Bottlehead Forum

General Category => General Discussion => Topic started by: Natural Sound on October 20, 2013, 10:01:06 AM

Title: Heat-sink recomendations for MJE350 transistors
Post by: Natural Sound on October 20, 2013, 10:01:06 AM

I was wondering if anyone can recommend a heat-sink that works well with MJE350 transistors. I recently installed an "Extended Foreplay" kit into my FPIII and the Shunt regulator transistors run a little hot. The same transistors on the C4S boards seem fine. I'm just looking for a little safety margin.

I'll be placing an order with Digikey next week for some other stuff so I'd like to use them as my source if possible. -Thanks.

Title: Re: Heat-sink recomendations for MJE350 transistors
Post by: Paul Birkeland on October 20, 2013, 10:21:55 AM

Replace them with MJE-5731A transistors (they face the other way).  No heatsink required. 

Title: Re: Heat-sink recomendations for MJE350 transistors
Post by: Grainger49 on October 20, 2013, 10:26:57 AM

BTW, Digi-Key offers a first class mail option that is truly cheap.

Title: Re: Heat-sink recomendations for MJE350 transistors
Post by: Natural Sound on October 21, 2013, 11:36:44 AM

Quote from: Caucasian Blackplate on October 20, 2013, 10:21:55 AM

Replace them with MJE-5731A transistors (they face the other way).  No heatsink required.

Thanks, thats what I'll order then. I take it the MJE-5731A is beefier and has a higher power/current rating?

Title: Re: Heat-sink recomendations for MJE350 transistors
Post by: Jim R. on October 21, 2013, 04:20:33 PM

Hi Tom,

I've got a couple more leftovers of some heatsinks that I've sent to 2wo and Deb -- I can send the last two (other than the ones I need) to you if you want. I think Deb posted a pic of her sr-45 amps in the sr-45 thread -- I've not mounted mine yet so Deb or John can tell you how the mounting and space worked out.

I'll look as I'm sure I ordered these from digikey too.

-- Jim

Title: Re: Heat-sink recomendations for MJE350 transistors
Post by: 2wo on October 21, 2013, 06:47:55 PM

Hi Jim, The heat sink fits fine on the board. I ran out of vertical space under my chassis, so I had to take it off till I rebuild. This is a very nice heat sink. It must be 8 or 10 times the size of the stock one and is surely up to the task...John 

Title: Re: Heat-sink recomendations for MJE350 transistors
Post by: Jim R. on October 22, 2013, 02:37:10 AM

Hi John,

That's good to know and I'm guessing your chassis is a bit shorter than the standard bh bases?

I'll look up the part number and post it here if people want to try these out for themselves.
I can't give everybody who wants a pair ttheir own.

-- Jim

Title: Re: Heat-sink recomendations for MJE350 transistors
Post by: Natural Sound on October 22, 2013, 08:14:39 AM

Quote from: Jim R. on October 21, 2013, 04:20:33 PM

Hi Tom,

I've got a couple more leftovers of some heatsinks that I've sent to 2wo and Deb -- I can send the last two (other than the ones I need) to you if you want. I think Deb posted a pic of her sr-45 amps in the sr-45 thread -- I've not mounted mine yet so Deb or John can tell you how the mounting and space worked out.

I'll look as I'm sure I ordered these from digikey too.

-- Jim

Hi Jim,

Thanks for the kind offer. I'm not sure of the dimensions but I think those are too big for my application. I ordered the MJE-5731A as PB recommended. After a little digging I found the specs on the two transistors. The MJE-5731A has twice the amperage and power capacity. I also ordered a couple of small TO-220 clip on heatsinks for good measure. I'm sure they are unnecessary but I'll put them on anyway if they fit in the available space.

Thanks again,
Tom