new tape drive control Revox B77
1.177.318 new developments
Yes, years ago we were asked if we'd like to create a new tape drive control system with motorised braking as well as mechanical braking! A friend, a Revox and Studer fan who no longer has a B77, was very persistent!
Development took a bit longer, and many hidden pitfalls had to be circumvented. It quickly became clear to us that we also wanted to use solid-state relays. The new board should definitely not perform worse than the original, and we had to adhere to the many specifications of the Revox B77 tape machine. Motorized braking was a MUST! Adjusting the sensitivity of the tape end sensor, galvanically isolating the motor voltages from the 5 V or 24 V operating voltage, and ensuring low power consumption were also MUST!
the technology
Solid State Relay
instead of triacs
4 modern solid state relays with zero voltage switches ensure galvanic isolation. We at Premium-Hifi have
The AC voltage of the motors is completely separated from the control voltage! This prevents interference in the AC voltage from being transmitted to the control voltage.
Four yellow LEDs
The LEDs indicate the motor control and the relay status. This provides a clear visual representation of the system's functionality.
Tape End Sensor
sensitivity
The sensitivity of the tape end sensor can be adjusted over a wide range using the trimmer R56.
Danger!
You can turn it down so far that it always shuts off or turn it up so far that it never shuts off!
Voltage regulator
switching regulator
To ensure low power consumption, we use an efficient clock regulator with an efficiency of 85% or higher. This is especially important when regulating from a high input voltage of 27 V down to just 5 V. Linear regulators are unsuitable!
DIL switch
for device version
mit Hilfe der DIL-Schalter Position 1 und 2 kann die Geräteversion eingestellt werden.
Dabei ist: 0 0 Super Low Speed
1 0 Low Speed
0 1 Standard Speed
1 1 High Speed
This serves to reduce loop formation and improve belt tension, better braking performance, etc.!
break resting
The latching pause can be switched on with DIL switch position 3.
0ff = Pause momentary for devices with cable remote control without modification and
ON = Pause latching for all other devices.
An additional pause circuit is not supported and may lead to malfunctions. DIL switch position 4 is still free or is used for testing.
Tape Tension
Connections
for the tape tension input.
At Premium-Hifi, we evaluate both the reel size and the selected speed. Unfortunately, with the MK I up to serial number 53,521, no signal is provided at all, and up to serial number 99,999, only the reel size is passed on to the drive control.
Only from serial number 100,000 onwards, from MK II, did Revox provide the drive control with both the reel size and the selected speed!
new tape tension board
So that you can evaluate both the reel size and the current speed for tape machines of the first series (Revox B77 MK I up to serial number 99,999), we have designed a new tape tension circuit board 1.177.138-22.
You'll receive instructions, a wiring harness, and matching screws for the circuit board. You'll need to remove the button from the old reel-size switch.
Tape Move Sensor
Connections
for the belt movement sensor.
The position is determined by the tape machine.
We've provided 6 connections here instead of the original 5. Pin 4 serves as a key to prevent incorrect connection.
Both the Revox B77 MKI and the MKII use only pins 1, 3, and 5. We at revox-online plan to use pin 6 for possible future options.
LEDs
green LEDs
Two green LEDs indicate the presence of 5 V and 24 V. If both LEDs appear to be equally bright, the voltages are OK. If there are significant differences in brightness, the board must be sent in for inspection and repair.
rote LEDs
Seven red LEDs indicate the status of the Revox B77. However, the LEDs can also be used for other purposes. For example, when programming, for example, function calls or the AD value of the tape tension input! There's no obligation to use the LEDs; anything is possible, up to the complete removal of the LEDs!
Motor
Brakes
why we are making the new board!
Brakes
Braking itself cannot be depicted visually!From fast forward or rewind, all subsequent new actions (stop, play, record, and pause) will brake electronically and mechanically until almost a stop. After that, only mechanical braking occurs until a complete stop, and the new function is activated.
Fast
Braking is very fast, similar to that of professional Studer studio machines.
The Revox B77 specifies the connections and their positions in the layout. The functions, their sequence, and their timing must also be correct and are subject to strict specifications from the Revox B77.
brand new drive control
1.177.318
for all Revox B77 you can find in our shop
