1. technology and computing
2. electronic components

HOW TO MAKE A MIXER UNIT FOR THE MUSIC CENTER
Copyright © 2014 Duncan Galloway, The Netherlands
ed. Peter K. Smith
pub. 22-08-2014
1: Components side of DIY completed mixer with external parts
Contents
INTRODUCTION
Impedance converter (SEL accessory part 5022)
For the 5005
For the 5001
For the 6000
Mixing amplifier (SEL accessory part 5012)
For the 5001 and 5005
For the 6000
Circuits and layouts
PCB dimensions
HANDS-ON JOB
A
PARTS LIST for a mixer unit 5012
Capacitors for mixer (13x)
Capacitors for VU-meter (6x)
Resistors for mixer (25+2x)
Resistors for VU-meter (10+1x)
Transistors for mixer (1+3)
Transistors for VU-meter (2)
Other components
Also required materials
B
BUYING
1.
2.
3.
4.
5.
6.
7.
8.
9.
THE COMPONENTS
Resistors.
Potentiometers.
Capacitors.
Note on the 0.5uF / 70V.
Transistors.
VU-meter (level indicator).
Rectifier or ‘double diode’.
Soldering tags
Plugs and sockets
C
MAKING THE COMPONENTS FIT ON CIRCUIT BOARD
D
SOLDERING COMPONENTS ON A CIRCUIT BOARD
E
ACTUAL FITTING AND SOLDERING OF COMPONENTS
F
CONNECTING TO MUSIC CENTER & SIGNAL SOURCE plus TESTING (5001)
Connecting via the 12-pin socket
Connecting NOT using the 12-pin socket
Working on the 5012 mixer
Working inside the 5001
Variation in X-rail connections
G
CONNECTING TO MUSIC CENTER & SIGNAL SOURCE plus TESTING (5005)
Connecting via the 12-pin socket
Connecting NOT using the 12-pin socket
H
CONNECTING TO MUSIC CENTER & SIGNAL SOURCE plus TESTING (6000)
Connecting via the 12-pin socket
Connecting NOT using the 12-pin socket
APPENDIX
PCB dimensions
Acknowledgments
Photos credits
INTRODUCTION
The Schaub Lorenz Music Centers did not have much of a choice when it came to source selection
for recording. The 5001 (table model with radio) was able to record directly from its radio. With
the 5005 (radiogram), you could either record from the radio or from its built-in record player.
The 6000 model (stereo ‘tape-deck’), as it was intended for the American market, originally had
4 CINCH bushes (2x L+R IN / 2x L+R OUT) to the right-hand side of the chassis (photo 2). These
CINCH bushes were often converted to DIN sockets at the rear, for which both holes are present.
There must have been some ‘thinking ahead’ as the 5001 and 5005 chassis have all these holes
too. The ingoing bushes could be used for various sources.
Common to all three types is a special 12-pin socket at the rear (photo 3). This socket, and the
matching plug, are rather unique and are hardly used elsewhere.
2. Holes for 4 CINCH sockets.
3. ‘Special’ 12-pin socket.
Impedance converter (SEL accessory part 5022)
For 5005 model
The impedance converter (or adaptor) is used to generate a correct ingoing signal from a record
player. The socket is present in the 5005 model as standard. Luckily, the designers did not bother
to integrate it on the other printed circuit boards (PCBs) and made a separate one. This sits on a
bracket below the record player and is wired into the system (photo 4). It was probably prepared
for a stereo version as the PCB has room for a second unit. (photo 5)
The record player is connected to it by a DIN socket and plug. Strangely enough, the socket on
the PCB has 5 pins over 180°, whereas the plug only has 3 pins over 180°. There is a spare hole
present for the fitting of another DIN socket, so again, it is possible that the designer had ‘stereo
preparation’ in mind. (photo 6)
In any case, this socket allows you to connect up the Music Center to a better quality record
player. The built-in Perpetuum Ebner type PE36, with fitted element PE188, is not of a very high
standard. A switch, actuated by the record player's speed selector activates the changeover from
radio to phono amplification and/or recording.
4. Bracket below record player.
5. Room for 2nd converter.
6. Different plug & socket.
For 5001 model
The optional accessory part was actually only for the 5001 as it only had one channel and so was
not suitable for the 6000 stereo model. However, ‘preparations’ had obviously been made as
there is sufficient room on the PCB for a second unit. It is to be connected to the 12-pin socket at
the rear of the Music Center. A switch in the adaptor performs the same function as the switch in
the record player.
