Comments on: Provided Speaker Protection Circuit In Philips Amplifier 22AH393

By: Matthew E

Matthew E — Fri, 03 May 2024 00:07:40 +0000

Where did you find the replacement output transistors, or do you know of any equivalent that is available?

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By: Chandralal Cooray

Chandralal Cooray — Sun, 04 Jun 2023 13:46:00 +0000

Hi, im chandralal Cooray from Sri Lanka, I have Philips Stereo Aplifier 22ah393 faulty need circuit diagram,if you have please send me great help for recovery of the equipment.

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By: Parasuraman Subramanian

Parasuraman Subramanian — Wed, 19 Jun 2019 13:25:31 +0000

In reply to Justice.

Kindly study the data of the IC used for protection. You can learn how it works and what it does from it.

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By: Justice

Justice — Wed, 19 Jun 2019 10:39:18 +0000

Thanks Parasuraman but I could not really understand the protection for the speakers. Is it the 2.5mA self-resetting thermal fuse as Albert's experience or is it something else?

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By: S Ramachandran

S Ramachandran — Sun, 16 Jun 2019 04:21:55 +0000

Dear, Mr parsuraman ,

nice idea of including speaker prot ckt .to avoid speaker failures.

in the early days of my repairs of amplifiers ..we use a capacitor in series with testing speakers to avoid coil getting burnt. also check for dc voltages present across speaker terminals with out load.

thanks for your nice presentation .

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By: Albert van Bemmelen

Albert van Bemmelen — Fri, 14 Jun 2019 16:59:32 +0000

Good thing that you were able to provide this amplifier with a speaker protection circuit. And it is a good warning to all of us to be careful when connecting the outputs to our speakers!
I've experienced almost such same problem with my 400 Watt Yamaha amplifier when it suddenly refused to play output to the left channel. The relay in my amplifier protected the amplifier components by being activated because of the reflex 2-way Bass speaker that had a shorted speakercoil. I never expected my speaker to blow or when it had happened. And to prevent this from happening again I now have soldered 2 selfrestoring thermal protection fuses of 2.5A in serie that activate within about 3 seconds if the current through the 50 Watt Bass speakers gets to high. And my 80 Watt ELAC peak 2-way boxes with good Westra speakers are probably safe for a long period of time now. Speakers that I was lucky to buy second hand on eBay because they are no longer manufactured or sold.

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By: Robert Calk Jr.

Robert Calk Jr. — Fri, 14 Jun 2019 15:41:13 +0000

Good job, Parasuraman!

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By: Anwar Shiekh

Anwar Shiekh — Fri, 14 Jun 2019 15:13:03 +0000

I like you self critical attitude; it is very healthy.

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By: George Greenfield

George Greenfield — Fri, 14 Jun 2019 15:07:36 +0000

Greetings Parasuraman,

Been there and done that as they say.
In my early years I fried a few speakers before coming up with 8 Ohm "dummy" loads.
I like the protection circuit. I may build one myself.

Well done !

George

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