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About Blueman2

  • Rank
    Limited Edition Bronze Participant

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  • Gender
  • Location
    Silicon Valley / Bay Area


  • Headphones
    SR-007mkii, SR-507, SR-Lambda Pro, SR-407
  • Headphone Amps
    KGSSHV Carbon, SRX-Plus, SRD-7 Pro
  • Sources
    Schiit Gungnir MultiBit, Gen5 USB, Balanced connections
  1. Blue Hawaii BJT Build thread

    Running like a dream now! Thanks mwl168 and sorenb for the fixes. I reduced the amp to +375v and -378v by overlaying 4M7 resistor in parallel to the 390K ones, and it is holding rock solid. Loaded or unloaded, same numbers. And with the 2R6 on the B- current limiter, it is handling the 135ma on that rail without issue. I did not have to change the B+ side current limiter. Frankly, I would never have solved the current limiter issue without your guidance, mwl168. Just spent about 10 minutes on the BH using some older Lambda Pro's that I use to test amps (if they get fried, I will not cry). Now to plug my 007's in and lose a couple hours of time....
  2. Blue Hawaii BJT Build thread

    Thanks. Is there much of an issue running a BH BJT at only 375V? Either that or I will get a 350V rated trafo. Just not sure the larger trafo will fit into this case. Things are really, really tight in there right now.
  3. Blue Hawaii BJT Build thread

    Details are: Raw AC from trfo: 2x 315V @ 330ma each Unregulated DC: 436V Regulated B+: +404 no load, +392 load Regulated B-: -410 no load, -383 load SiC drain is 8.3V under load. will measure other in a bit... Thanks sorenb.
  4. Blue Hawaii BJT Build thread

    I am moving the discussion from Carbon thread to here since it is more related to Blue Hawaii. Here is the prior discussion: I did not realize that the BH demands more current than the standard GRHV is set for. There is a 5R1 resistor in the GRHV that needs to be changed to allow it to provide enough current for the BH BJT. I am measuring current of 83ma on the B+ and 134ma on the B- on my build. B+ rail is fine, but I had to reduce the current limiting resistor in B- from 5R1 to to 3R in order to get enough current to drive the BH. Moving discussion here so that others can learn from my error.
  5. KGSSHV Carbon Build Thread

    Ah, I was not understanding how the current limiting resistor works. Looking at the schematic, does it give a reference voltage for the 2n3904 and that feeds back to the C2M? Doh! Sorry, mwl168, I was being dense. Now I understand the importance of that resistor!! Out of curiosity, how do I calculate the current limit imposed by the R11 (the current limiting resistor) in the circuit? What limit does the existing 5R1 impose? EDIT: Partial success!! I changed the current limiting resistors to 2R5 (paralleled 2 5R1s as mwl168 mentioned) and things did get better. Voltages no longer drop off over time. But bad news is they are still both around 390V, and fluxuate a bit as household devices such as refrigerators turn on/off. But stays in a range of about 390 +/-3v. Enough to allow me to get offsets down to under a volt and confirm the outputs to 20ma. As for the low voltage, I think I will now replace the trafo with one I have in one of SRX builds and see if that helps. Thanks mwl168 and mypasswordis!!!! Both for your guidance and your patience as I learn along the way.... EDIT2: Oh, and I could not resist giving it a try.......WE HAVE MUSIC!!! And sorry for polluting the Carbon thread with what turns out to be Blue Hawaii BJT issues. There was more discussion on the GRHV boards here, which is where I was guessing my issues where. I am moving the discussion back to the Blue Hawaii BJT build thread. EDIT3: Just for future reference, it appears that the SCT2H12NZGC11 does indeed work as a replacement for the C2M1000170D, so we appear to now have a backup when those go out of stock as they seem to do pretty often.
  6. KGSSHV Carbon Build Thread

    BTW, I am measuring 0.68V across my B- 5R1 resistor. So about 133ma, about what you predicted for B- rail. The voltage then drops slowly over time across both the current limiting resistor and the B- output itself. I am still of the mind that either the trafo is not keeping up or the SiC chip I am using is not working in the same manner that the original C2M was designed. And given the dropping unregulated voltage, I am thinking trafo issue. (see below; current limiting resistor is more likely cause, or at least, a contributing factor)
  7. KGSSHV Carbon Build Thread

    I am using the 5W 5R1 resistors. But not sure that explains the drop in unregulated voltage I am seeing. For the 5R1, is it the wattage or the value that needs adjusting?
  8. KGSSHV Carbon Build Thread

