Nak Tape Deck Calibration Procedure

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Last updated Februrary 10th, 2005

This is part 2 of my two part Nakamichi tape deck calibration procedure web page.
Part 1 can be found here

Calibration procedure from the Nakamichi 660 ZX service manual

6 ELECTRICAL ADJUSTMENTS AND MEASUREMENTS

6.1 Adjustment and Measurement Instructions
Note: Electrical adjustments should be performed after mechanical adjustment is completed.

STEP ITEM SIGNAL SOURCE OUTPUT CONNECTION MODE ADJUSTMENT REMARKS

1 Tape Speed 3 kHz Speed and Wow/Flutter
Tape (DA09006A) Frequency Counter to OUTPUT
Jacks Playback Speed Cal. P.C.B.
VR407 Adjust VR407 to obtain 3 kHz +/- 0.5%.

2 Tone Calibration Test Tone
400 Hz VTVM to TP101 (A)
TP201 (B) on the Main P.C.B. Record, Pause
Auto. A/Tone SW - CAL Switch P.C.B.
VR301 1. Set the Auto. A/Tone Switch to CAL.
     Turn output level control fully clockwise (maximum position).
2. Darn I forgot step 2.

3 Meter Level 400 Hz (0 dB /-10 dB/ -20dB)
to INPUT Jacks VTVM to TP101(A), TP201(B)
on the Main P.C.B. Record, Pause
Auto. A/Tone SW - CAL/OFF Main P.C.B.
VR102, VR202 1. Adjust VR102 (VR202) to obtain 0 dB on the level meters at 100 mV
     level on the VTVM.
2. Decrease input level by 10 dB/20 dB then short or open R149 (R249)
     to obtain minimum deviation for -10 dB/-20 dB on the level meters.
     (Perform at -10 dB and -20 dB.)
3. Again increase input level so that output will become 100 mV, then readjust
     VR102 (VR202) to obtain 0 dB on the level meters.

4 MPX Filter 19 kHz +/- 100 Hz to
INPUT Jacks VTVM to OUTPUT Jacks Auto. A/Tone SW - OFF
Dolby NR SW - OUT/MPX Main P.C.B.
L102, L202 1. Turn output level control fully clockwise (maximum position).
2. Adjust input lelve control to obtain 1 V on the VTVM.
3. Set the Dolby NR Switch to MPX position, then adjust L102 (L202) to
     obtain minimum reading on the VTVM (minimum reading will be less than
     -30 dB).

5 Playback Head Track
Alignment 1 kHz Track Alignment Tape
(DA09007A) VTVM to OUTPUT Jacks Playback
Auto A./Tone SW - OFF
Eq. SW - 70 us
Dolby NR SW - OUT Playback Head
Height Adj. Screw Adjust the Playback Head Height Adj. Screw to obtain minimum reading of
both L and R channels on the VTVM. See "Playback Head Height Adjustment
and Azimuth Alignment" in item 4.8.

6 Playback Head Azimuth
Alignment 15 kHz Azimuth Tape
(DA09004A) VTVM to OUTPUT Jacks Same as above Playback Head
Azimuth Alignment
Screw Adjust the Playback Head Azimuth Alignment Screw to obtain maximum
reading on both L and R channels on the VTVM. See "Playback Head Height
Adjustment and Azimuth Alignment" in item 4.8.
Note: Repeat steps 5 and 6 one or two times to obtain optimum performance.

7 Playback Level 400 Hz Level Tape
(DA09005A) VTVM to TP101, TP201
on the Main P.C.B. Same as above Main P.C.B.
VR101, VR201 Adjust VR101(VR201) to obtain 100 mV on the VTVM or 0dB on the level meters.

