kevin gilmore Posted April 25, 2015 Author Report Share Posted April 25, 2015 I think if I design it carefully enough you can put 2 boards together, one is double layer, the other a single layer. Quote Link to comment Share on other sites More sharing options...
insanity Posted April 25, 2015 Report Share Posted April 25, 2015 http://www.mouser.com/ds/2/405/snos633h-261427.pdf in this datasheet of the lm4040 to92 on page two the pinout is visible. I have another remark. Shouldn't there be a way to disable the servo for initial adjustment of the trimpots? Quote Link to comment Share on other sites More sharing options...
kevin gilmore Posted April 25, 2015 Author Report Share Posted April 25, 2015 this one, the servo is integral and required. Same as the T2 Quote Link to comment Share on other sites More sharing options...
spritzer Posted April 25, 2015 Report Share Posted April 25, 2015 Yeah, no way to shut this one off. Quote Link to comment Share on other sites More sharing options...
kevin gilmore Posted April 25, 2015 Author Report Share Posted April 25, 2015 someone please check these http://gilmore.chem.northwestern.edu/kgsshvcarbonv2.pdf http://gilmore.chem.northwestern.edu/kgsshvcarbon.jpg 1 Quote Link to comment Share on other sites More sharing options...
wokstarr26 Posted April 26, 2015 Report Share Posted April 26, 2015 Q19 should be 2x 2SK170 or LSK389 R48 and R49 should be 500K in pdf cct diagram Quote Link to comment Share on other sites More sharing options...
mwl168 Posted April 26, 2015 Report Share Posted April 26, 2015 (edited) Congratulations on the build mwl168 and happy to hear it's making sweet music. May i ask what temperature your reading on the heatsinks as they look pretty small.An update on the heatsinks temperature. I put the cover on my temporary chassis today and after two hours the heatsinks went from slightly warm to the touch to hot to the touch. I can rest my hands on the heatsinks without getting burned but they definitely feel uncomfortably hot after a few seconds. Also, the offset shot up to about 30V. The room temperature was about 65F. Both the 2SC4686a and 10m90s are rated to 150F and I've read comments that if you can put your hand on the heatsinks for more than 5 seconds then it's probably fine. So I am a bit concerned but not worried ) My thought is that the heatsinks I use are fine if they will be exposed to open air. I would probably use bigger ones if just for the peace of mind if they will be enclosed inside the case. I would love to hear the thoughts and advice of those that are more knowledgeable. Edited April 26, 2015 by mwl168 Quote Link to comment Share on other sites More sharing options...
wokstarr26 Posted April 26, 2015 Report Share Posted April 26, 2015 Regarding Kgsshvcarbon. Also found R25 and R56 in circuit diagram as 82R but in pcb layout as 50R in series with 50R trimpot Quote Link to comment Share on other sites More sharing options...
nopants Posted April 26, 2015 Report Share Posted April 26, 2015 is it a perforated cover? Quote Link to comment Share on other sites More sharing options...
insanity Posted April 26, 2015 Report Share Posted April 26, 2015 In the schematic the input resistors are 1k instead of 100ohms. Furthermore the 500k tying the inputs to gnd are missing. Quote Link to comment Share on other sites More sharing options...
mwl168 Posted April 26, 2015 Report Share Posted April 26, 2015 is it a perforated cover? Yes, the cover has cutouts for air circulation on both the top and the sides. I am surprised at how much the heatsinks temperature rises with the cover on. Quote Link to comment Share on other sites More sharing options...
nopants Posted April 26, 2015 Report Share Posted April 26, 2015 maybe apply some pressure on the heatsinks with the cover by raising them with standoffs, that's what I do for the Megatron power supply, can interface them too. I don't know if your heat dissipation is actually a problem or not Quote Link to comment Share on other sites More sharing options...
llamallama Posted April 27, 2015 Report Share Posted April 27, 2015 I'm finishing up a build but I can't seem to get the offset to zero. I understand to adjust the offset involves getting the Stax jack L+/L- and R+/R- close to zero, turning the trimpot. Currently I'm getting -90V on the Left channel and can't get it closer to 0. The Right channel is worse, something like 120V out. The board LEDs all light up, and everything is running cool/warm. I am using the rev0.2 amp and rev0.6 PSU boards. The multimeter is showing PSU: Probe on +450 and -450 reads 880V Probe on +450 and GND reads 440V Probe on -450 and GND reads 440V Probe on +15 and -15 reads 30V Amp: Probe on +VCC and -VCC reads 880V Probe on +VCC and GND reads 440V Probe on -VCC and GND reads 440V Probe on 15+ and 15- reads 30V Quote Link to comment Share on other sites More sharing options...
llamallama Posted April 27, 2015 Report Share Posted April 27, 2015 The rev0.2 amp has a set of connectors marked I+ I- GND -15 +15. I+/I+ connects to XLR pins 2 and 3, and -15/15+ connects to the PSU. Does the GND go to the star ground? This GND doesn't appear in johnwmclean's wiring diagram. I'm following this diagram and connecting XLR pin 1 (ground) to the raw chassis metal via a short wire. Quote Link to comment Share on other sites More sharing options...
