DC504A

The Tektronix DC504A is a 100 MHz, 6-digit frequency counter plug-in for the TM500 system.

Manuals – Specifications – Links – Pictures

It replaced the DC504.

Key Specifications

Frequency Range	DC (AC coupled: 10 Hz) to 100 MHz (rear interface 50 MHz)
Sensitivity	30 mVRMS sine wave to 100 MHz, 85 mVp-p pulse ≥5 ns
Input impedance	1 MΩ // 25 pF (rear interface 50 Ω)
Gate time	10 ms to 10 s in decade steps (autoranging 10 ms to 1 s)
Trigger Level Range	±2 V × attenuator setting
Totalize mode	1–999999 counts up to 10 MHz
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
Time Base	10 MHz, ±1×10-7, ±5 ppm from 0°C to +50°C, ±1×10-6 per year, Adjustable to within 5×10-8

Differences to DC504

The DC504A adds a 6^th display digit, extends the frequency range to 100 MHz, and single-shot resolution to 100 ns. It adds autorange and averaging, and a PLL that multiplies frequencies from 10 Hz to 25 kHz by 100.

Unlike its predecessor, the DC504A has no digital outputs on the rear interface, only signal and clock inputs. There is no int/ext front panel switch (replaced by an internal jumper), and no RPM mode/jumper.

Internals

The DC504A is built around an Intersil ICM7226 counter/7-segment driver IC. The prescaler for 10−100 MHz is an MC10138 ECL counter. The ×100 PLL circuit uses a CD4046.

Rear Interface

• 16A − Signal input (GND on 17A)
• 14A − External Clock (GND on 15A)

Pictures

• 

  DC504A

• 

  DC504A

• 

  DC504A left internal

• 

  DC504A right internal

• 

  DC504A 3/4 view

Components

Some Parts Used in the DC504A

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
ICM7226	156-1655-00	Monolithic integrated circuit	8-decade counter and 7-segment driver	DC504A • DC5004