7a. Converter 5022 front view.
7b. Converter 5022 rear view.
7c. A look inside the 5022.
There was no need to buy the accessory 5022 for the radiogram model 5005 as it was already
built-in as standard. Not the identical part, but a very similar one. There is a slight difference in
the built-in ‘±5022’ unit in a 5005 versus the 5022 accessory. Of the components in the outgoing
circuit, two capacitors and a resistor in the 5005 are: 10uf ; 50uF and 6,8K. While those in the
5022 are given as: 5uF ; 25uF and 4,7K. This should not affect the performance much.
For 6000 (stereo) model
No original accessory was available, but basically two (coupled) units are required.
Mixing amplifier (SEL accessory part 5012)
8a. An original 5012.
8b. Original 5012 from the rear.
8c. Original PCB components side.
For 5001 and 5005 models
In order to make recordings of, say, a discussion, a play or to mix one’s own ‘record programme’,
a mixer unit was available. It enabled you to connect a microphone and a record player. The level
of each signal going to the recorder can be regulated independently.
A level indicator (VU-meter) is provided. This 5012 unit also connects to the 12-pin socket like
the 5022 does. It includes a special circuit to cut off the radio signal when either or both slidinglevel adjusters are moved from rest. An instruction booklet was supplied with the mixer unit.
(photos 8a, 8b and 8c)
For 6000 (stereo) model
Again, as with the 5022, no original accessory was available but two coupled units are required.
The coupling can be made simply by utilizing so-called tandem or stereo potentiometers. A radio
cut-off switch is not required as there is no radio present.
Circuits and layouts
As both these 2 (3) accessories are difficult to find there was only one option left to me to BUILD
THEM MYSELF.
The electronic diagrams are included in Book 1 of the Service Manuals.
 Adaptor 5022
electrical diagrams of both variants in fig. 26, p. 18
printed circuits in figs. 27 & 28.
 Mixer 5012
electrical diagram fig. 34, p. 26
printed circuit fig. 35, p. 26
In order to make them suitable for a 6000 stereo model, you simply make two units. Of course
these can be assembled on one PCB but should be installed in one housing. The impedance
adaptor made suitable for a 6000 has already been ‘rationalised’ in Elektuur, June 1965 p. 640.
(See fig. 13 for the electrical diagram, the PCB layout is shown in fig. 13a).
Not all the plans for the PCB layouts in the Service Manual are to scale. The one for the mixer
5012 is size-wise usable with its dimensions of 130x105 mm. An original was measured at
128x103 mm (see Appendix).
HANDS-ON JOB
The PCBs are just as difficult to find as are complete mixer units, and so these have to be made
by hand too. In the past, I used to design and etch my own PCBs but no longer have the
equipment to do this. So I decided to use ready-made circuit board with a solder pad for each
individual hole. I chose this particular type for ease of designing the layout when converting it
from the electrical diagram. I think is it called Perfboard.
The holes are #56 (0.465 inch) or 1.1-1.2 mm on a grid of 0.100 inch or 2.54 mm. Some other
types and styles are, or used to be, available. This type still is available. (photo 9)
9. A typical prefab: ‘Perfboard’.
After a lot of puzzling, I arrived at a design that contained all the components excluding the
potentiometers, VU-meter, switch and sockets (photos 10a & 10b). These have to be connected
by wires, which also make it easier to fit it into a suitable housing of your own desire. My PCB is
quite a lot smaller at 100x67 mm. Whereas the original measures 128x103 mm, but supposedly
with room for a stereo version.
INFO
The VU-meter part of the mixer can be left out with no harm to the rest of
the mixer.
10a. Mixer PCB components side drawn by author.
10b. Mixer PCB copper side drawn by author.
For those wishing to etch their own original (Schaub Lorenz designed) circuit board, you should
note that the original drawing in Service Manual (Book 1) is rather blurred. I spent a lot of time
‘blackening’ fig. 35 on p. 26. Looking at the multitude of non-used copper islands, I think that
this PCB was also originally designed with stereo operation in mind. One day I may sit down and
figure out how to include all the extra components for a second channel on this layout! (photos
11 & 12)
INFO
An enthusiast intending to build this PCB should contact the website editor who can
exclusively supply you with A3 print-outs of the Perfboard design or the enhanced
original of fig.35, for a small fee to cover printing and postage.
