

Removing Chip Devices:

When removing a chip device, it is recommended to heat the terminals of the device repeatedly two or three times and then slide the chip device as described in the service manual illustrations (using a slide iron to slide the chip off).

Replacing Chip Devices:

1. After the device has been removed, make sure that no damage has occurred to the printed circuit board.

2. To replace a chip device, use a pair of tweezers to place the device where it is needed.

3. Then carefully solder the terminals to the printed circuit board.

4. After cooling, check for solder bridges or cold solder joints on the chip device.

4-bit Data Chart

4 bit Data(BCD)

D0 : 2^0

D1 : 2^1

D2 : 2^2

D3 : 2^3

Mode Selector Chart

Function Chart – CONTROL INPUTS

The function key input circuit uses a key matrix. The operational mode of the deck is determined by the combinations (timings) of the D10-D15 outputs and the R10-R13 input from the U905 microcomputer. For example, when the D14 output is High, and a High is input to R11, the U905 microcomputer determines that it has been ordered to enter rewind mode. The specific combination of active D line (output) and R line (input) corresponds to a specific function key press (e.g., REC, STOP, PLAY, PAUSE, FADE IN, REW, REC MUTE, EJECT, FADE OUT, COUNTER CLEAR, CPS, INTRO CHECK, REF, WRITE, MEMO, COUNTER MODE, TAPE LENGTH, AUTO CAL, READ).

The U905 key microcomputer basically reacts as follows in response to keyed input: When a key is operated, the U905 receives the keyed function command, but it will not accept a new command unless all the keys are turned off first. As a result of this, when multiple keys are depressed at the same time, the first key to be depressed will be received, regardless of when they are turned off. The four special cases of FF and REW, PLAY and REC, PLAY and PAUSE, and REC and PAUSE are treated differently. In addition, if the STOP key is depressed with any other key, the STOP key is given priority.

Table 2-1 Multiple Key Modes when Depressed

Table 2-2 Modes after Multiple Key Depression (Differences from Table 2-1 above)

The U905 key microcomputer receives an input from the key matrix and transfers the content to the U904 mechanical microcomputer after changing it to serial data. The serial data is composed of 4-bit key matrix return signals, placed one on each of DIG-1 to DIG-6. The U904, after receiving the serial data, determines the deck’s operation mode, and sends that status information to U905 after converting it to 5-bit data. The U904 checks the SI input at the breaking time of the SCK clock, and writes data if any is available. SI data is output from the U905 once each time a key switch is turned on or off.

Operations of the mechanical microcomputer U904:

1. Determines the deck’s function mode through serial data input, and creates 5-bit data.

2. Ro port goes High, and 5-bit data is output.

3. After outputting the 5-bit data, checks the status of the K3 input port. If a High is detected, the Ro port is returned to Low.

Operation of key microcomputer U905:

1. When D3 port input goes High, it writes the 5-bit data, and then changes D5 output port to High.

2. Checks the D3 port input, and if Low, then changes D5 port output to Low.

The 5-bit data output by U904 after it receives serial data from U905 is shown below:

The left or right channel audio signal, applied to pin6/pin 4 of UL01, is changed to DC current in response to its level and sent to the UL02 meter driver. The UL02 outputs a level meter light signal in response to this input signal, lighting the left and right channel meters alternatively every 0.5msec, as determined by an oscillator inside the I.C. The peak hold time is determined by the time constant circuit formed by RL11 and CL08, ranging from about 0.5 to 1.0 seconds. The meter scale numbers and the ∞ symbol are always lit.

EQ adjustment is performed twice, in the order of VCA (R,L), EQ(R,L), VCA(R,L), EQ(R,L), VCA(R,L). The adjustment process is the same as for the VCA level adjustment, except that a 12 kHz signal is used. The data format is shown in figure 12-17 of the PDF, and the timing is detailed in figure 12-19 of the PDF.

The fixed EQ adjust data is computed from the A value gained during matching in the comparative mode as follows:

If A is greater than 8, the fixed data is 8-(A-8)-1-(16-A)-1.

If 8 is greater than A, the fixed data is 8+(8-A)-1-(16-A)-1.

