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Showing content with the highest reputation on 05/02/2021 in all areas

  1. Got home from vacation very late last night/early this morning. Decided to enjoy the one nice day for the next several.
    7 points
  2. Got my new front brake pads put in. Much better; now if I brake hard, that motherfucker will stop in a hurry.
    5 points
  3. I'm stuck inside working all day but at least I was able to arrange for the Chairman of the Board to come by and play a set.
    4 points
  4. 4 points
  5. Woo, looks like the CPU board is working! Currently set at 20.29 Hz for 33.33rpm output. Got the front panel also working and now just need to solve the issue of the reflective IR Sensor (or go back to a magnet) - which I think might take a shroud to try and reduce stray light. The second display will then read out the actual platter speed as measured by the tach. Then I can adjust the speed in a feedback loop (PID). Still smells like a busted cap though
    4 points
  6. Actually, no but good question! I have three of these identical looking PSUs now - keeping the simple aesthetic. The PCB could be mounted that way though, but in my “case” it won’t. I plan on logging hours the TT is on (to estimate stylus wear) and how accurate the speed control is. I will retrieve that data off the USB port if needed. Here it is in action. The top display is the actual platter speed. Next to write the auto adjusting code. https://imgur.com/gallery/UXOn6R9
    3 points
  7. Salted Caramel, Lavender Blueberry and Lavender Blueberry, German Chocolate from http://www.sweetscoopsicecream.com/
    2 points
  8. Thanks. I think I'll pick one up. I've had the amp playing from 9:00 this morning (did I mention it really sounds great ) and batteries were down to 9.8V at 3:20PM. They are not perfectly balanced so one battery is at 3.1V which is below the minimum 3.3V recommended. So looks like I'm getting a little over six hours with these batteries (3x2000mAH). I can look for larger batteries and also play with some optimizations. I've also been running additional 5V and 3.3V supplies for the DAC that consume extra power. They're not needed for just the analog input. The balancer should have kicked in to turn off the battery pack, but it didn't. I suppose it would have at some point, but I plugged it back in to charge. I have a different and smaller balancer that I'm going to try. Maybe that will do a better job.
    2 points
  9. It was not one of Quad's finest moments that is for sure. And on one channel only, an electrolytic is right above a power resistor, and cooks. So remedial action is to replace the two 3.3k resistors with something that can actually dissipate 0.35W, and space above the board anyway. And remove the dead electrolytics and mount replacements on the other side of the board away from the heat. Then remove the crowbars and fit a half way decent DC offset disconnect. Like this https://neurochrome.com/products/guardian-86 or this http://www.velleman.co.uk/contents/en-uk/p193_m4701a.html or this http://www.signaltransfer.freeuk.com/protect.htm just for starters.
    1 point
  10. We've debated what we would do. Hard to know if it helps or hurts selling the house. (Which is not on the horizon at this point) You do recall that this kitchen renovation project started in 2018. Is that a thing to do? I'd imagine wood movement will crack the glue. I think I'd put a dot of silicone and let its weight hold it in place. Or else drill little mortises into the quartz and add some corresponding tenons to the frame to keep it from shifting
    1 point
  11. Attempt #1 in gluing quartz to wood. Definitely should have worked with the handplane before attempting this glue up. Not sure how well it is going to work. Also hung up the clampseses.
    1 point
  12. Doug sistered his floor joists as well. The 4 x 4 posts will certainly strengthen it a lot.
    1 point
  13. The kitchen floor here was pretty out of whack before the remodel, but they doubled up some of the joists in the basement and used 4x4 posts to help level it out a bit.
    1 point
  14. I have a feeling Doug's tolerances are closer than that.
    1 point
  15. At the bottom of the feet there are cutouts for adding leveling blocks to compensate for floor variance. I put the cabinets in place, level them with shims, measure the spaces with feeler gauge blocks and then plane down small pieces to fill in the gaps.
    1 point
  16. The amount of lumber I would waste trying to figure out how to properly do those joints in unfathomable. That thing is awesome.
    1 point
  17. Took a break from work to empty and scrub clean the kitty litter box. Put it on the patio to dry and when I returned some birds had used it for target practice. 🤦‍♂️
    1 point
  18. Great to hear about the new measurements which are in line with genuine 2SK216. When testing field effect transistors DY294 manual says “A short circuit should be formed between G and S pin. Otherwise the transistor can easily be damaged.” To make testing of k216/j79 a bit easier I’ve made a simple adapter for the DY294 tester.
