spritzer Posted August 16, 2010 Author Report Share Posted August 16, 2010 I do have access to some crazy expensive thermal camera if I ask nicely enough quite frankly I'm not too worried about the thermal properties of this thing. We'll see when I get the boards mounted though. As you might have spotted already, that riser in the side of the chassis doesn't work to fix the transistors in place. I'll have to a spreader and then mount that to the chassis. Quote Link to comment Share on other sites More sharing options...
luvdunhill Posted August 16, 2010 Report Share Posted August 16, 2010 As you might have spotted already, that riser in the side of the chassis doesn't work to fix the transistors in place. I'll have to a spreader and then mount that to the chassis. yeah, that's partly what I'm referring to. I'm wondering if the thermal junctions present in a normal case don't actually help lower junction temperature though. For example, in this design, the air around the fins provides a much higher thermal impedance than say the bottom of the case. But since it's all one large block of aluminum, it seems that natural convection to air would be sort of a "last resort". Also, if you've ever heated up a block of aluminum, you know it takes forever to cool down via natural convection. I'm wondering if the internal temperature will rise dramatically as well, despite any attempts to add holes for natural heat convection. Quote Link to comment Share on other sites More sharing options...
spritzer Posted August 16, 2010 Author Report Share Posted August 16, 2010 That's one of the reasons why this is a prototype. The heat has an easy route up and away from the boards but the main heatsinks might be a different matter. There is also the issue of warmup as this massive billet might take a while to heat up... Quote Link to comment Share on other sites More sharing options...
mrarroyo Posted August 16, 2010 Report Share Posted August 16, 2010 Maybe a pre-heater is needed! Quote Link to comment Share on other sites More sharing options...
spritzer Posted August 17, 2010 Author Report Share Posted August 17, 2010 Hmmm I could go all Rudistor and attach power resistors to the chassis fed off a spare filament transformer controlled by a thermostat... "Forget preheating the valves, I preheat the chassis!!!" Quote Link to comment Share on other sites More sharing options...
kevin gilmore Posted August 17, 2010 Report Share Posted August 17, 2010 You mean like this... http://gilmore.chem.northwestern.edu/heatsinkload.jpg Quote Link to comment Share on other sites More sharing options...
MASantos Posted August 17, 2010 Report Share Posted August 17, 2010 You mean like this... http://gilmore.chem.northwestern.edu/heatsinkload.jpg That's a nice winter bedtime heater! Birgir, really awesome chassis! Quote Link to comment Share on other sites More sharing options...
luvdunhill Posted August 17, 2010 Report Share Posted August 17, 2010 thinking out loud... the thermal resistance goes down of the heat sink itself as it heats up, but as that happens the junction temperature of the devices rise, which in this case are positive temperature coefficient devices (BJTs). The issue is that since the devices are paralleled, one device will hog the current as this happens. I wonder if you could add some sort of thermal feedback resistor/transistor/thermistor to the heat sink to help mitigate this effect to some extent. This feedback device would turn on at a low voltage and effectively regulate the bias voltage (i.e. in this case the CCS current) allowing it to slowly come up to spec. Quote Link to comment Share on other sites More sharing options...
spritzer Posted August 17, 2010 Author Report Share Posted August 17, 2010 I'm sure it can be done and has been done with the large SS power amps. You mean like this... http://gilmore.chem.northwestern.edu/heatsinkload.jpg Is this part of some new collaboration with Rudi? Quote Link to comment Share on other sites More sharing options...
kevin gilmore Posted August 17, 2010 Report Share Posted August 17, 2010 well nikongod wanted a rudistor like amplifier with a lower output impedance... The center 6 resistors in the center are .1 ohms each, and in parallel. I'll show you the output section tomorrow Quote Link to comment Share on other sites More sharing options...
nikongod Posted August 17, 2010 Report Share Posted August 17, 2010 I thought that was a dummy resistor for testing high power amps under load What are the resistors in series around the outer edge for? Quote Link to comment Share on other sites More sharing options...
kevin gilmore Posted August 17, 2010 Report Share Posted August 17, 2010 Why those are the resistors to warm up the other resistors of course... Wait till you see the picture tomorrow... Quote Link to comment Share on other sites More sharing options...
johnwmclean Posted August 18, 2010 Report Share Posted August 18, 2010 Oh my Jesus, spritzer your bins full. Quote Link to comment Share on other sites More sharing options...
