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Post by Deleted on Apr 4, 2009 23:24:34 GMT
Suns have gone into main amp tonight.
Insomniac, you have pm.
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insomniac
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Post by insomniac on Apr 5, 2009 1:33:26 GMT
Dave, I see an OPA Earth if I'm not mistaken, poking up through the case. indeed I have the OPA Earth in the PCM 1793 DAC nice how thick is the case looks to be about 2mm?? Your not mistaken Robert... that is indeed an OPA Earth peeking out... 10/10 for observation The case is 3mm extruded aluminium. That stuff looks the business and the fingers allow it to bend in a fairly tight radius by the look of it. I have never seen it before anywhere over here. Cool idea...
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Post by Deleted on Apr 5, 2009 22:16:47 GMT
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robertkd
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Post by robertkd on Apr 5, 2009 23:13:10 GMT
Chris, looks like there are some regulators in the PCB top picture atached to some aluminum heatsinks. do these supply the op amp supply rails? have they added series resistors in the actual feed to the op amps this is sometimes done to further decouple the power supply might also use a resistor and zener diode. If so the higher (much higher) current draw might cause to much of a voltage drop. So I would trace the power rails and see how they are derived. a word of caution these modules generate quite a bit of heat and when the case is back on might present a problem, just something to consider. I had noticed this when doing some testing, also the quiescent current rises and as I had series resistors in the supply rails for one of the test beds I got the LED's to start flashing and wow the module was hot in fact I thought I had toasted it all good through Robert
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Post by clausdk on Apr 6, 2009 17:22:06 GMT
If you guys think that the hole in the top of insomniacs dac is weird you schould see my zero, at the time being the module is hanging in the air, with rubberbands, it looks really odd... But the sound is just fantastic..
I am going to make something like Daves solution, but I want to be able to switch modules whitout tool, so I am trying to find out just how it has to be done.....
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Post by PinkFloyd on Apr 6, 2009 20:43:40 GMT
If you guys think that the hole in the top of insomniacs dac is weird you schould see my zero, at the time being the module is hanging in the air, with rubberbands, it looks really odd... But the sound is just fantastic.. I am going to make something like Daves solution, but I want to be able to switch modules whitout tool, so I am trying to find out just how it has to be done..... Pics please
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Post by Deleted on Apr 6, 2009 23:47:59 GMT
Chris, looks like there are some regulators in the PCB top picture atached to some aluminum heatsinks. do these supply the op amp supply rails? have they added series resistors in the actual feed to the op amps this is sometimes done to further decouple the power supply might also use a resistor and zener diode. If so the higher (much higher) current draw might cause to much of a voltage drop. So I would trace the power rails and see how they are derived. a word of caution these modules generate quite a bit of heat and when the case is back on might present a problem, just something to consider. I had noticed this when doing some testing, also the quiescent current rises and as I had series resistors in the supply rails for one of the test beds I got the LED's to start flashing and wow the module was hot in fact I thought I had toasted it all good through Robert Robert, As far as I can tell those regulators are only for the power amp section. I've done my best to trace to power rails back to source and come up with following (accuracy not guaranteed ) I won't be offended if you say it's misread s-h-1-t !
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Post by Deleted on Apr 7, 2009 0:04:19 GMT
Chris, looks like there are some regulators in the PCB top picture atached to some aluminum heatsinks. do these supply the op amp supply rails? have they added series resistors in the actual feed to the op amps this is sometimes done to further decouple the power supply might also use a resistor and zener diode. If so the higher (much higher) current draw might cause to much of a voltage drop. So I would trace the power rails and see how they are derived. a word of caution these modules generate quite a bit of heat and when the case is back on might present a problem, just something to consider. I had noticed this when doing some testing, also the quiescent current rises and as I had series resistors in the supply rails for one of the test beds I got the LED's to start flashing and wow the module was hot in fact I thought I had toasted it all good through Robert Robert, As far as I can tell those regulators are only for the power amp section. I've done my best to trace to power rails back to source and come up with following (accuracy not guaranteed ) I won't be offended if you say it's misread s-h-1-t ! Chris To avoid the risk of offending you, I will just think it ! For starters we really need the measured +-voltages to the main amplifier section, as well as the measured voltages at the opamp pins with a normal I.C. in situ. The voltages for the main amplifier would appear to be much higher than the opamps are capable of handling, so there must be either some regulation or dropping resistors. Alex
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Post by Deleted on Apr 7, 2009 0:32:32 GMT
Transformer = 28-0-28
TL072 x2 = pin 4 = 14.4 & 14.3 pin 8 = 14.6 & 14.6
Where would measure "voltages to main amplifier section"?
