The Wollensak 5750 is actually a triptych built upon a triad! The concept of "three" occurs quite frequently and may subliminally be part of the design appeal of this fascinating machine. The triptych (a three panel design where two of the panels are hinged and fold closed) is the three hinged cabinets; the left wing speaker, the main cabinet, the right wing speaker. The triad (which is a grouping of three elements that have a common function) is the main cabinet's three related sections; the left feed-reel, section, the "Control Central" (Wollensak's' name for it) that controls all functions of the tape recorder, and the right take-up reel section. This page will provide a tour of this interesting design, explain what all the controls do and how to use them.
<-- To Wing Speakers | To Internal Mechanism -->
The
Main Cabinet:
The
main cabinet of the Wollensak reel to reel tape recorder houses all the mechanical
parts of the machine, and we'll look that those later. Right now I will explain
the functions of the machine as accessed from the front panels.
First,
here is a list of the operating specifications of the vintage tape recorder
when it was "new":
- Frequency
Response: 40-17,000 Hz ± 3 dB @ 7-1/2 ips
- Wow & Flutter
.25% @ 7-1/2 ips
- S/N
(Signal to Noise) Ratio: 48 dB @ 7-1/2 ips
- Output
3 Watts music power with 5% THD (Total Harmonic Distortion)
Front Of Main
Cabinet
The front
of the main cabinet has all the controls and operating surface for the machine.
Everything is built around the center section, the "control central" (as
Wollensak ads called it).
Note that
the red "tongue" at the bottom of the cabinet is a speaker support
bar. Originally, this was a plastic piece, but it was broken off on the machine
I purchased. I made this replacement out of a piece of soft steel and covered
it with red piano felt, so it would not mar the speakers. The two red squares
seen inside the tape slot are the pressure pads for the combination erase/record/playback
head. I will discuss these in detail later.
Front
View:
(pass
mouse over image for labels - javascript must be enabled for this
to work.)
LEFT
Section (Feed Reel Area)
Feed
Reel Table - This is a plastic part held to the reel drums by three
screws, that is unique. It has a self-latching reel lock in the center (the
silver part). To use it, one places a reel on the table aligning the "fins" with
slots in the reel. Then one pulls up on the center spindle and turns. The "fins" on
the spindle press against the reel plastic (the spindle is spring loaded)
holding the reel in place when the machine is used in the vertical position
(it can also be used in the horizontal position). This eliminates the need
for rubber reel locks. Move the
mouse over the picture to see this in action - javascript must be enabled for this to work.
Mic
Input/Headphone Output Jacks - The Wollensak reel to reel tape recorder
uses standard 1/4-inch phone jacks for mic input and headphone output.
The mic input
jacks are isolated, that is, plugging a mic into left or right jack only
passes the signal to the corresponding part of the amplifier. Some machines
have a type of "jumper" so that when a mic is plugged into the
right jack, it is assumed the use is intended as mono, and the signal is
sent to both sides of the amplifier. This is NOT the case with the Wollensak
5750.
The
headphone is a standard 1/4-inch phone jack. Headphone volume is controlled
by the volume/tone control knobs. However, when I tested it, the wiring seemed
to be reversed. The left volume controlled the right headphone speaker and
vice-versa. I have no idea why this was the case, but I "repaired" it by
switching the connections to the jack inside the machine.
4-Digit
Tape Counter - A tape counter is simply a way of recording the amount of tape
that has passed from the feed reel. The values really do not correspond to
anything. But the counter is useful for "indexing".
For example,
suppose you record three songs. You would thread the tape and press the
tape counter button to re-set it to all zero's. Then you would make your
recording of the first song. You would then write down the reading from the
tape counter on a piece of paper, and write next to it the title of the SECOND
song (because this is where it begins to play). You would then record the
second song and stop the machine. You would write down the reading from the
tape counter on the piece of paper and the title of the THIRD song (because
this is where it will begin to play), and then record the song. You could
repeat this process throughout the recording.
