SWF-3500 Super Woofer

The Super Woofer is a neat black ghettoblaster in a beautiful black case with a lot of square and some diagonal edges, manufactured in 1988 according to the chip markings. One day, I found the Super Woofer on my staircase, asked the neighbors where it came from, and got told that it's trash and that I can have it. It wasn't trash, worked perfectly without even eating my tapes. People who grew up with silver zeppelin shaped CD players may not like it. Anyways about everybody who grew up in the eighties and sees it says: Wow, that's cool.

Since I didn't find a schematic or service manual, here're the results of my own research, with some potentially useful notes, pin-outs, and testpoints...

- Nocash



Rubber-Wheel and Drive Belts
The first thing I noticed when I got my SWF was that one the drives did have the small rubber wheel missing; anyways, I found it inside of the case, and justed needed to snap it back in.
As in all tape drives, drive belts tend to get worn-out after 10 years or so, causing the drive to spin slowly, or even to eat the tape. In my SWF, the belts are still okay (maybe they were already replaced some years ago), anyways, in case of problems it may be a good idea to buy some new belts.

Next, the volume and equalizer regulators produced ugly scratch noise when touching them, which I got fixed with some evil contact spray. It may be also good to put some spray on the various switches; When I tried to measure the Tuner/AUX/Tape contacts, I found only one 0 ohm contact, on the other contacts I measured absurde values like 20 kilo-ohms (although the switches still worked somehow). After some days the Deck-B output volume became extremly silent and muffled, after putting some spray on the Play/Record switch (S3) it seems to be working again (altough the problem may have been caused by something else, that days the room-temperature dropped to 12'C, so maybe the super woofer just got a cold).

Plastic Clips
There are some elastic plastic clips that seem to tend to break: Two rather unimportant clips that stabilize the big carrying handle in its vertical position. And, four rather important ones: Inside of each drive door, there seem to have been two plastic clips that pushed-down the cassettes, but all of them seem to have been broken long ago. In result, inserting tapes feels a bit as if the cassettes are a good bit too small for the huge drive opening. And, during operation, the cassettes are held down only by gravity... which is more at less working okay, but, if gravity doesn't do it's job, then the tape isn't wound-up properly, and the drive tends to eat the tape (eg. when turning the drive top-down, or when the cassette isn't well inserted). So it may be recommeded to remove the drive doors, and install some new plastic or metal clips inside of them.

                                   <------------ Insert Cas This Way
                 /          ---___              X--- Screws
   ###          /                 ------_X_     #### Drive Door Body
     ###       |    |####################|##    --__ Elastic Foil
      ###      |   X|--##################|##
       ##       \__/ #######################

                                   <------------ Insert Cas This Way
                        /   ---___              --__ Original Clip
   ###                            |             #### Drive Door Body
     ###             #######################
      ###            #######################
       ##            #######################

White Noise Problem...?
In my SWF, I am having some white noise on Deck-B, it's mainly audible when the tape is stopped (or even when no tape is inserted) (during playback, the music is louder than the noise, so it isn't too annoying although the noise is still there).
The noise disappers when Deck-B is deactivated (eg. when pressing Play/FF/Rew on Deck-A). Aside from the noise problem, my Deck-B produces slightly deeper sounds as than playing the same tape in Deck-A (of which, Deck-A tendencially sounds better).
I am not sure if there's something broken in my SWF, or if that problem appears to all SWFs - would be nice to know if it appears in other super woofers, too!


AC Power Switch/Power Light
The original "power" switch in the SWF merely switches the 15V off (or the 12V when using batteries), but keeps the transformator powered at 230V, so it's permanently wasting a few watts of energy. To the worst, the SWF doesn't have a Power LED, so it's easy to forget to switch off even the DC part, and so, to waste a good bunch of watts.
To fix that problem, I've installed a nice red 230V switch with built-in power lamp in the rear-plate.

Less messy Wires
If you want to do any repairs, you'll probably curse the nasty wires. With some efforts, the interiors can be made accessible in a more comfortable way:
- add a 6pin plug/socket in the wires that go to the rear-plate
- add a 8pin plug/socket in the wires that go to the front-plate
- replace W10,W11,W12 by longer wires
- add 2 contacts for injecting 12V and GND on the mainboard
For testing, it's best to remove the front-plate and rear-plate completely; the 12V/GND supply voltage can be injected from another external power-supply, and audio-output can be tested via headphone socket, so the transformator and speakers aren't needed at all.