The EQ adjustment process involves different mechanical modes (REC/PLAY), 4-bit data (Do-D3) for EQ adjust data format and comp data, mode select (Ro-R2) for EQ adjust mode format and comp mode, L/R select, 3kHz control, 12kHz control (OSC 12kHz), mute out, and reset out signals, as illustrated in the timing chart (Fig. 12-19 of the PDF).

The V-900X uses the RC-203 remote control unit, which is a two-lead wired type. Operation command signals are sent from the RC-203 to the V-900X as DC potentials (static signals).

The remote circuit in the V-900X detects the command content from these signals. Output signals from pins 13-16 of U904 turn Q909-Q912 on and off, changing the resistance value between pin 2 of U906 and ground. This results in the voltage potential of pin 1 (pin 5) of U906 becoming a step-form.

When a switch is pressed on the RC-203, a DC signal corresponding to that command is applied to pin 6 of U906. The potential of pin 5 of U906 enters a step-form (rises). When this potential reaches or exceeds that of pin 6, the output from pin 7 changes from Low to High. The U904 mechanical microcomputer detects this rise timing and determines the command content.

The RC-203 remote has switches for STOP, PAUSE, REC MUTE, CLEAR, MODE, MEMORY, CPS, FADE IN, FADE OUT, and RECORD, each associated with specific resistor values to generate the DC potentials.

The mechanical operation is controlled by a cam, which is driven by the cam motor. The U902 cam motor control I.C. controls the direction of the cam motor rotation. This is managed through a combination of Highs and Lows input from the mechanical microcomputer, U904, by way of the U903 unit.

The potential chart (Fig. 5-3 in the PDF) illustrates how U906 pin 5, 6, and 7 voltages change based on operations like REWIND or PLAY, corresponding to signals from U904 (pins 13-16) which control Q909-Q912.

The U902 Cam Motor Control operates as follows based on inputs IN1 and IN2 from U904:

U904 Inputs (R1, R2 giving IN1, IN2) -> U902 Outputs (OUT1, OUT2) -> CAM MOTOR Action

H, H (L, L on IN1, IN2) -> OFF, OFF -> No I.C. Operation

H, L (L, H on IN1, IN2) -> H, L -> Normal rotation

L, H (H, L on IN1, IN2) -> L, H -> Reverse rotation

L, L (H, H on IN1, IN2) -> L, L -> Brake

The cam is driven by the cam motor. Two oscillators are used to determine if the cam has reached the target position.

1. OSC-2: This is the cam interrupt oscillator, with a frequency of 500Hz and a time of 2.0 milliseconds. It provides an IRQ signal to U904.

2. OSC-1: This is the cam position oscillator, a voltage-controlled oscillator (VCO) controlled by the volume coupled to the cam. When the cam rotates, the output frequency of OSC-1 (ranging from f=83k to 120kHz) changes. This changed frequency (TC signal) is detected by U904, which counts the TC input to determine the cam position.

The output of the cam interrupt oscillator (clock of the IRQ pin of U-904) is taken as reference and sets the following timers:

CPS (Computomatic Program Search):

CPS is divided into CPSFF (searches tracks ahead) and CPSREW (searches tracks behind).

Intro Check:

This feature automatically creates a CPS count of ‘1’ in the CPSFF mode, searches out the first track, plays the first 10 seconds, and continues the process. The ‘CPS 1’ is processed inside the microcomputer, so the CPS counter display remains at ‘0’.

CPSFF (Intro Check) Operation:

The start of each track is detected, and the CPS counter is reduced by one each time. No track starts are detected within the first 0.1 seconds after starting CPSFF. If CPSFF is started from the middle of a track, that track is not counted. For example (Fig. 8-2 in PDF), if the current position is between E and F, and the third track (D) is selected, CPSFF detects each track start, lowering the count. When the count reaches zero, it’s the beginning of track D. If the start point was to the right of F, track B’s start wouldn’t be detected, and D would be the second track ahead. If to the left of E, track A’s start would be detected, and the third track would be C.

CPSREW Operation:

The start of each track is detected, and the CPS counter is lowered by one. Track starts within 0.1 seconds of the CPSREW start point are not detected. For example (Fig. 8-3 in PDF), if the current position is from f to g, and the third track is selected, the CPS count reduces to 0 at the beginning of track d. If the position is right of f, track a’s start is detected, and the third track becomes c. If left of g, track b’s start isn’t detected, and the third track will be e.