11. PCB copper side in Service Manual I, p.26, fig.35.
12. PCB copper side of an original 5012.
A
PARTS LIST for a mixer unit 5012
Capacitors for mixer (13x)
Qty
Capacity
Type
1x
0,5 uF
Elko 70V
6x
2 uF
Elko 15V
1x
25 uF
Elko 3V
3x
100 uF
Elko 3V
1x
100 uF
Elko 15V
1x
500 uF
Elko 15V
Capacitors for VU-meter (6x)
Qty
Capacity
Type
2x
10 uF
Elko 15V
1x
50 uF
Elko 15V
1x
100 uF
Elko 3V
1x
100 uF
Elko 25V
1x
250 uF
Elko 15V
Resistors for mixer (25+2x)
Qty
Ohm Watt Colour-code
1x
100
1/3
brown-black-brown
1x
120
1/3
brown-red-brown
3x
1K
1/3
brown-black-red
1x
1,5K 1/2
brown-green-red
1x
4,7K 1/3
yellow-purple-red
1x
5,6K 1/3
green-blue-red
1x
8,2K 1/3
grey-red-red
3x
22K
1/3
red-red-orange
1x
27K
1/3
red-purple-orange
1x
39K
1/3
orange-white-orange
2x
56K
1/3
green-blue-orange
1x
100K 1/3
brown-black-yellow
2x
180K 1/3
brown-grey-brown
1x
220K 1/3
red-red-yellow
1x
270K 1/3
red-purple-yellow
1x
330K 1/3
orange-orange-yellow
1x
560
1/3
green-blue-brown
1x
680K 1/3
blue-grey-brown
1x
1,2M 1/2
brown-red-green
1x
50K
log
potentiometer
1x
250K log
potentiometer
Resistors for VU-meter (10+1x)
Qty
Ohm Watt Colour-code
1x
180
1/3
brown-grey-brown
1x
390
1/3
orange-white-brown
1x
680
1/3
blue-grey-brown
1x
1K
1/3
brown-black-red
1x
4,7K 1/3
yellow-purple-red
1x
5,6K 1/3
green-blue-red
1x
15K
1/3
brown-red-orange
2x
33K
1/3
orange-orange-orange
1x
120K 1/3
brown-red-yellow
1x
2,5K lin
trimpot
Other components
1x VU-instrument ± 200uA
2x ‘double-diode’ V15/C25
1x switch (1x make)
OR
1x switch (1x changeover)
Transistors for mixer (1+3)
Qty
Type
alternatives
1x
BCY 51r
alternative BC169b etc.
3x
BFY 39 II
BC107 , BC171b , BC149
Transistors for VU-meter (2)
Qty
Type
alternatives
2x
BFY 39 II
BC107 , BC171b , BC149
(120 uA equals 100% and 180 uA = 150%)
(replace with 2x 1N4001 or similar, see B7)
(cut radio signal, linked to potentiometers and only for
5001/5005 if not integral with potentiometers, see B2)
(for 5001/5005 if NOT connected via the 12-pin socket)
Materials
Circuit board; some different coloured wires; thin coax cable cum signal cable (sheathed) wire;
plugs & sockets; 2 knobs (or 3, depending on potentiometers having a switch or not); a housing.
B
BUYING THE COMPONENTS
1. Resistors
These should not provide too much of a problem. But I cannot really see why two resistors are to
have a 1/2-watt rating instead of a 1/3-watt. Buy them anyway as such.
2. Potentiometers
13. Some different models of potentiometers.
Left is single with on/off switch, middle is single, right tandem/stereo, in front a sliding type.
Finding the stated values can be awkward, but substituting the 50K-log with a 47K-log and the
220K-log with a 250K-log causes no problems. Sliding potentiometers are preferred, as making
the level indicator scale is far easier. Unfortunately, these do not normally incorporate a switch.
The old-fashioned rotating ones do and this is very useful for our purpose and can be used for the
‘linked-in switch’. (photo 13)
If you connect the switches in parallel, and if one or both potentiometers is/are moved from rest,
the switch/switches closes/close thereby cutting out the radio signal. Look at the diagram and
you will see what I mean.
