MDA fuse for a glass fuse.

srinath

Member
2010-02-12 4:09 pm
This is fuses F1 and F2 in a B&K avr 507 - and if you find the schematic or any thing on it please send me the link too. Its got MDA 2 written on it, I dont have any other details on it, and I think it has to slow blow, cos that cap isn't filling up. Thanks so much.

Cool.
Srinath.
 
Sorry, I can't get the link to work. I will upload the service manual to my web site, post a link.
c:\users\jon\downloads\B_and_K_AVR-507_service_manual
 
Last edited:
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.
 

srinath

Member
2010-02-12 4:09 pm
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.
 

Attachments

  • B&K_Fuse_blow.jpg
    B&K_Fuse_blow.jpg
    83.5 KB · Views: 39

srinath

Member
2010-02-12 4:09 pm
Fills the caps

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.