  Tape Drives

The dual-tape deck is pretty straight ahead, without any ferro/chrome/metal detectors (there's only a record-lock detector), without auto-reverse, and any without dolby noise reduction, but with Hi-speed dubbing. And, most important, it's still having real mechanical Play/Stop switches, so it's just fun to be able to actually press the buttons.

Motor and Drive Belts
The dual-deck is having only a single motor shared for both drives, the advantage is that it's cheap, and eventually ensuring that both drives are spinning at exactly the same speed when copying one tape to another.

                                    |       |
                                    | Motor |              |
                      ____Brush____ |_______| ____Brush____|
      Deck-A Wheel   '     |||          |         \___/
     ==============--------------------===         |||          Deck-B Wheel
           ||       Belt to Deck-A     ===---------------------==============
           ||                           |      Belt to Deck-B        ||
When replacing the belts, they should be arranged as shown above, ie. Belt-A should be closer to the motor body, and Belt-B closer to the end of the axis.

Play/Fast Forward/Rewind
Each deck has a switch that senses when PLAY/FF/REW is pressed. When the switch on Deck-A is closed, then the output from Deck-B is muted. A rather strange result is that one cannot rewind a tape in Deck-A while playing another tape in Deck-B (however, it works vice-versa, rewind in Deck-B, and play in Deck-A).

  Disassembling the Case

The case consists of three components: The rear-plate, top-panel, and front.

Can be removed by loosening 6 long and 4 short screws. The rear-plate contains the AC socket, the transformator, the battery box, and the external antennae. The AC socket also contains a built-in switch that activates the battery supply when the AC cable is disconnected.

The top panel isn't attached by any screws nor snap-ins. Once when the rear-plate is removed, the top panel can be simply removed by pulling it to towards the rear side; there's some soft/sticky glue (no hardenend glue) at the front-end of the top panel, but that can be loosened quite easily. The top panel contains the main electronics: The tape drivers, the 3 circuit boards; cassette, tuner, equalizer, etc.

Consists of the front plate (and side/bottom walls), and contains the speakers: One set of large/tiny speakers (on each side, left and right), one single bass speaker (in the center), and a microphone (as part of the right speaker set, ie. underneath of the equalizers).

The channel selector unit consists of a large black plastic block with two large black wheels, located between the Tuner board and Equalizer board. Underneath of the tuner board is a white lever with notches at both ends of the lever, which rest on plastic edges inside of the horizontally arranged wheel. When removing and re-installing the tuner board: First remove BOTH the tuner board and channel selector mechanics. Then fit the lever on the wheel, and attach the tuner board to the mechanics with two screws. Then, attach the channel mechanics on the equalizer board with another two screws, which can be reached through holes in the tuner board.

Drive Doors
Can be removed easily. Push the two vertical clips inwards that stop the opened door after reaching the 45 degree positions. The door can be now lifted up to a 90 degree position, and there it can be removed.


The three circuit boards are:

Mainboard (CR-X100-02)
Contains the AC-to-DC voltage converter, the audio amplifiers, the tape drive electronics, and the AUX cinch sockets.

Tuner-board (CR-X100-01)
Contains the tuner, and most important: The Tape/Tuner/AUX select switch.

Equalizer-board (CR-X100-03)
Contains the equalizer, volume regulator, FMS-Switch and FMS-Led, bass-boost switch, and the infamous power switch (which is barely a energy wasting "standby" switch, since it doesn't disconnect the transformator). There's also a tiny daughterboard with the headphone socket and two resistors on it.


The circuit boards (and speakers and rear-plate) are interconnected with a mess of about 50 single wires (rather than using a handful of flat-cables), to the worst, the wires are soldered directly from one board to another (without any plugs/sockets).

