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Old 19th January 2010, 04:23 AM   #1
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Default SAE C3A blows fuses

i have a SAE C3A integrated amp that i got froma a friend who said it have a bad channel(R) and only needed one output transistor, i got 2 ecg 381 and 2 d 588, after a replaced the bad channel transistors i powerd the reciver and it blew both protection fuses, i desolderd the 2 just repaced transistor and put back fress fuses and i powerd again the amp and it did not blew any of the fuses. the left channel sounds ok but my right channel has no audio in the preamp stage but left does have. can somebody give me pointers in what might be wrong whit the amp and what to look for. my friend says tha the Ha 1457(ecg 1666) is bad is this ic could be the problem? if anybody had this problem before it be of help to me.bear in mind im no expert at this but i have some understanding in electronics. thanks and God bless.
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Old 19th January 2010, 10:09 AM   #2
jaycee is offline jaycee  United Kingdom
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Location: Norwich, UK
Firstly - stop using NTE/ECG parts, they are useless.
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Old 19th January 2010, 07:49 PM   #3
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i cant find original parts. they are kind of hard to find so i use what i have available.
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Old 19th January 2010, 08:23 PM   #4
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Location: Carlisle, England
You need to take a step back and get it working without output transistors.

I usually remove the output transistors and feed the VAS output back into the LTP feedback.

Then check the bias voltage is not silly and check the DC offset is not silly too.

If the bias circuit is faulty then you will just keep blowing output transistors.
Murton-Pike Systems PCBCAD51 pcb design software.
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Old 19th January 2010, 08:38 PM   #5
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Join Date: Feb 2003
Location: San Antonio, Texas
Here is a list I put together for SAE (Scientfic Audio Electronics) with the help of James Bongiorno, the amps designer.

SAE Audio Repair Tech Info - Part Number Cross Reference Table
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Old 19th January 2010, 09:02 PM   #6
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that it was i has done so far i desolderd the output transistors in the right channel and powerd again and it did not blew the fuses, i left the left channel transistors because it works fine. the problem is in the right channel. like i said im working whit a friend of mine that has more knoledge that what i have in electronics i will let him know. thanks for the help so far.
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Old 26th January 2010, 11:44 PM   #7
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well i have replaced the preamp ic(HA1457)and 2 disc capacitors_3 and 20_.and the 4.3volts i had in the right input at the amplificatin side is i have audio on the right side(whitout the power transistors) but the sound is kind of low compared to the left side at amplification side. i have chequed the resistors,diodes in the right amplification and preamp and they read good. does anybody knows what causes low volume in the right channel amp side compared to the left? thanks for the help.
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