For playback,
if you wanted to hear the second song, you would thread the tape, and then
press the counter reset button to register all zeros. You would then use
the fast forward lever to spin the tape until the counter came close to the
reading that you wrote down for the start of the second song. You would stop
the fast forward, and press the play button.
Obviously,
this process is not very accurate and is pretty much "hit or miss".
What makes
this tape counter unique to the Wollensak 5750 reel to reel tape recorder
is that is registers four digits. Most competing machines only registered
three digits. The fourth digit is important because of tape length. An 1800
foot reel of tape obviously contains 1800 feet. The counter registers revolutions
of the feed reel - not actual feet or inches. So the number of revolutions
it can record potentially is 1800 or more. A three digit counter will reset
to zero after the 999th revolution of the tape. What do you do then if you
are using the counter for an index?
The counter
on my vintage tape recorder was stuck and did not work. I repaired it by
removing it from the machine (it is made of plastic with some small springs
and gears) gave it a thorough washing and then lubricated it with a silicone
spray. It has worked fine ever since.
Tape
Detection Switch (Auto Shut-Off) - Many reel to reel tape recorders
had a tape-out detection switch as a convenience. This stopped the motor
of the machine (and sometimes the amplifier as well) when a tape "ran
out"
from the feed reel. This prevented the machine from "whipping" the
take-up reel, with hanging tape, around, and thus breaking the end of the
tape.
The
Wollensak tape recorder Tape Detection Switch is basically a small lever
that is connected mechanically to a spring loaded micro-switch (under the
face plate). The spring tries to force it up to the top of the arched slot,
opening the switch and cutting the electrical pathway to the motor. When
a tape is present between the lever and the slot, this cannot happen, so
the switch is closed and the machine runs. Watch the animated gif to see
this in action.
The Wollensak
5750 was designed to allow an optional, separate tuner module to be attached
and use the amplifier circuit. The Tape Detection Switch only interrupts
power to the tape recorder motor. The amplifier remains on. The switch can
be locked in the "open" setting by simply pressing the lever all
the way down. A small
"catch" under the face plate holds it. Flicking it up releases
it from the catch. The Tape Detection Switch also helps smooth out the feed
reel tape path during play and fast forward. However, the switch does NOT
disengage the tape recorder mechanism. So if the unit is in PLAY mode and
the tape runs out, the motor shuts off, but the pinch roller is still pressed
against the capstan. The unusual "power buttons" of the Wollensak
5750 require the motor to be running for the STOP button to work. The Tape
Detection Switch must be manually reset (locked in the lower position) to
feed power to the motor, and then the Stop button can be used to disengage
the tape mechanism.
Center Section
("Control Central")
The
Wollensak tape recorder "Control Central" manages all the mechanical
activity of the vintage tape recorder. The shape and layout are rather
interesting. It reminds me of a "face". The volume
knobs are the eyes, the VU meters are the eyebrows, the Rewind/Fast Forward
lever is the nose, the tape slot is the mouth and the power buttons are like
a goatee. The tone controls might even be tears (why is it crying-- because
I am trying too read to much into it?) Aside from this possible association,
the controls are as follows from the top down:
Upper
Controls (see image at right)
VU
Meters- There are two simplified VU meters at the top of the Control
Central. They are always active, both during playback and recording. They
respond to the level of volume set on the volume controls during play back
and both the volume and audio input during recording. They have no "scale
markings" as many VU meters of the time did. However, as long as the white
needle is in the black zone, there is no overload on the amplifier.
Tuner
Switch (located between the VU meters) - This is really a Hi-Level
audio input switch. The Wollensak 5750 tape recorder can accept audio input
from mics or a high level source, but not at the same time. This "tuner
switch" controls
which input the amplifier accepts. The name comes from a separate component
sold with the 5000 series, a tuner module that could play the radio through
the reel to reel tape recorder's amplifiers. The tuner switch on my vintage
tape recorder is a bit finicky due to dirt. I have cleaned it with tuner
spray, but it still makes a loud "pop" and scratch when used. I
should replace it, however, the wiring is a bit complicated. This is a project
for another time. The switch is a simple DPST (double pole, single throw)
unit.
