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Old 23rd April 2013, 09:52 AM   #11
AndrewT is offline AndrewT  Scotland
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Looking at the data for these slow blow fuses shows the big safety advantage of adopting close rated fusing.

Take a 240VA transformer running on 240Vac supply.
Close rated fuse is F1A, (240Va/240Vac=1).
Normal rated fuse is T3.2A, (3*240VA/240Vac=3).

Look at the data for time to rupture @ 30A fault current for these two fuse values.
~15ms for the T1A and ~300ms for the T3.2A.

I know which I would rather have in the mains supply to the transformer.
Yes it means I have to fit a soft start, but that is a small price to pay for a factor of 20 faster fuse blow.
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Old 23rd April 2013, 11:21 AM   #12
srinath is offline srinath  United States
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Oh wow, thank you thank you thank you.
Cool.
Srinath.
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Old 23rd April 2013, 12:12 PM   #13
srinath is offline srinath  United States
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Default F1 and F2

OK its blowing the fuses F1 and F2.
And I dont have any charge in one set of caps. I will find the right number of them.
The fuse on the right blows when neither of the amp boards are connected. That cap also has no charge at all.
The one on the left (I will get numbers for it F1 or F2 too) is blowing only when the left amp board is connected.
I will get part numbers for each of these in a bit.
Cool.
Srinath.
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Old 23rd April 2013, 12:14 PM   #14
AndrewT is offline AndrewT  Scotland
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Have you powered up via a bulb tester yet?
Does the bulb light, or flash, or glow dim, or what?
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Old 23rd April 2013, 12:15 PM   #15
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Check BR3 and BR4
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Old 23rd April 2013, 12:35 PM   #16
srinath is offline srinath  United States
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Oooo Harleyjon that was exactly what blew in my HK 800+ quad and my JVC 601.
I will get it opened up in a bit.

Thanks.
Srinath.
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Old 23rd April 2013, 12:37 PM   #17
srinath is offline srinath  United States
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Default No DBT

Quote:
Originally Posted by AndrewT View Post
Have you powered up via a bulb tester yet?
Does the bulb light, or flash, or glow dim, or what?
I dont have dbt but this amp was powered up all along, I wasn't worried about any more blow up's ... I yanked it from the wall to get it home.

Cool.
Srinath.
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Old 23rd April 2013, 05:12 PM   #18
srinath is offline srinath  United States
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Default Fills the caps

Quote:
Originally Posted by AndrewT View Post
Looking at the data for these slow blow fuses shows the big safety advantage of adopting close rated fusing.

Take a 240VA transformer running on 240Vac supply.
Close rated fuse is F1A, (240Va/240Vac=1).
Normal rated fuse is T3.2A, (3*240VA/240Vac=3).

Look at the data for time to rupture @ 30A fault current for these two fuse values.
~15ms for the T1A and ~300ms for the T3.2A.

I know which I would rather have in the mains supply to the transformer.
Yes it means I have to fit a soft start, but that is a small price to pay for a factor of 20 faster fuse blow.
This fuse fills the caps ... I think I have to have that slow blow in there. Else it blow all the time.
Cool.
Srinath.
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Old 23rd April 2013, 08:07 PM   #19
Spiny is offline Spiny  United Kingdom
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Check the bridge rectifiers, just use an DVM on diode setting. I would expect them to have shorted diodes. Amps should not blow fuses all the time!
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Old 23rd April 2013, 08:56 PM   #20
srinath is offline srinath  United States
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This amp has no BR4, the location on the board has never been soldered to.
The caps c17 and c18 are not charging up.
I am in the process of pulling it apart.

Thanks.
Srinath.
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