The
Wollensak 5750 reel to reel tape recorder has special internal mechanical
characteristics due to its unique overall design. Some of the elements used
are elegantly simple. This page will describe in detail an overview of the
internal mechanical parts of the Wollensak 5750 reel to reel tape recorder,
the Left Section, and what parts I had to replace or adjust to get the machine
into good working order.
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Machine Cabinet | To
Control Central-->
Full Transport
Below is
a simplified diagram of the vintage tape recorder transport. It is an animated
gif with a difference - you can roll your mouse over the image (you ned to
have Javascript enabed for this to work) and see the part labels. Operation
is explained below the image.
Power -
The motor always provides power to the capstan flywheel through a drive idler
wheel (in black). The speed at which the flywheel turns depends on the position
of the drive idler on the motor spindle. It is shown here at the
1-7/8 ips speed.
Neutral
Position - The motor always provides power to the capstan flywheel
through a drive idler wheel (in black). All other parts are disengaged except
the reel brakes (in green), which press against the feed reel and take-up
reel drums, preventing tape spills. The brakes are little rubber wheels and
are self adjusting due to some amount of "play" in the control lever (not
shown here).
Play
Position - The pinch roller (in red) presses against the capstan
shaft (in red), trapping the tape so it can be pulled at a constant speed
past the combination erase/record/play head (not shown). At the same time,
the reel brakes (in green) are lifted off the feed reel and take-up reel
drums (in white). The take up reel drum is driven by a clutch assembly (not
shown here) powered by a rubber belt (in black) driven by a pulley located
on the underside of the capstan flywheel. The feed reel drives the 4 digit
tape counter (in black) via a rubber belt (in black), and this also provides
some degree of "back tension" so the tape passes smoothly over the combination
head.
Fast
Forward
Position - The motor always provides power to the capstan flywheel
through a drive idler wheel (in black). The pinch roller (in red) is drawn
off the capstan shaft (in red), (if it was in play mode) and the pressure
pads (not shown here) are withdrawn from the combination erase/record/play
head (not shown). At the same time, the reel brakes (in green) are lifted
off the feed reel and take-up reel drums (in white). An idler wheel (in blue)
presses against both the capstan flywheel and the take up reel drum, transferring
motion and power to the take up reel drum above the clutch line. The speed
of rotation is directly proportional to the speed of the capstan flywheel
which is determined by the location of the motor idler wheel on the motor
pulley. The feed reel provides some back tension through the counter belt
(in black). The second rewind idler wheel is on a rocker arm (not shown)
and is not held against the feed reel drum by any spring, so it basically
is "just hanging there" and does not influence back tension.
Rewind
Position -
The motor always provides power to the capstan flywheel through a drive idler
wheel (in black). The pinch roller (in red) is drawn off the capstan shaft
(in red), (if it was in play mode) and the pressure pads (not shown here)
are withdrawn from the combination erase/record/play head (not shown). At
the same time, the reel brakes (in green) are lifted off the feed reel and
take-up reel drums (in white). An idler wheel (in blue) presses against both
the capstan flywheel and the second rewind idler wheel (necessary to change
the direction of rotation), transferring motion and power to the feed reel
drum. The speed of rotation is directly proportional
to the speed of the capstan flywheel which is determined by the location
of the motor idler wheel on the motor pulley. The take up reel provides some
back tension through the clutch drive (not shown here) which is lightly
engaged.
The photo
below shows the complete internal mechanical layout of the Wollensak 5750
vintage tape recorder. It is a lo-res animated gif (to keep file size down)
that shows the position of the idler wheels in fast forward, neutral and
rewind mode. It does not show the play mode engaged. Watch the positions
of the black idler wheels and the control lever to see the operation. The
dimples and hole in the capstan flywheel are made at the factory when the
wheel is balanced for completely smooth operation.
Full
View:
(large
lo-res animated gif)
LEFT
Section (Feed Reel Area)
The rewind
idler wheels that came with the Wollensak 5750 tape recorder I purchased
on E-Bay were dry and cracked and had flat spots on them. This was expected
after 40 years. I had them re-surfaced by Terry's
Rubber Rollers.
Terry was very careful with the work and the new idlers have very positive
grip. I did not need to have the brake rollers re-surfaced. I had to clean
the 4-digit counter and lubricate it with silicon spray, and I replaced the
counter belt with a belt sold by Turntable
Needles.com. They had categorized the belt by Wollensak Model number,
making ordering the replacement very easy. I also switched the leads on
the headphone jack so the channels were properly aligned to modern headphone
plugs. I re-greased where necessary and adjusted the springs. You can see
the age of the metal in this image,
and some of the pitting, probably caused by air pollution.
Pass your
mouse over the image below to see the various part labels (javascript must
be enabled for this to work.)
One interesting
problem that arose was with the locking latch spring for the different positions
of the transport plate (rewind, neutral and fast forward). Wollensak used
a formed, spring blue steel plate for this. While durable, this material
can fracture or crack due to fatigue and aging (remember that air pollution?),
and there is no way to repair it once this happens. The piece on my Wollensak
5750 was fractured and did not provide a positive lock in the "V" grooves.
(They look like exaggerated saw teeth in the image above, to the right of
the brake arm).
Bending blue
spring steel into shape requires specialized tools that I simply do not have,
even if I could get and cut a piece of blue spring steel to match the broken
spring in my reel to reel tape recorder. I came up with an alternative
solution, using materials I could cut, bend, and form.
My success
at replacing the spring came from a hobby store and an old pipe organ builder's
trick. I bought some sheet brass (.016 thick) at my local hobby shop and
cut a new piece using the old fractured one as a template. To give it added
strength, I incorporated a spring I made from .018 piano wire (that old organ
builder's trick). The spring is held in place by two screws
(visible in the picture) and these made a good anchor points for the wire
spring strengthener (brass is soft and needed some help).
The spring plate doesn't form a perfect "V" to lock into the grooves. The
slight roundedness of the brass "V" shape helps the spring release from the
groove and makes the action smoother, while it still holds the plate locked
in position. Below is a large picture of the replacement I made.
You can
pass your mouse over the image to see another view and labels (javascript
must be enabled for this to work.)
The operation
of this spring is important to the rewind and fast forward functions because
it locks the transport plate in position. Since the transport plate moves
the idler wheels and brake levers, it needs to lock in place or else the
plate can creep, causing the parts to slide off each other, with loss of
traction in the idler wheels and slippage of the brakes. The following lo-res
animated gif demonstrates this action.
Watch the
image carefully and also notice how the brakes are controlled by the small
plate under the rewind/fast forward control lever.
The
next page explains how the
"Control Central" is
laid out, and what I did with the "power Cam" that had a blown
tire on my vintage tape recorder.
<--To
Machine Cabinet | To
Control Central-->
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
