Will
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Post by Will on May 17, 2009 15:37:17 GMT
Hi Guys, you've been enjoying yourselves! After a marvellous day window blind shopping my thoughts are this. The trimpot that I have normally used is the offset leg version, in-fact I had to order the in-line version in for the class A. This is why I used it. No problem at all to place an additional hole to allow the use of both. Heatsinks, I like them big as, even if only dropping a couple volts. I have some of the ones here www.rapidonline.com/Electronic-Components/Semiconductor-Hardware/Heatsink/Compact-vertical-TO220-TO218-TO247-heatsink/60146/kw/aavid all the same width, but differing in height. As this board isn't going to be produced, but will hopefully be made by etchers (and hopefully encourage some to try it - see an upcoming post on that ) they will be drilling the 0.8mm and 1mm holes for the components (search ebay for UKdrills - they sell 0.8/1mm drills for not a lot in packs of 10). If you wish to use lugged heatsinks, you can drill holes for the heatsinks freestyle, all depending on what you are using. This is after all, DIY electronics. I'm leaving marking for any lugs off, for that reason. Led resistor - good idea. I used an in-line resistor for my scha, but it haunts me. I'll place a tap off point, with resistor, after the rectifiers across the +/- to spread the led draw (all 2mA!) across both lines, but before the main filtering cap. I sure the led wont mind! Yes, you may be dropping a large voltage, so I'll make the resisitor a large'un. I fed the led on my SCHA this way, and now one has died yet. Extend the mask to reduce the the amount of copper you need to etch? Too right! It was there before, and isn't now. Eagle seems to be a bit...'female' sometimes, and will do something one time, and not another. I'll try and re-introduce this. Keep the ideas coming. We may end up with a board worthy of the JLH PSRR yet! (shameless plug)
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robertkd
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Post by robertkd on May 18, 2009 10:30:45 GMT
See,.. Will likes em big too, you know what I always say the bigger the heatsink the cooler the silicon Robert
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Post by Deleted on May 18, 2009 10:54:15 GMT
See,.. Will likes em big too, you know what I always say the bigger the heatsink the cooler the silicon Robert Robert The one from Jaycar (HH8544) that I previously mentioned IS approx the same size and thermal resistance as the Aavid 38-4.and are the ones I am using in my Class A preamp with >100mA bias, which if my memory serves me correctly, is substantially more than you are running your similar SC HA output devices at ? Alex
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robertkd
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Post by robertkd on May 18, 2009 11:14:13 GMT
See,.. Will likes em big too, you know what I always say the bigger the heatsink the cooler the silicon Robert Robert The one from Jaycar (HH8544) that I previously mentioned IS approx the same size and thermal resistance as the Aavid 38-4.and are the ones I am using in my Class A preamp with >100mA bias, which if my memory serves me correctly, is substantially more than you are running your similar SC HA output devices at ? Alex yes, so that means you output devices are substantially hotter then mine, it also means if you went the 8.6 c/W it would be cooler Yes I'm currently running about 35mA still only about 0.6W vs your 1.5W Robert
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Post by Deleted on May 18, 2009 11:44:55 GMT
Robert They are already running quite cool enough, thank you. Besides, the HFE and Ft is a bit higher when they aren't at Pommy beer temperature. Alex
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robertkd
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Post by robertkd on May 18, 2009 13:13:07 GMT
Robert They are already running quite cool enough, thank you. Besides, the HFE and Ft is a bit higher when they aren't at Pommy beer temperature. Alex tubes work better when they warm up too
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Will
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Post by Will on May 18, 2009 21:29:42 GMT
OK, for those of us who like to etch, extra copper, the ability to use either in-line or offset trimpots and pads for an LED resisitor. to use the pads for the led resistor, wire link pad 7 to 8, install your resistor, and then pad 8 to the LED anode, pad 6 to the cathode. and a link to the etching file. www.mediafire.com/?m4tgejymzdnthe other download links have now been turned off. Board dimensions are 3" x 2.7"
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Post by Deleted on May 21, 2009 2:05:43 GMT
Hi Will,
I like you first PCB the best. Thrash the newer one.
Making a universal PCB never works, it has been attempted many times, which proves it can't be done.
regards Greg
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Post by Deleted on May 21, 2009 2:23:10 GMT
Hi Will, I like you first PCB the best. Thrash the newer one. Making a universal PCB never works, it has been attempted many times, which proves it can't be done. regards Greg Greg That's what happens when it's designed by a committee. Which do you prefer, Post 1, or reply 9 ? Alex
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Post by Deleted on May 21, 2009 4:30:00 GMT
post 1.
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Will
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Post by Will on May 21, 2009 8:01:53 GMT
Hi Greg, glad you like one of them! To be quite honest, I'm happy enough that people come up with suggestions and show an interest. A LM317/337 based board is hardly earth shattering in it's complexity, and I've built plenty on veroboard in the past. Now I'm building the class A amp, I wanted something a bit more permanent to power it, so came up with this layout. As I've 'taken' plenty from the RG in the past, I'd thought I would post this, just in case anybody wanted it. It developed due to other peoples suggestions, but at the end of the day, you cant please all of the people, all of the time. I have also been pleasantly entertained by Alex and Robert. I know which layout suits my own needs, and as you've shown a preference for the first, I've re-opened all of the download links so that members can DL whichever one they choose. Big sinks, little sinks, led resistors, inline or offset trimpots, all to choose from! Do I dare post the single rail version, though?
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Post by Deleted on May 21, 2009 8:10:54 GMT
Will I hope you don't take Robert's and my exchanges too seriously ! We are cool. Alex
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Will
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Post by Will on May 21, 2009 8:20:17 GMT
When you two are 'discussing' matters, my minds eye is two blokes having a laugh over a pint in the pub, so no, not too seriuosly at all!
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Will
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Post by Will on Jun 17, 2009 13:01:22 GMT
A little update. I've actually made one of these up now, and I'm pleased to say that it works! Voltages vary when you turn the trimpots and everything! (I know, easily pleased and all that....) With reference to the last picture, Ac in on the left hand side, DC out on the right. Top of the board is +ve, the bottom -ve. The two holes to the left of the rectifier diodes are for traffo tuning (see chart earlier in thread) and the six after are for links for LED resistor and wire posts. The board is that colour because I painted it (as you do) Component choice is entirely yours but as a guide, values are listed in post one.
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Post by Deleted on Jun 17, 2009 21:30:06 GMT
Will Looks like it means business, but don't paint boards in general, or some of them may not work as they are supposed to. Especially boards that use high gain, and high value resistors. e.g. Offset corrector boards. Alex
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Will
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Post by Will on Jun 18, 2009 6:08:48 GMT
Will Looks like it means business, but don't paint boards in general, or some of them may not work as they are supposed to. Especially boards that use high gain, and high value resistors. e.g. Offset corrector boards. Alex Really? That's an interesting thought. Is this in relations to Graham Slee's post regarding the effect of solvents,etc soaking onto the pcb? The paint is only on the top side, and before the holes were drilled. Good point though, it was definitely one of those "while I'm spraying" thoughts.
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Post by Deleted on Jun 18, 2009 6:27:03 GMT
Will I mentioned that I had problems with reusing offset corrector boards after cleaning. Graham replied saying he had similar problems himself with offset correctors that utilised high value resistors. e.g. 1 Megohm. Alex
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