THS720

Manuals – Specifications – Links – Pictures

The Tektronix THS720 is a portable 100 MHz, 500 MS/s (each channel) dual-channel digital oscilloscope with isolated inputs.

There were two variants, the THS720 STD and the THS720A. The primary difference is that the THS720A will trigger from the DMM input.

The THS720P includes features for electrical/power electronics measurements.

Murlan Kaufman designed the THS700 series high voltage isolated front end.

Key Specifications

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See THS720/Accessories for details on cables and other accessories.

Operation

Due to the isolated inputs, the probe ground must be connected even when compensating the probes with the "PROBE COMP" output. It can be used with any BNC probe but the scale factor pin found on many Tektronix probes is not used. The vertical menu has a scale factor entry (1×, 10×, 100×, 1000×) which can also be used for direct BNC inputs.

Recommended probes are the P5102 and the P6113B, both are 10× probes with protected grounds for isolated measurements. The P5102 has the best isolation, allowing 600 V between reference ground and earth ground.

Links

• EEVBlog Forum thread on The THS7XXX series scopes
• Tektronix THS700 Series Oscilloscope Mega Video by Near Far Media @ YouTube

Documents Referencing THS720

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Internals

Primary microprocessor is the Motorola/Freescale MC68331CFC16. An Intel E28F008SA120 Flash Memory chip is used for setup, cal and waveform storage. The switching power supply is run by a TL1451A, a TI two channel boost/buck controller. The DMM is a 3¾-digit Maxim MAX134CQH.

The analog scope section starts with an attenuator hybrid driven by four channels of HP (now Broadcom/Avago) optoisolators and NEC relays. The hybrid contains the AC coupling capacitor and many laser trimmed resistors along with a custom Tek chip (165-2545-00) in a BGA package. The signal then passes through a single-ended to differential transformer and goes to a custom-labeled Maxim two-channel high speed A/D converter (234-1503-20). Note that the differential signal layout for channel 2 is not as good as channel 1 since one side of channel 2 goes through 2 vias not found on channel 1. These optoisolators sometimes drift, causing a DC offset issue. They can be directly replaced with Broadcom/Avago part number HCNR201 (any of the -300E, -500E, -350E, or -550E variants will work) which are still readily available.

Firmware is updated using the 067-1436-00 Communication Pod with an adapter cable via an internal connector.

A THS710A and THS720A can be upgraded to a THS720P with the removal of a few resistors on the main board (see pictures for details). No adjustment/calibration is required after this modification.

NOTE: A THS710STD can be upgraded to a THS720STD, but due to main board differences, these models CANNOT be upgraded to a -A or -P model
Additionally, lower model scopes cannot be upgraded to a THS730A due to different input hybrid modules being used in the THS730A to provide the increased bandwidth.

Software

• DOS program to display FFT - 066-0109-00 (ZIP)
• THS General Extended Logging Feature Software - 066-0153-00 (ZIP, 48 KB)
• Wintek32 THS General BMP Extractor v2.0.5.21  Other versions: 066-0154-00 v2.01 (ZIP, 90 KB)
• Tektronix Wavestar 2012.05.09.11.07.29 16456 EN 066-0934-03 (ZIP, 102MB) Product Key: WSTRO618650124
• Docuwave 1.2 for DOS (ZIP, 704 KB)
• THS7XX HardCopy by Marco M. Schäck (ZIP, 63KB) www.schaeck-online.de

Pictures

THS720

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  THS720STD Displaying probe compensation waveform

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  THS720STD Top of Main PCB

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  THS720STD Back of Main PCB

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  THS720STD Attenuator with cover removed

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  THS720STD Operation without case

THS720A

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  THS720P Upgrade mod

THS720P

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  THS720P Top of Main PCB

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  THS720P Back of Main PCB

Accessories

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  Battery Charger

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  Battery Charger Internal

Components

Some Parts Used in the THS720

Part	Part Number(s)	Class	Description	Used in
Motorola 68000	156-1445-00	Monolithic integrated circuit	16-bit microprocessor	4041 • AM700 • DAS9200 • Keithley 182 • RTD710 • SG5030 • Prism 3002 • THS720