Tandem potentiometers for a stereo unit with a switch AND of the correct value may take some
finding. However, the stereo 6000 model does not include a radio so there will be no need to look
for these potentiometers.
3. Capacitors
These may prove to be more difficult. The recommended values and voltages date back to times
and series that have long since been replaced. So 25 uF will usually be available as 22 uF and
likewise 250 uF will become 220 uF and 500 uF may work out as 470 uF. All not too critical.
Note on the working voltages
The power supply for the mixer is the same as for all the other electronic circuits, i.e. 18V DC.
Only the 100uF / 25V (VU-meter) is critical, as that is connected almost directly across the 18V.
Otherwise, the voltage is not overcritical provided they meet the minimum specification.
4. Note on the 0.5uF / 70V
This will really prove to be a difficult one. An ELECTROLYTICAL capacitor is required. NOT an
ordinary polyester, paper, mica or tantalium one. What certainly is available is a 0.47uF / 100V
and this is OK. You may be lucky and find a 0.47uF / 63V which is fine.
TIP
A very similar capacitor like this one, but only half its value at 0.25 uF / 70V, is present in
the tape-control circuit. It protects the coil of the RX relay and is even harder to find.
Place 2x 0.47 uF /100V in series and it will do the trick.
5. Transistors
The types stated are a bit old fashioned but are still available. However, modern equivalents can
easily be obtained . Note that alternatives (or even alternative housings) may have different
connections so you will need to take extra care when fitting them.
6. VU-meter (level indicator)
14. The scale of a battery level indicator can be adapted for a VU-meter as in effect it IS a uA-meter to start with. In
front is an old set VU-meters with nice scales from a defunct tape deck.
Several nice little meters are available from 'dump stores'. You may also try removing one from
an old recorder and see whether it will also do the job. Whatever you use, you will have to set it
with trimpot 2.5K-lin for maximum level, or as the case may be, full scale.
See specification at A for currents versus scale readings. The Service Manual (Book 1, pp. 2427) also gives some settings on voltages at various points in the circuit. (photo 14)
7. Rectifier or ‘double diode’
Replace by two common rectifier diodes as listed. Their function is to ensure that the
(alternating) signal current runs through the instrument in the correct direction.
8. Soldering tags
Optional for connecting the wires to signal sockets & plug, potentiometers, instrument etc. IF,
then maximum 17 tags are needed.
9. Plugs and sockets
Depends on what you want. DIN is rather easy, but CINCH can be easily adapted for different and
more modern equipment. Leave this till the very last.
C
MAKING THE COMPONENTS FIT ON THE CIRCUIT BOARD
1. Having obtained all the required parts, check to see whether they are all correct (specs).
2. Then, see whether and how they can be fitted on the circuit board. Take each part and see
whether its leads will fit the holes they are intended to go through. Sometimes it may be
necessary to enlarge a hole slightly. For this PCB, enlarged holes are probably only needed for
radially mounted capacitors i.e. those with both leads on one side – see photo 15, and
perhaps for the soldering tags. Enlarge them now to avoid risky drilling later.
TIP
In my Perfboard design, I used 7 radially mounted capacitors and did bend another 6 to be
fitted in this way. If you are going to bend the wires of an axial capacitor that needs to be
fitted vertically (as a radial type, so to speak), it is preferable if you bend back the wire
that is attached to the housing (see 2nd from left in photo 15). That way it does not matter
if the wire touches the housing. If not, then insulate it! Usually the negative lead. The
positive is normally fitted with a rubber seal to the can.
15. Different types of capacitors. From the left: axial model, axial model bent for radial fitment, large and small radial
models. These four are electrolytic capacitors. At front: a (non-electrolytic) polyester type.
3. Make a note of which parts are to be fitted first, say in ‘order of appearance’. The layout may
be such that if, for example, you solder a transistor snugly to the board, you may not be able
to fit a resistor in the holes next to it. It needs to be mounted ‘high on its legs’.
4. Some parts must be mounted vertically. If so, insulate top wire where appropriate.
5. Check where you want the mounting holes for the PCB to be. Make sure that they do not
interfere with any electrical connection. Preferably drill them before soldering, as then there is
less risk of damaging a component. Dia. 3.2 for a M3 is OK.
