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Positive power supply rail at a different potential than negative rail?
Positive power supply rail at a different potential than negative rail?
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Old 7th October 2019, 04:45 PM   #11
Osvaldo de Banfield is offline Osvaldo de Banfield  Argentina
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10Hy is a very low value and then, few turns of copper wire.
The rails once rectified, looks equal, measured not to -bat , but to speaker ground?
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Old 7th October 2019, 04:59 PM   #12
The Lord Flashheart is offline The Lord Flashheart  United Kingdom
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If I have read the schematic correctly, the speaker ground are pins 1&3 on the speaker board, then the potentials are +- 26v as measured on the collectors of the output transistors.


Does that mean it's fine?
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Old 7th October 2019, 05:01 PM   #13
The Lord Flashheart is offline The Lord Flashheart  United Kingdom
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Thank you for your continuing help by the way Osvaldo, very much appreciated.
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Old 7th October 2019, 05:06 PM   #14
Osvaldo de Banfield is offline Osvaldo de Banfield  Argentina
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If between collectors and amp ground both rails measure equal, the no fault.

Note that battery - and circuit ground is separated by a resistor of 2.2KΩ (or so) and a 0.1F cap (C912 and R909), so, current flowing in this R alters your measurement.
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Old 7th October 2019, 05:12 PM   #15
The Lord Flashheart is offline The Lord Flashheart  United Kingdom
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Sadly not, not between speaker ground and the collectors.
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Old 7th October 2019, 05:16 PM   #16
Osvaldo de Banfield is offline Osvaldo de Banfield  Argentina
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But in post #12 you measured bot equal?, I'm getting lost :-(
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Old 7th October 2019, 05:19 PM   #17
Perry Babin is offline Perry Babin  United States
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Re-check R909 as was suggested. Do this with nothing connected to the amp. You should read 2.7k between the primary ground and the non-bridging speaker terminals.

Do you have a signal source plugged in while making these measurements?
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Old 7th October 2019, 05:43 PM   #18
Osvaldo de Banfield is offline Osvaldo de Banfield  Argentina
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Quote:
Originally Posted by The Lord Flashheart View Post
Thank you for your continuing help by the way Osvaldo, very much appreciated.
Don't worry, this is why I'm here.

I was thinking where are the measurement made. The oscillo and the voltmeter, respectively, if to bat ground or amp ground.

In other hands, I don't understand why to separate both systems, useless for me.
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Old 7th October 2019, 05:53 PM   #19
Perry Babin is offline Perry Babin  United States
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If you don't isolate primary and secondary grounds you will get 'engine noise' due to ground loops. This configuration is common in car amps. An alternative is to have the primary and secondary directly connected and use a balanced input on the signal input circuit.
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Old 7th October 2019, 05:57 PM   #20
Osvaldo de Banfield is offline Osvaldo de Banfield  Argentina
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OK, thanks for teach to me. I have little experience in such a car amplifiers, and sincerely, I dislike them per se. But in the few devices I repaired, both rails was only one.
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