8 Playback Frequency
Response Adjustment 400 Hz Level Tape
(DA09005A)
10 kHz PB Frequency
Response Tape (DA09003A)
15 kHz PB Frequency
Response Tape (DA09002A)
20 kHz PB Frequency
Response Tape (DA09001A) VTVM to OUTPUT Jacks Playback
Auto A./Tone SW - OFF
Eq. SW - 70 us
Dolby NR SW - OUT Main P.C.B.
R132, R232
R133, R233 1. Load the 400 Hz level tape and play it back. Adjust the output level
     control to a certain level (for example 0 dB).
2. Load 10 kHz, 15 kHz and 20 kHz PB frequency response tapes and
     adjust the playback head azimuth to give maximum levels on the VTVM
     with each tape.
     Short R132 (R232) or R133 (R233) to obtain the following levels against
     400 Hz level tape. Refer to Fig. 6.5.
        10 kHz: -20 dB -1 dB to +2 dB
        15 kHz: -20 dB -1 dB to +3 dB
        20 kHz: -20 dB -1 dB to +4 dB
3. Conduct step 6 "Playback Head Azimuth Alignment".
4. If above is not sufficient, refer to "Playback Frequency Response
    Adjustment" in item 6.2.

9 Bias Oscillation
Frequency
and Erase Current Connect an additional 0.1 Ohms
resistor in series to the
Erase Head VTVM and Frequency Counter
across the additional 0.1 Ohm
resistor Record, Pause
Tape SW - ZX
Eq. SW - 70 us
Dolby NR SW - OUT Main P.C.B.
T301
R304, R305 1. Adjust T301 to obtain 105 kHz on the frequency counter.
2. Check the erase current by the vtvm. Erase current will be in a range of
     310 mA to 400 mA (typically approx. 350 mA).
     If erase current is not sufficient, increase it by shorting R304 or R305.
3. After completion of the erase current adjustment, recheck the bias
     oscillation frequency.

10 Record Amplifier
Equalizer 23 kHz (-20 dB) to INPUT
Jacks VTVM to CN2-1, CN2-3
on the Main P.C.B. Record, Pause
Auto A./Tone SW - OFF
Tape SW - ZX
Eq. SW - 70 us
Dolby NR SW - OUT Main P.C.B.
L104, L204 1. Remove the bias-cut-jumper from the dip side of the Main P.C.B.
2. Adjust L104 (L204) to obtain peak reading at 23 kHz on the VTVM.
3. Re-solder the bias-cut-jumper.

11 Bias Trap
(Record Amp.) Remove input signals Same as above Same as above Main P.C.B.
L105, L205 Adjust L105 (L205) to obtain maximum reading on the VTVM

12 Bias Trap
(Playback Amp.) Remove input signals VTVM to Playback Eq. Amp.
Output;
Terminals 29, 30 on the
Main P.C.B. or
Terminals 1, 2 on the
Auto Azimuth P.C.B. Same as above Main P.C.B.
L103, L203 Adjust L103 (L203) to obtain minimum reading on the VTVM

