sorenb Posted October 28, 2015 Report Posted October 28, 2015 Mouser order came in today. Just tested the power supply after installing the new parts and jumper, and double checking everything. Nothing exploded. +/- 494 on the 500V rails and +/- 14V on the 15V. Feels good, and wouldn't be possible without all the help I've gotten here. Bias at the test point only reads about 520V though.4x 130V = 520V ? ....should be 3x 150V + 130V = 580V
mwl168 Posted October 28, 2015 Report Posted October 28, 2015 Also consider the fact that the zeners voltage will rise as they get warm.
spritzer Posted October 28, 2015 Report Posted October 28, 2015 They will but not by that much. Has to be the wrong zeners in there.
Tinkerer Posted October 28, 2015 Report Posted October 28, 2015 The values of the parts are correct, 3 150V's and a 130V. I guess one or more of them is damaged. I'll pull them and get them measured, see what else I need to buy.
Pars Posted October 28, 2015 Report Posted October 28, 2015 Could you measure across each one of them to see what they are actually dropping? Might only have one bad one. Also, what are typical zener tolerances? 5%? I guess that would result in around 551V if all were 5% low.
Tinkerer Posted October 28, 2015 Report Posted October 28, 2015 I just checked and they actually all measure within tolerance.130, 144, 148, 146Should be 568V total before warm up. But reading from the test point I'm getting 527V. I'm probably doing something stupid with the measurement, but I'm getting the same reading in front of the ballast resistor as the test point. I'll look at the schematic closer tomorrow with a fresh pair of eyes and see if I can't figure out where my screwup is.
spritzer Posted October 28, 2015 Report Posted October 28, 2015 I would just swap them out as the meter presents a load and then the zeners could be acting up.
Tinkerer Posted October 29, 2015 Report Posted October 29, 2015 Yeah. I put in an order for enough to redo it twice if I need to. They should be here in a couple of days. On the good news end though, since the amp driving parts are fine, I hooked up each amp board individually to test them after installing all the new parts. Everything fired up. Got the balance and offset set on the first one then let it warm up before I tweaked it again. Then I disconnected that one to test the second one and so I could install the servo jumper on the first board. Second one is still warming up but it's doing fine.
Tinkerer Posted October 31, 2015 Report Posted October 31, 2015 (edited) Got the new zeners in, and installed them. Still only getting 536V now at the bias test point, and that's basically tolerance difference. I'm guessing that means I need to replace either the IXYS 10m90s or the 3k resistor in front of the zener string. I don't really see what else it could be. Edited October 31, 2015 by Tinkerer
wink Posted October 31, 2015 Report Posted October 31, 2015 Get a zener with a higher voltage like 180v, and see how it goes. Or get a multimeter with a 10 megohm input impedance on the voltage scales.
Tinkerer Posted October 31, 2015 Report Posted October 31, 2015 Yeah, I was about to edit my post. I had a 50V laying around that I temporarily added in series. That jumped it up to 635. So I figured it just needed a little less. I tried swapping in a 150V in the 130 slot and it jumped up to about 610. So I just put it back to stock and it went back to 530. But I noticed the very last time I measured it, that it would start around 570 and then drop down to 530. It might be fine. All the changes add up about right. It's just the particular combination I need that's giving me funny numbers.
spritzer Posted October 31, 2015 Report Posted October 31, 2015 The input voltage could also be too low for the regulator.
sorenb Posted October 31, 2015 Report Posted October 31, 2015 (edited) Yeah, I was about to edit my post. I had a 50V laying around that I temporarily added in series. That jumped it up to 635. So I figured it just needed a little less. I tried swapping in a 150V in the 130 slot and it jumped up to about 610. So I just put it back to stock and it went back to 530. But I noticed the very last time I measured it, that it would start around 570 and then drop down to 530. It might be fine. All the changes add up about right. It's just the particular combination I need that's giving me funny numbers.adding 50V to the zener string made the voltage jump 100V?Swapping 130V with 150V make it jump 50V?Don't know how you've added the 50V zener or swapped the 130V/150V ...but it seems like you get the right voltage when tampering with the 130V zener ... might it be a bad connection on the board itself? Edited October 31, 2015 by sorenb
Tinkerer Posted October 31, 2015 Report Posted October 31, 2015 Yeah, it was really strange. But I was poking around the board and noticed something. I get 584V correctly where R39 connects to the string. It's just the test point and on the front connection of R40 where I'm getting 530V.
sorenb Posted October 31, 2015 Report Posted October 31, 2015 Yeah, it was really strange. But I was poking around the board and noticed something. I get 584V correctly where R39 connects to the string. It's just the test point and on the front connection of R40 where I'm getting 530V.so basically you get a drop on a piece of cobber trace? (by stating "front of R40" assuming you mean the end that connects directly to the r39+zenerstring ?)
sorenb Posted October 31, 2015 Report Posted October 31, 2015 Doh, meant R42.so the measurments refered to in the first two posts in this rgrd has been taken at various places? the first (3x150+130) made at R42, the (3x150+130+50) and (4x150) made at r39/zener connection?
