DM504A

Tektronix DM504A

4½ digit autoranging digital multimeter

Produced from 1989 to (?)

Manuals

ROM/PLD Images

File	Pos.	Checksum

160-5426-05 / 160-5426-03 / 160-5426-00 (27C64) please add

(Manuals are OCRed PDF files unless noted otherwise)

Manuals – Specifications – Links – Pictures

The Tektronix DM504A is an 4½ digit autoranging digital multimeter plug-in for the TM500 system.

Key Specifications

DC Voltage	200 mV to 1000 V in decade steps, ±0.05%; Input resistance 10 MΩ (200 kΩ in 0.2 and 2 V ranges if V_in >12 V)
AC Voltage	200 mV to 500 V in decade steps, ±0.6%; Input resistance 10 MΩ // 100 pF
DC current	200 μA to 2 A in decade steps, ±0.1%
AC current	200 μA to 2 A in decade steps, ±0.6%
Resistance	200 Ω to 20 MΩ in decade steps, 0.05% (0.1% in 2 and 20 MΩ ranges
Temperature	−62 °C to +230°C with P6602 2-wire PT-100 probe
Display	4½ digits, red LED, 2/s update rate
Features	Modes: DC Volts / mA, AC Volts/ mA (True RMS), Ohms, and Temperature Diode Test and Audible Continuity (Beeper) Modes

Links

DM504A @ barrytech.com (waybackarchive)
DM504A repair by VintageTEK Museum @ YouTube
Tektronix DM504A Restoration and Check In by Zenwizard Studios @ YouTube

Documents Referencing DM504A

(no results)

Internals

The DM504A has no rear interface I/O. The entire circuit is supplied from a +12/−12/+5 V floating power supply that uses a small mains-frequency transformer fed by one of the mainframe's 25 V_AC windings.

The circuit is based on an 80C31 microcontroller with a Texas Instruments TL500C integrating A/D front-end and a 1N827 temperature-compensated zener reference. The DM504A is software-calibrated, storing cal constants in a 93C46 EEPROM. Calibration is triggered by pressing Up and Down buttons simultaneously while the internal cal jumper is in the "enabled" position.

Pictures

DM504A
DM504A
DM504A LH Interior with HV shield in place
DM504A RH Interior with HV shield in place
DM504A LH Interior with HV shield removed
DM504A RH Interior with HV shield removed

Components

Some Parts Used in the DM504A

Part	Part Number(s)	Class	Description	Used in
AD737	156-3506-00	Monolithic integrated circuit	RMS/DC converter	DM504A • DMM870
Intel 8031	156-1684-00	Monolithic integrated circuit	8-bit microcontroller	11A33 • 11A71 • 11A72 • 11A81 • 11F10 • 1725 • 571 • ASG100 • DM504A • DM511 • DM5110