cspirou
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Posts posted by cspirou
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I assume the feedback resistors will be left off so we can set our own voltage? Or could we request different voltages?
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Interested as well. Also fine with unpopulated PCBs
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14 hours ago, Kerry said:
I've been utterly swamped at work, but I can get the Gerbers over to Kevin in the next week or so. I'd love for someone to do a group buy for assembled boards. I don't have the time for that.
Where would be a good place to get boards assembled?
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1 hour ago, masamoto said:
For some reason, my transformer just died. I had a 230v/2x24v with 50VA it get's a little warm but that's it normally.
I use it to power a 20V GRLV for a Susy. was that too much for it? I was sure that would be enough.
With 24vac you are getting 33Vdc before regulation. Thats a 13v drop and far more then you need. The problem though is for a given VA rating the current capacity goes down as the voltage goes up. You probably sourced too much current and burned out the windings.
get 2 x 18v instead
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True, not to mention that it's not even up to it's running temp.
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Thanks! Although I think its more likely the 10k feedback resistor is off by 5 ohms. Also I did a shitty job soldering that particular resistor. Redoing it might give me a better result. Or not.
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Success! After a few days of dealing with the regulators I finally got them soldered in properly.
+V: 20.00V, -V: -20.02V
of course the 0.02V offset is super annoying even if it is within 0.1%. I calculated that I would need to add a 23.8 Mohm resistor in the AOT spot to adjust the voltage to -20.00V. Not really worth it, although I might just add it to my next Mouser order.
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5 minutes ago, Pars said:
It shouldn't unless you decide you wanted to change voltages.
Thats only for the positive regulator. The negative regulator uses a feedback resistor to determine the voltage.
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Okay, I think I fixed it. I wont know for sure until I test it later tonight.
Just one question. The pins on the bottom of the negative regulator are bridged and I was having a hard time removing the excess solder. Then I noticed that all those pins were connected to the ground plane anyway. Does it matter if they are bridged?
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My brother got free next day shipping on his very first Mouser order. He also lives in Houston and Mouser is based in Dallas so I dont know if that had anything to do with it.
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32 minutes ago, mypasswordis said:
If you don't want to use a hot air rework station then you're going to need a stencil of that package and to make sure the oven is flat. Hot air station can be had for like 50 bucks
Believe me, I learned my lesson. If I attempt soldering this sort of chip again I'm using a stencil. I found them for $10.
http://www.kr4.us/QFN-20-0.65-mm-pitch-5-x-5-mm-body-3.1-x-3.1-mm-pad-Stainless-Steel-Stencil.html
Has anyone been successful applying the iron directly to the heatpad like in this video?
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The soldering iron I use has dual irons (one fine, one chisel) so removing the capacitors isnt so bad. I assumed I couldn't feed solder because the pins are under the chip but I'll try it out.
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So ive been using a toaster oven for reflow. I did a test and the result were promising. I was a little too confident and soldered the QFN chips for the Dynalo mini. First time I used a little too much paste and ended up with something like this.
the positive regulator is out of alignment and the negative regulator has the bridges. I decided to reflow a second time and nudge the chip into place. Now it looks like this.
i thought my problems were solved but when i powered up the positive regulator I only meaured a voltage of 7.87 V instead of the expected 14.4V. This means that only one of the 6.4V pins soldered. Very frustrating.
So what I am wondering is how many times can you reflow a board before the components are affected? Should I remove the capacitors first? I would prefer to use a hot air station but I dont have one.
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Thanks @luvdunhill! I'm using the buffer with the ubal/bal board which have a 1.3kohm resistor to ground on the output so i don't think an additional resistor is necessary. Plus I already have the PCBs and the pins match.
I am interested in buffers for another project though. Ill let you know.
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So I thought I would try out reflow oven soldering with a toaster oven.
The AMB regulators for the Dynalo Mini are $40 whereas the toaster oven was practically free. I figured trying to solder with the toaster would be worth a try. It would also help with all the other SMD projects I have. I don't have a controller for now so I did it manually. As a test I bought an SMT adjustable power supply kit from Nightfire electronics.
I had a little too much solder for the LM317 and one resistor didn't self-center but I'm pretty satisfied with the result.
I'm thinking about using this for the R2R attenuator board. Anyone know what the procedure is for doing reflow on 2 sided boards?
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When matching transistors do you only need to match complimentary pairs? Or do all the transistors on one channel need to be the same?
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Damn, i wish I knew chinese.
I see you made the TKD version @astro, would you mind posting the front panel layout?
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There's a fuse near the switch.
Nice work @astro! Where did you do your casing? Are those temperatures inside the enclosure? Are there holes underneath?
