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Old 3rd June 2010, 08:10 PM   #31
Globulator is offline Globulator  United Kingdom
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Quote:
Originally Posted by svokke View Post
Today I took one of the transistors apart. I think this looks like a bipolar. So it really could be the 2SA940 or KSA940, both PNP devices. Is this die about the correct shape and size for those transistors?
Can you measure the junctions still? It looks like just the bond wires have been blown away..
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Old 3rd June 2010, 08:48 PM   #32
svokke is offline svokke  Belgium
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The transistors measure completely open or short circuit between the pins. Not a single transistor measures like a PN-junction.
Edit:Maybe I interpreted your post wrong. Tomorrow I will try to measure directly on the junctions.
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Last edited by svokke; 3rd June 2010 at 08:52 PM.
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Old 3rd June 2010, 10:47 PM   #33
Nrik is offline Nrik  Denmark
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Originally Posted by svokke View Post
The most left pin of Q6 goes to the middle pin of Q1(=collector) in your picture. I have re-drawn the schematic.
In that case it is safe to say that all four transistors must be PNP.
Replace with four new ones and your amp should be as good ( ..or as bad ) as before.
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Old 23rd March 2017, 07:57 AM   #34
branet is offline branet  Croatia
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Which schematic is finally right?
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Old 23rd March 2017, 10:07 AM   #35
Kay Pirinha is online now Kay Pirinha  Germany
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...and is there really neither a bootstrapped or a CCS load to the VAS?

Best regards!
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Old 24th March 2017, 05:14 AM   #36
wg_ski is offline wg_ski  United States
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Quote:
Originally Posted by svokke View Post
Today I took one of the transistors apart. I think this looks like a bipolar. So it really could be the 2SA940 or KSA940, both PNP devices. Is this die about the correct shape and size for those transistors?
The A940 is a freaking driver transistor. It's not supposed to be any bigger. TIP 42 (or 2955) would be an improvement, as would MJE1503x or the D45 types.

But TO220s on a small heat sink - don't expect miracles.
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Old 25th March 2017, 09:09 PM   #37
djk is offline djk
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"allowing for loss in the resistors and mosfets you'd probably get 70wpc from it."

At 4Ω?

Maybe if going downhill, with the wind behind your back.
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Old 31st March 2017, 09:44 AM   #38
branet is offline branet  Croatia
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What I have to look at the specifications of the bipolar transistor to be replaced with other bipolar transistor?
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