Summary of all Wires
  W1  white   3pin                    (tuner to equalizer) (CURR-INPUT for OUTPUT)
  W2  black   3pin      (near supply) (mainboard to tuner) (TAPE for OUTPUT)
  W3  gray    3pin      (near cinch)  (mainboard to tuner) (AUX-IN for OUTPUT)
  W4  black   3pin      (near supply) (tuner to mainboard) (CURR-INPUT for RECORD)
  W5  brown   3pin      (near motor)  (mainboard to tuner) (TAPE for RECORD)
  W6  brown   3pin      (near cinch)  (mainboard to tuner) (AUX-IN for RECORD)
  W7  white   3pin      (main-center) (equalizer to mainboard)
  W8  N/A
  W9  N/A
  W10 orange  1pin stereo LED (tuner to equalizer board)    (replace by longer wire)
  W11 brown   1pin stereo switch (tuner to equalizer board) (replace by longer wire)
  W12 red     1pin stereo switch (tuner to equalizer board) (replace by longer wire)
  W13 white   2pin     (mainboard to equalizer board) (mono/beatcut?)
  W14 yellow  1pin BASS-SPEAKER minus (mainboard to boost-switch)
  W15 green   1pin BASS-SPEAKER plus  (mainboard to speaker)
  W16 black   1pin BASS-SPEAKER minus (boost-switch to speaker)
  W17 blue    1pin RIGHT              (mainboard to equalizer)
  W18 white   1pin LEFT               (mainboard to equalizer)
  W19 black   1pin                    (mainboard to equalizer)
  W20 orange  1pin +6.8V (permanent)  (near supply) (mainboard to equalizer)
  W21 black   1pin GND (near MIC)     (mainboard to equalizer)
  W22 brown   1pin +6.8V (when CAS on)(near supply) (tuner to mainboard)
  W23 orange  1pin +6.8V (permanent)  (near supply) (mainboard to tuner)
  W24 N/A
  W25 black   1pin GND (near W20/W23) (mainboard to tuner)
  W26 yellow  1pin  cas speed...      (mainboard-W26 to tuner-W27)
  W27 white   1pin                    (mainboard-W27 to tuner-W26)
  W28 green   1pin  dubbing (equalizer board to tuner)
  W29 magenta 1pin  dubbing (equalizer board to tuner)
  W30 magenta 1pin   LEFT-SPEAKER plus   (equalizer to speaker)
  W31 blue    1pin   RIGHT-SPEAKER plus  (equalizer to speaker)
  W32 black   1pin   ONE-SPEAKER minus   (equalizer to speaker)
  W33 black   1pin   OTHER-SPEAKER minus (equalizer to speaker)
  W34 N/A
  W35 N/A
  W36 N/A
  W37 yellow  1pin DECK-B Sense      (mainboard to Play/FF/Rew Switch B)
  W38 yellow  1pin DECK-B Sense      (mainboard to Play/FF/Rew Switch B)
  W39 magenta 1pin DECK-A Sense      (mainboard to Play/FF/Rew Switch A)
  W40 magenta 1pin DECK-A Sense      (mainboard to Play/FF/Rew Switch A)
  W41 orange  1pin MOTOR-Pin-B       (mainboard to tape motor)
  W42 red     1pin MOTOR-Pin-A       (mainboard to tape motor)
  W43 black   2pin MOTOR +/- Pins    (mainboard to tape motor)
  W44 gray    2pin DECK-B Erase Head (mainboard to drive head)
  W45 gray    3pin DECK-B Play/Rec R (mainboard to drive head) (red=play, white=record)
  W46 white   3pin DECK-B Play/Rec L (mainboard to drive head) (red=play, white=record)
  W47 brown   3pin DECK-A Play Head  (mainboard to drive head)
  MIC gray    2pin Microphone (mainboard to front-plate)
  J1  magenta 1pin          (mainboard to mainboard) (W40 to elsewhere)
  EXT.ANT red 1pin Antennae (tuner to rear-plate)   (replace by longer wire)
  NONAME      1pin brown (near W43)  (mainboard to Power Switch)
  NONAME GND  1pin black (near ...)  (mainboard to tape drive body)
  NONAME GND  1pin black (near ...)  (mainboard to cooling plate)
  ~      REAR.red   12VAC 2x1pin to AC-DC converter
  NONAME REAR.white 15VDC 1pin from AC-DC converter
  NONAME REAR.brown to Power Switch (15VDC; or 12VDC when using batteries)
  NONAME REAR.black GND   (Battery Minus)
  NONAME REAR.red   12VDC (Battery Plus)

Mis-named wires
The L/R markings for the two AUX-IN wires (W3 and W6) are wrong (left and right are vice-versa). W26 and W27 are somehow connected as crossed wires (ie. W26 on the mainboard connects to W27 on the tuner board, and W27 to W26).


