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Philips VR 948, S-VHS playback problem

Everithing works fine except the S-VHS playback image which is visible but distorted.
I have a Grundig GV 470 wich is similar and working fine, I took the S-VHS board from it and changed the Philips one with no result.
The unit recognizes the S-VHS cassette when it is inside as S-VHS, but when I play it on the display stays only VHS, it does not recognize the recording as S-VHS. The fault may be the S-VHS recognizing system, the vcr plays the S-VHS recording as a VHS recording and that produces the image distortion when playback.
The fault is probably in the main board, it may be a bad capacitor or ... .
Maybe someone can help.
Thank you!

Comments
petyka2
petyka2 picture

"Playback
On playback, the controlled FM signal from the tape is passed through
the head amplifier, the Family Board and plug contact 1530-(4) to the
emitter follower T7545. Subsequently, the signal path divides for
S-VHS and VHS playback.

– VHS Playback
After the emitter follower T7545, the FM signal is routed via a "FMPeaking"
circuit for VHS (C2555 / F1055) to an amplifier (T7565), at the
emitter of which a 9MHz trap (L5565 / C2565) is located. After delay
time correction - all-pass (F1060 / C2575 / C2577 / L5577) - and the
transistor T7585 which is turned on by the switching voltage U VHS
the signal is subjected to a 627kHz trap (C2587 / L5587). Subsequently,
it is supplied via the emitter follower T7588 to Pin 30 of IC7840.
In This IC, the FM signal is taken on one path via a lowpass and on
another path via a highpass and the limiting stage which follows to the
MIX circuit. Having passed through another limiting stage, the signal
is converted by the FM demodulator to a CVS signal. The de-emphasis
circuit (R3705 / C2705 / R3703) is operated via Pin 36. In IC7840, the
signal is also fed through a 2.5dB amplifier and arrives via Pin 4 and
a lowpass filter F1080 at IC7840-(14). In this IC, the CVS signal is taken
via a selection switch (S-VHS/VHS), the 5.3dB amplifier and the NLDE
stage to IC7840-(6). After the capacitor C2901, the signal is fed back
to Pin 8 of IC7840. Between the Pins 8 and 43 of IC7840, the essential
circuits the CVS signal has to pass through are stages for drop-out
compensation, noise reduction, frequency lifting "Picture Control"
(APT CONT), V-pulse insertion (A.L V/H) and for level control. Control
of high frequency lift is effected via the shift register 6,
IC7590-(11)…-(13), the D/A-converter (R3820…R3827) which follows
and Pin 40 of IC7840. Subsequently, the CVS signal is passed
from IC7840-(43) through plug contact 1530-(27) to the IN/OUT circuit
stage. Form this stage, it is supplied to the S-VHS socket and to the
EURO-AV sockets.

– S-VHS Playback
After the emitter follower T7545, the FM signal is routed via a "FMPeaking"
circuit for S-VHS (C2518 / F1050) to an amplifier (T7520) at
the emitter of which a 12.5MHz trap (L5520 / C2520) is located. After
delay time correction - allpass (F1052…C2540) - and the transistor
T7542 which is turned on by the switching voltage U S-VHS the signal
is subjected to a 627kHz trap (C2587 / L5587) and the emitter follower
T7588. Subsequently, it is supplied via a highpass filter (C2743 /
R3745) to IC7840-(26) and via a lowpass filter (R3730 / C2732) to
IC7840-(29). In this IC, the FM signal from Pin 29 is directly applied to
the MIX stage, the signal from Pin 26 arrives there via the limiting stage.
Having passed through another limiting stage, the signal is converted
by the FM demodulator to a CVS signal. The de-emphasis circuit
(R3705 / C2705 / R3703) is operated via Pin 36. Moreover, in IC7840
the signal is fed through a 2.5dB amplifier and arrives via Pin 4 and one
3MHz lowpass filter (F1080) and one 5MHz lowpass filter (F1090)
each at IC7930-(8), -(10). Dependent on the picture resolution (3MHz /
5MHz) one of the CVS signals is switched to Pin 6 and passed on to
IC7840-(16). Control of IC7930 is effected by the switching voltage
U COMP from shift register 5, IC7610-(13). In IC7840, the CVS signal
is taken via a selection switch (S-VHS/VHS), the 5.3dB amplifier and
the NLDE stage to IC7840-(6). After the S-VHS sub-emphasis (IC7898,
Pins 14 / 7) the signal is fed back into IC7840 at Pin 7. Between the
Pins 8 and 43 of IC7840, the essential circuits the CVS signal has to
pass through are stages for drop-out compensation, noise reduction,
high frequency lifting "Picture Control" (APT CONT), V-pulse insertion
(A.L V/H) and for level control. Control of high frequency lift is effected
via the shift register 6, IC7590-(11)…-(13), the D/A-converter
(R3820…R3827) which follows and Pin 40 of IC7840. Subsequently,
the CVS signal is passed from IC7840-(43) through plug contact
1530-(27) to the IN/OUT circuit stage. From this stage, it is supplied to
the modulator, the S-VHS socket and to the EURO-AV sockets."

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