GeorgeP Posted June 15, 2013 Report Posted June 15, 2013 Great, glad to hear it all worked out! Did you ever figure out what the problem was? 1
s_r Posted June 15, 2013 Report Posted June 15, 2013 Beats me as to what was the problem with the other board. I might put it up for sale for parts if anyone's interested.
eggil Posted June 15, 2013 Report Posted June 15, 2013 Congratulations S_R! It's not the alpha pot. I had a similar problem with my offboard build unit a goldpoint. There was a hum with the knob turned all the way down and only with the first step. Dead silent afterwards. Could not get rid of it. With my onboard build and using he alpha pot, it's dead silent.
spritzer Posted June 15, 2013 Report Posted June 15, 2013 That hum has to be a ground issue as at the extreme left there is max resistance between the input, viper and ground.
PICaudio Posted June 15, 2013 Report Posted June 15, 2013 Very good news for a fantastic job, I don't found the time to start with my amplifier and when I see a new KGSSHV is always an incentive to start this little adventure. Congratulations s_r -- o -- Rodrigo
TMoney Posted June 17, 2013 Report Posted June 17, 2013 My HV is now back up and running after the replacement trafo came in. To be on the safe side, I went from having a 100VA to a 150VA.
livewire Posted June 17, 2013 Report Posted June 17, 2013 Glad to hear it, good move on upping the trafo!
eslover Posted June 23, 2013 Report Posted June 23, 2013 I finished cabling the onboard version of the kgsshv (v0.2). I am running in some trouble with the amp boards and could use some help and pointers on how to resolve the problem(s) - Power supply is OK +/- 445V (I was going for ~450V), and +/-15.0V. - On the first amplifier board, one LED does not come on. That's the LED that is closest to the lsk379, towards the lower left corner of the board. The voltages at O+ and O- are the same as for +VCC (+443V). -VCC is -442V - On the other amp board, all LEDs are on. O+ and O- are approximately 20V apart, (+110 and +130V). +VCC and -VCC read the expected values (about +443 and -442V). All voltage measurement with respect to ground. All measurements with Khozmo attenuator set to lowest level. All transistors from respectable sources. Any help to jumpstart the troubleshooting would be appreciated. Thanks.
kevin gilmore Posted June 24, 2013 Author Report Posted June 24, 2013 The one board is clearly working, adjust the offset pot to get the outputs close to zero. On the other one, make sure the differential pot is set to the middle first and the offset pot set for the higher end of the resistance range.
eslover Posted June 24, 2013 Report Posted June 24, 2013 The one board is clearly working, adjust the offset pot to get the outputs close to zero. On the other one, make sure the differential pot is set to the middle first and the offset pot set for the higher end of the resistance range. Thank you Kevin. Though that may have to wait until next week-end, I will try and report.
Kerry Posted June 26, 2013 Report Posted June 26, 2013 (edited) I've been interested in building a smaller version of this amp so I started playing around with a chassis layout and board layouts for PS and the amp boards that could fit in a chassis that is approximately 8"x3"x14". I blended SMD in with the amp board. Makes it a bit more difficult, but I wanted to experiment. Here's the project so far: The power supply... Requires two boards (2.5" x 5" each). The Output MOSFETs will mount directly to the heat sinks. The small board on the left is the adjustable voltage doubler for the BIAS. The amp boards will mount vertically against the heat sinks. I'm going with Conrad MF20-75. They are 200mm x 75mm x 48 mm. I haven't gotten to the amp boards yet since I wanted to get the PS up and running first. These boards are 2.5" x 6" each. This will be the BIAS. It supports two different voltages. This one is set at 500V and 580V. Still in the experimentation phase, but moving along. Will keep posting as I go through this. Edited June 26, 2013 by Kerry
johnwmclean Posted June 26, 2013 Report Posted June 26, 2013 (edited) I like the dimensions, I wonder what would be the best way to support the psu boards in their upright position? The transformer diameter might be a factor as well. Edited June 26, 2013 by johnwmclean
Kerry Posted June 26, 2013 Report Posted June 26, 2013 I like the dimensions, I wonder what would be the best way to support the psu boards in their upright position? The transformer diameter might be a factor as well. The PSU boards will mount against the side plates using stand-offs (approximately 40mm). I had SUMR build me a transformer that is 2.3" tall and 3.7" diameter. That gives about .25" between the transformer and PS boards. I'm hoping this doesn't cause any induced hum in the PS. I'll test before I mill out the chassis plates.
eggil Posted June 26, 2013 Report Posted June 26, 2013 What an amazing job! How does it compare size wise with the compact version Spritzer is building?
spritzer Posted June 26, 2013 Report Posted June 26, 2013 Well I haven't done anything on that small one for months... Too much crap going on and currently thinking too much about DHT's... Ohh and my Tiny Triode amp PCB's just arrived for some true miniature fun.
Kerry Posted June 28, 2013 Report Posted June 28, 2013 I just tested the first board. Everything worked great I've got to adjust the voltage down a bit but that's a simple fix. Ignore the heat sink on the MOSFET. It's just while I'm doing the unloaded test.
headinclouds Posted June 28, 2013 Report Posted June 28, 2013 A very interesting design Kerry, I really like the way you've gone about this, thanks for posting it.Look forward to the outcome.
PICaudio Posted June 28, 2013 Report Posted June 28, 2013 (edited) Amazing job Kerry. I bought some 2SA1968 (Lots 1E4 and 9G2) and I'm not sure if these sands are original. I think that the aspect is similar of the originals, I measured Vbr with a DY294 and all units are over 1000v, but the HFE is lower than 20 (14 to 17) and I've read in the datasheet that HFE is between 20 and 50. Are these low values of HFE normal, or these sands are fakes? -- o -- Rodrigo Edited June 28, 2013 by PICaudio
kevin gilmore Posted June 28, 2013 Author Report Posted June 28, 2013 (edited) those look real in every way. And kerry, that's a great job. Edited June 28, 2013 by kevin gilmore
Lil Knight Posted June 28, 2013 Report Posted June 28, 2013 Kerry, that's a superb job! I'm almost done with the new mini boards. Just waiting for the peek screws and transformer then I can fire it up.
PICaudio Posted June 28, 2013 Report Posted June 28, 2013 those look real in every way. And kerry, that's a great job. Many thanks. -- o -- Rodrigo
eslover Posted June 28, 2013 Report Posted June 28, 2013 On 6/23/2013 at 8:17 PM, kevin gilmore said: The one board is clearly working, adjust the offset pot to get the outputs close to zero. On the other one, make sure the differential pot is set to the middle first and the offset pot set for the higher end of the resistance range. The outputs of problem board are unresponsive to offset or balance adjustments. Both are stuck at vcc. The LED that does not light up is the bottom right one on the picture. The LED in the middle will come off with high balance setting. Could it be the LSK389 that is faulty or fried? I adjusted the other board's outputs to 0v
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