In CPSFF and CPSREW, the U-904 mechanical microcomputer issues a stop command when the CPS counter reaches ‘0’. Due to inertial forces, the tape continues to travel beyond this point. This overtravel is compensated as follows:

Rotation pulses (4 pulses per revolution) from the right reel are input to the Rg port (pin 31) of U904. When the CPS count changes from ‘1’ to ‘0’, U904 issues a stop mode signal and counts the right reel pulses from that point until the tape stops moving. If this count is N, the tape would only need to be rewound N pulses for CPSFF compensation, or fast-forwarded N/2 pulses for CPSREW compensation. After this compensation, the tape stops, and then begins play.

9-1 Tape Counter Mode:

The count signal is produced by a photo-transistor detecting left reel rotation. The reel table has four holes, producing 4 pulses per revolution. These pulses are counted by the U905 key microcomputer to raise or lower the count by one digit for every two pulses detected.

9-2 Tape Remaining Time Counter Mode:

U905 has memorized varying data for different tape sizes and thicknesses. It selects the needed tape running data based on the tape length signal (C-90, C-60, C-46L) from the key matrix and the metal tape detector signal from pin 42. Additionally, it measures the revolution time of the left reel (average time for 4 pulses) and calculates the remaining time from this data.

9-3 TRT Counter Mode:

This mode signal is made up from the reference clock of the U905 key microcomputer.

The operation of the NR system (Dolby OUT, B, C) is determined by the voltage applied to pin 27 of the Dolby I.C. The Dolby NR becomes OUT during auto-calibration.

The signal path for NR OUT, Dolby B, and Dolby C is the same, except for the decoding/encoding of the signal inside the Dolby decoder/encoder.

Signal paths for different NR settings are as follows (referring to figures in the PDF):

dbx on: see figure 10-2 in the PDF.

dbx DISC on: see figure 10-3 in the PDF.

NR out, Dolby B, Dolby C: see figure 10-4 in the PDF.

When the sync switch is turned on, the tape monitor is automatically cued for play and rec/play modes. The source monitor is automatically cued for stop, FF, REW, pause, and rec/pause modes. REC MUTE, fade in/out, and auto calibrate are basically the REC/PLAY mode, and so are the tape monitor.

The monitoring selection (SOURCE, TAPE, or SYNC) depends on the state of the MONITOR SW, DECK MODE, and control signals Da, Do, Q913, Q914, Q610L, Q609L, Q612L, Q611L as detailed in the table in Fig. 10-5 of the PDF.

Fade in/out is handled by the electronic attenuator U601, which is controlled by output signals from U605.

When the fade in (or fade out) switch is pressed, U904 outputs the appropriate command to U605. U605 then outputs a signal to light the fade in(out) LED (from pin 1 or 2) and an up(down) Low-level signal from pin 7 (or 6). This up/down signal determines if it’s a fade in or fade out and starts U601’s internal oscillator for electronic attenuation.

An initial set signal is output from pin 5 of U605. Oscillator pulses from U601 are input to pin 8 of U605. When 34 pulses are reached, U601 (this should likely be U605, based on context of detecting completion) determines the fade in/out is complete. U605 then sends a fade in finish (or rec mute) signal to U904.

The auto-fader timing chart (Fig. 11-1 in the PDF) shows the attenuation levels (0dB, -40dB, -66dB) during different modes like FADE IN, REC/PLAY, FADE OUT, and REC MUTE, along with the states of U605 pins 5, 6, 7, and 8.

The oscillator (clock) output of U601 is input to 2 two-way shift registers connected in cascade. The register data is output, received at a latch circuit, and changes the analogue switch.

When pin 10 (U/D) of U601 is High, fade in (up) occurs.

When pin 10 of U601 is Low, fade out (down) occurs.

The fade in/out stops when 34 oscillator outpulses are detected at U605. For example, in fade out, as the count goes from 1-33, attenuation is increased in 2dB steps from 0 to -66 dB. Attenuation becomes infinite at 34 (the -68 dB step is not operational).

