power on delay ESV 700
for all Studer Revox A700
The switch-on delay prevents the disruptive switch-on signal, the loud pops and pops, from being transmitted to the speakers and the headphones during the switch-on phase of the Revox A700. The later versions of the Revox A700 have the on-delay as standard.
In addition, the rash of the pointer instruments is greatly reduced. This protects the analogue VU meters, which can quit the high ripple at the moment of switch-on with a failure of the VU meters!
The delay time is about 4 - 6 sec.
A700 with ESV
Later versions of the Revox A700 have factory built-in delay. This can be seen on the yellow relay (ITT A26xx) on the headphone amplifier board.
Replacement Relay
We also offer a suitable replacement for the relay ITT A 26xx with 18V. We can supply this replacement with 5 V, 12 V, 18 V, and 24 V. The switching capacity is, as in the original 2 A.
Installation ESV 700 for all Revox A700
Open A700
As always! First unplug the power plug!
230 V ~ can be deadly!
The back wall must be removed. For this purpose, 8 Phillips screws are loosened then tilt the rear wall slightly forward and remove carefully.
Audio unit
Technology that excites! Even today, after more than 45 years! Where else is there?
baseplate
remove with 3 screws the front and with 2 screws the rear baseboards. Since the plastic baseboards are often broken, we also offer matching aluminum baseboards for you Revox A700.
Remove mixer
remove the front plate with 2 screws. Of course, first remove the controls.
connector
Pull off 3 connections - Ingenious this structure!
That makes the difference to all other manufacturers!
Disconnect from the device
The complete audio component is attached to the Revox A700 with four large Phillips screws. loosen the screws and pull out the mixer part to the front.
Headphone amplifier
Remove. The headphone amplifier is attached to the connection board with only one screw!
Solder C12 and C22
Instead of the two capacitors, the new switch-on delay is soldered. C12 and C22 are then on the switch-on delay plus two bypass capacitors!
power supply
The supply voltage is connected to C1 UB and to
C2 -UB tapped. We drill a hole in the circuit board and lead through the wires of the power supply. As you can see in the photo, there is enough space.
For better localization, the components (C1, C2, C8, C18 and IC2) were labeled in red and are still without bypass capacitors!
ESV installed
If the relays are visible to the outside (in the direction of RCA sockets on the Revox A700), the switch-on delay is correctly equipped. Now the outputs are switched on delayed!
In addition to the ESV 700, we also offer the meter and the new LED VU meter as well as bearings, repair and condensing units, bulbs and much more.
fast turn off
In order to minimize the pop even when the Revox A700 is switched off, the S-OFF signal of the A700 is required (blue wire). The S-Off signal is picked up on J5a (headphone amplifier) or J6 on pin 1.
Delay headphone output
Disconnect trace
The traces Y3-OUT-L, pin 2 of the connector J5a and Y3-OUT-R, pin 3 of the connector J5a are separated on the connection board of the Revox A700.
Whether you make the separation with a small drill or with a sharp knife is up to you. The important thing is that the separation is complete!
connect with ESV
The same colored strands ge / ge or vio / vio are each soldered over the previously made separations.
This protects the headphone outputs as well as the VU meters from the harmful on and off switching signals.
Both the VU meters, the speakers and your hearing will thank you.
Finished
It should look the same with you or something like that!
Technical changes (availability of components, improvements and so on) must be reserved!
Now reassemble the Revox A700 in reverse order. Before all optically check all work and changes!
ESV 700
in our shop
Here you will find the switch-on delay for your Revox A700
Thomas Schröder
Schottjer Straße 30a
26529 Upgant-Schott
Germany
Schottjer Straße 30a
26529 Upgant-Schott
Germany
+49 4934 - 80 44 39
info@revox-online.de