I have completed two monoblock f2js the first one worked perfectly ,however in my rush to complete the second unit i connected the unit and there was a very loud hum.This happened on two occasions found that the speaker wires were touching.After sorting out the speaker cables noticed smoke coming from the irfp9240 .On removing the transistor found that transistors had not been tightened down to the heatsink on the irfp9240 was burnt .Replaced with new transistor left for an hour amplifier wii not bias higher than 4.7 volts dc .Any suggestions as to which components should have to be replaced Any help appreciated .Other amplifier works great will have to appreciate mono for now.Thanks Alrick
Did things the hard way complete rebuild of non working board.Now both boards working the sound is the best of any amplifier I have ever heard working with my lowther dx3s.My pm6a silver coil lowthers whilst worked didi not have much volume due to the impedance e of the speakers at 16ohm will experiment when the amplifiers have burnt in.Fronted by a oppo 105d player and the preamp being the home built b1 preamplifier kit purchased from Nelson Pass.I wil attempt to post a few pictures of the amplifiers.
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Here are the photos I promised to upload.spades0001
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Hello Kinku the speakers i have had for about 13 years originally they speakers themselves area m were fitted with fostex 206e .These have been changed to lowther in the last two years the speakers required a few front plate for mounting the lowthers,as the depth of lowther pm6a was different as well as mounting holes.The speakers themselves are a redesign of original fostex cabinet by Tony Gee of the netherlands a designer of some repute whom i believe appears some times on the diyAudio forum the speaker is called the solo 206.You may find a lnk to him also via google or put in a search on the forum for plans etc .Hope this helps rgards spades (Alrick)
Thanks Spades. What type of resistors have you used for 3 W types?
Papa mentioned before some of them are wirewoud for a using the inductive component.
Papa mentioned before some of them are wirewoud for a using the inductive component.
I used panasonic metal oxide for all 3 watt except 0.33 ohm here i used mills 5 watt resistors hopes this helps.Regards spades .
Quality of source resistors is important.
Mills in psu that less critical is luxury 😀
I like MPC74 | 5 watts non inductive metal plate Futaba.
They cost is moderate. You get values from 0.1 to 1R.
Interesting stuff to try
MPC74 0R47 J | Fukushima Futaba MPC Series Solder Metal Plate Resistor 470m? ±5% 5W ±350ppm/°C | Fukishima Futaba
or substitute one value by only one piece high rate resistor
Mills in psu that less critical is luxury 😀
I like MPC74 | 5 watts non inductive metal plate Futaba.
They cost is moderate. You get values from 0.1 to 1R.
Interesting stuff to try
MPC74 0R47 J | Fukushima Futaba MPC Series Solder Metal Plate Resistor 470m? ±5% 5W ±350ppm/°C | Fukishima Futaba
or substitute one value by only one piece high rate resistor
Thanks guys. I think the .33 ohm need to be inductive as Papa described once for the inductive elements forming LC filtering but others probably Panasonic is in the original design .
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