TIP
I usually design a layout in such a way that at least one row of soldering pads can be
removed from around a mounting hole. This means that the copper of a square island of
nine pads is removed by lightly twisting a drill bit between the fingers. Do not push too
hard; the copper will come away easy enough. (photo 16)
16. Twist drill after having just removed a copper soldering pad.
6. Lightly sand the copper side of the PCB with fine sandpaper grade 1000. You ONLY want to
remove any oxidation and I use the fine grade Scotch Brite. Finally, swab the copper side with
a tissue wetted with alcohol / acetone / petrol to degrease it.
D
SOLDERING OF COMPONENTS ON A CIRCUIT BOARD
IMPORTANT: To avoid corrosion, ONLY use resin flux core solder and nothing else!
1. There is a trick to soldering and that is to carefully heat the parts that have to be soldered
together. This means that you need to add slightly more heat to the bulkier part. Here, that is
the wire compared to the soldering pad. Do NOT overheat either wire (component may fail
because of it) or the pad on the PCB (may come unstuck).
2. Put the tip of the heated soldering iron, or soldering gun, against the protruding component
wire and almost immediately slide it down onto the pad of the PCB. That way the wire absorbs
a little heat before the pad does.
3. At the same time, add the end of the soldering wire. The resin flux in it will melt a fraction
before the solder, making the solder run and flow nicely. (photo 17)
17. Wire of component sticking through, iron against it sliding down; solder ready to be added.
4. If it doesn't flow, do not overheat. Instead, clean the joint and scrape away old resin and/or
solder, if necessary. Then try again, heating the iron a little more before you start. Check with
solder on tip whether it flows nicely but not too fiercely. Once finished, an electrical joint
should have a bright and shiny appearance. If it doesn't, then you have what's called a ‘cold
shut’ which will not be a good electrical conductor.
E
ACTUAL FITTING AND SOLDERING OF COMPONENTS
TIP
It can be very handy to use a coffee cup or a small cardboard box with a suitable hole cut
in one side to place the PCB on for soldering purposes.
1. Now refer to your notes (ref. C3) and see which part or parts you should fit and solder first.
You should have decided this in Section C.
2. If you didn't do this in Section C, carefully bend the wires, as required, to fit parts in the
holes. Do not bend too close to the actual part, unless this is unavoidable, as it may fail when
doing so. Use a pair of small round-nosed pliers or stout pincers, preferably NOT SERRATED,
to avoid damaging the leads. (photo 18)
18. Bending wire with round-nosed pliers- not too close to component. At right is about minimum.
3. Thread the wires through the holes and hold component tight to the board. (photo 19)
19. Use finger to hold down component tightly to board before bending or cutting.
4. If you need to connect to other holes, the wires on the copper side of the board can now be
bent in the correct direction. Any excess length should be cut off prior to soldering and the
wire laid flat against the board. (photo 20)
20. Component wire bend flat against board and ‘lead on’’ to another connection point.
5. If you do not need to go any further, cut the wires protruding 1.5mm (1/16 inch) on the
copper side.
6. Hold the component tightly to the board with a finger and solder one lead as described in D.
Exceptions are off course parts which shall be placed higher up as in C3.
7. If you put too much heat in, you will notice your finger will get very hot. Diodes and
transistors are particularly susceptible to overheating. Short leads do not help here.
8. Once all the parts are fitted and soldered, check and double check that all joints are firm.
Parts are stable and, most importantly, that ‘the right part is fitted on the right location’. You
will not be the first to get the colour coding or polarity of parts wrong. (photo 21)
21. Copper side of the completed (mono) mixer 5022 made by the author.
9. Sit back and look at your handiwork. See whether you made any false connections with a
small blob of stray solder. If you did, the easiest remedy is to carefully cut it away with a
small, sharp hobby knife. Correction by re-soldering is risky as it may overheat components.
10. Use different coloured wires, for easy recognition, to connect all the remaining parts not fitted
on the PCB. Make a list of these and double check before connecting, especially the polarity of
power supply leads.
F
CONNECTING TO MUSIC CENTER & SIGNAL SOURCE plus TESTING (5001)
Connecting via the 12-pin socket
1. The easiest way to connect your Mixer Unit to the Music Center is to use the 12-pin connector
at the back of the cabinet. The electrical diagram shows you which pins to use and what for.
