This tutorial covers the restoration of older generation RQ-S series with pad lifter. Models affected are manufactured between 1989 and August 1992: RQ-S1, RQ-S1D, RQ-S3, RQ-S5, RQ-S5V, RQ-S7F, RQ-S7R, RQ-S8, RQ-S4, RQ-S6, RQ-S11, RQ-S33, RQ-S55, RQ-S88, RQ-S55V, RQ-S45, RQ-S65, RQ-S77F, RQ-S15, RQ-S35, RQ-S35V, RQ-S75F, RQ-S60, RQ-S60V, RQ-S80, RQ-S20, RQ-S40, RQ-S40V There are 3 main problems on this mechanism: 1. Bent pinch roller bracket holding pins, which will make rollers sit at an angle. Note both rollers are affected, despite some people say only the FWD one needs repair. 2. Bent pad lifter. This can be straightened and reinforced or disabled. Since this pad lifter does have a purpose (to reduce tape/head friction during FF/REW), my recommendation is to repair despite disabling/removing it will seem the simpler solution. 3. Bent carriage. This is harder to adress and can cause head tilt problems. Not adressed at the moment in this tutorial, to be updated later. NOTE 1: It's very important to bend the 2 roller springs so the force is lower than in the original setup and also equal on both sides. Failing to do this will render: - the pad lifter to bend again in time; - tape speed and W&F be different FWD/REV; With a proper repair, the speed difference should be within 10-20Hz. If it's more than that, either one roller is putting more pressure on the capstan or one capstan bearing is worn, case in which mech needs to be replaced. NOTE 2: FWD capstan bearing tends to wear prematurely if unit is used without adressing this problem, since the FWD roller spring is much stiffer from factory. This is another reason why capstan bearing should be cleaned and lubricated. NOTE 3: It's very important to never leave cassettes in the unit when it's not in operation. The pad lifter sits in the raised position when mech is in stop position, meaning it will bend back in time if a cassette is left in the unit. NOTE 4: Recommend NOT replacing the pinch rollers on these units, unless it's absolutely necessary. That's because new rubber tires that are available will usually make the assembly eccentric. NOTE 5: Most of these units use a slim 220uF electrolytic capacitor, which sometimes can go bad causing increased motor hum. If you have the means to test it, do so. Otherwise it's a good idea to replace it. SMD tantalum is the way to go for the replacement.
DISASSEMBLY To be noted the case disassembly and PCB removal is for illustriation purposes only as this will vary from model to model. In pictures attached there is an RQ-S45. Case is usually held in by 4 screws, but some units have another extra on the back. On PCB, keep in mind the main things that need to be desoldered are: - motor (4 pins on all mechanisms); - solenoid; - negative battery terminal; - logic control buttons and tape in/EQ switches; - head flex (this needs to be desoldered for easy work on the carriage); Door is held the same on all units, having one screw and latch needing to be removed. On radio units, the door and PCB need to be removed together if you don't want to desolder the flex cables. Carriage is held the same on all units, you only need to remove one hinge for removal as shown.
CLEANING AND LUBRICATION OF MECHANISM Before adressing the carriage problems, first thing to do is clean all the pulleys from old belt residue and oil the main rotating parts of the mechanism: motor, capstan bearings, idler pulley, gear drive pulley. NOTE 1: Unlike most other walkmans, this Panasonic (and others Panasonic RQ-SX, RQ-JA) uses a full washer which needs to be dragged up the capstan in order to remove it. There are a total of 3 washers: a white one that holds the capstan/flywheel assembly, a black one underneath and another black one on the opposite side of the bearing. NOTE 2: Pulleys' grooves need to be cleaned thoroughly before re-installing the capstan/flywheel assemblies. There are 2 methods of doing this: - IPA + cotton swab for the soft residue and sandpaper for the hard part; - gasket cleaner (Loctite SF7200) + cottom swab; if gasket cleaner is to be used, be careful to clean everything with IPA after, as it will dissolve rubber; NOTE 3: Depending on serial number and model, just one flywheel has a retainer, some have retainers on both, while some none. This retainers aren't critical since the capstan is held in place by the washer. So process goes as this: - remove one capstan/flywheel assy, clean the grooves, clean the bushing and caspstan shaft. - add oil on the bottom part of the shaft and/or inside the bushing and re-install the assembly; - clean the extra oil with a piece of paper towel; - put the washers back; - clean the capstan with IPA; Note it will need further cleaning after operation; Motor lubrication is not shown, but process is similar to SONY ones shown here: https://stereo2go.com/forums/thread...-type-motor-in-sony-walkmans.7943/#post-59754 What's to be noted in this case is the coils PCB tends to be stuck to the brass posts. For this, remove the motor from chassis and heat the posts with soldering iron for easy removal.
CARRIAGE REPAIR This is the most tricky part of the repair and all steps must be followed exactly for best results. 1. Remove both pinch rollers and pad lifter from the carriage. 2. With a small pair of pliers bend the FWD pin until it becomes straight by eye. Note the pin will have significant play now. Don't worry, this is normal. 3. Install the FWD roller back, but WITHOUT the spring; 4. Engage the mechanism into FWD; 5. Install the carriage back and test alignment visually; 6. Repeat steps 2-3 until you get perfect alignment; 7. Glue the top of the pin while making sure the alignment remains perfect. Keep the roller pushed with your finger if needed until the glue starts to cure; 8. Double check the alignment. If good glue the bottom part of the pin as shown in pictures. 9. Let the glue cure and check the roller can rotate freely on the pin. If not, carefully remove the extra glue with a pair of tweezers. 10. Engaged REV on the mechanism as shown in pictures. Remove the cassette holding part on the opposite side for good visual path to the roller/capstan. Note the pad lifter and roller spring do NOT get installed at this step. 11. Repeat same steps as FWD pin until you get a perfect alignment. Note this side can't accomodate as much glue due to the pad lifter arm. 12. Bend the pad lifter so it become flush with the head again. Note both the holder part and the arm need to be bent. 13. Install the spring and roller and make sure the pad lifter moves back and forth easily, returning just by the force of the spring. 14. If everything is good, add glue on the 2 spots shown in picture to reinforce the pad lifter. 15. Bend the roller springs back so you reduce the roller tension. 16. Double-check by hand and re-adjust so force is similar on both sides. 17. Put the mechanism back into stop position (lever in the middle). 18. Re-install the carriage.
