GeorgeP Posted October 11, 2013 Report Share Posted October 11, 2013 Thanks for the advices. I think it's also worth to note that the first fuse blew during operation. I left it on during night because I was listening to it before I went to sleep and forgot to turn it off (not the first time.) When I woke up, the amp was off and the fuse was blown. I was also using 3A fuse tho with two thermistors in series to get the surge down. I was blowing through 3A fuses with only one thermistor. I used 4A this morning because I couldn't find the 3A fuse... The trafo was speced using Yun's BOM. 450V @ 125mA IIRC. There was always very faint hum with it, but I had to have my ear within inches of it to hear it. There was not loud hum whatsoever. ( It was humming loud this morning tho... I could hear it clearly standing 2 feet away from it.) Not going to add more skepticism now.. I'll report back when I have tested it. Did you happen to measure the offsets the second time your fuse blew? Curious to know whether one of them was sitting in the 400v range. If your traffo turns out to be fine you might want to sacrifice another fuse just to see (though there must be some type of short somewhere to blow the fuse). Quote Link to comment Share on other sites More sharing options...
jwzhan Posted October 11, 2013 Report Share Posted October 11, 2013 (edited) Did you happen to measure the offsets the second time your fuse blew? Curious to know whether one of them was sitting in the 400v range. If your traffo turns out to be fine you might want to sacrifice another fuse just to see (though there must be some type of short somewhere to blow the fuse). I just unplugged it from the circuit and tested it... exactly the same thing happened except this time it happened even faster. It blew through the fuse almost immediately. The secondaries shot up to 300V and died. Also, there was that burnt smell and loud humming again. I'll use a low voltage trafo and the LTSpice model to check if there are any damages to the main circuit. I guess SumR does suck... and I retract what I said earlier in the therad about having problem with everything except the SumR... I now have had problem with every single component the in the amp.... (I must have jinxed it. ) Edited October 11, 2013 by jwzhan Quote Link to comment Share on other sites More sharing options...
RiStaR Posted October 11, 2013 Report Share Posted October 11, 2013 May be hard to spot, depending if you have the onboard or offboard - but maybe check the 25 ohm resistors? This is the resistor that burnt out for me on the amp board (it took out an LED along the way or the other way round?) when I initially got it up. It's hard to spot/access between heatsinks for the onboard version Mine has been running fine daily since replacing those. Good luck! Quote Link to comment Share on other sites More sharing options...
jwzhan Posted October 11, 2013 Report Share Posted October 11, 2013 hmm... burt smell is definately from the trafo... it wasn't even connected to the circuit when I tested it the second time... and I've had resistor burn problem... it didn't smell anything that strong.. Quote Link to comment Share on other sites More sharing options...
GeorgeP Posted October 11, 2013 Report Share Posted October 11, 2013 May be hard to spot, depending if you have the onboard or offboard - but maybe check the 25 ohm resistors? This is the resistor that burnt out for me on the amp board (it took out an LED along the way or the other way round?) when I initially got it up. It's hard to spot/access between heatsinks for the onboard version Mine has been running fine daily since replacing those. Good luck! That was what I was thinking, but sounds like it is probably his traffo. Quote Link to comment Share on other sites More sharing options...
eggil Posted October 11, 2013 Report Share Posted October 11, 2013 I have used SumR also but haven't had any problems. Yet Left mine on all night by mistake and no problems. The question is, who to order future trafos from. Quote Link to comment Share on other sites More sharing options...
RiStaR Posted October 11, 2013 Report Share Posted October 11, 2013 I'm using a Toroidy that hasn't given me any problems, but its only been just under a year of daily use. Got it from a fellow forum member here. Quote Link to comment Share on other sites More sharing options...
livewire Posted October 11, 2013 Report Share Posted October 11, 2013 I have used SumR also but haven't had any problems. Yet Left mine on all night by mistake and no problems. The question is, who to order future trafos from. Sometimes ya get lucky. Just curious, what is the current rating of your SumR? Are you using inrush protection? (sorry, didn't feel like reading back) Quote Link to comment Share on other sites More sharing options...
eggil Posted October 11, 2013 Report Share Posted October 11, 2013 450x2 125 mA 15-0-15 No inrush protection Quote Link to comment Share on other sites More sharing options...
jwzhan Posted October 11, 2013 Report Share Posted October 11, 2013 I sent an email to SumR regarding it. His answer did not instill confidence. He basically said he is now in the 4th (2013) edition of the trafo.. and he has made it overkill and it won't happen again.. Sounds familiar? I'm probably not going to get anothet HV trafo from them now.. eggil... I really do hope you got lucky.. because it sucks not to have an amp:( Quote Link to comment Share on other sites More sharing options...
