These IRFP are from an another old forgiven project. They consist in a matched IRFP240 sextet and a matched IRFP9240 sextet.
Marc
Nice progress. I can't tell from photo but don't forget to flip 1N4148 direction relative to silk.
For folks building this amp, if you don't already have Vgs matched MOSFETs, it might be worth it to measure yourself.
Here is how:
http://www.diyaudio.com/forums/solid-state/299546-nelson-pass-easy-peasy-mosfet-vgs-measurement.html
Here is how:
http://www.diyaudio.com/forums/solid-state/299546-nelson-pass-easy-peasy-mosfet-vgs-measurement.html
Ide, remember that a fan works better if it is set up to push air into a restriction and has a clear intake side.
It does not work as well when it sucks, becaue the restriction on the input interferes with the flows and pressures.
When the fan is working hard, it does not matter if it blows horizontally into a sink or vertically.
But when you turn it down to be quiet it does make a difference. Fan at the bottom blowing up through a vertical sink acting as a chimney works better than blowing downwards or sucking downwards or working horizontally.
You can even turn the fan off and the chimney effect alone can give some cooling.
Ah the Grashof number...
It's interesting how many commercial forced convection products use the "suck" mode, that is, the fan is on the back blowing out, sucking air through the heatsink tunnels or the boxes. The sucking method will provide more uniform cooling of all things inside the box if air inlets are situated appropriately to draw a laminar flow past the heated objects. Whereas a fan blowing into the box will be turbulent and then circulate inside and re-heat rather than exiting after heated once. On some PA amps and high power computer rack servers there is a set of fans that blow and another that sucks but flow is straight down a narrow 1U rack.
It's interesting how many commercial forced convection products use the "suck" mode, that is, the fan is on the back blowing out, sucking air through the heatsink tunnels or the boxes. The sucking method will provide more uniform cooling of all things inside the box if air inlets are situated appropriately to draw a laminar flow past the heated objects. Whereas a fan blowing into the box will be turbulent and then circulate inside and re-heat rather than exiting after heated once. On some PA amps and high power computer rack servers there is a set of fans that blow and another that sucks but flow is straight down a narrow 1U rack.
fan blowing into a sink tunnel will probably result in turbulent air flow.
Turbulent air flow cools better than laminar air flow.
Passive cooling using the chimney draw will probably be laminar air flow.
It's the difference between turbulent cooling of a fast air flow and the laminar slow air flow of a chimney that makes the BIG difference in the cooling capacity of a fanned sink cf. a passive sink.
Turbulent air flow cools better than laminar air flow.
Passive cooling using the chimney draw will probably be laminar air flow.
It's the difference between turbulent cooling of a fast air flow and the laminar slow air flow of a chimney that makes the BIG difference in the cooling capacity of a fanned sink cf. a passive sink.
I agree completely.
It's just on say, a PC case where there is no tunnel, blowing air in causes it to mix around and leak out and there will be a residence time for the heated (warm) air before it exits. Maybe same happening with sucking but I think there is less recirculation of warm air.
In any event, a fan blowing by a heatsink is like 100x more effective than natural convection and heatsinks can be made much smaller and cost less.
many modern PCs now have a tunnel to ensure an unobstructed air supply from outside through the CPU heatsink. And that heatsink is blown, never sucked.
I think PCBs should be arriving at some of their destinations now abroad. Anyone else get your boards yet?
No, not at this point. But there maybe a couple of other folks who are interested and with 5 people another group buy could be organized.
Just got back home to find the boards here (along with extra bits 🙂 )
Thank you for putting this GB together XRK
I see soldering fumes in my near futures
Thank you for putting this GB together XRK
I see soldering fumes in my near futures
Great to hear Hajj! Amazing how mail to Lebanon is faster than a package to Canada or Mexico.
Perhaps evidence of reversal of NAFTA already 🙂
Perhaps evidence of reversal of NAFTA already 🙂
