Teleste AC2000, teardown of a 862 MHz cable TV amplifier

This Teleste AC2000 is a cable TV amplifier that is configurable through different insert jumpers for setting up attenuation/equalization, diplex filters, return amplifier or a transponder making it remote controllable.  This is a dual 39 dB amplifier in the range from 5 to 862 MHz which enables it of delivering 110 channels. 

This particular amplifier is set up for one input, a bypass for next amplifier in the chain and two outputs. There is no transponder installed.

These small amplifiers are used in houses where it is not practical to use a receiving antenna to get the signal from the broadcast headend transmitter. They are called a “service drop”

Instead CATV is used, short for community antenna TV, a large receiving antenna is used, a cable connection runs out to every house in the neighborhood and each house has one of these amplifiers. The return path amplifier can also send some of the signal back into the line to keep the signal good enough for the next house.

It is installed in a weather proof enclosure meant for outdoor wall installation where it is most practical to have the antenna input cable come up from the ground and from there on route cables into houses and apartments.

The internal power supply has a input voltage range from 27 to 65 VAC/35 to 90 VDC and has two output voltages. 24 VDC at 1400 mA maximum and 12 VDC at 900 mA maximum. 

The manufacturer specifications of this cable TV amplifier

  • 2-3 outputs by internal splitting
  • Spectrum analyser function
  • Plug-in module adjustments
  • Fixed station memory for electrical identification
  • Electrical gain & slope control modules
  • Optional high performance return amplifier
  • Downstream signal path 85…862 MHz (110 channels)
  • Input attenuator control range 20 dB
  • Input equaliser control range 25 dB
  • Mid-stage slope 8 dB
  • Flatness ± 0.4 dB
  • Upstream signal path 5…65 MHz

If transponder was installed:

  • US ingress monitoring
  • Return path ingress switches ON/ -6 dB / OFF control
  • 65 VAC voltage measurement
  • Local DC voltages, 12 V and 24 V
  • Temperature measurement
  • Gain and slope controlling in ALSC mode
  • Individual channel level measurement (AC6951)
  • Spectrum analyzer function
  • Lid status monitoring
  • Local connection indication at server
  • Configuration data stored in main board eeprom (station memory)

Attenuators, for all TVs manufactured after 1995, the signal strength at the TV should be between -10 dB and +15 dB, this is achieved with 20 dB range on inserts in this amplifier.

Equalizer or also called slope, is the difference in signal strength between the highest and lowest channels. This is also handled with inserts in a 25 dB range for input and 8 dB for mid-stage. To get a frequency response of ± 0.4 dB, also called flatness.

Attenuators and equalizer inserts are for the most a plastic container with the following content, a gold plated 3-legged 2-3 resistor setup.

A diplexer is a passive device that implements frequency-domain multiplexing. Two ports (e.g., L and H) are multiplexed onto a third port (e.g., S). The signals on ports L and H occupy disjoint frequency bands. Consequently, the signals on L and H can coexist on port S without interfering with each other.

The heart of this box is the CATV amplifier modules which was the popular choice of silicon in amplifiers of this type from the 1990’s.

Features of these hybrid amplifier modules for CATV systems operating over a frequency range of 40 to 450 MHz at a voltage supply of +24 V and intended for use as a line-extender.

  • Excellent linearity
  • Extremely low noise
  • Silicon nitride passivation
  • Rugged construction
  • TiPtAu metallized crystals

 The internal construction of the hybrid amplifier module can be seen below.

Close-up of the six transistors in the module.

Video with explanation of the different parts while the amplifier is being taken apart.

About Mads Barnkob

Electrician, experimenter and amateur scientist with experience in industry automation, programming and all kinds of high voltage generating electronics.
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