Power, radio cut-off and tape recorder signal-in all automatically go to the correct points in
the circuit of the recorder. The 12-pin plugs are hard to find and you may want to extend the
relevant wires to another type of socket & plug you have available.
How to make a plug for the 12-pin socket may be a subject for a future article.
2.
The pins of the 12-pin socket are numbered when seen as fitted to the chassis. Refer to
photo 3. With the slightly tapered end pointing to the right, the numbering is:
- pin 1 top right
- top middle is ‘blind’
- pin 6 top left
- pin 7 bottom right
- pin 12 is bottom left.
You will only need 5 of the available 12 pins, as shown in the electrical diagram for the mixer
5012.
Pin
3
4
6
7
12
Connects to:
Ground ingoing and outgoing signals (inside 5012 connected to pin 4)
Negative 18V
Positive 18V
Outgoing signal to tape recorder
Via cut-off switch connected to pins 3 and 4
3. The signal sources are connected to the corresponding signal-in sockets of the 5012 for the
record player and the microphone.
4. Set both potentiometers (level adjusters) to the rest position. If fitted with a switch, they
should be clicked to ‘off’.
5. If fitted, set the separate switch for radio cut-off to the ‘open’ position (radio will play first).
6. Turn on the Music Center with the pushbutton TR. The radio shall now produce sound.
7. Start the record player and move the level adjuster for it to a quarter of its range. Activate
separate switch for radio cut-off where fitted (is otherwise included in the level adjuster). The
record shall now sound through the set/amplifier. Possibly needing a bit more moving of the
level adjuster.
8. Move level adjuster for record player back to rest position. Leave cut-off switch activated
(ON).
9. Move the level adjuster for the microphone up a quarter of its range. Speak into the
microphone and your voice should sound through the set/amplifier.
IMPORTANT Be careful with the volume control, otherwise the sound may be picked up by the
microphone resulting in a nasty ‘howling’ sound as a result.
10. Now ALSO turn up the level adjuster for the record player slightly. Speak into the microphone
and your voice should sound together with the record being played. This way you can use the
mixer as a voice-over.
11. To fine-tune the level indicator and other settings in the mixer circuit, see pp. 22-27 of the
Service Manual.
Connecting NOT using the 12-pin socket
Working on the 5012 mixer
If, for some reason, you do not want to—or cannot use—the 12-pin socket, you will have to find
all the points to connect up to somewhere in the machine. The electrical diagram tells you the
what’s and where’s, but they may physically be different. You will have to work your way through
it.
TIP
It may be a good idea to run all the ‘outgoing' wires inside your Music Center to an added
supporting rail. From there, a 4-colour coax audio cable can go to a 5-pin socket. A
matching plug with similar cable goes to your mixer unit.
IMPORTANT Try to use an odd-type socket & plug to avoid mistakes with direct plugging
in of a microphone or record player. This is also probably why Schaub Lorenz
decided to use the 12-pin socket & plug.
Plan it out and make a list of the connections on your rail. The table below may helpful.
PCB
1
2
3
4
5
6
7
8
connects to:
micro IN
ground micro
ground OUT / negative 18V
ground phono
signal OUT
negative VU-meter
positive VU-meter
side ‘a’ phono level control
rail lip
n/a
n/a
n/a
n/a.
n/a
n/a
9
10
11
12
13
14
15
X
XX
phono IN
positive 18V
mid-contact phono level control
side ‘b’ phono level control
side ‘a’ micro level control
mid-contact micro level control
side ‘b’ micro level control
side ‘a’ cut-off switch
side ‘b’ cut-off switch
n/a
n/a
n/a
n/a
n/a
n/a
Working inside the 5001
1. Unplug the mains plug, open up the rear of the cabinet (4x M3 screws at bottom / 4x unhook
at top.
2. Power: 18V - 11,5 mA can be taken from rail X. This 3-lip rail is situated at the right bottom
of the vertical folding chassis. (photos 22a & 22b).
22a. The 3-lip rail X at RH-bottom of folding chassis.
22b. Rail X in close-up.
a)
b)
c)
d)
e)
f)
Variation in X-rail connections
There is a bit of a mix-up in the connections of this X-rail. According to the electronic
diagram, the 3 lips are numbered from outside in 1, 2, 3. But positive and negative may have
changed place, or at least that is how it appears on different machines in my possession.
