51 cards hand-built in total
Wasn't that bad, I built them in batches of 6 or 8 at a time. TPA first, then test in the bed of nails jig. Then I'd grab a random SMT part from the box of parts and solder that part on all the cards, then grab the next part, solder that on, rinse, repeat. Once all the SMT was done I'd scrub them in isopropyl alcohol to get the flux residue off, then do the through-hole parts, then program and final test.
Reflow looks really attractive as parts placement would be a lot quicker without the soldering part involved, and it looks like the boards come out of reflow looking clean (is an alcohol wash necessary?)
Any advice you've got I'll happily take.
51 cards?
No flux removal required! That's worth the price of admission right there.
PM sent on the reflow topic.
BK
If you do burn your wiener, list of casualties will be the TPA (30V), 78L05/oscons/electrolytics (35V), and a 78L05 failure could blow the AVR and the Q1 FET. All repairable/replaceable, though replacing the TPA itself will be a pain in the *** as it's soldered to the PCB.
Have a good 4/20 over in BC, bud
Right back at ya! Hope you had a good one!
So I had a chance to reconfigure the supply during my lunch break.
12v 40VA transformer --> big bridge rectifier --> Nippon Chemi-Con CEW 3300uF 50v "Black Negative" -->amp. I selected this cap because it fits in the chassis (as opposed to the 30,000uF 100v monster).
Under "normal" listening levels (from quiet to moderately loud) the voltage holds at about 17.4v. At "very loud" volume the voltage dips to as low as 16v, but at this point driver excursion becomes the limiting factor.
Regarding hum; there is just as much as there was before - which I actually consider to be negligible.
12v 40VA transformer --> big bridge rectifier --> Nippon Chemi-Con CEW 3300uF 50v "Black Negative" -->amp. I selected this cap because it fits in the chassis (as opposed to the 30,000uF 100v monster).
Under "normal" listening levels (from quiet to moderately loud) the voltage holds at about 17.4v. At "very loud" volume the voltage dips to as low as 16v, but at this point driver excursion becomes the limiting factor.
Regarding hum; there is just as much as there was before - which I actually consider to be negligible.
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A nice minimalist setup, with good results
If one is to spec a new transformer, select a 16V secondary to get you a little bit more headroom and up the VA rating to something like 60-100VA
An idea is use an old low power stereo as your chassis, just have to make sure the unreg is less than 28V. Also since the TPA is ground isolated you have to disconnect all speaker connections from (chassis) grounds
Yes, for speakers that can handle more power, I would choose something along the lines of what you describe. 16v (~22-24v after rectification) and 60VA (or more). TI's graphs show that 24v will get the best out of the amp. On the other hand, I am not certain I would ever hear a difference.
Maybe I'll dig through that pile of iron at the local electronics place if/when I get around to building speakers with more power handling. Still, I am very happy with the current setup. It plays really loud and remains very clean while doing so. The transformer cost me $6 (2 for $12 on ebay) and the rectifier and cap were harvested from a massive box of components I got from a guy on kijiji a couple of years ago, for $20.
Maybe I'll dig through that pile of iron at the local electronics place if/when I get around to building speakers with more power handling. Still, I am very happy with the current setup. It plays really loud and remains very clean while doing so. The transformer cost me $6 (2 for $12 on ebay) and the rectifier and cap were harvested from a massive box of components I got from a guy on kijiji a couple of years ago, for $20.
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Hi, Gary
I know you were going to use leftover boards/parts to fill late orders, but as the last guy to have paid (per post# 189), you probably just sent mine out last Thursday.
No reason to expect a problem and, slowish Canada Post service to my home... but I wonder if you could wait a bit longer to make sure that the original orders got delivered, before you fill those "new" orders?
Thanks, Ron
I know you were going to use leftover boards/parts to fill late orders, but as the last guy to have paid (per post# 189), you probably just sent mine out last Thursday.
No reason to expect a problem and, slowish Canada Post service to my home... but I wonder if you could wait a bit longer to make sure that the original orders got delivered, before you fill those "new" orders?
Thanks, Ron
power supply
Hi Cogitech,
Picture please? I got a used amplifier that I want to use for its chassis and transformer. The transformer is 110v AC input. I measure its output (unloaded) as 30v DC. I am thinking of getting a rectifier like this on ebay. Will it work to power 2 of Gary's wieners (I'm biamping the speakers). Is there some way to bring the DC power output down to 22V (+/- 2V) each for the 2 wieners? Thanks.
