| bzo |
Someone mentioning here that Richardson Electronics had a great price on the IRFP044 at about $0.90 a piece. Digkey sells them for about $2 each.
I tried ordering 50 yesterday. Unfortunately, I got a call today and was told that the minimum order for this was 350 pieces because it's a special order item.
It wouldn't take very many people to pool together to reach the 350 piece order. |
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| Magura |
Count me in for 5 pairs
Magura:) |
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| PrimeCase |
As I was the one who posted the original quote I'd be in for 50 and if people wanted I'd co-ordinate a bulk purchase
Kevin |
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| Magura |
Sounds good, but what would be real interesting is matched pairs. By buying so big numbers, it would be possible to get matched pairs out of all of them.....with none going to waste.
Magura:) |
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| bzo |
Kevin, I was hoping someone would step up to coordinate a group purchase! :D I would definately be in for 50 pcs. Btw, did you try to place an order and run into the same thing I did?
Magura, getting matched pairs would be ideal, but it sounds like a lot of work. Anyone willing to volunteer?;)
Incidentally, at an order quantity of 350pcs, the mosfets drop down to $0.87. Strangely, there are no further price reductions - even up to 25,000 pieces! |
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| Mark A. Gulbrandsen |
Guys, as along as you get these fomr the sdame batch code lot they will match up really nice. If they're selling random batch codes I wouldn't buy the.... Makes more the likelyhood of pairs that would be unmatchable. Also, matching mosfets is VERY easy!
Mark |
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| Coulomb |
Has anyone thought to use the IRFP054? They have a much lower IRDS and handle a little more power.
Regards
Anthony |
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| Magura |
| quote: | Originally posted by bzo
Magura, getting matched pairs would be ideal, but it sounds like a lot of work. Anyone willing to volunteer?;)
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I usually make the neighbours boy do stuff like that. If you can get the mosfets here, ill sort the matching.
Magura:) |
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| PrimeCase |
I didn't follow up on the "on order quote on the web page due to the fact I'm still making the chassis.
From Richardson you can get the r-theta E3093/wakefield 6274 in 18" lengths for $51!!! as far as I know they had 19 units in stock when I ordered mine.
The arrived un-anodised with a few cosmetic dings here and there but still an excellent price. A Bargain!!!!
Lastly if you need a source for transformers you can find a seller on e-bay selling 13v transformers on e-bay rated at over 50A for $25 each, these are from APC UPS's a pair of those with the secondaries in series makes good sense for 15-16v rails.
I'll get back to this thread shortly as I'm taking care of the wife after surgery and being in pain she's a little cranky so gotta go for now, speak soon.
Kevin |
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| stefanobilliani |
| quote: | Originally posted by bzo
It wouldn't take very many people to pool together to reach the 350 piece order. |
I am interested in 50 pieces .
:) |
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| Mark A. Gulbrandsen |
"From Richardson you can get the r-theta E3093/wakefield 6274 in 18" lengths for $51!!! as far as I know they had 19 units in stock when I ordered mine. "
I couldn't find either of these sinks on either manufacturers web site.......
Mark |
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| joensd |
I´m not sure if there´s a big difference between the IRFP044 and IRFP044N but at Reichelt you get the IRFP044N for 1.20€.
To be sure you´d have to call but usually they ship IR parts.
(2$ are 1.62€ at the moment ; 1.20€=1.47$.) |
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| audionut |
| I would be good for 50...is there going to be a sign up WIKI |
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| bigparsnip |
| I would also be in for 64 or so if this goes ahead. And I guess a wikiw would be quite useful for this one too. |
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| Magura |
I guess we need a "WIKI for dummies" thread ;)
I too dont know how to make a wiki, but a wiki is a must now.
Sporadic indications in a thread are no good.
Magura:) |
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| bigparsnip |
I can set one up quite happikly if people want. check back in about 10 or 20 minutes and I'll see what I can do.
Andrew. |
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| bigparsnip |
Ok, I have set up a basic WIKI page now and included everyone who has already posted here onto the list (274 so far, not too far of the target), but it would be good if the people organising this would add some of their own information to the page, as at the minute I'm not 100% sure of the price or definate part type.
Andrew.
IRFP044 Group Order WIKI Page |
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| PrimeCase |
the heatsink profiles I may have named incorrectly, here is the link on the wakefield site.
Wakefield extrusion
and the R-Theta site seems to be down right now.
Kevin |
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| PrimeCase |
Ok people.......there is a new thread titled IRFP044 Group Order over on the pass labs page, please submit andy and all enquiries to this page. I'll have it book marked. Anything else I guess you can send me an e-mail. Don't forget to update the wiki if you are interested.
Thanks Guys and Girls
Kevin |
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| leadbelly |
Oops, this group buy has come up too quick as I have yet to figure out how many IRFP's I can use.
I am going to be building a case made from the heatsinks shown in the attached picture. They are big (15.5" x 3" w/ 1.5" fins), but the fins are epoxied (!). I will use 5 per channel. They are surplus so I have no specs. I will be running +/- 18VDC rails at 10 amps per channel.
Must I limit myself to 1 IRFP per sink or can I run more? I know this is guesstimating, but any help is appreciated. |
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| PrimeCase |
Leadbelly
It honestly depends on the bias you'll be running but with extrusions that long I think you should be able to get away with 2 devices per sink if you keep the dissipation per device reasonable like 20W and under for each device. I'd suggest you get yourself a decent power resistor and mount it on the heatsink (use thermal compound) and run a test to see what the temperature rise over ambient will be for a given dissipation. With a 20v supply and a 50w 1 ohm resistor it will dissipate 20w, bolt that to the sink and see how much the temperature will rise over ambient, that will give you a decent idea. Try to keep your design at no more than 50-55 degrees C when running to help reliability and also saftey if you have children or pets.
Kevin |
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| PrimeCase |
Leadbelly
Just looking over your figures that's a fair amount of dissipation, I'm guessing that you are looking to make a pair of mono amps with 5 sections of this heatsink per side?
That may work just fine but I's seriously test a sink first to see what they will handle.
Kevin |
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| leadbelly |
| quote: | Originally posted by PrimeCase
but with extrusions that long |
| quote: | Originally posted by PrimeCase
Leadbelly
Just looking over your figures that's a fair amount of dissipation, I'm guessing that you are looking to make a pair of mono amps with 5 sections of this heatsink per side?
That may work just fine but I's seriously test a sink first to see what they will handle.
Kevin |
That's just it, they're not extrusions, the fins are epoxied on to the base. I don't know whether to expect them to have a similar coefficient to an extruded sink.
I was planning to make a stereo amp, common PS supplying 20A total, each channel using 5 of the heatsinks. |
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| PrimeCase |
Yep.....forgot about the epoxied fins LOL :)
I think you'll be better served being slightly less ambitious, remember that if you are using groups of 5 fets that is 20 fets per channel running 10A total bias?
So 4 devices per heatsink at around 72W per sink, this will give you a temperature rise of 50 degrees over ambient if you run with 10A bias assuming the heatsinks are as good as this particular extrusion Thermaflo example
have a look and maybe you'll revise your plans
Kevin |
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