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Old 9th August 2005, 06:55 AM   #1
diyAudio Member
Join Date: Jun 2005
Location: Oregon
Default My LM3886 GainClone almost works!

I got the gainclone bug bad after reading Decibel Dungeon, Electonet, and here. This is cool! I'm learning lots of stuff.

I have put together the Decibel Dungeon point-to-point inverted one, and Electronet's power supply pcb.

It makes good sound, with no humming or hissing, but it heats up real hot. Besides the heatsink, the resistors between pin 3 and the Zobel get too hot. They're two 0.47 ohm 5 watt ones in parallel.

Does this mean I've done something wrong with the grounding? The rails measure OK, -V-0-V+.

One thing I don't know what to do with, is the power cable's 3rd prong grounding wire. I had it soldered to the ground of the PS's pcb, where the capacitors come together. Then I moved it to the body of my transformer. I don't detect a difference. The transformer doesn't have a 3rd wire for the 115V power cord's ground.
Right turn, Clyde.
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Old 9th August 2005, 08:34 AM   #2
Join Date: Jan 2005
It is oscillating on a very high frequenzy, double check your connections and component values against the schematics.
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Old 9th August 2005, 08:52 AM   #3
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The grounding wire must go to the chassis. It's a security thing, not a sound issue.

Do wizards use spell checkers?
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Old 9th August 2005, 07:11 PM   #4
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Join Date: Jun 2005
Location: Oregon
Thanks for your replies! My posts are being looked at by the moderator, so it's a little slow for a while.

There's no amp chassis, but after I removed the ground wire from the transformer body, the heat problem stopped. Everything sounded good and worked well for about an hour and a half.

Then, I broke off the output pin.

The PCB on Electronet for the gainclone power supply, that's a handy thing. The guy who put that up, told me where to solder my AC ground wire. So, i'm gonna try again!
Right turn, Clyde.
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