Darlington TIP142 & 147 power amplifier. - diyAudio
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Old 16th June 2009, 02:14 AM   #1
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Default Darlington TIP142 & 147 power amplifier.

Hi, I found this circuit diagram on internet and I'm interested to make myself one, so I try to make one. First, I have found a version of this diagram using TIP41 as driver transistor. This version is working, just come out a lot of noise and the signal is abnormal when test with oscilloscope. A few days ago, I found another version (90% similar) diagram (pls see the attachment), this version is using TIP 42 as driver transistor. But when my current board change to use the TIP42 transistor, the power amp no longer working and just produce humming sound, I suspect something is wrong with the latest or the second circuit diagram, can anyone help me the rectify it? Thank you.
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Old 16th June 2009, 02:16 AM   #2
jaycee is offline jaycee  United Kingdom
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Looks like the John Tirone amp. Don't bother with it, it doesn't work well.
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Old 16th June 2009, 02:28 AM   #3
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is it even modify it, it still won't work well?
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Old 16th June 2009, 03:05 AM   #4
teemuk is offline teemuk  Finland
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This one again?

Isn't production of TIP142/TIP147 even discontinued now?
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Old 16th June 2009, 03:28 AM   #5
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Quote:
Originally posted by teemuk
This one again?

Isn't production of TIP142/TIP147 even discontinued now?

is it both tip142 and 147 discontinued already? I still can find it in my country, but don't know any countries still available or not.
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Old 16th June 2009, 03:51 AM   #6
llwhtt is offline llwhtt  United States
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The original amp used a TIP41(NPN) as Q3. The schematic you posted shows a TIP42(PNP) but the symbol is still an NPN. An NPN is usually used in that location, so I'm thinking the TIP42 is wrong. Probably why the amp doesn't work at all now. The schematic shown sure is drawn weird. I redrew it the way most amplifier schematics are drawn and it sure makes it easier to digest. As to the sound or well this amp works I have no idea, just commenting on Q3 and the schematic.

Craig
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Old 16th June 2009, 06:14 AM   #7
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Quote:
Originally posted by llwhtt
The original amp used a TIP41(NPN) as Q3. The schematic you posted shows a TIP42(PNP) but the symbol is still an NPN. An NPN is usually used in that location, so I'm thinking the TIP42 is wrong. Probably why the amp doesn't work at all now. The schematic shown sure is drawn weird. I redrew it the way most amplifier schematics are drawn and it sure makes it easier to digest. As to the sound or well this amp works I have no idea, just commenting on Q3 and the schematic.

Craig
Yeah, you are right, just now I also found that the Q3 isn't right, so changed to TIP41, it works. But the signal is abnormal when test with ocilloscope. Don't know what's wrong with it.
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Old 16th June 2009, 09:05 AM   #8
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Default you may

wana take a look at this

it can describe the darligton problems and why amplifiers working with them can fail very easilly if A Darling.......ton Story .... designed properly
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Old 16th June 2009, 11:56 AM   #9
wg_ski is offline wg_ski  United States
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Quote:
Originally posted by Matthewong


Yeah, you are right, just now I also found that the Q3 isn't right, so changed to TIP41, it works. But the signal is abnormal when test with ocilloscope. Don't know what's wrong with it.
Does it sound bad too, or does the waveform just look all funky? Is anything getting hot?

Could be crossover distortion, oscillating, or the BC558 pair severely out of balance.
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Old 16th June 2009, 12:26 PM   #10
Bone is offline Bone  United Kingdom
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This was originally designed (thrown together) as a guitar amplifier so don't expect Hi-Fi.

Original site http://members.fortunecity.com/jtfish/amp/ca100.htm

Tony.
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