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A/D/S power plate 80 and 100
A/D/S power plate 80 and 100
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Old 24th November 2020, 01:15 AM   #21
Rabbit 16v is offline Rabbit 16v
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150ish mV AC which makes no sense at all to me. Its also fluctuating and the waveform is very erratic.
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n00b, Fluke 87, Fluke 97 scopemeter (auto),Fluke TS1000, Fluke 376 FC, Lectrotech to-55
PS-106, 12v regulated power supply with crappy ammeter
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Old 24th November 2020, 01:22 AM   #22
Perry Babin is offline Perry Babin  United States
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How does the waveform compare to the input on the other rectifier. They should have the same input from the transformer if the rectifiers are center-tapped types.

Use the secondary ground or the negative speaker terminals (assuming that the amp isn't bridgeable) for the scope reference.
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Old 24th November 2020, 01:29 AM   #23
Rabbit 16v is offline Rabbit 16v
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Here are a couple of pics. There is only one bridge rectifier on the amp. I am probably missing something here... Ive been measuring at the output from the bridge rectifier as shown that has two wires going from it to the audio board. here are a couple pics of either side of the power supply board. The blue and red wires are the ones I am presuming are the rail voltage outputs from the rectifier. I am not certain the function of the b829s at this point.
Attached Images
File Type: jpg DSC_1625[1].jpg (1.07 MB, 38 views)
File Type: jpg DSC_1626[1].jpg (1,021.4 KB, 38 views)
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n00b, Fluke 87, Fluke 97 scopemeter (auto),Fluke TS1000, Fluke 376 FC, Lectrotech to-55
PS-106, 12v regulated power supply with crappy ammeter

Last edited by Rabbit 16v; 24th November 2020 at 01:43 AM.
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Old 24th November 2020, 01:41 AM   #24
Perry Babin is offline Perry Babin  United States
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The 2SB829 transistors drive the primary windings of the power transformer.

Bridge rectifiers are rare nowadays. If it has negative rail but no positive rail on the terminals of the rectifier, it likely has failed internally. You can't use a standard bridge rectifier in the amp. You need a high speed rectifier. Standard bridge rectifiers will quickly overheat and fail at the higher frequencies and square wave of a switching power supply.
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Old 24th November 2020, 01:44 AM   #25
Rabbit 16v is offline Rabbit 16v
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Sorry pics were being difficult to add. They should be up now. Ive tested the rectifier outside of the circuit and it tests fine.
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n00b, Fluke 87, Fluke 97 scopemeter (auto),Fluke TS1000, Fluke 376 FC, Lectrotech to-55
PS-106, 12v regulated power supply with crappy ammeter
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Old 24th November 2020, 01:47 AM   #26
Perry Babin is offline Perry Babin  United States
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Location: Louisiana
The connection internally could be intermittent. Did you reinstall it to see if you again had +rail?
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Old 24th November 2020, 01:58 AM   #27
Rabbit 16v is offline Rabbit 16v
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Yup, and swapped in another bridge rectifier that I had. Same results. no more than maybe 3VDC pos on the opposite rail.
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n00b, Fluke 87, Fluke 97 scopemeter (auto),Fluke TS1000, Fluke 376 FC, Lectrotech to-55
PS-106, 12v regulated power supply with crappy ammeter
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Old 24th November 2020, 02:02 AM   #28
Perry Babin is offline Perry Babin  United States
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Is the input waveform swinging equally above and below the secondary ground?
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Old 24th November 2020, 02:11 AM   #29
Rabbit 16v is offline Rabbit 16v
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Its pretty erratic. See attached. Might need to fire up the Lectrotech just to see a better waveform. The fluke is mainly for automotive use, so probably not up to par for this task.
Attached Images
File Type: jpg DSC_1628[1].jpg (1.02 MB, 37 views)
File Type: jpg DSC_1629[1].jpg (1.03 MB, 35 views)
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PS-106, 12v regulated power supply with crappy ammeter
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Old 24th November 2020, 02:21 AM   #30
Perry Babin is offline Perry Babin  United States
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I don't know how the auto varies but the 97 is a 50mHz scope which is good enough.

Set the scope to 10us and 5v/div and post the waveforms on the collectors of the 2 PS transistors.
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