mwl168 Posted April 27, 2015 Report Share Posted April 27, 2015 (edited) This may be stating something obvious. The readings between L+/L- and R+/R- are balance. The offset is between either of the output phases to ground. Adjust the balance and get it close to 0 first then adjust the offset. The two adjustments are controlled by two separate trim pots on each channel. You will likely need to go back and forth between the two adjustments to get both to 0. Also these adjustments need to be done without the servo activated. Edited April 27, 2015 by mwl168 Quote Link to comment Share on other sites More sharing options...
mwl168 Posted April 27, 2015 Report Share Posted April 27, 2015 (edited) I followed John's wiring diagram and read the excellent Rane papers as well ( Thanks John!). I connected the PSU ground (I use the one from the +/- 15V) to the star ground. No connection to the star ground from the amp boards. My amp is silent without any hum or buzz when no input signal is present. When I first wired my amp into the chassis I forgot to make the ground connection and I had problem with high offset voltage. Once I connected the PSU GND to the star ground I was able to adjust the offset to 0V. Edited April 27, 2015 by mwl168 Quote Link to comment Share on other sites More sharing options...
llamallama Posted April 27, 2015 Report Share Posted April 27, 2015 mwl168, thanks for the explanation! It's probably obvious, but just wasn't to me and I must have been adjusting the wrong trimpot. I followed this video: https://www.youtube.com/watch?v=TdMR9pZ3IcQ of adjusting the Headamp BHSE. The video didn't say what was being adjusted first, I just assumed he was adjusting offset first (L+/L-, R+/R-) when it's balance he's adjusting first! Quote Link to comment Share on other sites More sharing options...
mwl168 Posted April 27, 2015 Report Share Posted April 27, 2015 mwl168, thanks for the explanation! It's probably obvious, but just wasn't to me and I must have been adjusting the wrong trimpot. I followed this video: of adjusting the Headamp BHSE. The video didn't say what was being adjusted first, I just assumed he was adjusting offset first (L+/L-, R+/R-) when it's balance he's adjusting first! The video is for KGBH which I have no knowledge of. There are two trim pots on each channel of the kgsshv; the 2K one is for balance and the 1k for offset. I am assuming this is the same with the version you have (I have the V0.91 off board heat sink version). Hope this helps! Quote Link to comment Share on other sites More sharing options...
mwl168 Posted April 27, 2015 Report Share Posted April 27, 2015 maybe apply some pressure on the heatsinks with the cover by raising them with standoffs, that's what I do for the Megatron power supply, can interface them too. I don't know if your heat dissipation is actually a problem or not Thanks nopants. I had the amp running for more than 4 hours with the cover on. The heatsinks don't seem to get hotter after the first hour. The problem I have is, at the higher operating temperature, I run out of range on the offset adjustment. Activating the servo may get the offset close to 0 but I have not tried that yet. I am also not excited about the option of taking apart the amp board and heatsink assembly to replace the resistor in series with the offset trim pot to get wider adjustment range. Of course I may not have much choice come summer time with higher ambient temperature. My plan is still to re-case the amp in the coming winter. Quote Link to comment Share on other sites More sharing options...
johnwmclean Posted April 27, 2015 Report Share Posted April 27, 2015 I am also not excited about the option of taking apart the amp board and heatsink assembly to replace the resistor in series with the offset trim pot to get wider adjustment range. I think you have 2K installed at the moment? You probably need 1.5K. Here’s a solution, parallel a ~6K resistor with already installed 2K resistor i.e. 1.5 = 2 X 6 / (6+2). You won’t have to take the amp and heatsink assembly apart to do this. Just ensure your soldering is nice and clean. Quote Link to comment Share on other sites More sharing options...
mwl168 Posted April 27, 2015 Report Share Posted April 27, 2015 (edited) Thanks John. I do have the 2K resistor (R26) in series with the offset trim pot. I have considered using your trick (read your earlier post) and parallel another resistor on top but the space is rather tight where the 2K resistor is on this board. I may still do it since I was also thinking about using the same trick on R5/R6 to bring them down to around 100R. The good news is that there is plenty of space around R5 and R6. If I do so, I'll for sure need to lower R26 one way or another since I expect increasing the output current will raise the DC offset. Edited April 27, 2015 by mwl168 Quote Link to comment Share on other sites More sharing options...
johnwmclean Posted April 28, 2015 Report Share Posted April 28, 2015 (edited) $2.00 a pc from China. They look the real deal to me, at least very similar to the bdent parts. I anticipated obvious fakes... What do you think? Edited April 28, 2015 by johnwmclean Quote Link to comment Share on other sites More sharing options...
spritzer Posted April 28, 2015 Report Share Posted April 28, 2015 Well the fakes may become better but throw it on a tester to be sure. If it is a 900V+ PNP then it has to be real. Not many other options ever made. Quote Link to comment Share on other sites More sharing options...
insanity Posted April 28, 2015 Report Share Posted April 28, 2015 Yeah let us know if they are real. Quote Link to comment Share on other sites More sharing options...
JoaMat Posted April 29, 2015 Report Share Posted April 29, 2015 (edited) / Edited November 12, 2015 by JoaMat 2 Quote Link to comment Share on other sites More sharing options...
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