BD537 in place of 2n6491? - diyAudio
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Old 18th November 2007, 12:46 AM   #1
spooney is offline spooney  United States
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Default BD537 in place of 2n6491?

i was doing a cross reference search on fairchilds website and when i entered 2n6491 it came up with bd537 as a cross.It seems to me by looking at the data sheets that the bd537 is a lesser part.The main thing i noticed was a power dissipation of 50 watts on the bd537 and 75 watts on the 2n6491.I'm not sure if I'm missing something or what but it seems like the BD537 part wouldn't work in place of the 6491.Does anyone know if it indeed will work?It would be great if it did as the bd537 is quite a bit cheaper than the 6491.I might actually finally get my orion up and running.
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Old 18th November 2007, 02:32 AM   #2
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The BD537 is the Fairchild cross for the 2N6488 but it's not a good substitute.

The 537 is only rated for 8 amps. The 6488 is rated for 15 amps.

If you want a cheaper part, the BD911 and BD912 have been used successfully by several people here. I've never used them. I always use On-Semi 6488s and 6491s.
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Old 18th November 2007, 04:04 AM   #3
grjr is offline grjr  United States
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How much is too much for the 2N6491 ? I have quite a few of them on hand that are made by central semiconductor. I could sell you some if you'd like.

edit: mouser sells them for $0.73 each
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Old 18th November 2007, 08:28 PM   #4
spooney is offline spooney  United States
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its not really the 6491 i'm worried about.Its the 2n6488's.I need at least 25 of them and would really like to get 30.Even at just over a buck a piece they start getting expensive real quick.I'm also looking at getting at least 10 of the 6491's
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Old 18th November 2007, 11:32 PM   #5
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IMHO, pay the price for the 6488/6491's. It's not that much more expense, and their track record is well proven.

Again my opinion only, YMMV.

Tim
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Old 19th November 2007, 12:05 AM   #6
spooney is offline spooney  United States
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its only 10 bucks more for me to get the 6491's and 6488's so I'm gonna take everybodies advice and get the good parts.Thanks everybody for your help.
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Old 19th November 2007, 09:20 AM   #7
Clipped is offline Clipped  Thailand
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as perry said the ST microdevices bd911/912 is a good replacement, the BD 909/910 is a better match.

the 911/912 are 100 volts
the 909/910 are 80 volts

both 90 watts, 15 amps
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Old 19th November 2007, 12:23 PM   #8
Clipped is offline Clipped  Thailand
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you may want to check the mpsu57/07 pre drivers and drivers also.

those go bad more often than the output transistors from the old orions ive come across... when they go bad they can make the outputs appear to throw out dc, do to lack of either a negative or positive drive signal.

check the 5534 opamps too, especially the teardrop mylar thats connected to the power supply legs.

check out my post on : orion 2150sx

lots of good stuff in there...

good luck!
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Old 19th November 2007, 09:23 PM   #9
spooney is offline spooney  United States
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I've already got some new mpsu07's and 57's ready to go.I've actually got this thing playing cleanly But i've only got one set of output transistors in either channel and a partial set of power supply transistors.Every sink mounted transistor is being replaced as well as all the electrolytic caps.I've heard someone say that all the tantalum caps should be replaced as well although i'm not sure what the value of them are.It looks like the caps say 2u2 25 volt.I'm not sure if 2u2 means 2.2 microfarad or what.
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Old 20th November 2007, 01:57 AM   #10
Clipped is offline Clipped  Thailand
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i think i meant tantalum not mylar, the value is in my other post.

i had two go bad in the 2150sx i repaired one was at the 5534, the other was in the power supply at the mct2.
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