Chris
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Post by Deleted on Apr 7, 2009 0:58:42 GMT
Transformer = 28-0-28 TL072 x2 = pin 4 = 14.4 & 14.3 pin 8 = 14.6 & 14.6 Where would measure "voltages to main amplifier section"? Chris Chris You would need to refer to the schematic of the amplifier and PSU that you posted. I would expect around +39V or so, between the components connected to the top line of the drawing and earth, and -39V between the components connected to the bottom line of the schematic and earth/0volts This suggests that you most likely have voltage regulators or dropping resistors to drop around 25V, before it is supplied to the I.C.s. Alex
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Post by Deleted on Apr 7, 2009 1:12:15 GMT
.....41.9. Christ, I wish I knew what I was doing!
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robertkd
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Post by robertkd on Apr 7, 2009 1:28:16 GMT
.....41.9. Christ, I wish I knew what I was doing! whats 41.9?? I'd be surprised if there wasn't a zener diode and a dropping resistor for the op amp supply
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Post by Deleted on Apr 7, 2009 11:43:27 GMT
.....41.9. Christ, I wish I knew what I was doing! whats 41.9?? I'd be surprised if there wasn't a zener diode and a dropping resistor for the op amp supply Robert/Alex With ref to i300.photobucket.com/albums/nn7/cjarchez/Claymore%202/SupplyPower_AMP_2.jpg as per Alex's suggestion, R11 to ground = 40.8vdc R19 to ground = 41 vdc R18 to ground = 40 vdc Alex, I obviously can't read a board (double sided)
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robertkd
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Post by robertkd on Apr 7, 2009 12:00:33 GMT
Ok Chris, that's the the power amp stage and all looks as expected except maybe tr3 and 4, however that's not what were looking for. Can I assume that there is only one secondary for the amp that being the 28-0-28 VAC winding ? If so I would expect to see a resistor from the B+ and the B- to either likely some zener of perhaps possibly even a simple voltage divider, more likely a either a zener or some form of regulator, which I expect will supply the op-amps for the L and R channel as well as the phono pre-amp. Robert
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Post by Deleted on Apr 8, 2009 2:33:20 GMT
Chris In one of your photos, there are visible a couple of PCB tracks (above the switch with all the coloured leads) that go into a parallel group of 8 resistors. Are those tracks coming from the supply pins of the opamps ? If they are, see if they connect to any of those resistors. SandyK
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robertkd
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Post by robertkd on Apr 8, 2009 5:30:26 GMT
Chris, Op-Amp Supply rails ? I'm thinking these are the PSU/Filter Caps for the OP-Amps, Robert Alex not 100% but the ribbon cable looks to be input selection, it's not the easiest when it's not in front of you
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Post by Deleted on Apr 8, 2009 6:03:09 GMT
Robert Agreed. I was only referring to them for localisation purposes of the area above, where you have highlighted what may be one of the PSU feeds to the opamp.Chris will need to get out his DMM and check for continuity from opamp supply pins to this area. The double sided PCB makes it even harder. Alex
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Post by Deleted on Apr 8, 2009 14:56:03 GMT
Even with it in front of me! Yes, those parallel resistors are the input tracks. I have managed to gleen a bit more info from the guy who provided the circuit drawings. The drawing of mine I posted was nearly correct . Revised below 41vdc from the main caps and rectifier diodes through 16v zener diode, AND ALSO from the main caps and rectifier diodes via 1K resistor to the TL072s, giving 25ma and 14.5vdc. This same supply, after where the zeners and 1Ks seem to meet, also goes through 2K resistors (1 per rail) and the 470uf 16v caps that Robert circled, to the phono opamps OP27GP x 4 (I assume 2 for mm and 2 for mc, selected via dip switches) at 13vdc and again, I think, 25ma each. So I'll need to decrease the 1K (2w?) resistor to give enough ma for the Suns (I was also recommended to increase it to 5w) AND adjust the 2K resistors to return the OP27 supply to normal? All this at bottom left of piccy.. and more clearly here... 1K resistors are black marked 74ER 1KO, the 2k resistors are by the R5 identifier, zeners are D5 & D6. edit= opamp supply rails ARE as Robert marked. I've also contacted GDA with this info to see if they have any light to shine. Cheers, Chris
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robertkd
