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Old 21st December 2005, 08:15 PM   #1
3Dgeek is offline 3Dgeek  United Kingdom
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Default Amp overheating

Hi all,

Got this Korsun U2 a while back, suddenly its started overheating almost hot enough to burn your hand ! after about 30 mins..

I not changed anything in the system except adding a Pure DAB tuner

Is there any internal component falure which could cause this ?


Thanks
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Old 22nd December 2005, 12:45 AM   #2
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Do you know how to check and set the bias current?
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Old 22nd December 2005, 01:03 AM   #3
lineup is offline lineup  Sweden
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Either it is, like said,
too high bias current.
For some reason the setting has changed.
Usually this is set by a trim potentiometer in the circuit.
It is often not too far from big output transistors.

Or it can also be some form of oscillation.
If you put another pair of loudspeakers, does it still overheat?
Maybe you need a zobel filter at the output.
It is a cap in series with one resistor.

Can you measure the DC voltage and/or AC voltage
across the output terminals, with your speakers still attached?
With no signal both DC and AC should be close to 0.0 V.
Use the 2 volt range at your multimeter.
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Old 22nd December 2005, 01:36 AM   #4
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Try post the internal picture of it.
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Old 22nd December 2005, 04:04 PM   #5
3Dgeek is offline 3Dgeek  United Kingdom
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Thanks for the replys.

Yes is has been suggested to me that bias current has changed, not tested it with any other speakers yet.

I did change the op-amps a while back, but its only just started to overheat.

I'll check back when i've done some more tests.

Thanks again !
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Old 23rd December 2005, 02:54 AM   #6
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Default Heatsink Size

Good Day,

I am building this stereo amplifier capable of of 60W RMS per channel into an 8-ohm load. I would like to know whether the heatsink that I am using for this amplifier I am building is sufficient for the output devices. My output devices are MJ15003 and MJ15004 made by ON Semiconductor. DC supply to the amplifiers is +/- 43 Volts.
The picture in the attachment is the output devices on the heatsink. Let me know if the heatsink is too small for my desired output power. Thank you.
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File Type: jpg output stage of repeater 3.jpg (94.5 KB, 211 views)
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Old 23rd December 2005, 03:43 AM   #7
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Hi 3Dgeek,

Check the bias setting by all means, but you may just have triggered an instability and that is the cause of the sudden heating. You need to put a CRO on it. A window to what's happening.

Hi Raveenvijendren,

You need to run you're amplifier under normal operation and feel - if the cases are too hot to touch you need a bigger heatsink. In your country, as in ours, ambient temps can be searing, si it's good for your amp to pamper it a little, by giving it a larger than minimal heatsink. It will return the favour with reliability.

Cheers,
greg
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Old 23rd December 2005, 04:31 AM   #8
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Good Day,

Would adding a tiny computer fan be wise? i have existing 12VDC lines that power my protection circuit but would the fan generate electrical noise? Thank you.
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Old 23rd December 2005, 07:55 AM   #9
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Fans are unreliable (and cheating)...get a bigger heatsink.


.....and learn to apply thermal paste, fer Christ's sake!
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Old 24th December 2005, 01:41 PM   #10
K-amps is offline K-amps  United States
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Quote:
Originally posted by EchoWars
Fans are unreliable (and cheating)...get a bigger heatsink.


.....and learn to apply thermal paste, fer Christ's sake!

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