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Chip Amps Amplifiers based on integrated circuits

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Old 18th December 2004, 01:21 PM   #11
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btw, if you work the math backwards, a GC on a flat piece of aluminum can be run to a max of 8 watts before the thermal protection will kick in.
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Old 18th December 2004, 03:45 PM   #12
moamps is offline moamps  Croatia
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Quote:
Originally posted by Aunkst
...I tested this amp with the computer outputs. and I hear a HUM in the 200hz region. Definatly not 60hz. ...is only present when both RCAs are connected. If I disconnect either one The sound stops.... changed the grounding scheme several times and the hum never changed.
BrianGT LM3875 NIGC Gounding Scheme
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Old 18th December 2004, 07:47 PM   #13
Aunkst is offline Aunkst  United States
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It appears that you think I am some Hack.

The diode board is fine as is. It is elevated enough and is secured by small bolts. The only way there would be contact is if the case was dropped and some how was dented in the exact plase that the bridge is.

The Xfmr is also adequate. I ran it for hours yesterday at what I consider max volume. Nothing got warm. the case was not even hot to the touch. not even directly where the chip is bolted to the side panel
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The transformer doesn't look adequate. The one you are using looks to be from a 10 or 15 watt stereo -- this will overheat and fail.
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Old 18th December 2004, 10:18 PM   #14
Aunkst is offline Aunkst  United States
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My appologies for the from the hip defensiveness.

I looked at the photo again and realize that from that angle it appears the board is right down on the metal case.

I assure you that it is about a quarter inch above and secured tightly.

Good eye I am glad that there are those that keep an eye open for others.
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Old 20th December 2004, 11:52 AM   #15
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if the low frequency oscillations persist, and it's not 120Hz, try bypassing the 1000uF electrolytics with 10uF electrolytic (can be tantalum or aluminum electrolytic.) the bypass caps should be placed as close to the V+/V- pins as possible.
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