Hi Jason,
Thank you for shipping the boards 🙂
Can I use IRFP 9240/240 for pass mosfets?
Do you know a Mouser part number for a suitable heatsink?
Thanks.
Thank you for shipping the boards 🙂
Can I use IRFP 9240/240 for pass mosfets?
Do you know a Mouser part number for a suitable heatsink?
Thanks.
Something like this would do?
WV-T247-101E Ohmite | Mouser
How much power would the mosfets be able to handle with this heat sink?
About the LEDs - 2V forward voltage drop OK?
WV-T247-101E Ohmite | Mouser
How much power would the mosfets be able to handle with this heat sink?
About the LEDs - 2V forward voltage drop OK?
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You could, though the IRFP140 / IRFP9140 might be a better choice with similar price and availability. Basically go for the lowest Rds-ON specification you can get that will tolerate you planned voltages. In the case of a VSSA / PeeCeeBee build, that would have you shopping in the >=50V Vds category. It is also rather unimportant that the devices be 'compliments', so you don't have to constrain yourself as much when selecting devices.
Heat sinking requirements are rather light. I'd just cut a piece of aluminum sheet / angle about the width of the board and a little lower in height than the capacitors and mount the MOSFETs to that. The pass devices only drop about 2V or so, which means dissipation is low much of the time. Worst case is full power sine wave testing, where the devices might be asked to dissipate several watts.
The LEDs are best if they have a Vf about 1.6V, so old school GaAsP red LEDs are perfect, though a little higher Vf won't hurt anything. Worst case means selecting a new resistor value for the current sources.
Heat sinking requirements are rather light. I'd just cut a piece of aluminum sheet / angle about the width of the board and a little lower in height than the capacitors and mount the MOSFETs to that. The pass devices only drop about 2V or so, which means dissipation is low much of the time. Worst case is full power sine wave testing, where the devices might be asked to dissipate several watts.
The LEDs are best if they have a Vf about 1.6V, so old school GaAsP red LEDs are perfect, though a little higher Vf won't hurt anything. Worst case means selecting a new resistor value for the current sources.
I decided to use the same mosfets of the BOM you published. 😉
About the aluminium bar - that stuff from AKI (windows aluminium) is OK?
What about this: Aluminium Flat BAR Width From 10mm TO 25mm Choose Size Length | eBay
Thanks for your help! 🙂
About the aluminium bar - that stuff from AKI (windows aluminium) is OK?
What about this: Aluminium Flat BAR Width From 10mm TO 25mm Choose Size Length | eBay
Thanks for your help! 🙂
Many hardware or hobby stores sell aluminum or brass sheets or strips that would be suitable. Linked here is an example of what I have done with another project and envisioned much the same with this board. The metal is fairly thin, it is really surface area that matters most, no so much the thickness or mass.
http://www.diyaudio.com/forums/solid-state/248105-slewmaster-cfa-vs-vfa-rumble-149.html#post3874219
http://www.diyaudio.com/forums/solid-state/248105-slewmaster-cfa-vs-vfa-rumble-149.html#post3874219
Looks great!🙂
How did you cut the aluminium in so perfect straight lines? Did you use some kind of naife?
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No special tools, just a really old and rather large set of tin-snips. The bends were made against the jaws of a bench vise. Member jwilhelm does much the same , but he has access to a shear and box-pan or break press.
Did I ever make up a set of heat sinks for yours?
Attachments
I had to google "tin snip" to find out what it was.LOL it's a kind of scissors. I have something like that for cutting garden tree branches. Maybe it will do the job. 😉
What amazes me is how you cutted so well, so straight. Very very professional!🙂
Same to you, Jwilhelm, looks very well built! I'm envy! 😉
What amazes me is how you cutted so well, so straight. Very very professional!🙂
Same to you, Jwilhelm, looks very well built! I'm envy! 😉
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Here's a layout for the heatsinks. if you are bending these in a vice, shorten everything slightly.
IIRC, you said you made some but I haven't had anything interesting to reciprocate with or been in the neighborhood recently. I'll have to pop over some day and see what you have cooking.
I just ordered from eBay a 0.5mm tick aluminium sheet. Is it too thin? I was going to order 1mm but I tought it was too tick for easy bend. Now I don't know if I made the right choice...😕
That will be just fine. I ran mine at a 2V drop for a few hours with a pair of VSSA on it playing comfortably loud and the MOSFETs were just warm WITHOUT ANY heat sink on them at all.
Hi Jason,
I finished the capacitance multiplier but I don't know if it's working properly. I find very difficult to ajust it and I don't get a fixed voltage at the output, it goes up and down. Also, the trimmers seem to have some inercia, it takes a few complete turns to start going up or down in voltage and when it starts going the way I want it goes too much and I have to turn the trimmer the other way almost reaching the point where I started. Is this some sort of oscillation or is it the normal behavior?
I finished the capacitance multiplier but I don't know if it's working properly. I find very difficult to ajust it and I don't get a fixed voltage at the output, it goes up and down. Also, the trimmers seem to have some inercia, it takes a few complete turns to start going up or down in voltage and when it starts going the way I want it goes too much and I have to turn the trimmer the other way almost reaching the point where I started. Is this some sort of oscillation or is it the normal behavior?
Do you have a load on the output? You need something to draw some current to get 'normal' behaviour. Also remember it is a capacitance multiplier, so if the input varies slowly, the output will track it. You are looking to get about 2V across the D-S pins of each pass MOSFET.
A load drawing perhaps 100mA should do. The adjusters will react a little slow as the load has to drain off extra charge from the output capacitors as you make a change.