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Post by robertkd on Apr 9, 2009 6:52:37 GMT
Chris, so in theory you have something like this. the original design looks to be good for some 20mA depending on your design philosophy. given the OPA's draw some 55mA (says 50 but allow a margin) each plus allowing about 10mA for the phono amp your new design would have to provide about 120mA plus say 10mA for the zener giving a total of 130mA and allowing for average 35V supply i.e. some sag in the PSU under load driving speakers. 35V-14V = 21V drop across resistor @ 130ma = 160R so what to do 150R next preferred value . Ok where the fun begins is under normal conditions the zener will dissipate total current less load current or about 140ma -2*55 + about for the phono stage is 120ma so 20ma at 14 volts 280mw worst cast with no load 14V at 140ma so the zener would dissipate 2Watts, may need to upgrade to allow for this condition! Are you soldering the OPA's in ?? again worst case for the dropping resistors when the supply voltage is at about 40V the difference would be 40-14 = 26V the resistor dissipation will be about 3.6W even a 5W resistor gets bloody hot at 3W, a compromise might be 2 82R 5W in series giving our 160R initially calculated resistor (well 164R) value. There are other ways this could be done, half wave rectify the 28-0-28 winding will give you about 25-0-25 DC with 50Hz ripple but you in the realms of a 317/337 regulator and less at the mercy of variation of the main supply under varying load conditions,... food for thought Robert
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Post by Deleted on Apr 9, 2009 7:40:50 GMT
Robert Another alternative could be a 7815/7915 preceded by a LM317/LM337 pre-regulator,and all with suitable heatsinks . Whatever the answer, it is likely to be messy, and not a great deal of advantage (if any) over fitting sockets and LM4562HA in the previous locations, perhaps with a small amount of extra bypassing. Another reason for suggesting this, is that there already appears to be overheating in a couple of areas.(see bottom photo) Alex
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robertkd
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Post by robertkd on Apr 9, 2009 9:15:45 GMT
worse, I had a play with photo of the offending PSU area and think I need a photo of the underside to nut out the arrangement, alright at first I thought you got it a little how should I say "wrong" but figured near enough. Well all bets are off until I can verify WTFTHD clearly shows series arrangement of diode and 1KR but the capacitor connection is not clear. also the diodes are labeled Dx and maybe ordinary diodes! more input Steffane Robert PS, Alex given the conventional shunt regulator scenario I would almost agree, however it might be closer to the half wave rectifier arrangement and if so maynot take too much effort,... and what is this "perhaps with a small amount of extra bypassing" it ain't go any to start with ;D And don't start me with regulation
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Post by Deleted on Apr 9, 2009 9:40:27 GMT
;D I didn't want to be too uncharitable. In any case, simple zener regulation is not going to get the Audio-gd modules working to their full potential.
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robertkd
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Post by robertkd on Apr 9, 2009 10:08:57 GMT
;D I didn't want to be too uncharitable. In any case, simple zener regulation is not going to get the Audio-gd modules working to their full potential. well that's the way it is I'm afraid,... As for a suitable supply I'm kinda thinking the half wave rectifier option
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Post by Deleted on Apr 9, 2009 19:21:04 GMT
I hope it's simpler than that! I don't know the opamps involved but the author of the circuit drawings uses "removed the zener regulator and put a separate 11DQ10 diode bridge in for the pre stage in mine - that feeds 317/337 regulators." From the info I gave kingwa at GDA, same as my previous post without piccys, he suggested "only change the 1K to 330 ohms, than check the OP27 supply if normal will be OK." Following is a piccy of the PSU underbelly, I've labeled what I can see, the zeners are marked Z10, I think, very tough to see. i300.photobucket.com/albums/nn7/cjarchez/Claymore%202/PSUunderside.jpg praying for simple solution... Chris
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Post by Deleted on Apr 9, 2009 21:33:59 GMT
Chris Those regulators would then be dropping around 25V , and would be pretty hot,even with typical heatsinks fitted and with normal opamps. Did the guy who suggested this use ordinary opamps or the much heavier current drawing Audio-gd modules ? Alex
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