Thats just going to make a power supply with a 2 ohm source impedance. (ignoring the extra heat you will have to deal with)I might try the 28.7v transformer as a test, for I found two 2.2R 100W Arcol resistors in the spares box and at 2.5A they would dissipate 13.75W.
Another MoFo
#106 Re: Another MoFo
Whenever an honest man discovers that he's mistaken, he will either cease to be mistaken or he will cease to be honest.
#107 Re: Another MoFo
For mounting the Mosfet you could use two larger thread holes, one either side, and clamp the Mosfet in place with a shorth length of U channel; with your PCB you would need to have the Mosfet on short leads though, but then maybe leads with a connector would be useful if you plan to kill a few Mosfets?
Sorry, I couldn't resist!
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#108 Re: Another MoFo
Does the position of the resistor make a difference ?Nick wrote: ↑Thu Jul 02, 2020 12:43 pmThats just going to make a power supply with a 2 ohm source impedance. (ignoring the extra heat you will have to deal with)I might try the 28.7v transformer as a test, for I found two 2.2R 100W Arcol resistors in the spares box and at 2.5A they would dissipate 13.75W.
I was going to put it between 1st cap and 2nd choke.
The only thing necessary for the triumph of evil is for good men to do nothing.
Edmund Burke
G-Popz THE easy listening connoisseur. (Philip)
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#109 Re: Another MoFo
Could be a plan B.Ray P wrote: ↑Thu Jul 02, 2020 12:49 pm For mounting the Mosfet you could use two larger thread holes, one either side, and clamp the Mosfet in place with a shorth length of U channel; with your PCB you would need to have the Mosfet on short leads though, but then maybe leads with a connector would be useful if you plan to kill a few Mosfets?
I did a Rapid order yesterday cos I'd run out of red 28/0.2 wire, and I was going to get 2 more mosfets, but Rapid don't stock Irfp 250.
The only thing necessary for the triumph of evil is for good men to do nothing.
Edmund Burke
G-Popz THE easy listening connoisseur. (Philip)
Edmund Burke
G-Popz THE easy listening connoisseur. (Philip)
#110 Re: Another MoFo
I assume you mean second cap. It will be better. Depends on the size of the capspre65 wrote: ↑Thu Jul 02, 2020 12:52 pmDoes the position of the resistor make a difference ?Nick wrote: ↑Thu Jul 02, 2020 12:43 pmThats just going to make a power supply with a 2 ohm source impedance. (ignoring the extra heat you will have to deal with)I might try the 28.7v transformer as a test, for I found two 2.2R 100W Arcol resistors in the spares box and at 2.5A they would dissipate 13.75W.
I was going to put it between 1st cap and 2nd choke.
Whenever an honest man discovers that he's mistaken, he will either cease to be mistaken or he will cease to be honest.
#111 Re: Another MoFo
If you kill the mosfet, just cut the leads and solder the new ones to the only lead end. I would keep all leads as short as possible.Ray P wrote: ↑Thu Jul 02, 2020 12:49 pm For mounting the Mosfet you could use two larger thread holes, one either side, and clamp the Mosfet in place with a shorth length of U channel; with your PCB you would need to have the Mosfet on short leads though, but then maybe leads with a connector would be useful if you plan to kill a few Mosfets?
Whenever an honest man discovers that he's mistaken, he will either cease to be mistaken or he will cease to be honest.
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#112 Re: Another MoFo
I assume you mean second cap. It will be better. Depends on the size of the caps
[/quote]
47000uf low ESR Kemet soup tin size.
The only thing necessary for the triumph of evil is for good men to do nothing.
Edmund Burke
G-Popz THE easy listening connoisseur. (Philip)
Edmund Burke
G-Popz THE easy listening connoisseur. (Philip)
#113 Re: Another MoFo
Well the good news is that that will work as a reservoir, but the bad thing is it will take some time to charge back up through the resistor if you pull a peak from it. But unlikely with your music collection
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#114 Re: Another MoFo
The only thing necessary for the triumph of evil is for good men to do nothing.
Edmund Burke
G-Popz THE easy listening connoisseur. (Philip)
Edmund Burke
G-Popz THE easy listening connoisseur. (Philip)
#115 Re: Another MoFo
Agree, was only suggesting an extension long enough to get the Mosfet from being hidden under the board. As I understand this to be a 'prototype' I thought a bit of flexibility might be handy - can then go an optimal assembly on the proper build.
Sorry, I couldn't resist!
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#116 Re: Another MoFo
I've decided to stick with the 22V toroids for the MoFo.
The new ones, 28.7V will be saved for a future project.
I know it makes sense.
The new ones, 28.7V will be saved for a future project.
I know it makes sense.
The only thing necessary for the triumph of evil is for good men to do nothing.
Edmund Burke
G-Popz THE easy listening connoisseur. (Philip)
Edmund Burke
G-Popz THE easy listening connoisseur. (Philip)
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#117 Re: Another MoFo
According to the IRFP250 data sheet it has "an isolated central mounting hole".
The fixing data says M3, but the hole is bigger, big enough for an insulating top hat washer (for M3) but not big enough for M4.
I thought the first part meant it didn't need an insulating washer between it, and the heatsink but the fixing hole size makes me wonder.
Shall I just use an insulator (and a smidge of paste) and be safe ?
The fixing data says M3, but the hole is bigger, big enough for an insulating top hat washer (for M3) but not big enough for M4.
I thought the first part meant it didn't need an insulating washer between it, and the heatsink but the fixing hole size makes me wonder.
Shall I just use an insulator (and a smidge of paste) and be safe ?
The only thing necessary for the triumph of evil is for good men to do nothing.
Edmund Burke
G-Popz THE easy listening connoisseur. (Philip)
Edmund Burke
G-Popz THE easy listening connoisseur. (Philip)
#118 Re: Another MoFo
Still need the insulator and paste if the insulator requires it. The isolated hole means you don't need to countersink the hole as you would with a to220 device to isolate around the top hat washer sides.
Whenever an honest man discovers that he's mistaken, he will either cease to be mistaken or he will cease to be honest.
#119 Re: Another MoFo
Of course you also don't need the top hat washer. But use as large a flat washer as possible to spread the load.
Whenever an honest man discovers that he's mistaken, he will either cease to be mistaken or he will cease to be honest.
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#120 Re: Another MoFo
I seem to remember reading about using a coin as the flat washer, a 1p would do.
Mind you, I could be imprisoned for defacing a coin of the realm.
The only thing necessary for the triumph of evil is for good men to do nothing.
Edmund Burke
G-Popz THE easy listening connoisseur. (Philip)
Edmund Burke
G-Popz THE easy listening connoisseur. (Philip)