spritzer Posted March 14, 2011 Report Share Posted March 14, 2011 Ehhh what is up with the 7815 regulator? Can you take a close up picture of the 4 small caps on the PSU board as that doesn't look right... To measure the amp connect the black probe to the GND connection on the PSU board and then measure all the PSU outputs on the PSU board except the bias. You can just touch the top of the screw with the probe and the correct values are printed on the board. Everything is DC so set it to the highest DC scale. As for the mica caps on the amp board, yeah the KGSS has compensation caps. For some people this is supposed to be a bad thing but they have clearly never opened up a Stax amp... Quote Link to comment Share on other sites More sharing options...
Craig Sawyers Posted March 14, 2011 Report Share Posted March 14, 2011 Thank you Justin and n3rdling. To verify before I get started, I set up the voltmeter with the black prong plugged into the COMM and the red next to it. I believe the picture I posted had this setting in reverse. Should I power on the amp first and get started or position the prongs first and then turn the amp on? Justin, are you talking about the four flat screw blocks on the bottom of power supply board that have the black and red wires leading to it? Should I touch the prongs to the screws coordinating to the same color wires on each block? Or are you telling me I need to touch a GND (green) with one prong and the other prong to the screw head? I've just had a shudder moment. It looks to me like you are completely new to electronics - and the voltage inside any electrostatic amp is quite lethal. If you get it wrong, you can end up with many hundreds of volts with significant current capability from one hand to another - and that has a very high risk of stopping your heart. Please get someone to fix this for you - Justin already offered to do this if you sent it to him. Quote Link to comment Share on other sites More sharing options...
mypasswordis Posted March 14, 2011 Report Share Posted March 14, 2011 Ehhh what is up with the 7815 regulator? Can you take a close up picture of the 4 small caps on the PSU board as that doesn't look right... As for the mica caps on the amp board, yeah the KGSS has compensation caps. For some people this is supposed to be a bad thing but they have clearly never opened up a Stax amp... Yeah is that brown stuff supposed to be there? And thanks, yeah I mean those micas. I've just had a shudder moment. It looks to me like you are completely new to electronics - and the voltage inside any electrostatic amp is quite lethal. If you get it wrong, you can end up with many hundreds of volts with significant current capability from one hand to another - and that has a very high risk of stopping your heart. Is it true the most dangerous range of current is in the .1-.2A range, which causes fibrillation? Quote Link to comment Share on other sites More sharing options...
Craig Sawyers Posted March 14, 2011 Report Share Posted March 14, 2011 Is it true the most dangerous range of current is in the .1-.2A range, which causes fibrillation? Looks like it for DC http://hypertextbook.com/facts/2000/JackHsu.shtml To drive 100mA through the body at 700V rail to rail of a KGSS would need a body resistance of 7k. Typical hand to hand dry skin resistance can be way below that (a k or two) - and working with high voltage usually gives "sweaty palm syndrome", which makes the hazard even worse. Hence the excellent general advice of keeping one hand in the pocket at all times while taking measurements at modest levels. Quote Link to comment Share on other sites More sharing options...
RockCity Posted March 14, 2011 Author Report Share Posted March 14, 2011 Hi, I haven't touched anything yet except unscrew the bolt on the power transformer. I'm conservative about safety hence I've been requesting step by step explanations. This is not my field and I have no problems sending it in to Justin if he accepts. I received the amp recently in such condition. Spritzer, I will upload some better pictures for you shortly. Sorry if I gave anyone a Darwin Awards feeling. Quote Link to comment Share on other sites More sharing options...
spritzer Posted March 14, 2011 Report Share Posted March 14, 2011 To echo what the others have said, the KGSS can kill you so I would have somebody who knows what they are doing work on it. It's easy to blow it up just when measuring something. I would also scrap those Blue Velvet pots, the KGSS deserves so much better and channel matching with two pots is just a pain. The LM7815 doesn't look right though. Appears to have been tampered with but it is obviously working or you wouldn't get any sound at all. Quote Link to comment Share on other sites More sharing options...
RockCity Posted March 14, 2011 Author Report Share Posted March 14, 2011 Spritzer, here is the LM7815 you are talking about. http://img832.imageshack.us/img832/4822/p1020568.jpg The legs are criss-crossed but not touching. Hopefully Justin will see this later tonight and can tell me a little more about this particular machine and if it has been tempered with. Secondly, I hope to get an estimate for the repair as well as replacing the potentiometers with DACT pots to ease adjustments. Depending on this estimate, I will have to talk to the seller because it could end up costing me more than a new KGSS. This unit took a month of communication to procure. I'm pretty patient so I want to know all of my choices from Justin or Dr. Gilmore. Quote Link to comment Share on other sites More sharing options...
The Monkey Posted March 15, 2011 Report Share Posted March 15, 2011 Sorry if I gave anyone a Darwin Awards feeling. I think you're doing exactly what you should. Taking good pictures, being patient. A good way to approach the problem and we all can learn. Quote Link to comment Share on other sites More sharing options...
