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

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

Produced from 1975 to 1983

(All manuals in PDF format unless noted otherwise)

It was superseded by the DC504A in 1984.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