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BLF578 FM pallet amplifier!

 
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BLF578 FM pallet amplifier!
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tntmarcel
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Joined: 04 Mar 2012
Posts: 2

Post BLF578 FM pallet amplifier! Reply with quote
Hello to all and thank you for receiving me on the forum!
I builded an FM pallet amplifier using the NXP mosfet BLF578 and the original NXP schematic from the pdf with some minor changes(i added termal compensation for bias) but i discovered it has great mismatch(the mosfet is eating 40amps and delivering maximum 700w, already i burned 1 mosfet) so in conclusion the output values of the NXP schematic(cable lenghs and capacitor values) are not that correct(this only on the output stage, the input stage is behaving normal and it works ok)
This is how the pallet looks like so you can have an ideea: http://s18.postimage.org/d36a8ebmx/Fotografie0522.jpg
I have no equipment(only have wattmetter and dummy load) to measure mismatch and fiind the right combination for the cable lenghs and capacitor values on output, so i am asking for help to anyone ho makes such pallet amplifiers and has experience with them to please give me the right combination on output!
Thank you very much!
Wed Mar 07, 2012 4:06 pm View user's profile Send private message
pcs
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Joined: 18 Jan 2002
Posts: 3063
Location: Radio Land

Post Reply with quote
Try our pallet, I bet it will work much better than the one you built yourself.

_________________
Best regards,
Marko - PCS Electronics
--------------------------------------------------------
Turn your PC into a FM radio station!
http://www.pcs-electronics.com
fax +386 4 2316 128
Wed Mar 07, 2012 4:44 pm View user's profile Send private message Visit poster's website
tntmarcel
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Joined: 04 Mar 2012
Posts: 2

Post Reply with quote
pcs wrote:
Try our pallet, I bet it will work much better than the one you built yourself.


Well curently i cannot aford it.. i know you got great products because i purcesed 15w fm transmitter from you(with it i am driving the pallet)
Good news is my pallet doesent eat 40amps.. it deliveres 840w at 43v and eats 25amps.
But the thing that bothers me is the BLF gets very hot(in 4-5 seconds you cannont keep finger on it) and keeps getting hoter fast.
Is this normal behavior? my old amp with a BLF278 the mosfet stayd very vool even at 300w, and as you see in picture i have big heatsink on my curent pallet!
Fri Mar 23, 2012 5:08 pm View user's profile Send private message
pcs
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Joined: 18 Jan 2002
Posts: 3063
Location: Radio Land

Post Reply with quote
I cannot say from the distance, if you want diagnosis you have to go to the doctor, not send him an email

_________________
Best regards,
Marko - PCS Electronics
--------------------------------------------------------
Turn your PC into a FM radio station!
http://www.pcs-electronics.com
fax +386 4 2316 128
Tue Apr 03, 2012 10:16 am View user's profile Send private message Visit poster's website
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