Chipset Summary IC-1 N/A IC-2 1x8 pins (LA3160 9A8) (Sanyo) (Deck-A Play) IC-3 2x7 pins (Toshiba 8849U TA7658P M'SIA)(Deck-B Play/Rec) IC-4 1x12pins (NEC JAPAN uPC1278H 8808D) (Left/Right Speakers) IC-5 1x14pins (NEC JAPAN uPC1335V 8843B) (BASS Speaker) IC-x 2x11pins (AN7025K .864) (Tuner board) (Tuner)

IC-2 1x8 pins (LA3160 9A8) 2-Channel Preamplifier For Car Stereo (Deck-A Play) 1 CH1 IN ;via 10uF to W47.L 2 CH1 NF 3 CH1 OUT 4 VCC (recommended 9V, typ 13.2V, max 18V) 5 GND ;(W47.Shield) 6 CH2 OUT 7 CH2 NF 8 CH2 IN ;via 10uF to W47.R

IC-3 - Toshiba TA7658P - Dual Preamplifier for Tape Recorder (Deck-B Play/Rec) 1 Power Supply (VCC, min 3V, max 16V) (6V in SWF, permanently on) 2 Buffer amplifier output (L) 3 Preamplifier output (L) 4 NC 5 Preamplifier feedback (L) 6 Preamplifier input (L) [right in swf] 7 ALC control output (Automatic Level Control) 8 Ground (ALC side) 9 Preamplifier input (R) 10 Preamplifier feedback (R) 11 Ground 12 Preamplifier output (R) 13 Buffer amplifier output (R) 14 NC Above L/R are as suggested in the TA7658P datasheet (in the Super Woofer, L/R are connected vice-versa). ALC and Buffer-outputs are Record related (not Play related).

IC-4 12pins (NEC JAPAN uPC1278H) (Left/Right Speakers) UPC1278H, Dual-Channel Audio Power-Output Amplifier 1 GND (IN) 2 OUT1 3 CAP1 4 FILTER.IN 5 IN1- 6 IN1+ 7 IN2+ 8 IN2- 9 CAP2 10 FILTER.OUT 11 OUT2 12 GND (OUT)

IC-5 NEC JAPAN uPC1335V - Audio Power Amplifier (BASS Speaker) 1 Output 1 2 Boot Strap 1 3 Compensation 1 4 Input 1 5 NFB 1 6 GND (Input) 7 Filter 8 Input 2 9 NFB 2 10 Boot Strap 2 11 Compensation 2 12 VCC (MIN 6V, TYP 12V or 15V, MAX 20V) (+15VDC in SWF) 13 Output 2 14 GND (Output)

AN7025K - "AM Tuner/FM-IF + FM MPX" 1 AM Mixer Input 2 AM Mixer Output 3 AM Mixer By-pass 4 AM IF Input 5 AM AGC 6 AM Detector Output 7 AM AF Input 8 Stereo Indicator 9 GND 10 MPX Pilot Detector Filter or Mono/stereo switch 11 VCO 12 MPX Phase Detector Filter or FM/AM switch 13 L-Channel Output 14 R-Channel Output 15 MPX Input 16 IF Detector Output 17 Quad. detector coil 18 VCC (min 1.8V, max 6.6V) 19 IF By-pass 1 20 IF By-pass 2 21 FM IF Input 22 AM Local Oscillator

  Switches, Connectors, Regulators

Switches S1 tuner UKW/MW switch S? Tape/AUX/Tuner switch (on tuner board) (see below for details) S3 Play/Record Switch (on mainboard) (see below for details) S4 FM Stereo S5 N/A S6 Dubbing S7 Bass Boost Sv (inside headphone socket) Sw (inside AC socket at rear-plate) Sx 15VDC Power Switch Sy DECK-A Sense W39/W40 (when PLAY/FF/REW pressed) Sz DECK-B Sense W37/W38 (when PLAY/FF/REW pressed)

Regulators VR1 (on tuner board) VR2 Speed LO (on mainboard) VR3 Speed HI (on mainboard) VR4 Volume Left (on equalizer board) (A50K) (mono) VR5 Volume Right (on equalizer board) (A50K) (mono) VR6 Equalizer 10kHz (on equalizer board) (8H0 B100K) (stereo) VR7 Equalizer 3kHz (on equalizer board) (8H0 B100K) (stereo) VR8 Equalizer 1kHz (on equalizer board) (8H0 B100K) (stereo) VR9 Equalizer 300Hz (on equalizer board) (8H0 B100K) (stereo) VR10 Equalizer 100Hz (on equalizer board) (8H0 B100K) (stereo)

Connectors AC socket (with built-in DC battery switch) headphone socket (with built-in switches, and built-in resistors) AUX cinch inputs (for external CD player, or similar external stuff) Battery Box (eight 1.5V cells) (ie. 12V DC)