Volume/Tone
Controls - Rotary volume controls with concentric tone controls
sharing the same shaft. The tone controls have little "paddles" to operate them. I have
found that the volume controls, while they look wonderful, have a slick surface
(not knurled for grip) making it difficult to tell if one has a grasp. The
rotary action is smooth, however. The tone controls take a delicate touch
as it is easy to move the volume knob at the same time. Although they are
marked T (for Treble) and B (for bass), the tone controls are really filters,
not equalizers and simply have a muting effect on high frequencies.
Speaker
Switch (located between the volume/tone controls.) The Wollensak
5750 can act as a PA device, a radio, or a tape recorder. The speaker switch
allows it to be used as an audio PA device when a mic is plugged in. However,
one must be careful of acoustical feedback. The headphone jack does not cut
off the speakers, so the speaker switch must be turned off when using headphones
or the sound will go through both the speakers and the headphones.
Rewind/Fast
Forward Lever - The chrome rewind/fast forward lever is located
below the volume/tone controls. It has a great deal of "free play" when
in the neutral position (as sown in the picture) to allow the
reel brakes to "self adjust". If the tape recorder is in playback
mode and this lever is moved, it automatically triggers the stop button which
disengages the pinch roller from the capstan while engaging the fast forward
or rewind (depending on which position has been chosen) idler at the same
time. Occasionally, this can make the tape squeal. I find it is best to
press the stop button and then engage this lever.
If the tape
recorder is in record mode and this lever is moved, it disengages any record
buttons that have been pressed and activates the stop button at the same
time. Because the "power
cam" comes into play here on the 5750 EV (Early version) there is a "woo-wow-squeal"
sound from the tape as the head picks up the speed change momentarily. The
tape recorder does not have an internal speaker cut-off switch (many
competing tape recorders did) to prevent this unpleasant sound.
Wollensak
ads promoted the high speed rewind and fast forward capabilities of this
tape recorder. At the high speed of 7-1/2 ips, this is true, and the action
is very fast. However, since the power train takes off from the capstan flywheel,
when the machine is set to lower speeds (3-3/4 and
1-7/8 ips), the fast forward and rewind are proportionally slower.
Changing from
a higher to a lower tape speed while the tape recorder is engaged in
fast forward or rewind will result in massive tape spillage.
There is no interlock to prevent this.
Lower
Controls (see image at right)
Head
Cover -
There is a removable head cover over the tape thread slot. This allows one
to clean the combination erase/record/play head, clear jammed tape, and inspect
the capstan and pinch roller as well as the "power cam" for proper
operation. This
reel to reel tape recorder is unique in the use of the combination head.
The industry trend was to use separate heads for the erase, record, and play
functions (although often, the record and play functions were managed by
a single head.) I surmise that the Wollensak 5750 tape recorder used a
combination head to conserve space. At the time this machine was being produced,
there were several articles in audio magazines about the advantages and disadvantages
of different record head arrangements. The consensus was that separate heads
were better, but some combination heads performed very well.
Action
Buttons- The lowest portion of the "control central" contains the
action buttons. The stop button releases a catch that allows the "power
cam" to
work and disengage the transport using the capstan shaft as a driver.
The
start button releases a catch that allows the transport to engage under the
influence of powerful springs. There are separate record buttons for the
left and right channels. They have a safety interlock (not visible in the
picture) on the sides of the control central shell. One must press the safety
interlock in, hold it, and then press the record button while releasing the
safety interlock. It takes a bit of practice to get used to this arrangement.
