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Delaying Time Base 7B85

Delaying Time Base 7B85; Tektronix Guernsey (ID = 2579969) Equipment
Delaying Time Base 7B85; Tektronix Guernsey (ID = 2518614) Equipment Delaying Time Base 7B85; Tektronix Guernsey (ID = 2518615) Equipment
Delaying Time Base 7B85; Tektronix Guernsey (ID = 2518616) Equipment
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Delaying Time Base 7B85; Tektronix Guernsey (ID = 2518614) Equipment
Tektronix Guernsey: Delaying Time Base 7B85 [Equipment] ID = 2518614 1185x2100
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For model Delaying Time Base 7B85, Tektronix Guernsey Ltd. ; St.Peter Port
Country:  Guernsey
Manufacturer / Brand:  Tektronix Guernsey Ltd. ; St.Peter Port
Year: 1976–1990 ? Category: Service- or Lab Equipment
Semiconductors (the count is only for transistors) Semiconductors present.
Wave bands - without
Power type and voltage Powered by external power supply or a main unit.
Loudspeaker - - No sound reproduction output.
Power out
from Model: Delaying Time Base 7B85 - Tektronix Guernsey Ltd. ; St.
Material Metal case
Shape Chassis only or for «building in»

The Tektronix 7B85 is a 400 MHz delaying timebase for 7000-series scopes with digital delay and delta time read-out capability, typically used in the 7800 Series, e.g. 7844. It does not support X-Y mode.

The delay function differentiates the 7B85 from the otherwise similar 7B80. The 7B87 is also similar to the 7B85 but provides an acquisition clock for a digital storage mainframe instead of a delay.

The 7B85/7B80 combination was introduced in 1976 to replace the 200 MHz 7B71/7B70 that had no digital delay read-out. For the 7104 1 GHz-class scopes, the 7B15/7B10 provide the functionality of 7B85/7B80.


Sweep5 s/Div to 10 ns/Div in 1-2-5 sequence, ×10 magnifier down to 1 ns/Div, variable to ×2.5
Triggeringto 400 MHz
  • Digital read-out of delay and delta times
  • Variable Trigger Holdoff
  • Peak-to-peak Auto Triggering


The 7B85 uses a 155-0185-00 digital voltmeter IC (U686). A ramp generator is started when the trigger signal arrives. The delayed sweep is started when a comparator detects that the ramp has reached a control voltage, set by the front panel knobs on the 7B85. The control voltage is proportional to the amount of delay.

The digital voltmeter in the 7B85 digitizes the control voltage and displays it on the oscilloscope readout, thereby providing the operator with a precise readout of the delay.

Another way of setting up a precisely delayed timebase is to use a 7D11 digital delay module, or even a time mark generator such as the 180A, 181, 184, or 2901.

The 7B85 uses the +50 V supply provided by the mainframe.

Price in first year of sale 4'583.00 CHF
Mentioned in -- Original prospect or advert (Prospect & pricelist 1986)
Literature/Schematics (1) Instruction manual 7B85 first printing Jan 1976 revised Aug 1983

Model page created by Detlef Boeder. See "Data change" for further contributors.

All listed radios etc. from Tektronix Guernsey Ltd. ; St.Peter Port
Here you find 5 models, 5 with images and 1 with schematics for wireless sets etc. In French: TSF for Télégraphie sans fil.