Bidoux Posted August 18, 2010 Report Share Posted August 18, 2010 I don't know if it is a hot-water bottleas MASantos suggested, but otherwise, is it going to draw those 60A ? Quote Link to comment Share on other sites More sharing options...
kevin gilmore Posted August 18, 2010 Report Share Posted August 18, 2010 As a matter of fact it IS 60 amps... pictures in a few hours. Busy day today. Quote Link to comment Share on other sites More sharing options...
kevin gilmore Posted August 18, 2010 Report Share Posted August 18, 2010 here is the new rudistor power supply (+/-30 volts at 60 amps) http://gilmore.chem.northwestern.edu/heatsinkpower.jpg and the quad mono output stage, 12 x 10 amp transistors per output in parallel. http://gilmore.chem.northwestern.edu/heatsinkquad.jpg the difference between the men and the boys is clearly the size of their power supply Quote Link to comment Share on other sites More sharing options...
aardvark baguette Posted August 18, 2010 Report Share Posted August 18, 2010 What will that ultimately be powering? Headphones? Quote Link to comment Share on other sites More sharing options...
spritzer Posted August 18, 2010 Author Report Share Posted August 18, 2010 A better question would be, what the hell did KG pull that thing out off? Now where is the pic of that insane multi kV supply you sent me Kevin? Quote Link to comment Share on other sites More sharing options...
kevin gilmore Posted August 18, 2010 Report Share Posted August 18, 2010 All of that stuff came off the sector mass spec.. A Finnigan Mat 900. well over 1M$ 8 years ago. worth nothing today. The 3 pieces together drove the 4000 lb, 9 tesla water cooled electromagnet. This really would make a kickass quad mono, no feedback, ultra low output impedance single ended amplifier. The high voltage supply is from the FAB source on the same instrument. Makes a T2 look tiny. Quote Link to comment Share on other sites More sharing options...
spritzer Posted August 18, 2010 Author Report Share Posted August 18, 2010 There is onething we could build that would make the T2 look very small, a liquid cooled Class A speaker amp... Quote Link to comment Share on other sites More sharing options...
MASantos Posted August 18, 2010 Report Share Posted August 18, 2010 As a matter of fact it IS 60 amps... pictures in a few hours. Busy day today. Let's just hope it's not audio related then, or at least headphone audio related| Quote Link to comment Share on other sites More sharing options...
Nebby Posted August 18, 2010 Report Share Posted August 18, 2010 Let's just hope it's not audio related then, or at least headphone audio related| A little bird told me that you need 60 amps to properly drive the K701's. Quote Link to comment Share on other sites More sharing options...
MASantos Posted August 18, 2010 Report Share Posted August 18, 2010 That's a crazy little bird, everyone knows you need a 400bhp V8 for the 701! either that or a cmoy! Quote Link to comment Share on other sites More sharing options...
Nebby Posted August 18, 2010 Report Share Posted August 18, 2010 That's a crazy little bird, everyone knows you need a 400bhp V8 for the 701! either that or a cmoy! Wait, would this cmoy you speak of be encased in a wood enclosure? lol @ 400bhp V8 Quote Link to comment Share on other sites More sharing options...
MASantos Posted August 18, 2010 Report Share Posted August 18, 2010 It could be!! But only if the wood has been cryo treated and internal wiring is 12AWG BBBS wire!! Wait, would this cmoy you speak of be encased in a wood enclosure? lol @ 400bhp V8 Quote Link to comment Share on other sites More sharing options...
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