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Hello Brian or Russ, may I ask a few questions?
Questions regarding the power supplies:
(a) Both the LCDPS and the LCBPS show 220 uF caps in their schematics, but the text mentions six 470uF low-ESR apacitors. Which is correct?
(b) What is the difference between these two supplies? They seem identical, except that the LCDPS brings out the two voltages with seperate grounds, which is highly preferable. So why is there still an LCBPS? Did I miss something here?
(c) In the Buffalo combo pack, you include an LCDPS for the Buffalo and an LCBPS for the IVY. Why? Couldn't I use the same or another LCDPS for the IVY?
Other questions:
(d) Does the OPUS-version, as I can currently order it, already have the newer WM8741? Or is that something that comes in the next run of boards?
(e) When do you expect the SPDIF-receivers back in stock?
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a) I believe we are using 470uf now. Either value would work fine. b) LCDPS is a dual power with two separate positive voltage outputs. LCBPS is a single bipolar supply with a positive and a negative voltage and shared GND. c) Because IVY needs a bipolar supply and the Buffalo needs two positive supplies. d) We have shifted to the WM8741. e) We just got a new round of PCBs in so they will be ready to order soon. Cheers! Russ Edited by user Wednesday, July 2, 2008 6:36:45 AM(UTC)
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Ok...
(a) Either is fine, but I supply 470uF FM for better smoothing and higher reserve (plus they fit nice)
(b) The LCDPS uses two LM317 (positive) regulators. The LCBPS uses a LM317 (positive) and a LM337 (negative). You can easily wire a LCDPS for use as a biploar supply by tying one side's positive output to the other side's negative output, then using that tied output as GND. We created the separate bipolar supply to make it easier for builders. It also takes a lot less explanation and harder to make wiring mistakes.
(c) You would need two supplies either way. If you tried to use the same LCDPS to power both you would end up with a short when joining the two supply sides on the IVY. You could use two LCDPS wired as above, or just one of each, as we supply.
(d) All Opus DAC modules from here on out use the WM8741, unless someone requests a WM8740 version (I still have a few chips left). This includes yours.
(e) I have boards now. I just need to build up some inventory.
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I will be building a supply for a Squeezebox SB3, and was
thinking of using a LCDPS for the 5VDC. Since I need only
one voltage, could I parallel the outputs, carefully
adjusted to 5V, or would the sides 'fight' one another?
Also, for a surface-mount newbie, I could use some hints on
soldering in the little coils. I chased them around the board
for a long while while putting together the supply for my Opus.
I'm sure there's a better way than a massive dose of tranquilizers
to damp my palsied hand.
Thanks,
Skip
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That was a quick answer, thanks a lot. So, as I thought, the LCDPS is really universal. It may be configured as two positive voltages or two negative voltages or as bipolar voltages with common ground.
May I take the opportunity here to extend my thanks to you, Russ and Brian, for doing such excellent work and sharing it with all of us!
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Paralleling the sides would be a recipe for disaster in my opinion. From what I know of the SB, though it specs a 2A supply, it never actually draws more then 1A.
The best way I have found for mounting the coils with regular solder goes like this:
- add a small dab of solder to one of the four pads
- plop the coil into position and hold it down with something (tweezers, tip of some needlenose pliers, etc)
- stick the tip of your soldering iron against the solder/pad/coil junction until the solder "grabs" the part, then remove heat but keep holding the coil until the solder cools
- now that the coil is held in place by the first joint, solder each of the other pads
- go back and solder the first pad to make it look nice
A dab of flux on the coil pads can help as well.
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Sorry, maybe this is trivial, but I didn't find any info on it:
If I have two power supplies, one for the buffalo and one for the IVY, may I connect the two supplies to the same secondary transformer windings, or do I need a transformer with separate windings?
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You need separate windings to prevent a short.
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Brian/Russ,
I currently have a Buffalo/Ivy combo on order and need some clairifcation on the PS. The toroids that you list are 15 VA 15V + 15V. The little knowledge I have on them, along with a cut sheet from Avel, indicates that if I hook-up the primaries in parallel to 115 VAC supply and the secondaries in parallel, I will get a single output of 15 VAC @ 30 amps. If I hook-up the primaries in series to 115 VAC supply and leave the secondaries independent, I will get two seperate outputs of 15 VAC @ 15 amps. So my question is, since I will have to drive a LCBPS and a LCDPS, is the required amperage of each such that a single toroid (the 15 VA that you carry) will suffiently drive the two PS. This becomes increasingly important as I need to build a PS for a Squeezebox as well as a potential electronic crossover for a bi-amp and I really would like to avoid having to find real estate for 6 toroids if I couuld get by with just 4 or maybe even 3. Thanks.
Devodave
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I'm also interested in the answer to devodave's question above.
I'm in the processing of assembling the LCDPS and am wondering why conventional diodes (1n4007) are furnished instead of fast recovery diodes (uf4007). In other applications I have heard a marked improvement after upgrading the diodes.
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After doing a loy more investigating, I believe my approach will now be a single, custom wound toroid from Maryland Toroids with mulyiple secondaries to drive each load. As to the LCDPS, can I assume that it is rated at 1-2 amps max, based on the diodes provided? Since I also want to provide 5.0V for a SB, which requires 2-6 amps (depending on who you read & trust), could a LCDPS board handle that current?
By the way, the Buffalo and IVY boards and their PS look beautiful and I can't wait to get them completed.
Devodave
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The current the LCDPS can supply is limited by two main factors.
The first is the voltage drop across and the power dissipation of the resistor in the CRC, the practical limit here is something like 500ma with 15V secondaries and the stock supplied Rs. You can change or simply jumper the resistors in the CRC to get more output current.
The second factor is really the VREG IC (LM317) itself which is limited to 1.5A.
Thanks for the kind words.
Cheers!
Russ
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Hi Guys,
I'm trying to adjust a LCBPS to output +-12V. I have a 15V AMVECO transformer that is putting out 18V AC into the PS. When I measure the DC output I get between 17V and 24V stop to stop. I'm pretty sure I have all the parts in the correct orientation. If I've made a mistake where is it likely to be? If I haven't made a mistake can I change the out put by changing the values of R3 and R4? If so what values will work? If not what can I do?
Thanks for the help.
And thanks for the kits. They are very high quality.
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Hi,
These symptoms sound typical of one of two problems.
1) The VREGS in backward(this has only happened once that I know of)
2) the VREGS are swapped (LM317 where LM337 should be and vice versa).
Is it one of those two?
Cheers!
Russ
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Hi Russ,
Yes, I swapped them. Thanks for the quick reply. Now I get to test my desoldering skills.
Steve
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Hi Russ,
I put the VREGS in the right position and now every thing is working fine. Thanks again for your quick help. It saved me hours of staring at the board trying to figure out the problem. :-)
Steve
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No worries. :)
Glad to help.
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Hi! Anyone who can provide a picture or the scematics for the LCDPS?? The ones on the TP-webside are of the LCBPS... One of my outputs are dead. Think I might have mounted D1 the wrong way 
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It looks like the LCDPS pics are correct now. :)
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Thanks Russ!
My D1 was mounted the wrong way. Have corrected that, but the output is still competely dead. Any suggestions to other mistakes I might have done?
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