Pin 7 (INH) of U601 is set at High (+B) so that when it becomes Low it can stop U601 operation. To cancel the default -40 dB preset at power on and set attenuation to zero, the pin 5 output of U605 is used. About 0.5 seconds after the deck is turned on, a Low signal (approx. 50ms duration) is output by pin 5 of U605. This signal turns on Q609 and Q606. When Q606 is on, U601’s oscillator begins. At this time, pin 10 of U601 is High (via pull-up resistance), so the attenuator starts fade-in. The time constant (C652, R616) is short, making the oscillator frequency high, ending fade-in quickly and setting attenuation to zero. This initial set signal occurs at the start of fade in and the end of fade out.

When the fade-in switch is pressed, a Low signal is output from pin 5 and pin 6 of U605 for about 50 mseconds. The pin 5 signal causes Q609 and Q606 to turn on, starting the oscillator. The signal from pin 6 of U605 turns on Q608 and Q605, and pin 10 of U601 drops to Low, causing U601 to start fade-out operation, setting the attenuator to infinite attenuation instantly. 50 mseconds later, pin 5 and pin 6 of U605 become High, and pin 7 becomes Low. The Low signal from pin 7 causes Q607 and Q604 to turn on, starting the oscillator. At this time, pin 10 of U601 is High, so U601 starts fade-in, and attenuation gradually runs from infinite, -66dB, -64dB, … to 0dB. The fade speed control VRV01 controls the oscillator frequency (fosc = 1 / (0.7 x (R617 + VRV01) x C622)). High frequency means fast fade speed.

For fade-out, a Low signal is output from pin 6 of U605, turning on Q608 and Q605. When Q605 is on, pin 10 of U601 becomes Low, causing U601 to begin fade-out. After 34 pulses are input to pin 8 of U605, pin 6 of U605 goes High and sends a REC MUTE signal to U904, placing the deck into record mute mode. 50 mseconds later, a 50 msecond long Low signal is output from pin 5 of U605, returning the electronic attenuator to 0dB instantly (as for power on).

When auto-calibration starts (AUTO CAL SW ON), a 400Hz signal is recorded on the right channel. The deck checks if play output is present.

If play output is not present or is low (level not within present limits), the tape is advanced forward for 2 seconds (F.FWD 2 sec), and the 400Hz signal recording and play output check (Leader Tape Detection Process) is repeated.

If the play level is normal (within present limits), the calibration sequence (Rough Level Set, First Bias Adj., Second Bias Adj., First VCA Level Adj., First EQ Adj., Second VCA Level Adj., Second EQ Adj., Third VCA Level Adj.) is performed. If calibration is complete, the tape is rewound (REW), stopped, and the AUTO LED lights up (END LED: AUTO).

If at any point the play output is not present or the level is not within limits after the F.FWD step, and this happens again (second leader tape detection process fails), auto-calibration is cancelled. The tape is rewound (REW), stopped, and the REF LED lights up (END LED: REF).

(1) The deck enters REC/PLAY mode. The mute out of U605 goes High, switching the analogue switch of U606 to the oscillator side. Pins 3 and 4 of U605 both go Low, setting oscillator frequency to 400 Hz.

(2) For the first 10 ms, the mode select is 111 (reset), discharging U603’s hold condenser, resetting VCA L/R, EQ L/R, and D/A 1.

(3) After U603 reset, data is repetitively sent from U605 to U603 using the leader tape detection data format (Fig. 12-5 in PDF). VCA gain (R ch) is set to maximum. The preset 400 Hz signal is output from U603 and recorded.

(4) L/R select (pin 12 of U602, likely U605) is High (R ch play selected). Play signal charges C640. Comp in (U605) goes Low.

(5) About 1000 ms after starting leader tape detect, U605 reset output (pin 9) goes High for 150 ms, turning on Q625, discharging C640. Comp in changes from Low to High.

(6) Reset out returns to Low. C640 charges again. When U607 pin 2 exceeds pin 3, comp in becomes Low. If leader tape is not recorded (no output), pin 2 potential doesn’t rise, comp in doesn’t go Low.

(7) If, after reset out Low, comp in doesn’t go Low within 400 ms, U605 detects leader tape, fast forwards for 2 seconds, and performs leader tape detection again. If comp in doesn’t become Low on the second try, auto-calibration is cancelled, tape rewinds, unit stops. The 4-bit data and mode selector become the reference data format.

(8) If comp in becomes Low within 400 ms after reset out, it switches to comparative mode to check if recorded level is within acceptable limits.