    1 point
  19. Some more good progress. The amp is up and running I've got two issues on the board, but the amp, power supplies and USB-C PD / battery management are all working great. The wires going to the pot are temporary. There'll be a board for the analog/DAC inputs. The PD chips are small with lots of pins on them. I'm surprised I could solder them Lots of 0402 chips on the right side of the board... Here's the amp running with the battery (I need to have the input board done before I can put the batteries in the chassis). This is with the amp running and USB-C charger plugged in. Below, it is sending .18A to the batteries. The battery management will stop charging once the batteries are at about 12.5V. It drops the current as it gets closer to a full charge. With the charger plugged in and batteries fully charged, it doesn't draw any power from the batteries. At the moment, it negotiated 5V from the charger (source) and is boosting it to just above the battery voltage. If we wanted, we could source power so it could charge you phone too. I'll do a drawdown test tomorrow to see how long it will run on a charge. Overall, I'm very please with this amp. Kevin's amp design is fantastic. I've been listening to it for the last several hours with my SR-007's
    1 point
  20. Longish term modern DIY T2 reliability. I estimate its been used around 8+ hours (and more often than not 12 hours) a day almost every day since I built it. yesterday I took it apart for cleaning. I noticed all four 140K resistor strings connected to the voltage reference in the virtual batteries where somewhat discoloured.... hmmm... on further testing I found the D24 led on both channels did not light up at all not even dimly. :-(. but the amp seemed to work and sounded good. (on the left is a brand new resistor from the same pack as the 140Ks I removed from the virtual batteries.) I checked also psu voltages - good. I measured the voltage across the D24 led- about 1.4V. When the amp was originally built these leds definitely glowed as strongly as the others. All the leds where tested before soldering in and were from the same bag I even hand matched them just for overkill. The D24 leds are part of the circuit that provides base voltage and current to transistors that provide feed into the virtual batteries. I checked the virtual batteries - all were 741V on startup and the adjustment pots could adjust the output. So the batteries look good despite the slightly cooked resistors. I removed the voltage references and tested them in a glden reference LV - all good. The discoloured resistors can be explained by the fact they have about 0.423W flowing through them excluding base current draw from the 2 transistors and are on the underside of the board with little airflow - maybe1W would be better or some airflow holes in the pcb, or mount them to the topside of the pcb. So I decided to de-solder the 140K resistors for measuring and the 140K resistors have drifted slightly but all measure within 141.5K. So a little cooked but probably not the case of the problem. But why are the leds not lighting.... Looking at the circuit diagram the D24 leds should get about 0.5mA current excluding any draw from the bases of the transistors. (560V / (560K *2 resistor string to ground). I used the exact SAME leds for the other positions and it also looks like those leds get about 0.5mA excluding base transistor draw and they glow nice and bright. I de-soldered the leds and tested the D24 resistor string to ground. They spot on resistance and have not been damaged or drifted and so should provide 0.5mA current draw through the led. However the desoldered D24 leds would not glow at all with diode check on my brymen BM869s multimeter but do pass current and are not open or shorted. I tried my keithley 2015 in diode check mode (it has adjustable test current) and got absolutely no glow at 10 or 100micro amp but did get strong glow at 1mA - same situation on both D24 leds. I tested my remaining leds from the same bag and they glow on the brymen admittedly fairly dimly, and glow on the keithley at 100 micro amp again dimly but visibly. (I did test all of them on the brymen before soldering into the amp). So the leds in D24 have degraded over time . I used the same leds in the other places in the amp and they are all fine. This would explain why the batteries are working but the leds are off.... So the plan is to do some more testing on the leds and replace them with another model. But what's causing the leds to degrade in brightness on the -560V rail when the others have not? any ideas? regards and and I apologise for the long winded post James Update: I replaced the D24 leds... they now light brightly with a voltage drop across them of about 1.7V. I replaced the resistor strings with the same resistors but now placed on the top of the pcb, raised from the pcb by about 1cm. After a ten minutes with no lid on the amp the resistors reach 65C on the top and 71C on the sides. So its easy to see how on the underside of the pcb with the lid on they could reach temperatures which could cause discolouration.
    1 point
  21. So on the original T2, there are a lot of .5 watt resistors on the bottom of the board, lots of holes, lots of internal heatsinks, tubes completely inside, no ground plane of any kind, and the exterior gets to 55C. The inside gets to more like 75+C. On my T2, everything that generates more than .5 watt (with 2 resistor exceptions) is mounted directly to the heatsink. While more holes in the board is probably going to be a good idea, the tubes generate thermal flow that will pull air thru the unit. A thermal design program i'm playing with basically indicates that more holes is not always a good thing as it reduces air flow. I gave the board layout to the master (justin) and he will do some cleanup. Otherwise in less than 2 weeks i'm going to send the boards out.
    1 point
  22. The rated power for a resistor is in free air. So to push 0.42W into an 0.5W rating, it absolutely needs to be spaced from the board to allow convective air flow. If tight to the board, there is a hot area where it contacts the board and long term will lead to resistor failure. In fairness, even Tektronix have been guilty of that, with the board discolored under some resistors. Quad was less successful in the 405 power amp, where a 3.3k resistor feeding a 15V zener in underrated. In due course it fails open, putting one output to rail. The ridiculous crowbar then fires and short circuits the output. The power transistors and drivers then instantly fry. Then the crowbar itself blows up. Then the fuses blow.
    0 points
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