Many competing tape recorders marked the record buttons with red paint to
indicate what they were for. Wollensak apparently chose not to do this because
it would have marred the unity of the design. Although the image here seems
to show the printing for "Record R" as red, it is actually printed in black.
The red is a color aberration caused by the flash unit. (red eye?)
The stop button
automatically releases the record buttons.
There is an
advantage to this arrangement. It allows for four track mono recording, and
can be used to set the machine up for recording without actually activating
the tape drive. One can lock the record buttons down, adjust the volume while
watching the VU meters for proper audio levels, and then press the start
button to engage the mechanism of the tape recorder.
The action
buttons are very easy to use, since they are really just latches. In my vintage
reel to reel tape recorder, it appears that they are somewhat askew, but
there is no adjustment provided so that's just the way they are. It's unfortunate,
it looks like a bad set of teeth and detracts from the appearance of an otherwise
quite elegant machine. Of course, it does make it look old and used... which
it is. In any case, I could not find any adjustment for them, and I was reluctant
to try and bend any internal parts to change the way they look.
RIGHT Section
(Take Up Reel Area)
Take
Up Reel
Table - This part is identical to the feed reel table. This is
a plastic part that is unique. It has a self-latching reel lock in the center
(the silver part). To use it, one places a reel on the table aligning the "fins" with
slots in the reel. Then one pulls up on the center spindle and turns. The "fins" on
the spindle press against the reel plastic (the spindle is spring loaded)
holding the reel in place when the machine is used in the vertical position
(it can also be used in the horizontal position). This eliminates the need
for rubber reel locks. Move the mouse over the picture to see this
in action - javascript must be enabled for this to work.
Pause
Lever -
The Wollensak reel to reel tape recorder features a non-locking pause lever.
This simply pulls the transport mechanism down disengaging the capstan pinch
roller and applying the feed reel brake. When the machine is in STOP mode,
it does nothing. It works in record mode and playback mode. Move the mouse
over the image to see it in action - javascript must be enabled for this to work.
It is interesting
to note that had Wollensak designed this part slightly differently, the pause
lever could have worked as an emergency over ride in case the "power
cam"
failed, by pulling the transport mechanism back far enough that the start
button latch would engage it (when pressed, the start button releases the
latch). On the Wollensak 5750 EV (Early Version-the machine I have), this
is not possible. I have seen schematics that suggest that later versions
of the model 5750 MAY have had this much needed disengagement function.
Speed
Control- the Wollensak 5750 EV (Early Version) reel to reel tape
recorder uses a unique speed control, a rotary "thumbwheel" that
is both a switch and a mechanical control.
As a switch,
it changes the equalization characteristics to optimize the audio amplifier
for the speed chosen.
As a mechanical
control, it engages a rack and pinion assembly inside the machine that moves
the drive idler wheel up and down the motor pulley to change the speeds.
It has an unusual characteristic. You cannot change to a higher speed (lower
pulley step) when the machine is turned off.
The idler
wheel is ALWAYS engaged between the motor and the capstan flywheel, and the
speed change from lower to higher speed forces the specially shaped idler
wheel (it has a bevel on the underside) to "slide
off" the
motor pulley to the next step. This can only happen when the motor is running
because its rotation is key to this process; it "throws" the idler wheel
off itself. Watch the animated gif to see how this works. The perspective
of the image is a little faulty and makes it look like the idler wheel is
between the motor pulley and the take up reel drum. In fact, they are not,
there is room for the idler wheel to move. The very top part of the
motor pulley would drive the machine at the 15/16 ips slow speed offered
on machines produced around 1965, but the speed control thumbwheel is blocked
by a ring clip from ever moving the drive idler wheel up to that level and
there is no equalization circuit and no marking on the
thumbwheel for that speed.
Power
ON/OFF Switch - This push button switch is illuminated by a 110
volt neon lamb inside a lens. The indicator is actually not the switch, but
a lamp affixed to a metal bracket. The lower part of the bracket pushes
a "push on/push off" standard lamp switch located deep inside the
machine. There is a noticeable click when this switch is activated.