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STEP	ITEM	SIGNAL SOURCE	OUTPUT CONNECTION	MODE	ADJUSTMENT	REMARKS
1	Tape Speed	3 kHz Speed and Wow/Flutter Tape (DA09006A)	Frequency Counter to OUTPUT Jacks	Playback	Speed Cal. P.C.B. VR407	Adjust VR407 to obtain 3 kHz +/- 0.5%.
2	Tone Calibration	Test Tone 400 Hz	VTVM to TP101 (A) TP201 (B) on the Main P.C.B.	Record, Pause Auto. A/Tone SW - CAL	Switch P.C.B. VR301	1. Set the Auto. A/Tone Switch to CAL. Turn output level control fully clockwise (maximum position). 2. Darn I forgot step 2.
3	Meter Level	400 Hz (0 dB /-10 dB/ -20dB) to INPUT Jacks	VTVM to TP101(A), TP201(B) on the Main P.C.B.	Record, Pause Auto. A/Tone SW - CAL/OFF	Main P.C.B. VR102, VR202	1. Adjust VR102 (VR202) to obtain 0 dB on the level meters at 100 mV level on the VTVM. 2. Decrease input level by 10 dB/20 dB then short or open R149 (R249) to obtain minimum deviation for -10 dB/-20 dB on the level meters. (Perform at -10 dB and -20 dB.) 3. Again increase input level so that output will become 100 mV, then readjust VR102 (VR202) to obtain 0 dB on the level meters.
4	MPX Filter	19 kHz +/- 100 Hz to INPUT Jacks	VTVM to OUTPUT Jacks	Auto. A/Tone SW - OFF Dolby NR SW - OUT/MPX	Main P.C.B. L102, L202	1. Turn output level control fully clockwise (maximum position). 2. Adjust input lelve control to obtain 1 V on the VTVM. 3. Set the Dolby NR Switch to MPX position, then adjust L102 (L202) to obtain minimum reading on the VTVM (minimum reading will be less than -30 dB).
5	Playback Head Track Alignment	1 kHz Track Alignment Tape (DA09007A)	VTVM to OUTPUT Jacks	Playback Auto A./Tone SW - OFF Eq. SW - 70 us Dolby NR SW - OUT	Playback Head Height Adj. Screw	Adjust the Playback Head Height Adj. Screw to obtain minimum reading of both L and R channels on the VTVM. See "Playback Head Height Adjustment and Azimuth Alignment" in item 4.8.
6	Playback Head Azimuth Alignment	15 kHz Azimuth Tape (DA09004A)	VTVM to OUTPUT Jacks	Same as above	Playback Head Azimuth Alignment Screw	Adjust the Playback Head Azimuth Alignment Screw to obtain maximum reading on both L and R channels on the VTVM. See "Playback Head Height Adjustment and Azimuth Alignment" in item 4.8. Note: Repeat steps 5 and 6 one or two times to obtain optimum performance.
7	Playback Level	400 Hz Level Tape (DA09005A)	VTVM to TP101, TP201 on the Main P.C.B.	Same as above	Main P.C.B. VR101, VR201	Adjust VR101(VR201) to obtain 100 mV on the VTVM or 0dB on the level meters.
8	Playback Frequency Response Adjustment	400 Hz Level Tape (DA09005A) 10 kHz PB Frequency Response Tape (DA09003A) 15 kHz PB Frequency Response Tape (DA09002A) 20 kHz PB Frequency Response Tape (DA09001A)	VTVM to OUTPUT Jacks	Playback Auto A./Tone SW - OFF Eq. SW - 70 us Dolby NR SW - OUT	Main P.C.B. R132, R232 R133, R233	1. Load the 400 Hz level tape and play it back. Adjust the output level control to a certain level (for example 0 dB). 2. Load 10 kHz, 15 kHz and 20 kHz PB frequency response tapes and adjust the playback head azimuth to give maximum levels on the VTVM with each tape. Short R132 (R232) or R133 (R233) to obtain the following levels against 400 Hz level tape. Refer to Fig. 6.5. 10 kHz: -20 dB -1 dB to +2 dB 15 kHz: -20 dB -1 dB to +3 dB 20 kHz: -20 dB -1 dB to +4 dB 3. Conduct step 6 "Playback Head Azimuth Alignment". 4. If above is not sufficient, refer to "Playback Frequency Response Adjustment" in item 6.2.
9	Bias Oscillation Frequency and Erase Current	Connect an additional 0.1 Ohms resistor in series to the Erase Head	VTVM and Frequency Counter across the additional 0.1 Ohm resistor	Record, Pause Tape SW - ZX Eq. SW - 70 us Dolby NR SW - OUT	Main P.C.B. T301 R304, R305	1. Adjust T301 to obtain 105 kHz on the frequency counter. 2. Check the erase current by the vtvm. Erase current will be in a range of 310 mA to 400 mA (typically approx. 350 mA). If erase current is not sufficient, increase it by shorting R304 or R305. 3. After completion of the erase current adjustment, recheck the bias oscillation frequency.
10	Record Amplifier Equalizer	23 kHz (-20 dB) to INPUT Jacks	VTVM to CN2-1, CN2-3 on the Main P.C.B.	Record, Pause Auto A./Tone SW - OFF Tape SW - ZX Eq. SW - 70 us Dolby NR SW - OUT	Main P.C.B. L104, L204	1. Remove the bias-cut-jumper from the dip side of the Main P.C.B. 2. Adjust L104 (L204) to obtain peak reading at 23 kHz on the VTVM. 3. Re-solder the bias-cut-jumper.
11	Bias Trap (Record Amp.)	Remove input signals	Same as above	Same as above	Main P.C.B. L105, L205	Adjust L105 (L205) to obtain maximum reading on the VTVM
12	Bias Trap (Playback Amp.)	Remove input signals	VTVM to Playback Eq. Amp. Output; Terminals 29, 30 on the Main P.C.B. or Terminals 1, 2 on the Auto Azimuth P.C.B.	Same as above	Main P.C.B. L103, L203	Adjust L103 (L203) to obtain minimum reading on the VTVM