The 5001 and 5005 models usually seem to have WHITE wires for NEGATIVE and BROWN
wires for POSITIVE. In the 6000 model, however, it is WHITE for NEGATIVE and GREY for
POSITIVE.
In the 5001/5005 models, there are 1x thick and 4x thin wires for each colour (4 PCBs on the
folding chassis). On the 6000 model, this is 1x thick and 3x thin (only 3 PCBs on folding
chassis as there is no pre-amplifier present).
But also the actual use of the lips varies.
In the electrical diagram for 5001/5005 models, the short, thick white wire, which goes with a
screw to ground on the back side of the chassis near rail X, is on lip 1 (outside). In the 6000
diagram, however, the wire is shown as located on lip 2 (middle). Neither diagram shows a
bridge to any of the other lips. I find that the centre-lip (2) is usually bridged to the lip
containing the WHITE leads. (5 out of 5)
The 5001/5005 diagram does not indicate any positive or negative to the lips. The 6000
diagram gives the polarity as: lip X1 negative and lip X2 positive.
On the 5001/5005 models, the 18V power is also present on the 12-pin socket. Pin 4 is
negative and pin 6 is positive. With the 6000 models, the feed to the 12-pin plug is not
consistent. Probably caused by the fact that most were sold in kit-form for final assembly by a
hobbyist.
Summary of the variations I have come across:
Model
5001
5005
6000
Lip 1 (outside)
negative
1+4x white
negative
4x white
Positive
1+3x grey
Bridge
2 to 1
Lip 2 (middle)
1x white to chassis
2 to 1
1x white
+ 1x white to chassis
negative
1+3x white
2 to 3
Lip 3 (inside)
positive
1+4x brown
positive
1+4x brown
1x white to chassis
3. Radio signal cut-off:
The easiest way to do this is to run a wire from 12-pin socket pin number 12 and connect it
as shown in the diagram.
a) If you do not do it that way, you will have to unplug the small recessed 9-pin noval plug. This
is the plug with 7 wires WITHOUT the extra rim around it – it is the rearmost one. The other,
WITH an extra rim, only has 5 wires and is for volume and sound control.
b) Based on the electrical diagram and on my actual testing, the radio signal comes in on pin 5,
so unsolder that one. It is the core of a small coax cable. Extend it as necessary with some
coax cable. Also connect a sufficiently long piece to the now empty pin 5 and lead both wires
to the support rail.
c) Your switch set-up now has to be different. A simple ‘make’ is not good enough and so you
will need a ‘change-over’ type. The core of the wire from noval plug pin 5 will go to the centre
contact of your switch, the (unsoldered) radio signal to one of the side contacts of your
switch. (later the signal from your mixer unit to the other side contact)
d) Connect the 2 sheaths and connect them to ground - this is the negative 18V.
TIP
You may have to insulate the switch and then wrap it in aluminium foil to avoid
interference.
IMPORTANT
Check to make sure that you have unsoldered the correct wire at 3b. Refit the
noval plug. The ‘radio signal' wire and the ‘pin 5 extension’ are on the support
rail. Switch on set and the radio lights up but will not play. Then bridge the 2 lips
on your support rail, signal passes and the radio should sound. If all is well, then
switch off and unplug the mains plug. If not, then double check connections. If
still failing to produce sound, make a connection between the original ‘radio
signal' wire and noval plug pin 5.
4. Signal-out:
'Outgoing' from the mixer, that is, but 'incoming' to the tape recorder. The sheath of the
signal cable that goes to ground/chassis and is the negative 18V. It is already on the added
supporting rail with 2x sheath from radio signal cable modification. The core of the ‘incoming'
mixer signal cable goes to a side contact of the change-over switch. From there through the
centre contact to pin 5 on the noval plug. Refer to 3 Radio signal cut-off.
5. Initial testing and fine-tuning is done by following steps F2-11 of Connecting via 12-pin socket
for 5001.
G
CONNECTING TO MUSIC CENTER & SIGNAL SOURCE plus TESTING (5005)
Connecting via the 12-pin socket
1. The chassis of a radiogram is mounted in a 90 degree tilted position. The 12-pin socket is now
located at the bottom. Due to the presence of the built-in record player, the 12-pin socket on
the chassis is already occupied. No problem really, as the wires from the plug occupying it run
to the additional 12-pin socket on the bracket below the record player. So simply use that
socket.