Rear Of Main
Cabinet
The design
of the Wollensak 5750 reel to reel tape recorder's main cabinet is interesting.
The shell or box is composed of two parts. There is a box made of particle
boards covered with a bumpy gray vinyl that actually
holds the framework of the machine. This is surrounded by a wooden frame
which is attached by screws accessible from inside the machine.
Rear
View:
(pass
mouse over image for labels - javascript must be enabled for this
to work.)
RIGHT Channel
Side (Left as you view it)
Input-output
jacks - There are three RCA female audio input/output jacks. The
top jack is the radio/phono (hi-level) input. This is normally the "line
out" from a stereo amplifier
for the right channel. The middle jack is the pre-amp output of the
Wollensak 5750 tape recorder. This could be connected to the hi level inputs
of a stereo system, or to the input of a self-powered speaker system (i.e.
computer speakers), or the line input of a computer. The bottom jack
(shown with the red plug) is the right speaker output. It is marked: "EXT.
SPKR." meaning external speaker, but there is no internal speaker in the
5750. This plate may have been used on Wollensak models that had internal
speakers and for economy was used on the 5750 as well.
Not shown
in the photo is the motor vent cage located below this panel. The cage extends
away from the back of the machine, requiring special rubber feet to create
clearance when the machine is used in the horizontal position.
LEFT Channel
Side (right as you view it)
Input-output
jacks - There are three RCA female audio input/output jacks. The
top jack is the radio/phono (hi-level) input. This is normally the "line
out" from
a stereo amplifier for the left channel. The middle jack is the pre-amp
output of the Wollensak 5750 tape recorder. This could be connected to the
hi level inputs of a stereo system, or to the input of a self-powered speaker
system (i.e. computer speakers), or the line input of a computer.
The bottom jack is the left speaker output.
The small
red button is for a circuit breaker. The Wollensak 5750 was a bit advanced
by including a circuit breaker in the machine. Most competing tape recorders
used a replaceable glass fuse.
Below the
jacks is the space for the power cord socket. I have blocked this off because
I "hard-wired" the tape recorder using a 3-conductor computer power cable.
Cabinet Handle
A note about
the handle is appropriate here. The Wollensak 5750 has an inset collapsible
plastic handle with brass fittings as can be seen in the image below. Notice
that my success at refinishing the cabinet gave the wood grain much more
prominence and the color tone matches the plastic handle closely. The machine
weighs approx. 28 lbs. and this handle is 40 years old. While it still supports
the machine, I tend to carry my Wollensak reel to reel tape recorder cradled
in my arms (as one would carry a kitten) to prevent the handle breaking
and what might happen to my foot if it did!
The two red/white
dots between the speaker cabinets and main cabinet are bumper spacers. They
are actually completely red, but JPEGing this image added the whitish artifacts.
The original bumper spacers were little (1/8" diameter) dots
of brown felt. I replaced them (they had hardened out) with red piano felt.
A piano is a fine musical instrument and I consider this Wollensak tape recorder
to be a fine musical instrument, so the use of the red felt seemed appropriate.
(Move your
mouse over the image below to see the handle expanded - javascript must be
enabled for this to work.)
In
the next page I will show the internal mechanical parts of the Wollensak
5750 (EV - Early Version) reel to reel tape recorder and explain what I did
in the restoration/rebuild to get the machine back into working condition.
<--
To Wing Speakers | To
Internal Mechanism -->
Please
note that ClydeSight Productions DOES NOT rebuild or sell vintage
reel to reel tape recorders, nor can we help anyone involved in such a project.
The tape recorders shown in these pages are part of a personal collection
and are not for sale. We Do Not recommend
that unqualified or inexperienced persons attempt to restore vintage audio
equipment.
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www.clydesight.com Master Site
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Productions - 2007
