new drive board B77
1.177.318 new development
Yes, years ago we were asked whether we wanted to make a new undercarriage control and then brake not only mechanically but also electronically! A friend and Revox and Studer fan who no longer has a B77 was very stubborn!
The development took a little longer, many cliffs that were not visible in this way had to be circumnavigated. It quickly became clear to us that we also wanted to use solid-state relays. In no case should the new circuit board behave worse than the original and we had to adhere to the many specifications of the Revox B77 tape machine. The electronic braking was a MUST! The setting of the sensitivity of the tape end sensor, the galvanic isolation of the motor voltages with the 5 V or 24 V operating voltage and the low power consumption are also a MUST!
the technique
Solid State Relais
instead of triacs
4 modern solid state relays with zero voltage switches ensure galvanic isolation. We at revox-online have completely separated the AC voltage of the motors from the control voltage! This means that disturbances on the AC voltage are no longer transmitted to the control voltage.
Four yellow LEDs
indicate the control of the motors and the status of the relays.
Tape End Sensor
sensitivity
The sensitivity of the tape end sensor can be adjusted over a wide range using the trimmer R56.
Caution!
You can turn it down so it always shuts down, or turn it up so it never shuts down!
voltage regulator
switching regulator
To ensure low consumption, we use an efficient clock controller with an efficiency of 85% or higher. This is particularly important when regulating down to just 5 V with a high input voltage of 27 V.
DIL switch
for device version
The device version can be set using the DIL switch positions 1 and 2.
Where: 0 0 Super Low Speed
1 0 low speed
0 1 standard speed
1 1 high speed
This serves to reduce the formation of loops and an improved tape tension, better braking behavior, etc.!
Pause rastend
The latching pause can be switched on with DIL switch position 3.
0ff = pause momentary for devices with wired remote control without modification and
ON = Pause maintained for all other devices.
An additional pause circuit is not supported and can lead to malfunctions. DIL switch position 4 is still free or is used for tests!
Tape Tension
connections
for the tape tension input.
We at revox-online evaluate both the bobbin 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 make the reel size and the selected speed available to the drive control!
new tape tension board
We have designed a new tape tension circuit board 1.177.138-22 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).
You will receive instructions, a wiring harness and suitable screws for the circuit board. You have to pull the knob off the old reel size switch.
Tape Move Sensor
connections
for the belt movement sensor.
The position is determined by the tape machine.
We have provided 6 connections here instead of the original 5 connections. Pin 4 serves as a key to avoid incorrect plugging.
Both the Revox B77 MKI and the MKII only use pins 1, 3 and 5. We at revox-online want to use pin 6 for any later options.
LEDs
green LEDs
Two green LEDs indicate the presence of the 5V and the 24V. If both LEDs are visibly equally bright, the voltages are OK. If there are large differences in brightness, the circuit board must be sent in for inspection and repair.
rote LEDs
7 red LEDs indicate the status of the Revox B77. The LEDs can also be used for other purposes. When programming e.g. B. the function calls or the AD value of the tape tension input! There is no claim to the LEDs, everything is included until the LEDs are completely gone!
electronic braking
why we are making the new circuit board
brakes
The braking itself cannot be illustrated!From fast forward or rewind, all further new actions (stop, play, record and pause) are braked electronically and mechanically until they almost come to a standstill. After that, it is only braked mechanically until it comes to a complete standstill and the new function is activated.
Fast
The braking is very fast, similar to that of the professional Studer tape machines.
The Revox B77 specifies the connections and their positions in the layout. The functions, their sequence and the timing must also fit and are subject to the strict specifications of the Revox B77.
brand new drive controller
1,177,318
for all Revox B77 can be found in our shop
Thomas Schröder
Schottjer Straße 30
26529 Upgant-Schott
Germany
Schottjer Straße 30
26529 Upgant-Schott
Germany
49 4934 - 80 44 39
info@revox-online.de