[sdiy] blowing fuses

ColinMuirDorward colindorward at gmail.com
Sun Feb 16 19:28:31 CET 2020


Thanks, Neil.
I can see two transformers, each one is maybe half a fist size. There is
also a massive blue can, a capacitor?  Must be two inches long and one inch
diameter. It's a Lambda PSU. I've searched the model number but can't find
any data.

How does this magnetized transformer problem work? Doesn't that magnetism
dissipate after a short time? Reason I'm asking is because last time I
waited overnight before turning it back on again, by which point I thought
any residual charges/magnetism would have dissipated, but it blew the fuse
nevertheless.

Sorry if I'm dragging this out!
Colin.

On Sun, Feb 16, 2020, 10:19 AM Neil Johnson, <neil.johnson71 at gmail.com>
wrote:

> Don't use quick-blow, use (T)ime delay (slow blow) fuses.  I'm
> guessing the transformer is quite large, the magnetising current
> "thump" is probaby killing the QB fuse.
>
> Neil
>
> On Sun, 16 Feb 2020 at 18:06, ColinMuirDorward <colindorward at gmail.com>
> wrote:
> >
> > Unfortunately, there seems to be no mention of a fuse.
> >
> > On Sun, Feb 16, 2020, 9:46 AM Richie Burnett, <
> rburnett at richieburnett.co.uk> wrote:
> >>
> >> Usually the rating label tells you what fuse to fit?
> >>
> >> -Richie,
> >>
> >>
> >>
> >> -----Original Message-----
> >> From: ColinMuirDorward
> >> Sent: Sunday, February 16, 2020 2:43 PM
> >> To: Richie Burnett
> >> Cc: *SYNTH DIY
> >> Subject: Re: [sdiy] blowing fuses
> >>
> >>
> >> Thanks Richie.
> >> I should have mentioned, it's a transformer/linear supply.
> >> Not only us it eating fuses for breakfast, but dinner, too. In a couple
> >> hours, I'll be able to test lunch.
> >> So I suppose there is some faulty (or non-existant) inrush current
> >> protector, and it's costing me one fuse to charge up whatever is sucking
> >> those amps?
> >>
> >>
> >>
> >> On Sun, Feb 16, 2020 at 12:36 PM Richie Burnett
> >> <rburnett at richieburnett.co.uk> wrote:
> >> If it's a SMPS the inrush current at turn-on will probably eat
> quick-blow
> >> fuses for breakfast.
> >>
> >> -Richie,
> >>
> >>
> >>
> >> -----Original Message-----
> >> From: ColinMuirDorward
> >> Sent: Sunday, February 16, 2020 2:21 PM
> >> To: *SYNTH DIY
> >> Subject: [sdiy] blowing fuses
> >>
> >>
> >> Maybe someone has some suggestions for me.
> >>
> >> I'm blowing fuses on my "industrial" power supply. This is a salvaged
> >> +/-15v, 3a supply housed in a rugged metal enclosure. I've wired it up
> with
> >> a fuse on the AC mains side, and fuses on the +/-15v side. The AC/mains
> fuse
> >> is giving me grief.
> >>
> >> Step1) I can turn the unit on, and everything is fine. My synth is only
> >> drawing 1/2 an amp (or nothing when disconnected).
> >> Step2) Turn the unit off. At this point, I can remove the mains fuse,
> and
> >> test it: yes, still good.
> >> Step3) Re-install fuse, switch on. Nothing. Remove fuse and test again,
> now
> >> it's blown.
> >> Step4) Install new fuse. Go to Step1)
> >>
> >> I haven't used the PSU much yet, but I've powered it on and off loads of
> >> times and this problem never manifested till now. The fuses are 2amp,
> 250v,
> >> which I think is fine, but here is maybe my mistake: they are quick blow
> >> type. I'm uncertain, though. Wondering if I need to try to find a fault
> in
> >> the PSU, or just order the new fuses. But why didn't those quick blow
> fuses
> >> break before?
> >>
> >> Thanks for reading!
> >> Colin
> >>
> >>
> >> --
> >>
> >> https://www.instagram.com/colinmuirdorward/
> >> -
> >>
> >> https://www.instagram.com/ssdp_synthesis/
> >>
> >> Virus-free. www.avg.com
> >>
> >>
> >>
> >>
> >>
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> >>
> >>
> >>
> >>
> >> --
> >>
> >> https://www.instagram.com/colinmuirdorward/
> >> -
> >>
> >> https://www.instagram.com/ssdp_synthesis/
> >>
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> >>
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