PICaudio Posted June 18, 2013 Report Posted June 18, 2013 Could change MJF15031 for MJE15031? I bought more transistors and I have four MJF15030 (lot: SPB16 - HFE=175,178,182,184) and 4 MJE15031 (I'm not sure of the manufacturer, lot: MA0 5K - HFE=180,185,190,190). Can I combine these MJF and MJE in this amp? -- o -- Rodrigo
kevin gilmore Posted June 18, 2013 Author Report Posted June 18, 2013 sure as long as you use thermal isolation washers and in the one place isolate the two of them on the one bolt.
PICaudio Posted June 18, 2013 Report Posted June 18, 2013 (edited) Ok, many thanks Kevin. Edited June 18, 2013 by PICaudio
kevin gilmore Posted June 21, 2013 Author Report Posted June 21, 2013 (edited) this is the original krell heatsink mouser 532-513102B25 Edited June 21, 2013 by kevin gilmore
spritzer Posted June 21, 2013 Report Posted June 21, 2013 So I'm the only one using the 2.5" sinks? They fit the chassis so why not... I got my panels back from the laser but the guy destroyed the front panel (don't ask). So I'll either have to use the back which is the suck in terms of finish or steal a fresh one from my stock and get a replacement sent with the next order.
kevin gilmore Posted June 21, 2013 Author Report Posted June 21, 2013 (edited) I have the bigger heatsinks but one of the holes seems to limit The thermal efficiency. Will test... Would be nice if there was a taller heatsink with only one hole Edited June 21, 2013 by kevin gilmore
spritzer Posted June 21, 2013 Report Posted June 21, 2013 The mounting is not as nice, that for sure. One odd thing, I've ordered a lot of the larger 2.5" sinks and some have shown up with the cutouts while others have just had one mounting hole. Same Mouser number... Would be nice if there was a taller heatsink with only one hole *Calling Steve to the local Krell thread.... Steve to the Krell thread....*
kevin gilmore Posted June 22, 2013 Author Report Posted June 22, 2013 (edited) so what we really want is avid part number 513202b02500g which is 2.0 inches high or 513302b02500g which is 2.5 inches high which is the to220 only version neither of which are stocked by digikey or mouser instock at Newark Edited June 22, 2013 by kevin gilmore 1
fordgtlover Posted June 22, 2013 Report Posted June 22, 2013 Would these suit? 532-529902B25G - 2 inch 532-530002B02500G - 2.5 inch
Lil Knight Posted June 22, 2013 Report Posted June 22, 2013 Those are larger. The needed ones are thinner.
Inu Posted June 26, 2013 Report Posted June 26, 2013 What is the current draw in each output transistor on the original unit? When I set it for 100mA, 1.5inch heatsink gets really hot.
luvdunhill Posted June 26, 2013 Report Posted June 26, 2013 I was wondering this as well. Seems like too much heat to get rid of.
swt61 Posted June 26, 2013 Report Posted June 26, 2013 The mounting is not as nice, that for sure. One odd thing, I've ordered a lot of the larger 2.5" sinks and some have shown up with the cutouts while others have just had one mounting hole. Same Mouser number... *Calling Steve to the local Krell thread.... Steve to the Krell thread....* Damn! Another missed opportunity.
kevin gilmore Posted June 26, 2013 Author Report Posted June 26, 2013 What is the current draw in each output transistor on the original unit? When I set it for 100mA, 1.5inch heatsink gets really hot. its less than that, but I have that info at home. will look later. specific voltage across the emitter resistors.
spritzer Posted June 26, 2013 Report Posted June 26, 2013 It should be between 180-200mV if I remember correctly.
kevin gilmore Posted June 26, 2013 Author Report Posted June 26, 2013 That would work out to 2 watts per transistor, 8 watts, per channel. A bit too much, should be about 5 watts, about 1.25 watts per transistor. so about 125 mv.
kevin gilmore Posted June 26, 2013 Author Report Posted June 26, 2013 ok, so the krell documentation is a little questionable, but when they measure the bias they do it from emitter to emitter. so the number is twice as big as the two test points I put on the board. specifically its 250 millivolts emitter to emitter cold, and 180 to 200mv hot. so at the two test points provided its 125 millivolts emitter to output no load cold a,d 90 to 100 millivolts hot. which sounds about right.
Inu Posted June 26, 2013 Report Posted June 26, 2013 Thank you. When set Ic to 62.5mA@22V, surface temperature is down to 122F (50℃) Total current = +22V 400mA (with current to the Relays) / -22V 380mA
trident900fi Posted June 27, 2013 Report Posted June 27, 2013 Mine is finish since a week, and when I start it, he smoke After some reseach, I found that the 500R ajustable was 500K !! Mouser make a little mistake ! I hope that with the good value, everything will be fine...
trident900fi Posted June 27, 2013 Report Posted June 27, 2013 Thank you. When set Ic to 62.5mA@22V, surface temperature is down to 122F (50℃) Total current = +22V 400mA (with current to the Relays) / -22V 380mA How does it sound ? As good as expected from a Krell device !
kevin gilmore Posted June 27, 2013 Author Report Posted June 27, 2013 Mine is finish since a week, and when I start it, he smoke After some reseach, I found that the 500R ajustable was 500K !! Mouser make a little mistake ! I hope that with the good value, everything will be fine... yep that is going to cause smoke.
trident900fi Posted June 27, 2013 Report Posted June 27, 2013 yep that is going to cause smoke. I just hope that nothing else is broken... My PSU can give 300VA per side and there were in short cut !!
kevin gilmore Posted June 27, 2013 Author Report Posted June 27, 2013 my guess is that the output transistors and the 2 ohm resistors are toast.
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