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chinese psu kit
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OM222O:
he mentioned a bridge rectifier, so I assumed something small cooled with a PC fan. the most insane ones are these delta fans used for server racks which require a lot of static pressure to force the air through:

this one is a mid range one and as you can see it's rated for less than 24 watts!
their top of the line ones can draw about 60 watts but will literally fly off due to their own force if not secured properly and sound like a jet engine too!
Simon:
Yes and as I just said I have used fans just like that from ebmpapst that pull 125W! yes they sound like a jet and have enough force to move themselves around and do a lot of damage. We once put a cooler for a server rack for a submarine in a door with about 12 of those fans. The ones I use come in a 32.5W, 65W and 125W variety but all look identical, they just go faster and faster topping out at 11'000rpm. doubling power into a fan will only get you a 20% increase in speed but a 40% increase in pressure so going up to 125W is not that insane when you think that it is only pushing 20% more air than a 65W fan.
Kleinstein:
There is nothing bad with using a 50 A rated bridge rectifier at a lower current. However there is a problem with using 100 mF of filtering cap - this causes quite some current peaks, that can cause quite some ripple if not careful with the layout. For beginner It's better to start small - so more like the original size, reduced to some 1.5-2A.

As already noted the proposed the 2N3055 is good for something like 2 A max at some 35 V input voltage. So it could work to higher current, but it is not such a good idea to use the simple circuit to much higher power. It's likely better to use a slightly more complicated circuit and get away with about half the heat sink and fan power. Another point is the drop on the shunt: with higher current it gets attractive to reduce the drop at the shunt and use a better OP instead of a higher power resistor. Already the original configuration produces a lot of heat and thus not really stable current regulation. The .22 Ohms 25 W shunt would be more suitable for 2-3 A.

When replacing the rectifier, filter caps, shunt, power transistors, OPs there is not that much left of the kit that can be reduced. Expect very low quality pots to come with the kit - so better replace them too.
m3vuv:
dont you guys read?,firstly the bridge is what i have to hand secondly the fan is a small one to cool the heatsinks i have for 6x 3055 pass transistors,if i need that many,the filter cap is 100 thousand uf at 50v rating not 100 uf,i want to try and controll the 3055s with this psu for more current outputthe pass transistors will be off the pcb on heatsinks,i could use a 723 but i like the cc idea of this psu,having the value of the sense resistor should let it produce 2x the current as i see it,as long as the other components ie output transistors bridge etc are man enough?,thats basicaly what i was asking ie if it wouls work,not a sermon on heatsinks etc which i already know!.,ppl not reading the post properly or reading too much into it make this forum hard going!!
Simon:
Listen, if you don't like what people have to say then sod off! No one here is under any contract to tell you what you want to hear and you have been told: It's a bad idea, just make a suitable power supply for whatever it is you want to power. Why are you taking this shitty thing and trying to turn it into something it is clearly not? you either buy something for what it is or just build something from scratch.

What are you trying to power with it?
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