DefQon Posted July 6, 2015 Report Share Posted July 6, 2015 One for spritzer: I'm a bit stumped with trying to fix a borked SRM-3 (half populated Xh board on output stage only piggy backed by a separate power supply for those that don't know), this one came to me with one of the resistors R19 (other channel R19 measured 270ohms) blown apart with scorch marks in the heatsink and next to it a missing 2SA1156 (regular Xh board's use 2SA1091 and R19 is 400ohms). This one has been sitting here for a quite a while now because it became a PITA to source the HV output devices and I needed 8 (Sanyo 2SC4630's). I already had a few left over 2SA1156 so I did do some quick troubleshooting the last time I tested the amp with a new A1156 and 270ohm resistor populated where missing. The 270ohm resistor started burning and the onboard LED for each channel never lit up. So I left it till today. I tested all the transistors (8 2SC4630, 8 2SC2705, 4 2SA1413, 4 2SA1156 and the dual JFET pairs 2SJ109GR's, also tested all the diodes and resistors for shorts and all were fine. They all tested fine except for the 2SC4630, while diode testing the BCE connectors all gave relevant results, when I did a DC current gain hFe test it read 0 on my meter. My new 2SC4630's read between 39-45 (datasheet states a minimum of 30 so it's all good). I replaced all the 4630's with the new ones and put in what I had the closest 287ohm resistors in place of both R19 (only had Panny 240 and 47ohm's at hand to give a closer result to 270). Powering it up the amp doesn't power on, front LED doesn't light up, no smoke, no burns, onboard LED's doesn't light, 1.5A fuse still intact, odd readings from 100uf 400v filter caps in the PS on the offboard pcb connected to the transformer. I even did a diode test on the LED's to be sure they work, and sure enough they do emit when connected from DMM. There is a multi-tap voltage jumper selector on the side of the PCB, currently wired for 100v. To rewire for 240v, I'm assuming 120v - 0 and other one is 120 - 0? Currently for 100v its as seen in the picture, 100 to 100 and 0 to 0 SRM-Xh Quote Link to comment Share on other sites More sharing options...
TMoney Posted July 6, 2015 Report Share Posted July 6, 2015 (edited) I don't know what the hell Stax did to fix the excess treble energy in the 009s, but my goodness, the latest revision is just fantastic. 009s + Your Gilmore Amp of Choice + SACDs is audio crack. Edited July 6, 2015 by TMoney 2 Quote Link to comment Share on other sites More sharing options...
nopants Posted July 6, 2015 Report Share Posted July 6, 2015 birgir really did a great job with the kgst, pretty solid pairing. I'm pretty sure I prefer it to the bhse 009 at this point. as a result I'm still shopping around for carbonv1 cases, but my impatience is starting to get the better of me Quote Link to comment Share on other sites More sharing options...
spritzer Posted July 6, 2015 Report Share Posted July 6, 2015 Wait, I thought Stax didn't do anything to fix the 009's.... As for the SRM-3, this one has clearly been tampered with. What in the world are those huge caps suspended above the PCB? I can't remember the exact details of that schematic but I assume the resistor in question sits between the output transistor and the - rail? Not much that can be wrong except a shorted transistor, the pull down to ground is off or the voltages are wrong. Which brings me to the 240V setting, its is simply the former 120 connected to the 0V next to it. Nothing else. Quote Link to comment Share on other sites More sharing options...
DefQon Posted July 7, 2015 Report Share Posted July 7, 2015 You mean the black caps? They are 100uf 400v rated caps, looks to be from factory and identical to the ones in my stock SRM1 MK2 Pro C series based serial number batch. I'll disconnect the amplifier board completely from the power supply to rule out any short on the amp board preventing the amp turning on. Quote Link to comment Share on other sites More sharing options...
spritzer Posted July 7, 2015 Report Share Posted July 7, 2015 Ahh never mind, the last pic is from a SRM-Xh. See it now. Quote Link to comment Share on other sites More sharing options...
DefQon Posted July 9, 2015 Report Share Posted July 9, 2015 Yeah its odd, my other chance is desoldering all the diodes on the PS board and testing them individually. Disconnected the amp board from the power supply and no go, would not power on still. Quote Link to comment Share on other sites More sharing options...
spritzer Posted July 9, 2015 Report Share Posted July 9, 2015 Did you fix the primary setup? The way it is set in those pics it won't work at 230V. Quote Link to comment Share on other sites More sharing options...
