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Chip Amps Amplifiers based on integrated circuits

Repair and re-use PC speaker amp circuit?
Repair and re-use PC speaker amp circuit?
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Old 30th March 2016, 12:49 AM   #1
BasicHIFI1 is offline BasicHIFI1  Sri Lanka
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Default Repair and re-use PC speaker amp circuit?

This circuit is not working, uses 120 V AC but was probably connected to 220 VAC which caused a minor overload.

Troubleshooting and fixing should be fun, any suggestions? First get the chip specs and see the input voltage, then connect a 9V batt and see where the power comes up to and where it stops.

Hope the chip is not blown.
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File Type: jpg pcs2close.jpg (243.0 KB, 303 views)
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Old 30th March 2016, 02:45 AM   #2
joesphanlu is offline joesphanlu  United States
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probably a fuse, some are the ones you find in christmas lights, others are shaped like diodes. to pass UL or the fcc i think it has to have a fuse.. check the power supply board for it too.
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Old 30th March 2016, 02:52 AM   #3
joesphanlu is offline joesphanlu  United States
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not too high end in my opinion:
http://rohmfs.rohm.com/en/products/d...r/ba5406-e.pdf
but if you're driving casual speakers in a casual environment, the 0.3% thd is good enough in my opinion.
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Old 31st March 2016, 06:16 AM   #4
BasicHIFI1 is offline BasicHIFI1  Sri Lanka
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I tried out the following:

Cut the AC input wires from the transformer and connected a 9V battery to the terminals.

No output. Some crackling noises when the battery terminals were touched with the wires.

No contact across switch. Removed switch and shorted wires. removed input wires - they looked burned out and shorted. Connected input wires to the bass and treble output. No sound yet.

Maybe it is the diode bridge? Will find output from diode bridge and connect the 9V to that, but with the correct polarity.

Went through this:

Troubleshooting and Repair of Consumer Electronic Equipment

Apparently no output points to a power problem and is relatively easy to fix.
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Old 31st March 2016, 11:21 AM   #5
wwenze is offline wwenze  Singapore
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It has a transformer...

How old is this ****
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Old 1st April 2016, 12:49 AM   #6
BasicHIFI1 is offline BasicHIFI1  Sri Lanka
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It is before 2000. I see that the 1 and 12 pins are for input voltage. WIll connect direct give input and see if it works

Otherwise I will remove all components and connect them on a breadboard.
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Old 12th April 2016, 12:17 AM   #7
BasicHIFI1 is offline BasicHIFI1  Sri Lanka
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I connected a 9 volt battery to the pins 1 and 12, not thinking about polarity, maybe that put paid to whatever was left of the chip, however I could not get any sound except a crackle when attaching the speakers. As far as I know the input signal was OK.

From the circuit board it looks like the power supply goes directly to the pins, so that would make sense, so a 220 volt supply converted to 24 V ac instead of 12 V AC would have gone directly to the chip and shorted it out.

I will be abandoning this project and looking for a different amplifier board. I plan to take apart this board and re-use the components after checking each one, should be fun.

Maybe I will buy a BA 5406 chip, its cheap.

BA5406 Audio Amplifier IC Free Shipping | eBay
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Old 26th December 2017, 11:42 AM   #8
BasicHIFI1 is offline BasicHIFI1  Sri Lanka
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Reviving this project, hope to repair it or get it repaired. First step is to power it up and check if power is reaching pin 1 and 14 . Next see how it responds to input signal.
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Old 31st December 2017, 04:42 AM   #9
BasicHIFI1 is offline BasicHIFI1  Sri Lanka
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First, some reading up:

Troubleshooting Audio Electronics Without Tears

Troubleshooting & Repair Guide

A nice free book:

ELECTRONICS REPAIRING AND LEARNING CIRCUITS FOR FREE: TESTING ELECTRONIC COMPONENTS


And this interesting video:

YouTube
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Old 1st January 2018, 03:20 AM   #10
BasicHIFI1 is offline BasicHIFI1  Sri Lanka
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Photo of the circuit board and connections. Some of the labels are visible, some can be deduced from the original wiring.

Test :

1) Connect 9V to the AC in wiring and check if Pin 1 on the BA 5406 receives any power, ie check voltage between pin 1 and 12.

2) If this is OK, then connect an audio source to input and check if there is an output signal on each channel.


"To find out if current is flowing though a circuit or a low-value resistor, turn the project ON and measure the voltage either across the component or the voltage on one end then the other."

ELECTRONICS REPAIRING AND LEARNING CIRCUITS FOR FREE: TESTING ELECTRONIC COMPONENTS
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Last edited by BasicHIFI1; 1st January 2018 at 03:27 AM. Reason: Sources
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