Grundig PA 2 Serviceanleitung Seite 44

Adjustment Procedures
Cassette Deck
Test Equipment:
Frequency counter, AF voltmeter, AF generator, distortion analyzer, wow and flutter meter, Cr test cassette 448 A, torque test cassette 456.
1. Tape speed Frequency counter to Pin 1 resp. 5 of P106. With adjustment control R482 (Logic board) set the
Insert test cassette 448 A. frequency to 3150 Hz+0.1% .
Play back 3150Hz.
On START, the torque should be 30 to 60 x 104 Nm
= 40 g-cm.
Load the torque test cassette 456.
Function: Start.
2. Take-up torque on
Start
Wow and flutter meter to Pin 1 resp. 5 of P106. Deviation < 0.2% (IEC unwtd).
Load test cassette 448 A. Playback measuring time = 30 seconds.
Play back 3150Hz.
3. Wow and flutter
Tape direction: "Normal"
With the head adjustment screw [E] set the left or right
channel to maximum level.
Connect AF voltmeter to Pin 5 of P106 (left channel) or to
Pin 1 of P106 (right channel).
Load test cassette 448 A, play back 10kHz.
4. Head gap angle
(Azimuth)
Then connect the left channel in parallel with the right
channel (Pin 1 and 5 of P106). By minimum re-adjustment
of the head adjustment screw [E] set the output level to
maximum.
Turn around the test cassette.
Tape direction: "Reverse"
Adjustment with head adjustment screw/[F] is the same as
in the "Normal" tape direction.
Tape run
"Reverse"
<+——_
Tape run
"Normal"
_—
Set the playback level with the adjustment controls R135
(left) or R136 (right) to 308mV + 0.5dB.
AF voltmeter to test point © D1 (left channel) or O D2
(right channel).
Insert test cassette 448 A.
Play back 315Hz (250 nWb/m).
Dolby off.
5. Playback level
Reference tape
scanning
(Dolby level)
When using a test cassette with 200 nWb/m set the
playback level to 245mV + 0.5dB.
Frequency counter to test point O L1 (R263). The oscillator frequency should be 85kHz + 10kHz.
Insert a recordable cassette, Cr tape (IEC Il). Adjust with L111.
Function: Record-Start.
6. Erase frequency
Erase current: 150 mA + 10% measuredat R263
= 150mV + 10%.
AF voltmeter to test point © L1 (in parallel with R263).
Insert a recordable cassette with Cr tape (IEC Il).
Function: Record-Start.
7. Erase current
Adjust for minimum RF with F111 at test point O TPS (left
channel) and F112 at test point O TP4 (tight channel).
Connectthe AF voitmeter to test point © TP3 (left channel)
or to test point O TP4 (right channel) on the audio circuit
board.
Insert a recordable cassette with Cr tape (IEC Il).
Function: Record-Start.
8. Record blocking
circuits
(bias filter)
Set AF Generator output during Record so that at 315Hz
the voltage measured at the test points > ID1 and © D2
is U, = 245mV (= OdB).
At 19kHz = U, <47.7mV (< —30dB).
9. MPX-filter
(19kHz stereo pilot
tone)
Connect the AF generator (f, = 315Hz, f, = 19kHz, ca.
400mV) to the Pin 2 and 4 of P106.
Connect the AF voltmeter to the
test points © D1 (left channel)
or © D2 {right channel).
Function: Record-Start, ALC OFF, Dolby off.
Adjust with F101 (left channel) or F 102 jig ht channel).
AF voltmeter to test point © D1 (left channel) or test point
© D2 (right channel).
Insert test cassette 448 A.
Play back the 250Hz/ 12.5 kHz frequency recording on the
tape.
If the levels between U f, (250Hz) and U,f, (4 2.5kHz) at O
D1 and © D2 differ by more than + 1.5dB cut the bridges
B1 (C101), B2 (C103) left channel, or the bridges B3
(C102), B4 (C104) right channel.
10. Frequency
response on
Playback
V,f, (12.5kHz)
Dolby off = +1+0.5dB
V,f, (250Hz)
2-5 GRAUNDIG Service