luvdunhill

Final prototyping BOM: https://www.mouser.com/ProjectManager/ProjectDetail.aspx?AccessID=69a573ab56

don't Google around for DIY options then A Microprocessor Controlled Here's a different approach though: Tube Tester analyzes tubes by Transcendent Sound

couldn't be any more expensive and not use a wall-wart. Duh.

you mean the non-cancer causing ones? Quite a few actually. You have to be very careful using Kapton film. How thin are you considering going? Remember, now you have three thermal junctions as you need interface material on both sides of the Kapton (edit: depends if you consider Kapton rigid, like mica. I do.). Also, look at the thermal conductivity of Kapton, not just its thermal resistance. In this comparison, Kapton performs pretty marginally. You can help things out by going thinner, but once you look at how thin you must go, it begins to be a non-option. Just as an example, compare AL2O3 pads to Kapton and you'll see what I mean. Just drill a hole at an angle under the device and use a thermocouple. That's the most accurate I've found.

you mean the non-cancer causing ones? Quite a few actually. You have to be very careful using Kapton film. How thin are you considering going? Remember, now you have three thermal junctions as you need interface material on both sides of the Kapton. Also, look at the thermal conductivity of Kapton, not just its thermal resistance. In this comparison, Kapton performs pretty marginally. You can help things out by going thinner, but once you look at how thin you must go, it begins to be a non-option. Just as an example, compare AL2O3 pads to Kapton and you'll see what I mean. Just drill a hole at an angle under the device and use a thermocouple. That's the most accurate I've found.

My datasheet (RCA Receiving Tube Manual 1966) says 250V max plate voltage in a class A1 amplifier. So, I say .... pony up and do the video!

yeah, the datasheet says up to 11.5mm max tab diameter, see how they jut out a bit further in? The pad widths are available in 1mm increments, so 12mm, 13mm, or 14mm would be the reasonable choices. Better than hand trimming the pads, right?! I'm betting they are simply non-RoHS devices. The ones I have were dropped shipped from Renesas and have different case markings. I'll post a pic sometime soon.

what about a 12mm wide pad? datasheet for MOSFETs with case dimensions: http://documentation.renesas.com/eng/products/transistor/rej03g0122_2sj76ds.pdf

Those have the older package markings, they're probably Hitachis (or an eariler non-RoHS version I suppose). Anyways, so, does that mean there is 0.02" between the two devices? wowza, I would have guessed more. Thanks again!

shit, I didn't even think about pics... definitely, dew eet!

Here's the really counter intuitive thing I've found. Two 6" x 6" heat sinks perform better than one 6" x 12" heat sink (assuming same type, and for argument's sake there is a single output device in the center of each 6"x6" and spaced out similarly for the 6"x12" heat sinks), even when strapped together like proposed in that GB.

I was wondering if Pars or Jacob or perhaps someone else with Dynahi boards could answer something for me. What is the maximum width of a thermal pad that could be used and there not be any overlap between the pads? Not that this is bad, but looks kinda funny and is wasteful. I'm talking with a company that makes isolation pads that perform orders of magnitude better than the products available at Mouser / Digikey. To give you an idea, thermal conductivity of 8.0 W/mK and thermal resistance of 0.07 K/W. This is around 8 times better than for example Thermalsil III... and so far I'm seeing around a 8 degree temperature drop which is consistent with this. This is rather amazing result, IMHO (think about how much larger heat sink you would have to use to get this sort of drop!)... Since we're going to have to order pads anyways for the part kits, I was considering using these ... I'd have to get them custom cut, and there is a lead time, but I think it would be worth it for those interested.

please repeat for the 6S4A

it may take a while to get through to the seller. I think you could use the F5 boards I sold you, but try and get the devices as far as possible apart, or look into using heat spreaders to make sure you are using the depth of the heat sink to its maximal potential. Also, consider looking at the more exotic isolator materials, as I'm finding these to be an excellent performance increase. As long as you're not absolutely set on hitting the bias used in the First Watt, I think you'll be okay. If you actually going to do the math instead of a simple "hand test" after the fact, remember you have to derate the Conrad heat sinks as the C/W is quoted at a much higher ambient temperature than you want to run your devices at (80 C). One you start to really look at the numbers, (and appropriate implications due to the fact that powder coating doesn't perform as well as anodizing) these IMHO are not optimal for use in a power amplifier. But given the caveats above, you should be okay. edit: The R-Theta GB (which is ending soon, as is under the title Aavid Thermalloy), IMHO would be a better choice for a F5.

Input transformers have arrived. If you would like yours *before* the semiconductor kit, please let me know. You'll have to pay shipping and packaging twice, but it won't be more than a few dollars more probably. Just let me know.

dude, there is a board game version of that now, check Target, etc.

If anyone is still interested in these, Chris is doing another GB IIRC.

uh huh. nods. yes. right-o.

can you get some?

obviously

interesting idea. Seems that you'd be running the opamp very close to its limit. Here's another interesting one: http://www.mskennedy.com/client_images/catalog19680/pages/files/131r-.pdf Even lists electrostatic transducers as a typical application. Datasheet is prelim though, but at least it's a new production device. Wonder if I can get "samples". Looks to be a pretty impressive little device.

hm, I always assumed they were of Russian design, as I see a lot of people there working them on the metro and what not.

sounds like a feature to me!

thanks guys, I'm talking to a US distributor and trying to pretend to be a company Also, looks like PcX sale that includes 20% off resistors is coming at a perfect time for us!