I greet all the members.
Over the years, thanks to many of you and previous experience over the years of repairs, I learned a lot about class D amplifiers of all types.
This is one of those things I hope to learn today.
In the korean amplifiers, built by ZENON or S&I (but also others that make use of the IRS21844S chips and maybe also other chips) I have often noticed the presence of transient suppressor diodes, many times these diodes have broken due to a catastrophic failure of the output stage, but to my surprise, these are not just fast diodes.
The abbreviation of these diodes is "P6KE250A", simple zeners?
As I already mentioned in another thread, very often, due to lack of availability, I simply removed these diodes and the amplifier always worked without any problems.
Obviously, if they have been used, there will be a reason, but I can't understand which one.
Who is kind enough to make me understand?
Over the years, thanks to many of you and previous experience over the years of repairs, I learned a lot about class D amplifiers of all types.
This is one of those things I hope to learn today.
In the korean amplifiers, built by ZENON or S&I (but also others that make use of the IRS21844S chips and maybe also other chips) I have often noticed the presence of transient suppressor diodes, many times these diodes have broken due to a catastrophic failure of the output stage, but to my surprise, these are not just fast diodes.
The abbreviation of these diodes is "P6KE250A", simple zeners?
As I already mentioned in another thread, very often, due to lack of availability, I simply removed these diodes and the amplifier always worked without any problems.
Obviously, if they have been used, there will be a reason, but I can't understand which one.
Who is kind enough to make me understand?
They act like zener diodes, but are specifically designed to eat large short transient high current pulses.
In the 1980's there were certain cars known for huge negative voltage spikes on the electrical system. The large Ford 4 door sedans often used as police cars were the worse offenders. I worked at Motorola, and was responsible for figuring out why police radios would burst into flames when the car was started even though the radio was off. We even got an old Ford Crown Victoria cop car to experiment on.
The car has an air conditioning compressor containing an electromagnetic clutch, basically a large copper and iron inductor that is connected directly to the switched 12 volt supply when the AC and the car is running. If the car is switched off with the AC on, the connection to the low impedance car battery is broken. The stored magnetic energy in the clutch coil will create a large high energy negative voltage spike that would be absorbed by the car's battery, except that connection was severed when the ignition (and accessory power) was turned off. That spike sent a large negative voltage into the radio blowing up several parts, but this wold not be obvious until power was turned back on with shorted transistors.
The transient protection diodes were added to the radio which fixed the dead radio problem. Ford eventually added the diode directly on the clutch coil under the hood, which also helped solve other dead electronics issues, including their own EEC systems.
Today's cars have many electromechanical devices (relays and solenoids) which can create all sorts of transient events on the car's electrical system. Traditional electronics for the automotive market are usually rated for brief surges up to +/- 60 volts. These diodes bear the brunt of this, but voltage regulator chips are also usually specified for the automotive market.
Yes, the amp will work fine without the diodes, but one day it will just appear dead for no reason (probably blown outputs, or power supply switch fets)......it might have survived with the diodes in place. finding blown diodes are an indication that a big spike occurred....or the polarity was reversed.
In the 1980's there were certain cars known for huge negative voltage spikes on the electrical system. The large Ford 4 door sedans often used as police cars were the worse offenders. I worked at Motorola, and was responsible for figuring out why police radios would burst into flames when the car was started even though the radio was off. We even got an old Ford Crown Victoria cop car to experiment on.
The car has an air conditioning compressor containing an electromagnetic clutch, basically a large copper and iron inductor that is connected directly to the switched 12 volt supply when the AC and the car is running. If the car is switched off with the AC on, the connection to the low impedance car battery is broken. The stored magnetic energy in the clutch coil will create a large high energy negative voltage spike that would be absorbed by the car's battery, except that connection was severed when the ignition (and accessory power) was turned off. That spike sent a large negative voltage into the radio blowing up several parts, but this wold not be obvious until power was turned back on with shorted transistors.
The transient protection diodes were added to the radio which fixed the dead radio problem. Ford eventually added the diode directly on the clutch coil under the hood, which also helped solve other dead electronics issues, including their own EEC systems.
Today's cars have many electromechanical devices (relays and solenoids) which can create all sorts of transient events on the car's electrical system. Traditional electronics for the automotive market are usually rated for brief surges up to +/- 60 volts. These diodes bear the brunt of this, but voltage regulator chips are also usually specified for the automotive market.
Yes, the amp will work fine without the diodes, but one day it will just appear dead for no reason (probably blown outputs, or power supply switch fets)......it might have survived with the diodes in place. finding blown diodes are an indication that a big spike occurred....or the polarity was reversed.
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