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Alpine 3545 blows all fuses after 5 seconds of power
Alpine 3545 blows all fuses after 5 seconds of power
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Old 4th December 2017, 09:41 PM   #81
bmore5077 is offline bmore5077  United States
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Does anyone know how close the transistor pairs should be. Above when I tested leg 3 of the npn and pnp transistors there was 3 pairs and they read 1.0, 1.1 and 1.3mv. Is that close enough or about how close should they be. Thanks
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Old 4th December 2017, 09:44 PM   #82
Perry Babin is offline Perry Babin  United States
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If you went back through, did those numbers remain the same for all 3?
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Old 4th December 2017, 09:55 PM   #83
bmore5077 is offline bmore5077  United States
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After 20 min the bad side. 1st pair went from 1.1 to 1.7 second pair went from 1.3 to 1.9mv. Thanks
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Old 4th December 2017, 10:00 PM   #84
Perry Babin is offline Perry Babin  United States
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After the temperature stabilizes, if they're about the same across all 2/3 pairs, I think it's OK. For tests to see if current sharing is good for all transistors, it's better to test with a sine wave at higher power into a load. If you use all matching parts from the same batch and the emitter resistors are within tolerance, it's likely OK. It's not something to really worry about. The initial tests where the bias went to 7.whatever mv was what concerned me initially. All appears OK for now.
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Old 4th December 2017, 10:24 PM   #85
bmore5077 is offline bmore5077  United States
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Thanks again. So I guess I'll let it warm up at the 1 mv you had me set it at and then set it to 4mv from the testpoint as the service manual states. Thanks
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Old 4th December 2017, 10:59 PM   #86
Perry Babin is offline Perry Babin  United States
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4mv is too high, in my opinion. I'd leave it around 1mv.
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Old 4th December 2017, 11:17 PM   #87
bmore5077 is offline bmore5077  United States
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Ok sounds good. Thanks
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Old 13th December 2017, 07:41 PM   #88
bmore5077 is offline bmore5077  United States
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Ok so I replaced the non and pnp transistors on the one channel and adjusted both to 1mv idle current but the one repaired channel still plays much lower than the other. Not sure what's going on. Thanks
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Old 13th December 2017, 07:51 PM   #89
bmore5077 is offline bmore5077  United States
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Actually it starts off louder than it cuts it down. Maybe thermal but not sure
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Old 13th December 2017, 10:07 PM   #90
Perry Babin is offline Perry Babin  United States
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That sounds like a preamp problem. Check the signal level for both channels where the preamp signal goes into the main board.
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