Psu Lm3886

[ppcblaster]

The maunal sucks.

What type and size fuse do I need?

Also my avil transformer has dual pirmary and dual secondaries.

I am confused how to connect the wires and where to mount the

two, on board terminal blocks and on what boards.


Boards assembled, only 3 bandaids on my fingers,

Thank You..

[!]

Fuse depends on multiple factors, I'm not familiar with that kit but in general unless you have gobs of PSU capacitance or are doing a 3+ chip paralled or bridged amp, a 2A slow-blow should suffice, but 3A slow would be a more conservative choice. This assumes it is a mains-side fuse, not after the transformer. If after the transformer, just apply the figures in a in/out ratio multiplier fashion to the above amperage figures, fudging a bit since such low single digit numbers leave some margain for error.

[AndrewT]

Hi Ppc,
please think about your questions and make them less ambiguous.
What fuse? What equipment are you feeding? What mains voltage? Is there soft start? Are there timed relays? What rail voltage? What smoothing capacitance? What speaker impedance?

Help us to help you.

[ppcblaster]

BrianGT suggests a 3A slow blow.

[desert_rainbow]

suggest AC+-25~+-28V

[Jackson Audio]

Hello all.

Fusing is dependant on power draw. If, for example, a 150VA transformer is being used, then you don't want the transformer to draw more than its continuous power rating from the mains. In the example above, which assumes that the transformer is properly sized to the application, 150VA / 120VAC would yield a current draw of 1.25 Amps. Size your fuse for that rating, or just a wee bit more, and you'll be in the clear. The use of a slow blow will help combat inrush current concerns, but again, if the transformer is sized properly to the job and is not crazily oversized (read 750VA when 150VA will do fine) then a standard fast blow as above should suffice.

Hope this helps.

[AndrewT]

Hi Jackson,
Ppc has not told us what he wants to fuse yet.

[!]

Unless the amp has current inrush limiting (which it should, really), the fuse rating will need be either slow-blow or significantly higher current rating than would seem necessary from the transformer VA rating.

IOW, an example might be a 300VA transformer and a few tens of thousands uF capacitance, it may blow a fast-blow 3A fuse (on primary winding @ 110VAC) at turn on, eventually, even if not the first few times the amp is turned on.

[ppcblaster]

I have the amp working, a

BrianGT Stereo Chip Amp, about 35vdc rail voltage,

I (solved the fuse problem), The directions state a 3A SB.

I am using a Pentium 2 slot 1 heatsink, The amp sounds great!

my consern is, I had to try it out to see if it worked with 4ohm

Automotive speakers. The heatsink was very warm after

about three songs on a CD. I used a portable CD player as

the input until I find a volume control. I also turned up the sound

to hear what it would do, I am impressed!

I have searched all over, Where can I get one heatsink for

both channels?

Thanks

[ianpengelly]

Originally posted by Mayday
BTW, I think someone else said it first, about dual trafos i meen.

I did start a thread about using a single transformer and more than one psu board and that it resulted in thread, solutions were 1 psu or 2 transformers (assuming a 2 channel setup). For your boom box a single transformer and single psu board to feed both channels will be just fine.

Hope this helps.