(9) In comparative mode, D/A 2 is selected on U603, 4-bit data is converted to analogue (DC) signals by D/A 2, and applied to pin 3 of U607 comparator.

(10) VCA, EQ, D/A 1 values in U603 are maintained as during leader tape detection.

(11) 4-bit data (D/A 2) changes from 0000 (max voltage) to 1111 (min voltage).

(12) When 0000 is detected, U607 pin 3 exceeds pin 2, comp in goes High.

(13) As 4-bit data changes, U607 pin 3 potential falls. When it drops below pin 2, comp in goes Low (negative edge). This is detected by U605, determining if recording level is acceptable, moving to level adjustment 5 ms later.

(14) If comp in doesn’t go Low within 200 ms in comparative mode, U605 detects a problem, advances tape FF 2 seconds, performs second leader tape detection.

(15) Reasons for comp in not detecting negative edge: recording level too low (pin 3 doesn’t drop below pin 2 even at 1111) or too high (pin 3 doesn’t exceed pin 2 even at 0000, as VCA R ch gain is max).

(1) Mode select enters reset mode for 10 ms, discharging U603’s hold condenser, resetting data stored at tape detection.

(2) After reset, the 400 Hz signal is recorded as per the level adjust data format (Fig. 12-11 in PDF). For normal recording without auto-calibrate, VCA, EQ, bias values are set by reference data format (Fig. 12-12 in PDF).

(3) A 150 ms long reset out signal is output. Unit enters comparative mode 190 ms after comp in detects the negative edge. This comparative mode is similar to leader tape detection. After comp in becomes Low, there is a 190 ms delay until the recorded signal is picked up by the play head.

(4) When comp in of U605 detects the negative edge in comparative mode, rough level data is determined from the 4-bit data. The 4-bit BCD data is converted to base 10. Example: 0111 (BCD) = 7 (decimal).

(5) A rough data decimal is computed: If base 10 value > 8, rough decimal = 16 – (base 10 number). If 8 > base 10 value, rough decimal = 16 – (base 10 number) (Note: The PDF states “8 + (8 – base 10 number)” which simplifies to 16 – base 10, same as “8 – (base 10 number – 8)”). Example: if 4-bit data is 1001 (‘9’), rough level data becomes 0111 (‘7’).

(6) 3 ms after comp in detects the negative edge in comparative mode, it shifts to bias adjustment.

Bias adjustment takes about 8 seconds (250 ms x 32 steps).

(1) The 4-bit data (D/A 1) is changed one step at a time from 1111 (minimum bias) to 0000 (maximum bias). The recording level is checked in comparative mode each step. The minimum comparative data (maximum recording level) is held. The 4-bit data at this point (bias value) is termed data A.

(2) The 4-bit data (D/A 1) is shifted one step at a time from 0000 (maximum bias) to 1111 (minimum bias), yielding data B through the same process.

(3) The bias data is computed using A and B values: bias data = (A + B) / 2 – 1.

The mode select for bias adjustment uses D/A 1 (BIAS) with R2=1, R1=1, R0=0. The 4-bit data changes from 0000 to 1111 one step at a time. Data from rough level adjustment is used for VCA R and VCA L during this process (Fig. 12-15 in PDF).

VCA level adjustment is performed three times after bias adjustment, in the order: VCA (R,L), EQ(R,L), VCA(R,L), EQ(R,L), VCA(R,L). The method is similar to rough level adjustment, but data formats differ (Fig. 12-17 in PDF).

Data used for VCA Level Adjustment (Fig. 12-17 in PDF):

*1 D/A 1 (BIAS): Fix data received during bias adjust.

*2 VCA R, VCA L:

– First time: Data gained during right channel rough level adjustment is used on both channels.

– Second time: Right and left channel data gained from the first VCA level adjust is used.

– Third time: Right and left channel data gained during the second VCA level adjust is used. Data gained during the third time is fixed.

*3 EQ R, EQ L:

– First time: Both left and right channels use ‘0101’ (weight 5).

– Second time: Right and left channel data gained during the first EQ adjust is used. Data gained during the second time is fixed.

The auto-calibration process ends after the third VCA level adjustment. The tape rewinds to the start, entering REC/PAUSE mode.