Creek 5350 fuse position..is it OK?

[ashok]

Hi,
Have a look at the picture of the power supply section of the Creek 5350. It looks like the fuse is located is located before the bridge rectifier which is a normal 6A diode (?) .
The fuse will be subject to the in rush current everytime the unit is switched on. This will cause it to slowly weaken and break one day even without an overload.
Wouldn't you think so ?

[Frank Berry]

"Wouldn't you think so ?"

Probably not. The fuse must be on the primary of the power transformer if it is to protect the entire amplifier.

The diodes may be rated at 6 amps but they are on the secondary of the transformer. The primary current will probably be somewhat lower.

I wouldn't worry.

[ashok]

Hi Frank,
I would have thought that the primary currents would be a scaled down version of the secondary currents. Fuse ratings would also be lower. Switch on surge current would be quite high even though the duration is very short.
True that it would protect the whole amp, being located on the primary side.
Hmm.......... I guess with proper choice it should be OK.
Cheers.

[ashok]

I tried to post a bigger picture. Here it is.

[Frank Berry]

The inrush current will be limited by the power transformer.

I'll bet that the fuse (or fuses) are of the Slo-Blo variety.
They should be okay.

[ashok]

I'll bet that the fuse (or fuses) are of the Slo-Blo variety.

But of course .. I guess they can withstand those surges without weakening with time. They also handle both channels and so will have reasonable ratings. In fact from the picture it does look like a slo-blo fuse. The wide fuse element seems to be visible.
Cheers,
Ashok.

[x-pro]

Originally posted by ashok
Hi,
Have a look at the picture of the power supply section of the Creek 5350. It looks like the fuse is located is located before the bridge rectifier which is a normal 6A diode (?) .
The fuse will be subject to the in rush current everytime the unit is switched on. This will cause it to slowly weaken and break one day even without an overload.
Wouldn't you think so ?

I thought it would be right for me to answer as I've designed this amplifier . Fuses are indeed of a "slow blow" variety, and I didn't heard even of one case when they blew from the inrush current. They positioned as described - between the secondary of the transformer and the bridge rectifier. On top of that there is a usual mains fuse on the primary side - inside the mains socket.

Regards

x-pro

[destroyer X]

In normal conditions, they are slow to burn, this way, inrush, as a slow time current will be ignored.
Of course if well calculated fuse, wrong value will blow easy when inrush happens.....and if the wrong value, was higher than the correct one....hehe, will burn after other part already burned.

The main reason, is to protect the board and circuits against heavy shorts, to avoid fire in the circuit boards, because transistor is fast to burn, and to call some others to burn with it too!... a sequence of shorts... each one makes the current drain increase....in microseconds all them goes to "heaven"...or "hell" if you prefer....in miliseconds the fuse will burn to avoid flame.

I do not think fuse can protect parts....it is too slow....either the fast ones, i thing it is usefull to tell you that something is going wrong.

This way, when a correct fuse blows, something may be wrong in the circuit, at least the bias moved to a higher value of current, and many reasons can make that, as some example:
temperature drift, rust in bias adjustment trimpot or mechanical vibration.

Avoid fire!, that's the work really done.

Maybe this is obvious to you, but there are young boys that do not know that, if not usefull to you, can be good for them.

I am sorry if you are one expert and i am telling those simple things to you, in the reality, i never write to only one, always i am thinking the young guys problems, those, without experience, will be happy.

In Army, my Sargeant, Ottmar Albert Furrer, helped me a lot; now it's my time to pay my bill to mankind.

regards,

Carlos

[ashok]

Hi X-pro and Carlos,
Thanks for your posts.
X-pro ,
The amp looks very nice too ! I like the surface finish which looks like silver satin anodising in the picture.
I have a question. I notice that the inputs are selected by a motorised switch with long signal traces between input and the switch. Would DIP relays at the rear have turned out to be far more expensive ? Would it have detracted from the sound ?
Thanks.

Carlos,
You should keep up your long informative posts. It will help lots of budding DIY guys and refresh the memories of some of the older guys.
Great to see you are having a wonderful time on this forum.

Cheers,
Ashok.

[x-pro]

Originally posted by ashok

X-pro ,
The amp looks very nice too ! I like the surface finish which looks like silver satin anodising in the picture.
I have a question. I notice that the inputs are selected by a motorised switch with long signal traces between input and the switch. Would DIP relays at the rear have turned out to be far more expensive ? Would it have detracted from the sound ?

Relays would not be more expencive and I suppose same soundwise, but a motorised switch has an important advantage - you could change the inputs both from remote and from the front panel in a usual manner plus it stays where you put it when the power is off - without additional complications, like non-volatile memory etc.

x-pro