Tinkerer Posted October 31, 2015 Report Posted October 31, 2015 (edited) so the measurments refered to in the first two posts in this rgrd has been taken at various places? the first (3x150+130) made at R42, the (3x150+130+50) and (4x150) made at r39/zener connection?The measurements referred to in the first two posts were taken at both the board's bias test point on the other side of C21 and at R42 each time where they were concurrent with each other. I just went and measured where R39 connected directly to the zeners later after all that because it was the most direct. It did make me realize something. If I measure on either side of R42, I get about a 50V drop on my multimeter. R40 is also a 100k resistor. So 580 -50 from the R40 is why I was getting 530V and why it measures fine at R39. It turns out I was just being stupid this whole time. So it seems everything is well and my issues with the bias were just cheap multimeter problems. Sorry to bother you guys about all that. EDIT: And wink called it Edited October 31, 2015 by Tinkerer
sorenb Posted October 31, 2015 Report Posted October 31, 2015 The measurements referred to in the first two posts were taken at both the board's bias test point on the other side of C21 and at R42 each time where they were concurrent with each other. I just went and measured where R39 connected directly to the zeners later after all that because it was the most direct. It did make me realize something. If I measure on either side of R42, I get about a 50V drop on my multimeter. R40 is also a 100k resistor. So 580 -50 from the R40 is why I was getting 530V and why it measures fine at R39. It turns out I was just being stupid this whole time. So it seems everything is well and my issues with the bias were just cheap multimeter problems. Sorry to bother you guys about all that.Thanks a bunch for sharing anyways ... you are not the only one who have been chasing a red herring from time to time
Tinkerer Posted October 31, 2015 Report Posted October 31, 2015 (edited) Well, at least it's all worth it in the end. After all the questions and parts and time, she lives! And sounds great. The servos keep the IXYS parts within one volt balance and offset even at cold start. Only thing that didn't turn out so good is the attenuator I used that came with it. Unbalanced as hell and even has one volume click where one channel cuts out completely. Gotta get something better. At least max volume is just a jumpered connection so I can just use my preamp to control volume until then. The pictures aren't so great since it's storming like hell outside so natural lighting is pretty bad, but she turned out swell Edited November 1, 2015 by Tinkerer
sorenb Posted October 31, 2015 Report Posted October 31, 2015 Well, at least it's all worth it in the end. After all the questions and parts and time, she lives! And sounds great. The servos keep the IXYS parts within one volt balance and offset even at cold start. Only thing that didn't turn out so good is the attenuator I used that came with it. Unbalanced as hell and even has one volume click where one channel cuts out completely. Gotta get something better. At least max volume is just a jumpered connection so I can just use my preamp to control volume until then. The pictures aren't so great since it's storming like hell outside so natural lighting is pretty bad, but she turned out swellso bottom line .... having bought someones unfinished project, was it worth it?
Tinkerer Posted October 31, 2015 Report Posted October 31, 2015 so bottom line .... having bought someones unfinished project, was it worth it?Yeah, if only for the overall cost and most of the casework, though I still had to drill a number of things like the feet, RCA plugs, switches, half the case screws were missing, that sort of thing. Board-wise, I'd prefer doing that from scratch. A lot less headaches. But there's a certain satisfaction in saving something from unfinished purgatory too.
sorenb Posted October 31, 2015 Report Posted October 31, 2015 unfinished purgatoryok, might be pushing it a bit too far I guess
Tinkerer Posted October 31, 2015 Report Posted October 31, 2015 (edited) Just taking a crack at how many "get around to it" projects tend to sit in a box for years. Limbo probably would have been a better word choice. Congrats, well done. Enjoy.Thanks. I'm looking forward to just kicking back and listening to it for awhile. It certainly sounds great. Edited October 31, 2015 by Tinkerer
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