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Post by PinkFloyd on Dec 18, 2008 9:01:47 GMT
I was just thinking about it and, realistically, you would be talking anywhere from £250 to £1000 depending on what components / enclosure you had utilised.
Factor in your time as well and the SCHA could be classed as a relatively "high priced" item if you were to build one and put it up for sale in a shop next to the likes of a Graham Slee Solo for example..... in fact, it could be classed as "high end" in direct comparison to commercial offerings especially if you have employed boutique parts / stepped attenuators / JLH ripple eater etc.
I wouldn't sell mine as I have put many hours into it but, if I were to sell it "realistically" then the buyer wouldn't get much change from £700 and that's CHEAP if I factor in the time spent on it and even valued my time at the cheapest rate of £5 per hour..... Also factor in the "time" spent looking for parts.....
Have a good think about it guys......... what price do you think you'd put on yours if you were to sell the completed article in a shop?
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Post by nickyboyo on Dec 20, 2008 9:05:59 GMT
Not having even started the build yet, but parts alone, jlh, stepped attenuator, various components from suggested tweaks from the more electrical engineering aware folks here and parts for the casing- not much change from AU$250. I would estimate 20 hours for the build including the case work ( i am hoping my idea for the casework will come into fruition and will end up looking very smik ), so say AU $10 per hour for labour. Add in the Carlton Draughts to keep me refreshed as i toil, AU$500 bottom line zero profit cost price.
From what i have read from other members posts regarding the output sound quality of the amp, i would think (and hoping) it would be a heck of a lot of amp for the money you would spend on buying the complete pre assembled unit at AU$500.
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Post by Deleted on Dec 20, 2008 9:29:54 GMT
Nick Which transformer did you get, the Altronics, or the Jaycar? Do you have your JLH and bits yet ?
Worth AU$500 ? A couple of mine went very cheaply then! ;D
Alex
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Post by Deleted on Dec 20, 2008 20:39:47 GMT
Miguel my friend, you give as good as you get ! You seem quite good at returning fire. Are you still able to compare with the Mapletree ? Alex
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Post by Deleted on Dec 21, 2008 1:32:17 GMT
Miguel Did you save the aluminium plate from under the transformer ? Alex
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leo
Been here a while!
Team wtf is it?
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Post by leo on Dec 21, 2008 1:42:55 GMT
Sorry to hear that Miguel. No need to feel an idiot, this hobby does not always go as planned
Can you take some pictures of the damage? We can try and give advice on what to check to fix if your up for it?
Is it the transformer thats blown or parts of the actual amp pcb?
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Post by nickyboyo on Dec 21, 2008 2:02:44 GMT
Commiserations Miguel, at least you didn't get fried mate
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Post by Deleted on Dec 21, 2008 2:07:25 GMT
Miguel Leo's suggestion makes sense, even if you aren't game to try and fix it. Send any photos to me, and I will include the usual little group in the post mortem. Did you have the Attenuator fitted at the time ? If a rebuild is needed, the original aluminium base plate would save hours of work. I do also have a set of spare working modules, as well as a suitable transformer. Alex
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Post by Deleted on Dec 21, 2008 14:48:30 GMT
Don't forget the first one would go down as R&D, once you've settled on a design any subsequent builds would be much faster and not wasteful of components. If in the shops the R&D would be spread over a predetermined quantity of units, depending on how quickly that expenditure needs to be recovered, market forces/projected sales blah blah. So if you built another one, figure the costing on that. Then, for those of us who have had copious help from other members, cost in consultation! MINEFIELD. --------------------------------------------- MIGUEL I do sympathise with you on the demise of your SCHA. Just when you think you can handle the work involved, it all goes horribly wrong (fortunately for me those caps won't even fit in mine, so I won't be going there)
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Post by Deleted on Dec 21, 2008 19:59:29 GMT
Miguel When it comes time for the rebuild, just send me the attenuator and that metal plate. That will save me having to cut another piece of aluminium, and work out again how and where I mounted the PSU PCB. It's a shame that you didn't manage to save the JLH board as well. Anyway, I have the rest of the stuff already,including those polyropylene capacitors, so there will be no insurmountable problems. I currently have 2 units working with those caps installed. The transformer and toggle switch are most likely O.K. , but I can understand that you would be reluctant to reuse them again. Alex
