The AKAI 1720 model reel to reel tape recorder described in this Manual is quite an old unit - circa late 1960's. As a consequence, the description of the mechanical details - and adjustments thereof - is quite critical. The manual does this quite well. The schematics are also well presented and have detailed PCB overlays. Probably the only negative is that some half-tone detail has been lost from the original manual as it has been scanned in simple B&W.
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Text excerpt from page 12 (click to view)
20AR23
� SERVICE ADJUSTMENT
RF AGC Adjustment
1. Receive a good local channel. 2. Enter the service mode signal category and select the service adjustment "AGC". 3. Set the data value to point where no noise or beat appears. 4. Select another channel to confirm that no noise or beat appears.
CHROMA ADJUSTMENT
No. Adjusting point 1 SUB-TINT (I2C BUS CONTROL) Adjusting procedure/conditions 1. Receive the "Colour Bar" signal through AV in. 2. Connect the oscilloscope to TP853 (Pin (5) of P882) BLUE-OUT. » Range : 100mV/div. (AC)(Use Probe 10:1) » Sweep time : 10 µsec/div. 3. Call the "SUB-TINT" mode in service mode. Adjust the "SUB-TINT" bus data to obtain the waveform shown as Fig 1. 4. "SUB-TINT" bus data decrease 4 steps to get final waveform. (Fig 2.) 5. Clear the SERVICE mode. Waveform and others
WAVEFORM 1
SAME LEVEL
FINAL WAVEFORM
W Y CY G MG R B
Fig 1
Fig 2
HORIZONTAL AND VERTICAL DEFLECTION LOOP ADJUSTMENT
No. Adjusting point 1 V-SLOPE(I2C BUS CONTROL) Adjusting procedure/conditions 1. Receive Monoscope Pattern Signal. 2. Call the "V-LIN" mode. 3. Increase or decrease "V-LIN" by Volume key till the horizontal line in the center of monoscope is just at the position where the blanking starts. Waveform and others
2
V-CENTER (I2C 1. Call the "V-CENT" mode. BUS CONTROL) 2. Increase or decrease "V-CENT" by Volume key till the picture is centered. 1. Call the "V-AMP" mode. 2. Increase or decrease "V - AMP" by Volume key to set overscan of 10.0% typical. Adjustment Spec 10.0% range ±1%.
3
V - AMP (I2C BUS CONTROL)
4
S-CORRECTION (I2C BUS CONTROL) H - CENTER
FIXED DATA, NO NEED TO ADJUST.
5 1. Call the "H-CENT" mode. 2. Increase or decrease "H-CENT" by Volume key to center the picture horizontal. 1. Receive the "Monoscope Pattern" signal. 2. Press R/C to set Picture NORMAL condition. 3. Adjust the focus control to get the best focus.