S3 (Play/Record Switch) Consists of 9 simultaneous switching two-position switches. Each three pins are a separate two-position switch, with a common middle pin. _______ ______ ______ ________ ________ ________ ________ ________ ________ | : : : : : : : : | | 1 2 3 :4 5 6 :7 8 9 :10 11 12:13 14 15:16 17 18:19 20 21:22 23 24:25 26 27| |_______:______:______:________:________:________:________:________:________| 1 GND (play) (not used) 2 GND (common) (low=enable) 3 ERASE (rec) (erase) --------- 4 .. (play) (?) 5 GND (common) (?) 6 .. (rec) (?) --------- 7 NC (play) (not used) 8 NC (common) (not used) 9 NC (rec) (not used) --------- 10 W46.L (play) (deck-b record left) 11 GND (common) (low=mute) 12 W46.R (rec) (deck-b play left) --------- 13 W46.R (play) (deck-b play left) 14 .. (common) (?) 15 .. (rec) (?) --------- 16 W45.L (play) (deck-b record right) 17 GND (common) (low=mute) 18 W45.R (rec) (deck-b play right) --------- 19 W45.R (play) (deck-b play right) 20 .. (common) (?) 21 .. (rec) (?) --------- 22 NC (play) (not used) 23 GND (common) (?) 24 .. (rec) (?) --------- 25 .. (play) (?) 26 .. (common) (?) 27 NC (rec) (not used)

Input Select Switch (Tuner/AUX/Tape) Consists of 6 simultaneous switching three-position switches. _____________________________________________ | | : : | | | A B C D :E F G H :I J K L | | | 1 2 3 4 :5 6 7 8 :9 10 11 12 | | |_______________:______________:______________| | ______________________________________________________| <--- board edge 1 W27/W28 (tuner) (W27, aka W26 at mainboard side) 2 W27/W28 (aux) (W27, aka W26 at mainboard side) 3 W26 white (common) (W26, aka W27 at mainboard side) (cas speed...) 4 W29 magenta (tape) ----------------------- 5 (tuner) 6 W3.R gray (aux) 7 W1.R white (common) 8 W2.R black (tape) ----------------------- 9 (tuner) 10 W3.L gray (aux) 11 W1.L white (common) 12 W2.L black (tape) ----------------------- A (tuner) B NC (aux) C W23 orange (common) +6.8V (permanent) D W22 brown (tape) +6.8V (when CAS on) ----------------------- E (tuner) F W6.R (aux) G W4.R (common) H W5.R (tape) ----------------------- I (tuner) J W6.L (aux) K W4.L (common) L W5.L (tape)

AUX Inputs (Cinch) The left/right AUX inputs are connected with voltage dividers like so, Cinch.L Cinch.R | | +----+----+ +----+----+ | | | | [47K] [47K] [47K] [47K] | | | | W6.L ---+ +--- W3.L W6.R ---+ +--- W3.R | | | | [1.5K] [22K] [1.5K] [22K] | | | | +----+----+ +----+----+ | | GND GND W6 and W3 are then passed to the Input Select switch. Mind that L/R are accidently named R/L on the mainboard.

Tuner Left/Right-Output Tuner IC Tuner IC Pin13 (L) Pin14 (R) | | o o | wire | wire o o |__||__GND |__||__GND | || | || | C34 2A135K | C33 2A135K +| +| === C36 === C35 -| 1uF 10V -| 1uF 10V __|__ __|__ | | | | L10 ~ === C38 L9 ~ === C37 |__ __| 182J |__ __| 182J | | |__||__GND |__||__GND | || | || | C39 2A222K | C40 2A222K __|__ __|__ | | | | R21 [ ] [ ] R78 R22 [ ] [ ] R79 150K |__ | 5K6 150K |__ | 5K6 | | | | | | R35 [ ] | | R36 [ ] | | 1K5 | | | 1K5 | | | GND | | GND | | | | | | Input Select Switch Input Select Switch


The audio signals are routed somehow like so:

Drive Head ---> Pre-Amp ---> Input Switch ---> Power Amp's ---> Speakers

For some reason, each audio input is passed twice to the Input Switch (not sure, maybe one signal is for recording, and the other for output to the speakers).
For speaker output, there are two separate Power Amplifiers, one for normal left/right speakers (and left/right headphone), and one for the Bass speaker (used when the Bass Boost switch is on).
When overloading the 6.8V supply (when dragging 2 Amperes or so), Q5 begins to smoke. 6.8V isn't always that voltage, another day I've measured 7.4V for whatever reason.