Voltron Posted March 15, 2011 Report Share Posted March 15, 2011 I don't know shit, but how could it be correct to switch the ground and output pins on a voltage regulator? And is it in backwards? Quote Link to comment Share on other sites More sharing options...
recstar24 Posted March 15, 2011 Report Share Posted March 15, 2011 Maybe it's reversed on the Board itself? Quote Link to comment Share on other sites More sharing options...
digger945 Posted March 15, 2011 Report Share Posted March 15, 2011 (edited) I don't know shit, but... I beg to differ ...if it's like my board, then the part should have been inserted pin for pin without crossing anything, like you have indicated. And is it in backwards? The physical body of the part is oriented correctly. Perhaps someone else could look at the positive pin on the rectifier bridge. It kinda looks a little stressed, perhaps. Maybe we could have a looksy at the parts that this regulator feeds, on the amp board. Edited March 15, 2011 by digger945 Quote Link to comment Share on other sites More sharing options...
Voltron Posted March 15, 2011 Report Share Posted March 15, 2011 (edited) . Edited March 15, 2011 by Voltron Quote Link to comment Share on other sites More sharing options...
Voltron Posted March 15, 2011 Report Share Posted March 15, 2011 I still don't know shit, but the board would have to be screwed up to call for a part with pins 1-2-3 to be soldered 1-3-2. And digger reminds me that it looks like the input pin is not connected or not adequately connected but the picture isn't clear. Quote Link to comment Share on other sites More sharing options...
The Monkey Posted March 15, 2011 Report Share Posted March 15, 2011 RockCity, who sold this KGSS to you? Quote Link to comment Share on other sites More sharing options...
digger945 Posted March 15, 2011 Report Share Posted March 15, 2011 (edited) You're right Al. It doesn't look good from any angle. Sloppy mess for a dollar part. One more thing. What in the sam hell is going on with the input of the left channel here? No 1N914 diodes? Crossed wires from the 389(bypassing said diodes actually)? Edited March 15, 2011 by digger945 Quote Link to comment Share on other sites More sharing options...
morphsci Posted March 15, 2011 Report Share Posted March 15, 2011 RockCity, who sold this KGSS to you? Quote Link to comment Share on other sites More sharing options...
RockCity Posted March 15, 2011 Author Report Share Posted March 15, 2011 I will not disclose the seller information's until Justin gives his review. If necessary, the information will be given to the correct party in PM. I do not want any of these speculations to tarnish the person's reputation, especially when the person is not here to defend themselves. I have been in contact with the seller and I have forwarded this thread since it started so he may read the ongoings. I've asked the seller before the transaction began if the unit had every been repaired through first or third party and if it has even been opened. I believe in their honest answer that it has not. The unaccounted variable is that the seller is the second owner. Therefore, I cannot recall the original ownership. However, my seller has claims the unit to be problem-free under his ownership. Quote Link to comment Share on other sites More sharing options...
RockCity Posted March 15, 2011 Author Report Share Posted March 15, 2011 Please do not bring up Mikhail. At this point people can be randomly criticizing third parties or even Justin since the seller is not DIY. Quote Link to comment Share on other sites More sharing options...
digger945 Posted March 15, 2011 Report Share Posted March 15, 2011 Provided there is not a serious problem with the pcb layout, one would have to be deaf not to notice the out of whack soundstage that would result from one channel being out of phase. Quote Link to comment Share on other sites More sharing options...
RockCity Posted March 15, 2011 Author Report Share Posted March 15, 2011 Hi digger945, I will try to answer your questions the best I can. The diodes are not being bypassed. Here is a different angle. http://img4.imageshack.us/img4/4765/p1020571h.jpg Quote Link to comment Share on other sites More sharing options...
Pars Posted March 15, 2011 Report Share Posted March 15, 2011 (edited) It appears that the bias for the 2sk389 has been flipped, but I don't see why you would want to do that. I also don't see that this would flip the input phase? Assuming the headwize schematic is still accurate. Of course I could be missing something Edited March 16, 2011 by Pars Quote Link to comment Share on other sites More sharing options...
digger945 Posted March 15, 2011 Report Share Posted March 15, 2011 The phase could be corrected at the outputs, but I'm with Pars, I don't see why the need for the extra wiring and butchering. And it looks like one of the diodes is missing, unless there is yet another angle to be seen. Quote Link to comment Share on other sites More sharing options...
Pars Posted March 15, 2011 Report Share Posted March 15, 2011 (edited) Nah, both the diodes are there. I just don't see any point to this "mod". Of course I haven't seen the bottom side of the board.Both diodes are being fed by a CCS, which should be equal current in each leg. The pot can vary that between legs, I presume for offset adjustment. Note, I've never built a KGSS, so might be talking out my arse. Edited March 15, 2011 by Pars Quote Link to comment Share on other sites More sharing options...
The Monkey Posted March 15, 2011 Report Share Posted March 15, 2011 That's one of the many reasons to know the amp's ownership history. Not to drag past owners through the mud, but because the KGSS is relatively easy to trace and one can sometimes learn a lot from past owners. Quote Link to comment Share on other sites More sharing options...
RockCity Posted March 15, 2011 Author Report Share Posted March 15, 2011 (edited) I asked for the original owner's history, however, the seller does not know. Communications lasted a month before the transaction even began. I am very thorough with sales details and I asked the seller to confirm that the amp was stock and in working condition. I'm not sure if Justin can pull out the record of the purchaser by the serial no. on the board. Please keep the discussion going so I can learn as much as possible. Edit: I will re-upload the images on imageshack since photobucket keeps resizing. Edited March 15, 2011 by RockCity Quote Link to comment Share on other sites More sharing options...
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