DefQon Posted July 9, 2015 Report Share Posted July 9, 2015 Yeah I did I wired the centre 120v tap with the 0v as you suggested. Even wired the amp for 120v and same thing, doesn't power on. Quote Link to comment Share on other sites More sharing options...
spritzer Posted July 10, 2015 Report Share Posted July 10, 2015 Are the 120V primaries cut in some way? A fried transformer is not all that common a fault. Quote Link to comment Share on other sites More sharing options...
DefQon Posted July 10, 2015 Report Share Posted July 10, 2015 (edited) Nope not cut. Amp came to me as 100v I tested it twice while back off a step down and it was fine except the R19 blew again. Tested it again recently with new transistors and didn`t power on. Then I changed the primary to 240 and 120 and those didn`t work either. Also eliminated the switch as being the culprit. EDIT: Facepalm. Turns out my step down trafo blew its fuse (even though the front switch led is on), oddly enough a possible short in the SRM-3 after I replaced the transistors and R19 it did not blow its internal 1.5A fuse. Will try it again. But yes uncommon for a trafo to suddenly turn out to be faulty. EDIT2: Nope no go, trafo is borked. What's the ratings on these units? Edited July 13, 2015 by DefQon Quote Link to comment Share on other sites More sharing options...
astrostar59 Posted July 13, 2015 Report Share Posted July 13, 2015 Change of subject. It might be a dumb question, but I had an SR-007 MK2 Black UK import and the serial number was SZ3-1074. That pair was second hand so about a 2012 model. I just got a new pair of 007A's from PJ today, and the serial is SZ2-2140. I know these are the silver Japanese version, but confused, are the SZ3 units to WW exports numbered different to the Japanese units? Seems odd I have a series 2 MK2 unit as new. The box is faultless, the case plastic sealed, the cables plastic sealed. It all looks brand new. No way my outer box is 3 years old, it would be yellowed and aged it stored that long, it is pure white and glossy with the serial on the box outer as well and the phones. Next question, these 007s sound really damb good. I have the 009s in my other setup, but these sound to my memory a bit clearer and faster than the Black 007s I had before with the same source and 717 amp. Has Stax altered the drivers in the last few years (in the Mk2s). I know the Mk1s are very different. Sorry 2 questions. Any insight would be great. Quote Link to comment Share on other sites More sharing options...
mwl168 Posted July 14, 2015 Report Share Posted July 14, 2015 Stax is believed to have altered the 007 Mk2 driver sometime last year which significantly improved the sound. Check Birgir's posting# 9573 and subsequent discussions. Quote Link to comment Share on other sites More sharing options...
DefQon Posted July 14, 2015 Report Share Posted July 14, 2015 Buy another O2 and tell us about the differences. Quote Link to comment Share on other sites More sharing options...
astrostar59 Posted July 14, 2015 Report Share Posted July 14, 2015 I was the one who wrote that list so no, I don' have a Mk2.5. It is something new. I think you are right Spritzer. I have a new 007A from PJ, arrived yesterday. Last year I had a 2012 Black MK2 SZ3-xxxx, and this one is a lot smoother and less flabby in the bass. The treble seems smoother as well, but it still has a slightly reduced treble output compared to my Horn speakers and my 009s, which is not surprising and is expected. I really think Stax has done something here, whatever it is, it is an improvement that should be quite obvious to folk who have the previous MK2 IMO. I note your post on the serial number chaos. This 007A is a SZ2-xxxx and is spanking new, new box, sealed plastic bag. Go figure..... Anyway, I am very happy with them, surprised even. My 009s are still my preferred phone but on this smaller setup I have here the 007 is better. Out of the 717 amp the 009s are a bit too bright/unforgiving IMO. My setup in Spain is more complex than this tight little system. I kinda like the simplicity of it: MacBook Pro - Metrum DAC - basic cables - 717 - 007s My other system is MacMini and screen sharing from an iMac, M2Tech EVO stack (3 boxes) Audio Note DAC 4.1 (valves x 4) silly cables - KGSShv - 009s. Quote Link to comment Share on other sites More sharing options...
spritzer Posted July 14, 2015 Report Share Posted July 14, 2015 This is Stax so serial numbers have always been meaningless. They are just a rough guide, nothing more. Quote Link to comment Share on other sites More sharing options...
