Opinions on adding fuses to power amp

clattering

I thought the OP said something did actually fall inside ?

Thankfully not too often. I do recall one time about 30 yrs ago when I withdrew a Bulgin mains lead and the earth prong of the equipment connector came out with it though ! They were just held in place with screws !

Graham

With surface mount that's the typical way. It's called infra-red reflow.

See my comment about lead-free (wrt your Behringer EP2500) in a.ap.l-s.

Graham

I've seen something similar done intentionally and neatly inside a couple of amplifiers.

The power trace has a number of tinned copper wire 'links' in parallel with it on the 'top' of the pcb. Quite clever since it can be done with auto-insert machinery.

Personally I prefer to use equipment cable to deliver power to where it's needed rather than string it out along pcb traces.

Graham

clattering

Maybe

withdrew a

it

They were held in by the same screw that held the cable iirc

I once found the entire tip and centre core of a jackplug neatly welded twixt power transistor and heatsink. Presumably some clown snapped off the plug, so pushed it right through with another.

The one thing most designers fail to allow for is the stupidity of the end user.

Ron(UK)

>

traces

I get the impression board layout designers just use what has worked before as far as track dimensions etc and don't actually consider in great detail catastrophic failure modes. Yes this kit does support the CE mark. I've not been able to find design data/tables for such traces. I may dig out a low voltage 60 amp transformer fed via a variac and sacrifice some otherwise unaffected tracks on this board to determine what sort of amperage to cause excessive heating and then another bit of track to find the rupture current. Having to avoid localised failure at my test join-points with a lot of distributed solder.

clattering

withdrew a

with it

There was another one - oh actually I think that terminal section did actually have a male thread on it.

LOL !

'Tis often true.

Graham

There are published guidelines for temp rise vs current, copper thickness and track width. You'll find a chart of same in IEC60065 (electrical safety) in fact.

The board layout guy will only use the data supplied by the design engineer. They're not psychic. Some 'design engineers' have a clue however.

Good designers will design for that.

So what's the damn make and model FFS ! Why are you refusing to tell us one of the most important pieces of information ?

Graham

On a well designed circuit board, you can often see which traces are involved with each part of the circuit. Broad traces carry the heavy current, spidery ones are the signal path. I remember a time when some quality gear actually had the signal path screened onto the component side of the board, together with typical voltages etc. That was when they actually wanted us to repair the stuff.

I dont think any designer worries too much about 'catastrophic failure'!

. Yes this kit does support the CE mark.

You still havent shared with us the make and model

Ron(UK)

Eeyore wrote: I do recall one time about 30 yrs ago when I withdrew a

with it

have a

Aye that`s right, and when they came loose, Johnny guitar would try to tighten it by sticking a screwdriver (table knife) in the slot in the pin and twist, neatly snapping half the pin off!

Ron(UK)

Just interested ... Do you actually make a living out of repairing this stuff ? If I spent as much time as you seem to, worrying about esoteric things like how much current a track will take before it vapourises, I would long since have ceased to earn enough money to get by on. These days, I find that it has to be 'wheel it in, fix it, wheel it out , invoice it, next please'. If the bit called 'fix it' takes longer than an hour, and the value of the kit is less than 150 quid, that bit changes to 'bin it' ...

Arfa

There are uses for sine, square, multiple sine, and complex waveforms in testing. I suggest using each for what it will make esily visible in the performance.

--
 JosephKK
 Gegen dummheit kampfen die Gotter Selbst, vergebens.  
  --Schiller

I don't feel like whipping up bulk supply simulation right now, please run yours and tell me the ripple voltages at 10% conduction and 6.25 % conduction.

--
 JosephKK
 Gegen dummheit kampfen die Gotter Selbst, vergebens.  
  --Schiller

I've been repairing Crown, Sondcraftsman, Peavey etc...for many years. I've used audio tones many many times. I suggested the music for this experimental endeavor that Cook may undertake as a quick way to see what value fuses would (hopefully) blow and what wouldn't. But nothing is etched in stone and being knowledgeable, Cook may try multiple approaches.

before

and

in

engineer.

one of

I was having a play with track width calculator

and assuming it is still sort of valid at very high temps. Putting the melting point of copper of 1080 deg C then for 3.5mm strip of presumably 1 oz copper then the rupture current would be about 48 amps which seems reasonable. I knew it must be higher than 12 amps as that calculation was for round wire. By 1080 deg C we can forget about the solder run beefings. I think I'll leave my 60 amp transformer on the shelf - I'm happy with 48 amps

-- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on

thickness

solder

I think, assuming they survive ordinary power-ups a few times, I'll settle on a mains side 4 amp anti-surge , with a 5 amp A/S ready to hand spare and

2 off 10 amp quick-blow in the DC lines.

-- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on

I refuse to run such a simulation: this is the sort of stuff that was discussed in two pages of a 1930's-era electronics textbook in the beginning of a chapter on power supplies. Math is what a high-school student was expected to know. You might as well ask me to run a simulation to prove that 1 volt across 1kohm gives 1mA :-).

I'll give you the result: at 10% conduction angle, ripple is 5%. (If you have a pocket calculator, the voltage at the bottom of the ripple is Vpeak*cos(.1*pi).) At 6.25% conduction angle, the ripple is 2%.

Other handy results: 15% conduction angle, ripple is 11%. 20% conduction angle gives ripple of 19%.

If you look a little later in the 70-year old electronics texts, they get into I2R and other losses in transformers and making the proper economic choice in sizing transformers and capcitors. They also get into my favorite filtering method, choke-input! (A method at least mentioned in the better of the more modern textbooks).

Tim.