    Well, things did not blow up, but I have run into a problem using the part. I tested both PSUs and they tested fine unloaded. +404 and -410. I then loaded with 15K 20W resistor on each supply, and the voltages held perfectly. I then hooked up to a new Blue Hawaii BJT I am building, and each side of the BH worked, though voltages did drop a bit from the +404 and -410. The B- was the most impacted, dropping to -400 but still working. I then hooked up both sides of the Blue Hawaii and voltages on both B+ and B- dropped by several hundred volts. My conclusion is that the new part is for some reason not able to keep the current levels I need. What surprises me is that PSUs could drive the 15K resistor without any issues at all. I guess the Blue Hawaii BJT demands a heck of a lot more power than the 10 Watts demanded by the 15K resistors. I will try loading both resistors on B- rail (so 7500 ohms) to give that rail a 20W test. But at this point, it appears my gamble did not pay off in using the alternative part. (This was a wrong assumption. Apparently the part is just fine. Read about 6 posts down) Was worth a try I guess!! EDIT: Loading the 15K resistors in parallel (doubling the draw to 20W) did drop the voltage down about 2 volts on each rail (to +402 and -408). So that should not happen, right? I do not have any lower value high wattage resistors to test with, but clearly something is wrong with both PSUs, and probably the part I used SiC. Only other possible issue could be the transformer. I will double check unregulated voltage to see if that is staying stable.... EDIT2: Well, maybe it is the trafo?? Trafo is giving 312 VAC on each side. Unregulated (after rectifier), I am measuring 436 VDC on both sides. When loaded, the Positive side unregulated voltage drops to 395 for a second then recovers to 407. The Negative side unregulated (which takes the most drain when using a Blue Hawaii) drops to 390V then recovers to 393V, and then slowly drops from there. Clearly, the trafo is not keeping up. It is a brand new one from Antek. I measured about 50VA HV load from side of the Blue Hawaii. The trafo is rated for 100VA per side, so I do not appear to be exceeding the trafo rating. I think I will pull a trafo from one of my SRX-Plus builds to see if I can confirm the issue. Maybe I was too quick to blame the replacement SiC?
  9. Blue Hawaii BJT Build thread

    Thanks guys! Just ordered a 10 pack of 0.3Ω 5W resistors and will get that voltage down to 6.0V - 6.3V range. You see any harm leaving at 6.8V for now until I get the parts? As mwl68 says, that is still within 10%. Just barely. EDIT: I did find the spec sheet on the Tung Sol EL34Bs I am using. It gives Filament range of 5.5-7.0. So I guess I should be OK with limited use until my resistors arrive.... el34b-tungsol.pdf
  10. Blue Hawaii BJT Build thread

    Hmm. Then more like a 0.3Ω resistor is called for. Or, if I am willing to live with a bit shorter tube life, is 6.7 to 6.8 VAC something I can live with without reducing? This makes me realize that my 2 SRX-Plus amps are probably also being driven too high for filament voltage.
  11. Blue Hawaii BJT Build thread

    I got the BH BJT up and running today. Everything seems great and I was able to dial all the voltages and currents in just right. One issue I am seeing is filament voltage. My Antek PSU is giving me 6.8V under load for the EL34s. Our voltage here is always around 125V, and the PSU was rated for 115, thus the higher value for the 6.3 feeds. I put a pair of 5W 1Ω resistors in parallel to create a 0.5Ω resistor for each amp board filament supply. That got the voltage down to 5.5VAC. Is that too low or should I go out and buy another 1Ω resistor to add in parallel?
  12. KGSSHV Carbon Build Thread

    Great news! But I just finished soldering in a pair of SCT2H12NZGC11's into my GRHV boards about 30 minutes ago! I will give them a try to see how they perform. It will be a fun experiment to have a backup SKU if needed in the future.
  13. KGSSHV Carbon Build Thread

    Not sure I would want to run this when the LV is not working correctly. I would wait to get that nailed before even powering the Carbon boards. For the LV trafo, it is a 2x16, right? For me, it DID matter which wires you put together for the CT connection on the board. If it is right, the other 2 will measure 35V or so. If it is wrong, they will measure only 17. Try that. I will say I like the Molex connectors. Never seen that before and it has some real advantages. EDIT: Yes, I just checked my amp, and I had Color1 to one 15V, Color2 to other 15V, and Color1/2 together on CT. It looks like you have it different?
  14. Blue Hawaii BJT Build thread

    For the delay start of HV on the GRHV boards, what value resistor should I use for driving the CPC1117N Opto using 15V? The spec sheet was unclear on this, but I was assuming I should add a 3K or so resistor (?). EDIT: Well, to answer my own question, I was able to find the forward voltage drop of the diode in the CPC1117N using my meter. It is 1.2V. So with 15V supply, that leaves voltage of 13.8V to get rid of. The turn on amps for the 1117N is 1ma min to 50ma max. Assuming 10ma as a safe target, I get R=13.8V/.010A=1.38K resistor. Since 2.2K is a common value, I will go with that which will provide about 6ma current to trigger the opto relay. EDIT2: Yes, these values worked fine. Here is a crude drawing of the circuit. I am measuring about 5ma to the CPC1117N input, which is about what I wanted. A 3K resistor would probably work just fine as well and would lower the current even more to the CPC diode. I am using THIS device, 12V version, from eBay as the timer. It works great for this application and is cheap. I have it set for delay on of 60s. You can also put jumper on S5 on the device and it will provide the VCC without the additional wire from Vcc to relay COM.
  15. Blue Hawaii BJT Build thread

    For the silicon that connects to the offboard heatsinks, are the 10M90S's the only ones that require aluminum oxide pads and non-metallic peek screws? Everything else appears to be fully encased. The 8N80C even appears encased and might not need the aluminum oxide pad and peek screws (?). I wanted to confirm before I soldered those on..... EDIT: Here is what I have done for pads. Al oxide for the 10m90s and silicone rubber for the rest.