One more P 1.7 layout......

[Kari]

Well, here is one more (!) P 1.7 layout. PS is still missing from the board and so is the groundplane, which is going to be on the top layer.

I actually needed a project to draw, as i moved from Eagle to Altium Designer 6.0. Now i just need to finish up this one so i can start with the PLH project.....

[Kari]

Some updates....

[wayne325]

Ok so it's not that small of an issue perhaps. Or perhaps it's
fine.

I believe (you should confirm) that the MOSFETS are dissipating
on the order of 1W each. Are you planning to reject that heat
somehow ? If there isn't adequate cooling, methinks those
devices are going to not last too long.

Also - Q20 and Q19 have their backing plates close or touching
it appears. Those plates are electrically connected to the drain
I think. You will have to electrically insulate them if the two
drains of Q20 and Q19 are not electrically connected. Come to
think of it I can see a trace going from the middle pin of Q20 to
the right pin of Q19 so that means there is an electrical isolation
of the two backing plates required.

Not saying anything is wrong - I don't have a schematic
or the package drawings in front of me. I'm just suggesting
that you look into these things if you haven't already accounted
for them.

Over and Out.

W.

[wayne325]

I just noticed you are from Stockholm. I was there 2 weeks
ago. Cool place :-). Literally. And you Swedes are a good
lot to hang out with. Class A amps are good for there. You
can use it to heat your apartment or house.

[Kari]

Q20 and Q19 needs to be isolated. This can easily be done with a silpad. The fets would survive without a heatsink and i have seen a couple examples of this. I could of course rotate the fest 90degrees and have them mounted to a heatsink, still i do not think this is needed. If a sink is needed that could be easily attached as they do not need that big sinks.

Thx for your input!

/Kari

[Nisbeth]

I think putting the FETs inlinealong the upper edge of the board would be a better idea, even if it slightly increases the size of the PCB. That you you can easily just bolt the heatsinks to a piece of aluminum for heatsinking and you don't have to worry about accidental shorts from the tabs


/U.

[harryeng]

Hi Kari,

Nice and clean layout!

As you said, PS is still missing. As far as I can see that means just the two capacitors, one more resistor and two connections.

On the P1.7 board I have now, the mosfets only get luke-warm, but when you buch them up like this, they heat up more. Still, no problem I think. When you enlarge the board for the capacitors you can always flip the middle-upper section to get the mosfets facing outwards.

One remark, more about the BOSOZ boards you did before (and sound great); you should try out the Elma Silmic capacitors. I think they sound better, but they are somewhat larger than average capacitors. I ended up rising them from the board with wooden spacers to fit them in

Greetings, Harry

[jleaman]

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