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[post_date] => 2021-04-29 17:00:58
[post_date_gmt] => 2021-04-30 00:00:58
[post_content] =>
Modification
Increase LED timing circuit.
Difficulty Level
3 - Moderate - removal or replacement of internal components.
Components Required
- Capacitor:
- 220 µfd, 16V, ~2 minutes
- 470 µfd, 16V, ~4 minutes
- 1000 µfd, 16V, ~5 minutes
Instructions
- Remove and replace C3 on the main PC board of the LEF Series master station with a different value capacitor to achieve the desired LED timing length.
- LEDs will stay illuminated for the duration of the timing circuit from the moment the last sub station places a call.
LEF Master Stations
Locate and replace capacitor C3. Change value to a higher level to reach the desired timing circuit length.
- 220 µfd, 16V, ~2 minutes
- 470 µfd, 16V, ~4 minutes
- 1000 µfd, 16V, ~5 minutes
[mkb-info]The capacitor is in the same area on the PC board for both the LEF and LEF-C master stations.[/mkb-info]
LEF-10C Master station
Locate and replace capacitor C3. Change value to a higher level to reach the desired timing circuit length.
- 220 µfd, 16V, ~2 minutes
- 470 µfd, 16V, ~4 minutes
- 1000 µfd, 16V, ~5 minutes
[post_title] => Increase timing circuit of call-in LED
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[post_date] => 2021-04-29 17:03:29
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Modification
Reducing RF interference when too close to a radio station tower, or other source emitting RF noise.
Difficulty Level
4 - Moderate/Hard - internal connection or component addition.
Components Required
- Choke coil: 180 µH inductance.
- Capacitors:
- 0.01 µfd, 25V
- 0.02 µfd, 25V
- AC plug adaptor: 3-prong to 2-prong type.
Instructions
- Install the 3-prong to 2-prong adaptor on PS-12C power supply.
- Install choke coil and capacitors as shown on schematic diagram.
- Cut the circuit as illustrated on the schematic diagram.
- If the RF interference is not reduced to an acceptable level, shielded cable will need to be installed to further reduce the interference. Depending on the severity of the interference, the above suggestions may or may not eliminate the interference.
LEF-3
[mkb-info]Add .01µfd capacitor and 180µH choke coil as shown. Add .02µfd capacitors from each number terminal to ground.[/mkb-info]
LEF-5/10/10S
[mkb-info]Add .01µfd capacitor and 180µH choke coil as shown. Add .02µfd capacitors from each number terminal to ground.[/mkb-info]
[post_title] => Reducing Radio Frequency Interference
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[post_author] => 23
[post_date] => 2021-04-29 17:13:03
[post_date_gmt] => 2021-04-30 00:13:03
[post_content] =>
Summary
Modern intercom systems, with solid state circuitry, are much more efficient and compact than older systems with relays, coils, and vacuum tubes. Unfortunately, they are also more susceptible to malfunction or failure due to transient overvoltage, such as lightning and AC power surges.
Lightning
Lightning overvoltage is caused by a strike of lightning to or near a conductor or shield of an intercom cable. Shielded wire does not provide complete protection against lightning damage. When lightning or other voltage spikes flow on the shield of a cable, voltage is induced between the internal conductors and the shield. The amount of induced current depends on the resistance of the shield material and construction of the cable.
AC Power Surge
A typical example of power surge is the voltage spike that occurs when heavy duty generators are powered up, or when surges occur on the main electrical system. Lightning can also create power surges in AC power lines. Ranging in amplitude from harmless amounts just above normal voltage to several kilovolts. If the intercom cables are run with the AC power lines (which is strongly discouraged), the AC power surge can bleed over into the intercom cables.
About Metal Oxide Varistors
Voltage spikes affect all semiconductors, which are intolerant of voltage transients in excess of their ratings. Even a slight amount of excess voltage can cause a semiconductor to fail or be degraded enough to shorten its useful life. Most lightning damage to intercom systems is caused by lightning opening or shorting semiconductors. A voltage clamping device such as a metal oxide varistor (MOV) is recommended to absorb the voltage spike before it enters the intercom unit. An MOV has the best volt-ampere characteristics, energy absorption, and peak current capabilities compared to other voltage clamping devices. The specifications for an MOV used on an Aiphone system are as follows:
- Continuous DC voltage: 50 ~ 100 V
- Transient Peak Current: » 250 A
- Maximum Clamping Voltage: 100 ~ 150 V
One MOV is to be installed between each wire in the cable and an earth ground for each intercom unit. In lightning-prone areas and where power surges are possible, surge protection should be installed.
Modification
Prevention of AC power surge and/or lightning damage.
Difficulty Level
2 - Easy/Moderate - component connection to external points.
Components Required
- SA-1: surge arrestors, one for every two terminals being protected.
- Surge sensitive power strip.
Instructions
- Plug all system power supplies into surge sensitive power strip, then plug the strip into an AC outlet.
- Wire SA-1s on all intercom terminals as shown on the diagram, with output side connected to an earth ground.
- SA-1s are recommended to be installed on master stations only and are not necessary on remote stations.
[mkb-info]Installation of surge arrestors will not guarantee absolute protection from power surge or lightning strike damage. The SA-1 is designed to aid in the prevention of power surge and lightning strike damage and to reduce component failure within the Aiphone intercom equipment should a surge or strike occur.[/mkb-info]
[post_title] => LEF Power Surge Prevention
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[post_date] => 2021-04-29 17:15:42
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Modification
Eliminate incoming call tone from sub station at a master station.
Difficulty Level
3 - Moderate - removal or replacement of internal components.
Components Required
N/A
Instructions
- LEF-3/3C: remove transistor TR7.
- LEF-5/5C: remove transistor TR7.
- LEF-10/10S: remove transistor TR8.
- LEF-10C: remove transistor T7.
LEF-3
LEF-5
LEF-10
[post_title] => Eliminating Call Tone from Sub Station at LEF Master Station
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[post_content] =>
Modification
Increase LED timing circuit.
Difficulty Level
3 - Moderate - removal or replacement of internal components.
Components Required
- Capacitor:
- 220 µfd, 16V, ~2 minutes
- 470 µfd, 16V, ~4 minutes
- 1000 µfd, 16V, ~5 minutes
Instructions
- Remove and replace C3 on the main PC board of the LEF Series master station with a different value capacitor to achieve the desired LED timing length.
- LEDs will stay illuminated for the duration of the timing circuit from the moment the last sub station places a call.
LEF Master Stations
Locate and replace capacitor C3. Change value to a higher level to reach the desired timing circuit length.
- 220 µfd, 16V, ~2 minutes
- 470 µfd, 16V, ~4 minutes
- 1000 µfd, 16V, ~5 minutes
[mkb-info]The capacitor is in the same area on the PC board for both the LEF and LEF-C master stations.[/mkb-info]
LEF-10C Master station
Locate and replace capacitor C3. Change value to a higher level to reach the desired timing circuit length.
- 220 µfd, 16V, ~2 minutes
- 470 µfd, 16V, ~4 minutes
- 1000 µfd, 16V, ~5 minutes
[post_title] => Increase timing circuit of call-in LED
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