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Old 22nd February 2012, 05:01 PM   #1
m4ick is offline m4ick  United States
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Default Alpine MRV-1002

This amp had 2 shorted outputs and one blown power supply. The other power supply is still in tact. The power supply that was still in tact is being regulated and the one that I am using the 3205s in has a wider pulse width indicating to me that that power supply is working harder to maintain voltage.

When I power the amp on I get -46V on the secondary CT and on the RCA shields. I'm not sure what is causing it, any help would be appreciated.
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Last edited by m4ick; 22nd February 2012 at 05:03 PM.
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Old 22nd February 2012, 05:06 PM   #2
m4ick is offline m4ick  United States
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As a side note, the secondary CT starts at -18 volts and moments later jumps to -46.
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Old 22nd February 2012, 05:25 PM   #3
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Do you have both positive and negative rail voltage on the output transistors?
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Old 22nd February 2012, 05:56 PM   #4
m4ick is offline m4ick  United States
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Referenced from secondary CT I have +- rail voltage.

Referenced from amplifier ground I have approximately +1.8 and -96.
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Old 22nd February 2012, 07:03 PM   #5
m4ick is offline m4ick  United States
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Just for your information this amp uses 2 494Cs, one for each power supply. Each power supply generates separate rail voltage for each channel. + rail on one channel is not directly connected to + rail on the other.

Each of the 494s has .25vdc on pin 4 yet each one is showing different dead times.
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Old 22nd February 2012, 07:55 PM   #6
m4ick is offline m4ick  United States
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Nevermind the different dead times, there's a pot for each 494 that feeds pin 1. Is there a certain pulse width I should set this to?

Other than setting the dead time, the only issue I have now is the -46v on the secondary CT. Referenced from secondary CT I have about +-48v. Both sets of rails are having the same symptoms, -46V at secondary ground.
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Old 22nd February 2012, 08:07 PM   #7
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Is one of the rectifiers or outputs shorted to the heatsink?
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Old 22nd February 2012, 08:16 PM   #8
m4ick is offline m4ick  United States
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The rectifiers are in plastic cases and I don't get continuity between the center leg of any outputs and the metal plate.

Also, from a cold start the sec CT is at -18V, as soon as I turn off my power supply it jumps to the -40s and begins to discharge. Each time I start it after that without allowing it to fully discharge it goes directly to -46v.
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Old 22nd February 2012, 08:40 PM   #9
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Email me.

babin_perry@yahoo.com
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