Hi Cogitech,
Picture please? I got a used amplifier that I want to use for its chassis and transformer. The transformer is 110v AC input. I measure its output (unloaded) as 30v DC. I am thinking of getting a rectifier like this on ebay. Will it work to power 2 of Gary's wieners (I'm biamping the speakers). Is there some way to bring the DC power output down to 22V (+/- 2V) each for the 2 wieners? Thanks.
You don't really need to spend your money on that unit. A simple rectifier like this is all you need. KBPC5010 1000 Volt Rectifier 50 Amp 50A Metal Case 1000V Diode Bridge | eBay
Then just add a fairly big smoothing cap. The two components can be had for very little money.
However, the resulting voltage in your situation will end up being 30v * 1.414 = ~42v. You would then need a regulator that can pull that down to ~24v. I am not certain what part (if any) can do this.
Another option (perhaps the best option if you want to use the chassis and transformer on hand) would be to build a simple half-wave rectification circuit, which would result in 15v * 1.414 = ~21v. All you need is a diode which can handle the expected current (5A?) and then throw in a big smoothing cap (as you would with the full-wave rectifier).
Look here Power Diodes used as Half-wave Rectifiers and scroll down to the "Half-Wave Rectification" section for more info. Then look at the final section which includes the smoothing capacitor.
Dead simple and cheap to build.
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Since you asked...
The red and black wires from both the rectifier and the capacitor are connected to the DC + and - terminals of the Wiener. I could have connected the capacitor (observing polarity) to the +/- DC tabs of the rectifier, too. Same thing.
An externally hosted image should be here but it was not working when we last tested it.
The red and black wires from both the rectifier and the capacitor are connected to the DC + and - terminals of the Wiener. I could have connected the capacitor (observing polarity) to the +/- DC tabs of the rectifier, too. Same thing.
30V ... AC/DC what is it? big difference!!
So lets use a 50A bridge, just in case
Regarding AC/DC, a very good point. If it is already DC, then no rectification is necessary. When I hear/read "transformer", I have trained myself to think AC-->AC.
Regarding rectifier, I just found one that looks like the one I am using, because I know it works. I have dozens of them, some larger, sitting here so that's what I use.
Nothing wrong with a little overkill, right?
But what do I know? I just figure this stuff out as I go along.
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I totally missed the part where Linkfan mentioned 30v DC.
I assumed AC, because he asked about a rectifier.
Linkfan, all you need to do is regulate that 30v down to ~24v. That should be easy enough to do. I just don't know enough to recommend the right part. I think an LM138/338 would do it, but not 100% sure. I was looking at the data sheet yesterday and couldn't figure out the difference between LM338 and LM138: http://www.ti.com/lit/ds/symlink/lm138.pdf
I only breezed through it, though...
I assumed AC, because he asked about a rectifier.
Linkfan, all you need to do is regulate that 30v down to ~24v. That should be easy enough to do. I just don't know enough to recommend the right part. I think an LM138/338 would do it, but not 100% sure. I was looking at the data sheet yesterday and couldn't figure out the difference between LM338 and LM138: http://www.ti.com/lit/ds/symlink/lm138.pdf
I only breezed through it, though...
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...this might be the ticket: 5 Amps 1 5 TO 32V Adjustable Voltage Regulator Module | eBay
I didn't look to see if there are cheaper ones, but I bet there are.
I didn't look to see if there are cheaper ones, but I bet there are.
Doh! My electronics knowledge has rusted for 30 years. It is 30v AC of course. The amp is a Knoll MA205. I don't know how to upload images to show you what it looks like inside.
Please take me as a total beginner and give me a list of parts to buy. You guys are a fantastic bunch.
Please take me as a total beginner and give me a list of parts to buy. You guys are a fantastic bunch.
It's tricky, because full-wave rectification takes you all the way up to ~42v. The LM338 module discussed above cannot handle 42v input. Not sure what part can...
Half-wave rectification might be the way to go. You essentially lose half your power, but at least it gets you into the right voltage region for the Wiener. There are other "negatives" about half-wave rectification, as discussed here: Half Wave Rectifier Circuit with Diagram - Learn Operation & Working
All you need is a 5 amp diode, a resistor and a fat capacitor for smoothing. Follow the circuit diagrams on that page to build it. The resistor needs to be a value greater than the forward resistance of the diode.
Half-wave rectification might be the way to go. You essentially lose half your power, but at least it gets you into the right voltage region for the Wiener. There are other "negatives" about half-wave rectification, as discussed here: Half Wave Rectifier Circuit with Diagram - Learn Operation & Working
All you need is a 5 amp diode, a resistor and a fat capacitor for smoothing. Follow the circuit diagrams on that page to build it. The resistor needs to be a value greater than the forward resistance of the diode.