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Old 5th July 2010, 07:42 PM   #1
FlyAndy is offline FlyAndy  Australia
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Default Jims Audio - 30A Speaker Protection Kit

Hi,

I am a little confused about one of the connections to this kit. On the ebay page:

eBay.ph: Speaker protection circuit stereo kit 30A protection ! (item 320496814744 end time Aug 02, 2010 00:32:49 PHT)

It shows a connector with "Power Amp Output Connection"
I also attach the schematic with the connector circled.

Initially, I thought that this required connection to the 'output' of the amplifier - but this cant be the case, why would they not do this routing on the board?

Can anyone shed some light on the purpose of this connector?

Many thanks for your help!

Cheers,

Andy
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File Type: jpg Spk protection 30A.jpg (56.3 KB, 1275 views)
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Old 5th July 2010, 08:07 PM   #2
gootee is offline gootee  United States
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Where did you get the schematic? I couldn't read yours so I went to the ebay page through your link, but can't find it.
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Old 5th July 2010, 08:28 PM   #3
FlyAndy is offline FlyAndy  Australia
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Hi Gootee,

I received the schematic after I purchased the kit.
If you click on the thumbnail, the image should enlarge. If you still are having trouble reading it, PM me your email address and I will email you a copy.

Many thanks.

Regards,

Andrew
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Old 5th July 2010, 08:47 PM   #4
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Your schematic is barely readable, but it must be a protection for unwanted DC voltages in the output (OR gate = either channel).
It will cut both outputs if DC is detected, which would damage speakers, for K1 is a dual relay.
Regards,
Max.
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Last edited by smartx21; 5th July 2010 at 09:11 PM.
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Old 6th July 2010, 12:56 AM   #5
FlyAndy is offline FlyAndy  Australia
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I have put a copy of the schematic on the web - hopefully it is more easy to read:

http://img682.imageshack.us/img682/8...tection30a.jpg

Click the image to open in full size.
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Old 6th July 2010, 01:15 AM   #6
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Could you post detailed scanned images of PCB, both sides?
This would help finding any mistake in schematic.
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Andres
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Old 6th July 2010, 06:12 AM   #7
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Hi Andy
I see the difficulty you are having when I compare this circuit (which is sketchy to say the least) with Silicon Chip Magazine's newest universal design. Don't discount the probability that this circuit may have to work in tandem with similar circuitry, a headphone switching arrangement, fuse or even crowbar circuit. With 30 amp rating, it's bound to attract pro. attention where such features are common. Consequently, there will be a need to sense faults upstream of these circuits and so the separate leads.

There are two other sensor circuits shown there, probably a thermal switch (lower) and a muting connection to a 12V control circuit. Are they real or just suggested to add this feature? If they are onboard, a connection to a sense point or 12V circuit might help them to work.

I suggest you check for continuity between the input points,the relay contacts and the 22k sense resistors anyway and let logic take its course. If no connection, you will have to add it, here or upstream as you prefer.
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Last edited by Ian Finch; 6th July 2010 at 06:19 AM.
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Old 6th July 2010, 03:52 PM   #8
Nrik is offline Nrik  Denmark
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Oh...that is not too hard.
If the PCB actually is what the schematic promise, then you can see all the light-grey textmarkers at the 'empty' pins, telling exactly where it is connected to. I marked the different stuff:
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File Type: jpg spkprotection30a.jpg (63.2 KB, 965 views)
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Old 6th July 2010, 03:57 PM   #9
Nrik is offline Nrik  Denmark
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The overload protection circuit will react when the voltage over the emitter resistor is above 0.5-0.6Volts. So if the emitter resistor is 0.22 ohms, it will be at 0.5/0.22 = 2.2 ampere, or 39Watt peak (19,5W rms) in 8 ohms.
To increase the allowed output current, add a resistor-divider between the emitter-resistor and the sensor input.
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Old 11th December 2010, 09:30 PM   #10
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Quote:
Originally Posted by FlyAndy View Post
Hi,

I am a little confused about one of the connections to this kit. On the ebay page:

eBay.ph: Speaker protection circuit stereo kit 30A protection ! (item 320496814744 end time Aug 02, 2010 00:32:49 PHT)

It shows a connector with "Power Amp Output Connection"
I also attach the schematic with the connector circled.

Initially, I thought that this required connection to the 'output' of the amplifier - but this cant be the case, why would they not do this routing on the board?

Can anyone shed some light on the purpose of this connector?

Many thanks for your help!

Cheers,

Andy

Anyone know what gets wired to the "L", "R"?
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File Type: jpg Speaker_protection_circuit_30A_connectio.jpg (85.7 KB, 851 views)
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