June 3, 20206 yr Received my boards. They look great! Time to build a Mini T2 to go with my Carbon. Thanks Michael.
June 4, 20206 yr Just received my boards today with the extra 1.6mm PS. Glad I ordered the partially built GRHV78xxx, that's some fine work. Time to order parts and find a toroidal that works for this project. Appreciate your time and careful shipping Michael.
June 6, 20206 yr Got my boards today. Guess it is time to place a Mouser order. Thanks for everything mwl168
June 6, 20206 yr Author All GB packages have been shipped as of today except for two. One of the two is pending the participant's response to my shipping payment request. Most of you have PayPal'ed me the shipping cost. Thanks! For those who have not yet PayPal'ed me the shipping cost please check your PM or PM me. I have been keeping track but there were 50 packages so may have missed a few. Shipping cost for US address is a flat rate of $8.4 US. For non-US address it depends on the location and weight and I added $1 US for the bubble envelop used. This GB is now officially closed. Happy building!
June 12, 20206 yr Author On 6/8/2020 at 4:37 PM, lkong said: Got my board! Thanks for the extra PS board. I was not able to PM you so had to message you here. Please PayPal me $8.4 US for the shipping cost. @Orso_Aquilano: please check PM for shipping of your package.
June 14, 20206 yr On 3/14/2019 at 2:04 PM, mwl168 said: I am moving Kerry's mini GRHV\GRLV GB discussion to its dedicated thread here. I also included JoaMat's mini T2 here to see if we have enough interest for a GB. BOM: GR78xx - V2 .xlsx 21.88 kB · 22 downloads GR79xx - V2.xlsx 25.74 kB · 18 downloads I believe there is a small error in the BOM for the GR79xx. Q2 is stated as "PNP silicon kst42 or MMBTA92" but the kst42 is NPN I believe it should be a kst92, given in the golden reference through hole, the transistor at that position is a PNP AND the MMBTA92 is a PNP. Edited June 14, 20206 yr by jamesmking
June 17, 20206 yr has anyone built a gr78xx and tested it yet? my gr78xx refuses to regulate. 😞 I just finished building 2 gr78xx. tested both for shorts and not connected components. each in turn to a DC power supply, with current limiting set to 50mA, nothing connected to the gr78xx output except a multimeter. Things started well, D2 just barely started to glow at 1.8V input to the gr78xx, as the input increased D2 glow increased... D1 suddenly started to glow at 16.3V input and the output voltage at this point was 15.088V. Current draw from the dc power supply was around 20mA, no bangs no surprises... but when I increased the input voltage more the ouput voltage just followed it. At 18.26 input the output was 17.073V.... I checked the voltage ref 10.005V between pins 4 and 6. No components feel overly hot. Both gr78xx have been ultrasonically cleaned. Both the gr78xx behave exactly the same way. On a DC load the output voltage drops with increasing current draw at 250mA the output is 14.58V BUT D1 and D2 remain lit with no change in brightness compared to no load on the output. any ideas what could be the problem? Edited June 17, 20206 yr by jamesmking
June 17, 20206 yr Author I did successfully build both GR78 and GR79 using the GB boards. First of all, you need some capacitance on the output for the regulators to work. That's the first thing I would try. I did have an issue with GR78 at first and finally figured out I used the wrong part (used HN4A51J instead of HN4C51J). But try adding some capacitance on the output ends first.
June 17, 20206 yr 10 hours ago, mwl168 said: I did successfully build both GR78 and GR79 using the GB boards. First of all, you need some capacitance on the output for the regulators to work. That's the first thing I would try. I did have an issue with GR78 at first and finally figured out I used the wrong part (used HN4A51J instead of HN4C51J). But try adding some capacitance on the output ends first. Thank you for the quick reply You are absolutely right about the output capacitance. I recreated the golden ref through hole output cap setup of a 220uF and 4.7uF in parallel and that did the trick. D1 now slowly comes on when the input goes above 17.5v and behaves much more like the golden reference through hole and the gr78xx is now happily regulating at 15.014V with no load. At 18.26v the output is now 15.015v. 50mA load the output is down from 15.015v to 15.003V, 100mA output is 14.991V, 200mA output is 14.967V all with 18.26v input and no heatsinking. Switching off the 200mA load the output is straight back to 15.015V. Playing around a little more regulation works with just the 4.7uF film cap on one of the two boards but results in the other board increasing the output voltage with increasing load! putting back the 220uF caps makes the second board behave like the first with similar voltage drops with increasing current draw. The silkscreen for the gr78xx says hn4a51j which is a pnp part which is consistent with the through hole golden ref which uses 2x ksp92ta which is also a pnp transistor... now if i could get more voltage references I could build the gr79xx boards.... Edited June 18, 20206 yr by jamesmking
June 18, 20206 yr I suppose we still have the same transformers specs like the full-sized GRHV? 330vac for 400vdc and 360vac for 450vdc outputs?
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