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Old 11th August 2004, 07:43 AM   #1
Hayden is offline Hayden  Australia
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Default Eti 480 trouble

Ive built an Eti 480 amp (not the best amp I know) the problem is that the output volume is low, when I turn up the input signal the amp gets to about 30% of its potential then its distorts. I have checked all the components if their in working order and if their in the right spots. I keep setting vr1 to get the right voltage but it keeps changing.
Can any one help? Are there any well known problems with this amp?

Thanks
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Old 11th August 2004, 04:14 PM   #2
Netlist is offline Netlist  Belgium
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Hayden
Do you have a link to a schematic?

/Hugo
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Old 11th August 2004, 04:28 PM   #3
Netlist is offline Netlist  Belgium
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Found it...
What happens to the rail voltages? Are they stable?

/Hugo
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Old 12th August 2004, 02:43 AM   #4
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The general consensus ive seen is -it was stable with Transistors available at its time of design but now,not so!

http://www.alphalink.com.au/~cambie/ETI480/ETI480.zip

http://www.alphalink.com.au/~cambie/
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Old 12th August 2004, 04:44 AM   #5
Hayden is offline Hayden  Australia
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rails are OK
drops about 5v when inputs are high
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Old 12th August 2004, 05:52 AM   #6
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Check voltage across zener ZD1 (should be about 5.6V) and voltages across resistors R5 and R10 (should be about 5V each).

Also, with input shorted, is there any measurable DC or AC voltage on the output?

Cheers
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Old 12th August 2004, 11:33 AM   #7
Hayden is offline Hayden  Australia
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OK just blown the 2 protection resistors
Where can I get the schematic that shows the voltages of each component etc?
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Old 12th August 2004, 02:57 PM   #8
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Protection resistors?? this amp has no protection. Which resistors do you mean?

BTW which version did you build - the 50W (2 transistors) or 100W (4 transistors) ?

Cheers
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Old 12th August 2004, 10:42 PM   #9
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hi Hayden,

Did you look at the Cambie site as mentioned by mikee12345?

http://www.alphalink.com.au/~cambie/

This site has more info on the ETI480 than you probably want to know.
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Old 13th August 2004, 01:17 AM   #10
Hayden is offline Hayden  Australia
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100w it is
100 ohms across the fuse went up in smoke.
don't know why I haven't changed anything since I last powered it up.
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