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1 hour ago, Pars said:
Does it do hfe? If not, it would be kinda worthless for matching transistors. Not clear from the write up what exactly it does do.
Sent from my iPhone using TapatalkThey should be able too. All these transistor testers are based on some open source project
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1 hour ago, justin said:
Verical has stock of both 3324/1312 and i'm sure some are on ebay too
i also have a lot of them
Verical has 2sc3324-GR but not 2sc3324-BL. KG mentioned that the highest hfe should be used which is the BL version.
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Digikey says that 2SC3324/2SA1312 is NRND and is recommending 2SC2713/2SA1163 as a substitute. Any reason why I wouldn't be able to use the 2SC2713/2SA1163 transistors for the unbalanced/balanced board and diamond buffer?
Comparing the datasheets for 2SC3324 and 2SC2713 it seems like the 2SC3324 has a lower noise figure, but otherwise have identical specs. 0.2dB and 1dB max vs 1dB vs 10dB max respectively. Seems like I should go for the original pair while I still can. Too bad it's backordered on Mouser until March.
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I got lucky and was able to make a small order. Minimum order is 1000 pieces. If there was a group buy with a minimum of 20 each we might be able to reach that. A lot of people bought multiple pots so maybe someone is kind enough to sell one to you.
otherwise it’s probably better to do the version with the TKD pot, which you can order direct. Or air wire an ALPS pot like someone else here did.
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On 8/31/2017 at 9:01 PM, Skooby said:
I took a stab at Mouser BOMs for the diamond_buffer and unbal_2_bal SMD boards. Can someone kindly enough to check and correct the BOMs? Many thanks!
**** Edit ****
The below lists hadd these changes (thanks to mypasswordis!):
LED from 2V to 1.9V
300-Ohm LED resistors from 250-Ohm
0.1uf C2/C3/C7/C8 caps to 0603 package
10uF C1/C4 to X7R
Other note: OP27G U1/U2 can be changed to other op-amp
**************Unbal_2_bal SMD
Mouser # Description Order Qty.
757-2SC3324GRTE85LF Bipolar Transistors - BJT Audio Freq Low Audio Freq Low 7
757-2SA1312BLTE85LF Bipolar Transistors - BJT PNP Trans -0.1A LN -120V VCEO 7
284-APC1206B1K00N Thin Film Resistors - SMD 1KOhm 0.1% 1206 25 PPM 4
667-ERA-8AEB103V Thin Film Resistors - SMD 1206 10Kohm 0.1% 25ppm 12
667-ERA-8AEB132V Thin Film Resistors - SMD 1206 1.3Kohm 0.1% 25ppm 2
647-UWX1E101MCL1 Aluminum Electrolytic Capacitors - SMD 25volts 100uF 8x5.4 20% 2
584-OP27GSZ-R Precision Amplifiers LOW-NOISE PREC IC 2.8V/uS 2
581-06033C104K4T4A Multilayer Ceramic Capacitors MLCC - SMD/SMT 25V .1uF X7R 4
710-885012209028 Multilayer Ceramic Capacitors MLCC - SMD/SMT 2
710-150120SS75000 Standard LEDs - SMD WL-SMCW SMDMono TpVw Waterclr 1206 4
603-RT1206BRD07300RL Thin Film Resistors - SMD 1/4W 300 ohm .1% 25ppm 6Diamond_buffer SMD
Mouser # Description Order Qty.
649-68016-404HLF Headers & Wire Housings 4POS R/A HDR SnPb 1
279-CPF1206B10RE1 Thin Film Resistors - SMD CPF 1206 10R 0.1% 25PPM 1K RL 4
279-CPF1206B24R9E1 Thin Film Resistors - SMD CPF 1206 24R9 0.1% 25PPM 1K RL 2
756-PCF1206R-20KBT1 Thin Film Resistors - SMD .125W 20K ohm 0.1% 25ppm 1
757-2SC3324GRTE85LF Bipolar Transistors - BJT Audio Freq Low Audio Freq Low 4
757-2SA1312BLTE85LF Bipolar Transistors - BJT PNP Trans -0.1A LN -120V VCEO 4
710-150120SS75000 Standard LEDs - SMD WL-SMCW SMDMono TpVw Waterclr 1206 2
603-RT1206BRD07300RL Thin Film Resistors - SMD 1/4W 300 ohm .1% 25ppm 6
Another edit to your BOM. The transistors should be the BL type, not the GR. So the 2SC3324 transistor should have mouser part 757-2SC3324BLTE85LF
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goldenreference low voltage power supply
in Do It Yourself
Posted
Very nice @Kerry! That pinout looks compatible with the Dynalo Mini board.