2. From here on, follow steps F2-11 of Connecting via 12-pin socket for 5001.
Connecting NOT using the 12-pin socket
1. Basically the same as steps F1-4 as in Connecting NOT...
2. Note that the switch for the radio cut-off CANNOT be fitted in parallel with the one
underneath the record player in the 5005 model (photo 23). Although this switch is used for
the changeover from radio to record player, it will not work correctly if you close both sets of
contacts using the parallel switch. Refer to the electrical diagrams.
23. The radio cut-off switch under the built-in record player of the 5005.
In rest position, the left and middle contacts are connected so the radio can be heard.
When a record speed is chosen, the cam turns. The cam lever operates the middle arm, causing the right and middle
contacts to connect. Then the record can be heard.
H
CONNECTING TO MUSIC CENTER & SIGNAL SOURCE plus TESTING (6000)
Connecting via the 12-pin socket
1. Basically all the same as for the 5001 model, but now for two units in stereo operation.
2. Double check 12-pin socket for correct pin occupation. You will have to trace and/or modify
these yourself when using a 5012 mixer unit. The Service Manual is intended for the
5001/5005 models and does not cover the 12-pin socket on a 6000 model in any detail. Many
of the 6000 Music Centers went out into the world in kit-form accompanied by a book with
basic building instructions. These did include an electrical diagram!
3. Note that NO radio cut-off switch is required as there is no radio.
4. Initial testing and fine-tuning is done by following steps F2-11 of Connecting via 12-pin socket
for 5001.
Connecting NOT using the 12-pin socket
1. Since there is no radio signal to cut-off, things are a lot easier. However, it is a good idea to
run all the ‘outgoing' wires to an added supporting rail (see at 5001).
2. Power: it will be a bit higher as the 18V - 11,5 mA as there are 2 mixers present. Can still be
taken from rail X. This 3-lip rail is situated at the right bottom of the vertical folding chassis
(photos 22a & 22b). See info with table under 5001 for possible variations.
3. Signal-out: 'Outgoing' from the mixer unit, that is, but 'incoming' to the tape recorder,
simply goes to the bushes IN on the tape recorder.
24. PCB copper side in Service Manual I, p.26, fig. 35 – less red to show components
APPENDIX
ACTUAL dimensions of original printed circuit boards (PCB) of Schaub Lorenz Music Centers
Netzteil 5001 / 5005 220V
Netzteil 6000 110V for USA
108 x 100 mm.
no PCB present
Power unit 5001 / 5005 220V
Power unit 6000 110V for USA (see photos)
Tape Steuerteil (relais)
165 x 130 mm.
Tape control unit (relay)
A/W Verstärker - HF-generator
Pilottonverstärker
Austeuerungsregler
NF verstärker
138
138
138
138
Record/Playback amplifier – RF generator
Pilot signal amplifier
Level control amplifier
AF amplifier
U K M L Radio
175 x 170 mm.
x 170 mm.
x 81 mm.
x 81 mm.
x 81 mm.
Phono Impedanz Wandler (±5022) 170 x
47 mm.
Impedanz Adaptor 5022
___ x __ / __
Mischpult 5012
103 x 128 mm.
220V power unit from a 5005 (equal for a 5001)
fuse + fuse holder added, connector goes to record player
Compiled by Duncan Galloway, The Netherlands, Jul 2014
(from Ausgabes 10 and 12)
U K M L radio
Phono impedance converter (±5022)
(as built into 5005)
Impedance converter 5022 (info from P.K. Smith)
(as an accessory)
Mixer Unit 5012
(info from P.K. Smith)
(as an accessory)
110V power unit from an original 6000 USA model
3 fuse holders on heatsink added by author
APPENDIX
Acknowledgements
Many thanks to Duncan Galloway for supplying various images, including enhanced circuit
diagrams and various technical drawings, to the Schaub website owner for dissemination to DIY
enthusiasts.
Photo credits
All photos in this article originate from the author of this article with the exception of photos of
the original accessories 5012 (8a, 8b, 8c & 12) which were supplied by Bryan McAlley and 5022
(7a, 7b & 7c) which were supplied by P.K. Smith.