June 20, 200917 yr Author Let's see.. 20K in the middle and 10K on the sides. I think that's right :/ I use two types of solder. Johnson IA-423 ternary eutectic (4.7% silver, 217C melting temperature) solder with various fluxes and WBT 8020 (4% silver, 180C melting point). The Johnson is much "slower" solder, making it ideal for certain types of uses, where the WBT is "faster".. I think you're probably seeing some of both on this board, heh. The Johnson is harder for me to get a hold of, but now it seems that PcX sells it with a different flux than I'm using now. You can buy direct from them in 1 lb spools and get just about any diameter / flux combination. I think it runs around $25 / lb from them direct, but I bought 3 lbs from them 2 years ago, so it might have gone up, who knows. Nice stuff. You can make it flow faster by adding extra flux, and I do this quite often, as you can see from the top of the boards there... I really want to look into getting a more aggressive flux cleaner, as on larger boards alcohol + air can doesn't work so well, but haven't gotten around to looking at the Johnson site to see what they recommend.
June 20, 200917 yr Yep, 20k in middle and 10k on sides. x10 on the flux cleaner solution, I'll have something different before I start building these and test it on some boards to see how it works. I would prefer something handy in an aerosol can, some other folks claim good results with products like this but comment that it can be a bit harsh on the capacitor labeling/wrapping sometimes.
June 20, 200917 yr From top to bottom, left to right I have: JJJJ KKKK (not populated yet) ACC CAC ACA AAC AC CC AA AC AA JJ KK CC That's what I get, and of the resistors I can see everything looks good. I'll assume the 4 resistors to the far right and left behind the buffers are the 5ohms. It looked like the fourth "A" emitter pin (first pin or left most pin) had a ball of solder on the leg. Your first rate pic and lettering scheme makes it easy to help out. I gotta figure out how to post pics like that sometime, with thumbs that pop up and are click resizable.
June 21, 200917 yr Author Heat sinks and brackets are ready after using 600 grit sand paper, if I apply a bit of oil and rub the surfaces I end up with a black rag (um... okay, anyways) I'm not sure why this is, or what would be black, besides perhaps the sandpaper? Who knows.... Then, I mated them together with oil and couldn't get them apart... wish I had a vise or something... I ended up putting a small gouge in the heat sink when I finally got them apart by putting a lot of force on the assembly by using the angle as a cantilever of sorts... Looked through all my power resistors can don't have anything low enough (HV junkie), without paralleling 50 or so resistors together... so I'll have to head up to Frys, as I sorta want to test the sigma22 at load before doing much else. Hopefully this number of holes to secure the bracket to the heat sink will put me as the secure leader in team overkill, with digger945 in second place with plans of a measly "2 maybe 3 #6 screws"
June 21, 200917 yr Heat sinks and brackets are ready after using 600 grit sand paper, if I apply a bit of oil and rub the surfaces I end up with a black rag (um... okay, anyways) I'm not sure why this is, or what would be black, besides perhaps the sandpaper? The black is probably aluminum rubbed off onto the cloth.
June 21, 200917 yr Author The black is probably aluminum rubbed off onto the cloth. oh ok. The cloth was clean as a whistle with water and a plain dry cloth. It wasn't until I added the oil that the black started come off.. and it was pitch black. Do you think there is a fixed amount of tiny particles on the heat sink, or it would keep rubbing off black as long as I tried to rub down the heat sink with oil?
June 21, 200917 yr Yea, I think you have safely secured number one spot in team "overly adequate clamping force between heatsink and bracket with uniformly smooth mating surfaces". Congrats. When I lapped my Conrads with a piece of glass it left the sandpaper black, I didn't use oil though, just did it dry. When I handle aluminum foil faced insulation at work it leaves my fingertips black too. That's just aluminium I guess. EDIT: Hey are those a pair of the Justin HS's with holes and bars?(I haven't even opened mine up yet)
June 21, 200917 yr I used a very, and I mean very thin layer of thermal goo on mine. They are all but impossible to seperate or move once in position.
June 21, 200917 yr Author I used a very, and I mean very thin layer of thermal goo on mine. They are all but impossible to seperate or move once in position. nope, a bit larger than Justin's and are custom milled so that rails won't be necessary, as they are integrated into the heat sinks themselves. They are the largest profile Conrad makes. yeah, I'm hoping the phase change compound will make them easier to separate, but more on that later, as I'm still playing with it
June 25, 200917 yr Author well, after tapping 8 holes at #6 instead of #4 , I had to order some parts from Mouser and they just arrived. Namely, the four #6 standoffs and the nylon clad steel screws. Since I cannot fit a shoulder washer anymore to isolate the MOSFETs, I decided to try some nylon. With these fancy screws I cannot get as much torque as using just plain nylon unfortunately, as the inside screw starts to spin a bit... So, I may go back to pure nylon... Anyways, sorta got lucky this worked out. Perhaps there are some other creative solutions, but I couldn't think of any that didn't require tapping and milling my heat sink and/or bracket. Meters show ~+-30V drawing 1.2A. Things get rather toasty Now to get the FETs mounted to the DynaFET boards and get this show on the road!
June 25, 200917 yr I like the display!! got all the parts from marc. Now i got no time... As i'm doing lots of Singlepower Midwest support
June 25, 200917 yr Author Jacob: One more thing. You can fit in a three pin Molex connector (similar to the one below C13A) right below C1B, oriented perpendicular to C1B. Connect one pin to ground, one pin to R55 and one pin to R56. Then it would be easy to adjust the gain remotely. Of course a DPDT (or 4PDT) relay or something to keep the signal short here in the feedback would be cooler and fantastic if integrated into the UberController project!
June 26, 200917 yr Author .....erm, more infos pls. still playing with it. Starts out with 0.1 offset gets down to less than 0.1mV (the resolution of my hand held DMM). This is the trimmers set at 500 and not touched at all. I'd say they are sorta not needed. Much better than my Dynahi version. I'd say these heat sinks are rather perfect, and the long hours of matching are rather worth it. The minimum bias with the 20K pot is 750mA. Lamers may need to up this value. Accidentally had the bias at 3A for a bit... oops. Running at 1A now. The transistors in the buffer are hot, I cannot touch them for more than a second. Edited June 26, 200917 yr by luvdunhill
June 26, 200917 yr I want moar bias as moar is always better. Have you plugged it into anything and made noise, that's what we really wanna know.
June 26, 200917 yr Author What's the output voltage of the servo sitting at? hm, pin 6 is 18.3V to ground .....
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