jamesmking Posted June 18, 2020 Report Posted June 18, 2020 (edited) GR78xx build notes: Writing direction on the opamp and voltage reference match the writing direction on the pcb I suggest checking the led orientation with a multi-meter in diode test mode, finding out which way round the multi-meter leads need to be to make the diode light and then marking either the positive end of the led with a red pen or the negative with a black pen whilst holding the led with twisters - if you don't hold the led with twisters it has a nasty habit of sticking to the pen tip. The leds face opposite directions. Positive and negative ends are marked in the picture with red and black lines respectively. All transistors are shown with their case markings. Its a good idea to solder the leds in first and then check. D2 has the end closest to the Vin pins connected ground and so its easy to check its orientation is correct, the other led is opposite orientation. The DN2540 is a depletion device so if you measure resistance between pins, two of the pins will appear to be shorted - this is normal and shown on the picture. The tab is also electrically connected to the centre pin... The top left pin of the hn4a51j is also connected to the bottom middle pin on the ocb and will therefore also measure as a short. The pmsta devices have 3 digit case codes the first digit being the place of manufacture, the kst devices have two digit codes. Be aware Both the pmsta42 and kst42 have codes 1D but the pmsta42 has a t or other letter before the 1D for the manufacturing location. voltage ref should have 10V between pins 4 and 6 If you test the board by itself it must have capacitance connected to the output in excess of 20uF in order to regulate and not do strange things like increase the output voltage when the load increases. When setup for 15V output, input voltages bellow about 1.7V should result in very little current draw <1mA and no leds lit . At around 1.7V input D2 show glow dimly and increasing the input voltage should result in D2 glowing brighter, the current draw increasing and the output voltage increasing. When D2 is fully bright the current draw should be about 10mA. At about 17.5V input D1 should begin to light . Increasing the input voltage further will make D1 brighter and the current draw increase towards 10mA current the draw when the led is fully bright. At around 18.3V input the output should stabilise at around 15V and increasing the input voltage further should have no effect on the output voltage or current draw. The second 78xx I built required 0.2V more to regulate fully despite having a 8mV lower output. Load testing Expect approximately a 23mV decrease in output for each 100mA of load current drawn from the gr78xx. At 200mA the components on the board should be warm but easy to touch and leave your finger on. The MJW211 should also be a little warm. NOTE the metal tab of the MJW is live so don't short it to something. Voltage drop under load test, no heat-sinking, MJW211 close up against the pcb, 18.3V input. The drop in output voltage is the same using a 47uF output cap as 220uF. 100mA 23mV drop 200mA 46mV drop 300mA 69mV drop 400mA 93mV drop 500mA 116mV drop (note tab of mjw gets too hold to touch for more than a moment after a few minutes of this load. heat-sinking recommended) The second 78xx I built had voltage drops within 2mV of the first. The voltage drop under load is a bit more than a traditional 7815 to-220 voltage regulator under the same conditions. Removing the load results in the output voltage of the gr78xx going back to within 1mv of the original no load output almost instantly, even from the hot 500mA load. the voltage drop is fairly linear with load. Otuput voltage drift under constant load as the device heats up or cools down is very low. LED direction verification for gr78xx lower led D2 multimeter in diode check mode red probe on top of led black probe on bottom (as indicated in photo bellow) you should get about 0.89V drop led will not light. probes reversed meter should say OL upper led D1 multimeter in diode check mode black probe on top of led red probe on bottom (as indicated in photo bellow) you should get about 1.66V drop led will light. probes reversed meter should say OL 79xx build notes All polar caps, Zener and LEDs are in the opposite orientation to the 78xx, All resistors are in more or less the same positions and orientations as the 78xx, all transistors that are xx42xx become xx92xx and visa versa. NOTE in the BOM Q6 and Q4 appear to be the same on both the 78xx and 79xx however, on the silk screen the physical positions of Q4 and Q6 swapped in all other cases the transistors change in the BOM rather than the silkscreen designations moving. The opamp and LT voltage reference are in the same orientation as the 78xx. The HN4A51J becomes HN4C51J and the MJW211 changes from 94 to 93. All positions that hold a KST device continue to do so and the same is true for the PMSTA. Only the type of device swaps from NPN or PNP i.e. from kst42 to kst92 and visa versa or pmsta42 to pmsa92 and visa versa. The 79xx has similar load behaviour to the 78xx. LED direction verification for gr79xx lower led D2 multimeter in diode check mode red probe on bottom of led black probe on top (as indicated in photo bellow) you should get about 0.89V drop led will not light. probes reversed meter should say OL upper led D1 multimeter in diode check mode black probe on bottom of led red probe on top (as indicated in photo bellow) you should get about 1.66V drop led will light. probes reversed meter should say OL Edited June 14, 2021 by jamesmking R1 incorrectly positioned in 79xx, spotted by Joamat 5 1
mwl168 Posted June 18, 2020 Author Report Posted June 18, 2020 (edited) May I suggest moving the build notes and related discussions to the build thread? Edited June 18, 2020 by mwl168 1
JoaMat Posted June 21, 2020 Report Posted June 21, 2020 On 6/18/2020 at 11:19 AM, jamesmking said: Shouldn't R1 be between Q1_source and -Vout? 1
HatIsMyFriend Posted June 25, 2020 Report Posted June 25, 2020 Got the boards this morning, thanks a lot!
judo Posted July 7, 2020 Report Posted July 7, 2020 Anybody else who have not received the boards yet?
Discom Posted July 7, 2020 Report Posted July 7, 2020 I've not received them yet either. I suspect they are stuck in customs. Either that or the local post dropped them off at a pickup point, forgot to tell me about it, and happily shipped them back after a week, which has happened before. Or they've disappeared...
judo Posted July 7, 2020 Report Posted July 7, 2020 1 hour ago, Discom said: I've not received them yet either. I suspect they are stuck in customs. Either that or the local post dropped them off at a pickup point, forgot to tell me about it, and happily shipped them back after a week, which has happened before. Or they've disappeared... Yes, these are the options about here(Hungary). Not usual to lose something but the times are not usual too. 12 minutes ago, MLA said: Mine just cleared customs... So there was some delay we will see. Thanks for the answers!
steefdebruijn Posted July 7, 2020 Report Posted July 7, 2020 Netherlands here. Package not arrived yet.
johnwmclean Posted July 7, 2020 Report Posted July 7, 2020 Hi Michael, my package arrived safely, thanks very much for all your hard work.
mwl168 Posted July 8, 2020 Author Report Posted July 8, 2020 Thanks for letting me know John! Hope all will receive your packages soon. I have no clue how much time the packages take to reach different countries/recipients based on past experience - there seem to be quite a bit of variance. Sometimes the customs plays a part and I was also warned that the COVID pandemic may cause some delay as well.
Makoto Posted July 26, 2020 Report Posted July 26, 2020 Got my borads as well, thanks for all of this!
mwl168 Posted July 27, 2020 Author Report Posted July 27, 2020 13 hours ago, Makoto said: Got my borads as well, thanks for all of this! Did it just arrive today?
MLA Posted July 27, 2020 Report Posted July 27, 2020 Forgot to post; my boards came in last week. Thanks!
judo Posted August 11, 2020 Report Posted August 11, 2020 My boards have arrived finally! More than two months from the US is a shipping time record. Thanks Michael!
jose Posted August 13, 2020 Report Posted August 13, 2020 Unfortunately my package has not arrived yet although I am used to long waits. 1
steefdebruijn Posted August 13, 2020 Report Posted August 13, 2020 I was about to declare my package lost but to my surprise it arrived at my doorstep today (Netherlands). thx for the GB Steef
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