[sdiy] blowing fuses

Neil Johnson neil.johnson71 at gmail.com
Sun Feb 16 19:18:53 CET 2020


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
>>
>>
>> --
>>
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>>
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>>
>>
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