Pars Posted October 11, 2013 Report Share Posted October 11, 2013 Is Richard (SumR) handling these faulty trafos, or do you have to buy a new one from him? Doesn't sound good, whatever. Quote Link to comment Share on other sites More sharing options...
jwzhan Posted October 11, 2013 Report Share Posted October 11, 2013 (edited) well... he did not suggest replacing it. The trafo was ordered Aug 2012, so it's just a little over a year. I wasn't expecting him to replace it anyway. He was actually a little defensive when I told him that I just burned through his trafo and suggested to reinforce any future HV trafos.. It's because of his attitude that made me not want to buy more HV trafo from him... I know he definately can make high quality trafo that can withstand the abuse from these demanding amps... but I'm not sure he will, given his attitude.. Especially when he is already on the 4th edition trying to overcome the issue that has been present for a couple of years already. I have my doubts on the 4th edition trafo, so my replacement will not be from him. I don't know who to buy from yet.. Palchiu is kind enough to lend me his 450V 150mA trafo for now; however, that trafo runs on 110V, not US 120V, so it might result in too much heat. But if it's good enough, I might just get a 120V version from whoever he is getting his trafo from. Edited October 11, 2013 by jwzhan Quote Link to comment Share on other sites More sharing options...
palchiu Posted October 12, 2013 Report Share Posted October 12, 2013 jwzhan, Trafo's input voltage is set@115V, We're used same voltage as US. Quote Link to comment Share on other sites More sharing options...
eggil Posted October 12, 2013 Report Share Posted October 12, 2013 And where did you get it from? Quote Link to comment Share on other sites More sharing options...
palchiu Posted October 12, 2013 Report Share Posted October 12, 2013 And where did you get it from? My power transformer? Quote Link to comment Share on other sites More sharing options...
eggil Posted October 12, 2013 Report Share Posted October 12, 2013 yes Quote Link to comment Share on other sites More sharing options...
nopants Posted October 12, 2013 Report Share Posted October 12, 2013 Seems more relevant to chime in here than the other thread, but I've noticed my megatron transformer from SumR started humming, which has turned into a buzz. Maybe I'm running it too hard? I used the specs from Tran's page: Pri: 110v/220v. Sec: 2x 420v/130mA, 16v-0-16v/500mA Quote Link to comment Share on other sites More sharing options...
palchiu Posted October 12, 2013 Report Share Posted October 12, 2013 yes Mine was custom order from a local transformer factory. Quote Link to comment Share on other sites More sharing options...
insanity Posted October 12, 2013 Report Share Posted October 12, 2013 (edited) Guys looks like I have to bother you with another question. After moving the amp to another room to do a provisional listening setup until I manage to case everything up, a hum developed on the right channel. I still hear music on that channel, there is just a medium loud hum. When I disconnect the inputs and short them to ground, the hum is not noticeable anymore. Does this speak for a grounding problem, or could the input j-fets or anything else be broken? Edit: If this helps: The hum gets louder shortly, when I power off the amp (this has something to do with servo, as the Led D1 also lights up a bit more when powering off - but this is the same on both channels and not cause of the problem). Edited October 12, 2013 by insanity Quote Link to comment Share on other sites More sharing options...
livewire Posted October 12, 2013 Report Share Posted October 12, 2013 Sounds like it could be a grounding issue. Move it back and see if the problem goes away (or not?) Quote Link to comment Share on other sites More sharing options...
spritzer Posted October 12, 2013 Report Share Posted October 12, 2013 The SumR unit in my first KGSSHV blew up so Richard sent me two replacements to see what the hell is going on. I'm working on getting them through customs now without it costing an arm and a leg. Seems more relevant to chime in here than the other thread, but I've noticed my megatron transformer from SumR started humming, which has turned into a buzz. Maybe I'm running it too hard? I used the specs from Tran's page: Pri: 110v/220v. Sec: 2x 420v/130mA, 16v-0-16v/500mA That is too low for a Megatron. I'd go with 420V/200ma as you are driving 8 EL34's. How hot is the transformer at full load? I'll probably use a 2*335V/200mA Edcor transformer as I have a few sitting here and running it at +/-400V is a good idea in my book. Less heat and all that... Quote Link to comment Share on other sites More sharing options...
nopants Posted October 12, 2013 Report Share Posted October 12, 2013 It gets somewhat hot, nothing crazy. However, it's encapsulated so that probably obscures my perception somewhat. This was using it in the open, I just shoved it into something loosely resembling a case. I'll get back to you with a number when possible. Quote Link to comment Share on other sites More sharing options...
insanity Posted October 12, 2013 Report Share Posted October 12, 2013 (edited) Sounds like it could be a grounding issue. Move it back and see if the problem goes away (or not?) after moving everything around a bit, the hum is still there. I noticed that even when I ground the inputs via 250ohm resistors, the hum shortly returned during the described turn off phase. I even switched the position of the two boards and the hum goes with the board. I think that makes a grounding issue very unlikely. Furthermore the "hum" sounds a bit rougher than the classical 50hz hum we get to hear in grounding issues. Is there any particular device you would start on checking/replacing? Rather inputstage or output? The fact that grounding the inputs reduced the problem, make me think it is more input related. Thanks Edited October 12, 2013 by insanity Quote Link to comment Share on other sites More sharing options...
insanity Posted October 12, 2013 Report Share Posted October 12, 2013 Looks like my nose (with a bit unexperienced brain) was right. Replaced the lsk389 and the adjacent mpsw06 and the problem is seems solved. Quote Link to comment Share on other sites More sharing options...
jwzhan Posted October 12, 2013 Report Share Posted October 12, 2013 I sent Richard another e-mail, and he said replacing the trafo for me is fine. (Maybe I mis-interpreted his tone in the last mail?) He also asked me to provide some detail. Why not, I guess it doesn't hurt to have a HV trafo for back up. We'll see if it will be strong enough. @insanity congrats on solving the problem. Quote Link to comment Share on other sites More sharing options...
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