Chris There is nothing in the immediate area of the capacitor mounting, that should be capable of causing such a problem, so it may have been due to a small offcut of wire or, a loose blob of solder somewhere.TBH, I have no idea what could have caused such a problem! Alex
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Post by Deleted on Dec 21, 2008 21:28:20 GMT
Miguel Keep the transformer. I think it is most likely O.K. but will just add too much extra to the cost of your package. P.S. My son has briefly stopped over in Miami a couple of times, a few years back. His wife comes from Suriname. Alex
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Post by Deleted on Dec 21, 2008 22:37:44 GMT
There is nothing in the immediate area of the capacitor mounting, that should be capable of causing such a problem, so it may have been due to a small offcut of wire or, a loose blob of solder somewhere.TBH, I have no idea what could have caused such a problem! Alex Thanks for the thought, even I first thought of errant solder. I have already successfully popped in the Wimas, I definitely don't have physical room (without leaving VERY long legs) for the recommended biggies. Cheers
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Post by Deleted on Dec 21, 2008 23:04:27 GMT
Chris I am wondering if some of those Asian manufactured (presumably) MF resistors had a coating that was inflamnable, and instead of just going open circuit, caught alight. I have seen that once before when an emitter resistor charred a small section of PCB with a fault situation. I was under the impression that the majority of modern resistors used a NON flammable coating. Alex
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Post by Deleted on Dec 22, 2008 1:40:12 GMT
Miguel Suriname is above Brazil, and next to French Guiana.
I guess we will never know what happened. Do you remember the general area where the smoke /flame first appeared to come from ?
Alex
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Post by PinkFloyd on Dec 22, 2008 14:31:17 GMT
Am I the only one who feels like bursting out laughing here? ;D What the HELL did you do to it to almost cause a fire Miguel? It seems bad now but you will look back on it and see the amusing side, we've all been there One of the worst shocks I ever had was with a WNA amp.... I'd built it and turned her on, nothing except hum so I went down and peered at the board.... CRACKO! one of the caps blew, I had fitted it the wrong way round Seriously man, I nearly shit myself! a few seconds later CRACKO! another one blew! I had fitted ALL of them the wrong way round! I tell you, you really don't want your face 4 inches from a cap when she blows, especially if she's a big Mama Honker Don't worry Miguel, all these things are a blessing in disguise and teach you things
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Post by Deleted on Dec 22, 2008 23:53:14 GMT
Miguel A fault like that is usually due to a stray bit of wire offcut, or a piece/blob of solder , or even a mounting nut getting wedged in the components. Other possibilities could be power supply wires being connected back in the wrong positions on the 3 pin socket. The PCB was solder masked, so it is fairly difficult to inadvertently bridge circuit board tracks etc. Don't worry about it ! I have lost the occasional lock washer in a PCB over the years. You can shake the PCB, but they always seem to get stuck somewhere where they can cause mischief later on. They usually aren't easy to spot either, even if you know they are somewhere in the guts of it ! You can turn the damn thing upside down and bang on the case, but they still stay stuck .Other very common mistakes on amplifiers are things like being in a hurry, and forgetting to fully tighten up a power transistor to it's heatsink. As Mike has said, almost every constructor has at some time or another, shoved an electrolytic capacitor in the wrong way, with startling results. Alex
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Post by Deleted on Dec 23, 2008 4:35:05 GMT
Miguel That's where what you did comes in. All it would take is a flat steel washer or shakeproof washer, from the disassembly time, to lodge in the wrong place and not be noticed. Believe me, I have had that happen. Even a fine strand from the shield of the input cables when you were reconnecting them. They are so fine, you often don't even notice them. That's why when I do mods, I always turn it upside down with the cover off, and give the bottom a few hard whacks, and a good shaking. Alex
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Post by Deleted on Dec 24, 2008 11:03:41 GMT
Miguel As bad as it may seem at the momemt, you are a rank beginner compared with a couple of the guys that I used to work with. One was nicknamed "shagger", because everything he touched, he ...... The other guy was a very likeable chap from Croatia, whose nickname was "N.F.I." Alex
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