blown fuse while amp is "off"

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Re: blown fuse while amp is "off"

Postby Dean Jr. on Thu Sep 15, 2016 10:12 pm

oildrops, the power switch should have to be in the 'on' position before the standby switch can have anything to do with what goes on. IF the standby light is/can be lit up with the power switch in the OFF position, something is wrong....do not turn the amp on again. IF the stand by cannot be 'lit up' with the power switch in the 'OFF' position, then perhaps what is going on here is operator confusion?? (;^) But....you said that the stand by light lights up even when the power switch is in the off position....that is NOT what should be happening. Again....I would suggest that you not turn this amp on again.
Have you talked to the tech who did the work?? IF so, what was the explanation for the situation?
The power switch feeds the amp the AC to the power transformer PT. The standby should be downstream of the PT's secondaries.....therefore the standby cannot show a light without the power switch being in the ON position unless the circuit is grossly miswired, ime. IF the tech cannot give you an explanation of the error as well as an apology for the mistake, then you need to never do business with that tech again and you need to ignore all of the advice from whomever gave you the reference to that tech.
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Re: blown fuse while amp is "off"

Postby oildrops on Thu Sep 15, 2016 11:05 pm

Yes, the standby light comes on while the power switch is off. I've talked with a couple of other techs and they agree that something is not correct and that the amp is unsafe. Is there any way that another failed part in the amp could result in this scenario? Something I just talked to suggested a shorted cap or diode could be the problem, but that doesn't make sense to me.
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Re: blown fuse while amp is "off"

Postby Dean Jr. on Thu Sep 15, 2016 11:13 pm

oildrops, the amp needs to be in the hands of someone who understands what needs to be done. I agree that the amp needs to be recapped,, but until the power switch is in the ON position, there should be NO CURRENT anywhere in the amp and therefor the standby light should NOT be lit with the power switch OFF. Find a tech who understands this, and then let that tech work on the amp. They should also appreciate the age of the electrolytics, but that is NOT the problem with the power and standby switch situation.
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Re: blown fuse while amp is "off"

Postby Unit_1 on Fri Sep 16, 2016 3:20 am

+1,000,000,000

Your amp has been mis-wired. If you touch it barefoot with wet feet you will probably wake up dead.
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Re: blown fuse while amp is "off"

Postby stratele52 on Fri Sep 16, 2016 11:01 am

Shematic show about Stanby Switch :

In Stanby position , light is ON and amp can't play .
In Play position, Stanby lamp is OFF and amp play.
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Re: blown fuse while amp is "off"

Postby Dean Jr. on Fri Sep 16, 2016 4:13 pm

stratele52 wrote:Shematic show about Stanby Switch :

In Stanby position , light is ON and amp can't play .
In Play position, Stanby lamp is OFF and amp play.



that may be....but oildrops is reporting that the Standby circuit has current available with the power switch in the OFF position. That should not be.
This amp has a strange standby switch position in the circuit....I've never seen anything like this. Learning is for me.
This is a standby switch which imho certainly has no reason to be...if any standby switch is necessary. AS I see it, the standby merely takes the preamp signal to ground prior to the phase inverter, correct? When in play mode, then the lamp is out of the circuit as you say, stratele52. This may support an earlier suggestion that in oildrops' amp there is a leg of the AC source...either hot or neutral...that is grounded????? At any rate, the 'repair' job by the tech may well have this amp set up to be dangerous to the user.

http://bmamps.com/Schematics/Supro/supro_s6651.pdf
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