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Tektronix DC504
80 MHz, 5-digit frequency counter
Tektronix DC504

Produced from 1975 to 1983

(All manuals in PDF format unless noted otherwise)
Manuals – Specifications – Links – Pictures

The Tektronix DC504 is a 80 MHz, 5-digit frequency counter plug-in for the TM500 system.

It was superseded by the DC504A in 1984.

Key Specifications

Frequency Range DC (AC coupled: 10 Hz) to at least 80 MHz
Sensitivity 20 mVRMS sine wave below 15 MHz, 35 mVRMS to 50 MHz, derated down to 175 mVRMS at 80 MHz
Input impedance 1 MΩ // 20 pF
Trigger Level Range −1.5 V to +1.5 V
Frequency Resolution kHz ranges: 0.1 Hz; 1 Hz and 10 Hz (7 digit resolution possible in overflow kHz position); MHz ranges: 100 Hz, 1 kHz (9 digit resolution possible in overflow kHz position)
Period resolution ms ranges: 1 µs, 10 µs; s ranges: 10 ms, 1 ms, 0.1 ms
Display Time Variable ~0.1 s ... ~10 s and HOLD mode
Standard Time Base 1 MHz, ±1×10-5 from 0°C to +50°C, ±1×10-5 per month, Adjustable to within 1×10-7
Opt. 1 Time Base 5 MHz, ±1×10-7 from 0°C to +50°C, ±1×10-7 per month, Adjustable to within 1×10-9

An internal "RPM" mode switch stretches gate times sixfold, giving a longest gate time of 1 minute with a display scaled in revolutions per minute.


Documents Referencing DC504

Document Class Title Authors Year Links
070-2088-00.pdf Book TM500 Series Rear Interface Data Book 1975
070-2088-01.pdf Book TM500 Series Rear Interface Data Book 1976
070-2088-04.pdf Book TM500 Series Rear Interface Data Book 1985

Rear Interface

28B − Gate Out, Totalize Start/Stop 28A − Hold
27B − Decimal point
26A − /Reset
25A − TS1 (digit select 1, MSD)
24B − Scan clock out 24A − TS2 (digit select 2)
23B − Overflow 23A − TS3 (digit select 3)
22A − TS4 (digit select 4)
21B − BCD out 2 21A − TS5 (digit select 5, LSD)
20B − BCD out 8 20A − BCD out 4
19B − Latch Out (Data Good) 19A − BCD out 1
17A – Signal Input GND
16A − Signal input
15A – External Clock GND
14A − External Clock (GND on 15A)


The DC504 uses a Mostek MK5009P PMOS oscillator/counter IC to control gate times. The first counter stage is a Signetics 82S90 85(100) MHz decade counter, followed by four 7490 decade counters, 7475 latches, and 7401s to multiplex the output/display.



Some Parts Used in the DC504

Part Part Number(s) Class Description Used in
2N4249 151-0342-00 Discrete component PNP Si low noise amp. DC501 DC502 DC503 DC503A DC504 DC504A DC505 DC505A DC508 DC508A DC509 DC510
Mostek MK5009 156-0410-00 Monolithic integrated circuit oscillator/counter DC504
Signetics 82S90 156-0482-01 Monolithic integrated circuit 85(100) MHz decade counter DC504