nopants Posted July 14, 2015 Report Share Posted July 14, 2015 I think you are right Spritzer. I have a new 007A from PJ, arrived yesterday. Last year I had a 2012 Black MK2 SZ3-xxxx, and this one is a lot smoother and less flabby in the bass. The treble seems smoother as well, but it still has a slightly reduced treble output compared to my Horn speakers and my 009s, which is not surprising and is expected. I really think Stax has done something here, whatever it is, it is an improvement that should be quite obvious to folk who have the previous MK2 IMO. I note your post on the serial number chaos. This 007A is a SZ2-xxxx and is spanking new, new box, sealed plastic bag. Go figure..... Anyway, I am very happy with them, surprised even. My 009s are still my preferred phone but on this smaller setup I have here the 007 is better. Out of the 717 amp the 009s are a bit too bright/unforgiving IMO. My setup in Spain is more complex than this tight little system. I kinda like the simplicity of it: MacBook Pro - Metrum DAC - basic cables - 717 - 007s My other system is MacMini and screen sharing from an iMac, M2Tech EVO stack (3 boxes) Audio Note DAC 4.1 (valves x 4) silly cables - KGSShv - 009s. can't you keep the text walls to headfi? Quote Link to comment Share on other sites More sharing options...
DefQon Posted July 14, 2015 Report Share Posted July 14, 2015 (edited) I`m surprised he didn`t come here telling us all how much his O2`s improved with burn in. On the other hand, 20vdc or there abouts with offset measurement on L+/- with SRM 1 MK2 Pro powered on for an hour, confirmed sound on all output, no obvious damage all other checks and opposite channel adjusted as close possible to 0vdc just left channel has mentioned problem, any idea on cause spritzer? Trimpot already maxed with turns. Sent from my LG-D855 using Tapatalk Edited July 14, 2015 by DefQon Quote Link to comment Share on other sites More sharing options...
spritzer Posted July 14, 2015 Report Share Posted July 14, 2015 Carbon resistors way out of spec? 1 Quote Link to comment Share on other sites More sharing options...
DefQon Posted July 15, 2015 Report Share Posted July 15, 2015 Carbon resistors way out of spec? Bingo, although my one looks to be the ones with 1/2 metal resistors all over, so far only picked up R102 and R202 on the channel input being completely out of spec, schematics say 910K, R-Input measures 33ohms and L-Input measures 11.2ohms. Measured the array of HV resistors on output all fine and the resistors near the trimpot area so far fine as well. Quote Link to comment Share on other sites More sharing options...
nopants Posted July 15, 2015 Report Share Posted July 15, 2015 loosely related to this amplifier troubleshoot, does anyone have the original headwize articles for the kgss and bh? Quote Link to comment Share on other sites More sharing options...
iwik Posted July 15, 2015 Report Share Posted July 15, 2015 See here http://web.archive.org/web/20150314234648/http://headwize.com/ Les 1 Quote Link to comment Share on other sites More sharing options...
DefQon Posted July 17, 2015 Report Share Posted July 17, 2015 (edited) That dirty SRA-3S I posted pictures on headfi while back has been rebuilt for about a month now. Running fine. Decided to add pro-bias, looking at the only available circuit diagram there is a 560v tap from the voltage doubler just before the voltage divider, found out and measured if the 300kohm resistor in series to the 390kohm and other end reference to ground is changed to 390kohm this gives 580-582vdc just after the second diode which is perfect for pro-bias. My test purpose only 202's sound rather nice with the slight coloration of the tubes and a little heft to the low-end. All that is left to fix is the dud SRM-3 and waiting for my spare 2SC1167 output transistors to arrive to finalise my SRA-12S repair. Edited July 17, 2015 by DefQon Quote Link to comment Share on other sites More sharing options...
HemiSam Posted July 17, 2015 Report Share Posted July 17, 2015 Anyone compare the KGST to the Carbon with 007's or 009's? Curious if there is much difference. Absolutely impressed with the KGST thus far listening with new run 007A's bought directly from Japan (streaming FLAC files to Ygg DAC balanced out to KGST with nothing special cables). HS Quote Link to comment Share on other sites More sharing options...
purk Posted July 17, 2015 Report Share Posted July 17, 2015 Anyone compare the KGST to the Carbon with 007's or 009's? Curious if there is much difference. Absolutely impressed with the KGST thus far listening with new run 007A's bought directly from Japan (streaming FLAC files to Ygg DAC balanced out to KGST with nothing special cables). HS If the Carbon is said to be near if not on the same level as the BHSE, then the difference should be enough to discern. Mulveling bought my KGST and he also like his full-sized KGSSHVs better (He has both the Sanyo & IXY versions). A full-sized KGSSHV just has better resolving ability compared to the KGST that I used to have. Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.