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Homebrew Equipment A place to show, design and discuss the weird and wonderful electronic creations from the hands of individual members. |
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11th Oct 2017, 12:57 pm | #41 | |
Dekatron
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Re: The perils of homebrewing equipment
Quote:
Surely 20 * 0.6W is 12W? Why did they fall off at 9W? Bunching effect (like cores in a cable)?
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11th Oct 2017, 1:07 pm | #42 |
Hexode
Join Date: Jun 2005
Location: Aberystwyth, Wales, UK.
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Re: The perils of homebrewing equipment
I built two nearly identical curve tracers in the 1980'2, one from pnp transistors and one from npn transistors. I think it was a Elecktor design. They both worked, I needed the two as the pnp version only tested pnp and the npn version only tested npn. I played wit them for about a week and then put them away for future use, I think they are still in the shed.
Dave GW7ONS |
11th Oct 2017, 1:20 pm | #43 |
Dekatron
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Re: The perils of homebrewing equipment
That's probably where mine would end up if it worked Dave!
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David. BVWS Member. G-QRP Club member 1339. |
11th Oct 2017, 1:28 pm | #44 |
Dekatron
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Re: The perils of homebrewing equipment
Here are the other two pages of the original article - not very good copies I'm afraid.
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David. BVWS Member. G-QRP Club member 1339. |
11th Oct 2017, 1:55 pm | #45 |
Hexode
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Re: The perils of homebrewing equipment
I think this is the curve tracer I made.
Dave GW7ONS |
11th Oct 2017, 2:39 pm | #46 |
Dekatron
Join Date: Feb 2003
Location: Cottingham, East Yorkshire, UK.
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Re: The perils of homebrewing equipment
Oh dear - don't tempt me!
Noted the 'TUP - TUN - DUG' in the specified parts. Elektor 'TUPTUNDUGDUS' - t'was once, but is no more. 'Transistor PNP Universal, Transistor NPN Universal; Diode Universal Germanium, Diode Universal Silicon'. Back then, nothing was sprinkled with 'fairy dust' or endowed with magical qualities. 'It's an NPN transistor innit? Well bung it in then'. Happy days!
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11th Oct 2017, 3:14 pm | #47 |
Octode
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Location: Bletchley, Buckinghamshire, UK.
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Re: The perils of homebrewing equipment
I think a transistor curve tracer is well worth having - you should definitely persevere with it.
Mine is an old Heathkit that works with an x-y scope and it is really useful for testing and matching transistors. |
11th Oct 2017, 3:24 pm | #48 |
Dekatron
Join Date: Jun 2016
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Re: The perils of homebrewing equipment
Sorry should have been more clear above. They were 0.25W not 0.6W. This is where I fudged the maths by calculating for 0.6W as I normally buy them. Ran them at 3/4 power (9W) instead of about 4W.
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11th Oct 2017, 5:49 pm | #49 | |
Octode
Join Date: Jan 2014
Location: Oban, Scotland, UK.
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Re: The perils of homebrewing equipment
Quote:
I've opened an item of test equipment that looked homebuilt and commented "hmmm, nicely made...." and took a few minutes to realise that I'd made it! Circuit diagram? Board layout? Not a chance! In my defence it was over 10 years ago but............ |
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11th Oct 2017, 5:51 pm | #50 |
Rest in Peace
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Location: Hexham, Northumberland, UK.
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Re: The perils of homebrewing equipment
Ah yes, the good old programmable uni-junction transistor. These seemed to become popular in the eighties in home construction but I haven't seen or heard much of them since. It would appear that I am very like you David. I am an obsessive constructor. Not just electronics but all sorts of things. I've always been like that. Right from early days of making flying models and all the rest of it. I think the posh word for it is "creative"! I have projects dating back at least twenty years, and sometimes when rummaging about for other things, I find a box full of interesting bits which is a complete kit for a half finished something that I have forgotten about. So out it comes and I spend too much time finishing it off. Then the novelty wears off and back it goes on a shelf. I think one attraction of doing this is that you sort of enter a time warp, as it takes you back. I am sure that there is a medical explanation for this but who cares? It's who I am and I am very happy with that.
Alan. |
11th Oct 2017, 8:10 pm | #51 | |
Dekatron
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Location: Wiltshire, UK.
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Re: The perils of homebrewing equipment
Quote:
I always loved Elektor for the TUP-TUN-DUG-DUS simplicity of their designs. "Nothing special needed here - use what you've got!" |
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12th Oct 2017, 4:06 am | #52 | |
Nonode
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Re: The perils of homebrewing equipment
Quote:
They are used, but still perfectly serviceable. Terry |
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12th Oct 2017, 7:44 am | #53 |
Dekatron
Join Date: Jun 2016
Location: London, UK.
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Re: The perils of homebrewing equipment
Will have a look on there. That’s certainly less than the £11 I was going to spend on a caddock MP850
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12th Oct 2017, 8:57 am | #54 |
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Re: The perils of homebrewing equipment
Ah, David, sussed what you are doing. You are trying to get us all to debug your curve tracer!
If we all build one and only one works, what will that signify? But if they all work, you are going to have to make all the lovely wooden boxes for us all, that's only fair. Does look to be a clever design though, too clever for its own good? Is there a working example in the cosmos? Home brews suffers from lack of factory air inside, difficult to capture. |
12th Oct 2017, 5:07 pm | #55 | |
Dekatron
Join Date: Feb 2003
Location: Cottingham, East Yorkshire, UK.
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Re: The perils of homebrewing equipment
Quote:
As to the design being 'too clever for its own good' I have to entertain the possibility that maybe I'm too dim for my own good! I suppose there must have been at least one working model in the cosmos - that of the author's.
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12th Oct 2017, 5:33 pm | #56 |
Moderator
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Re: The perils of homebrewing equipment
That's the danger. Someone builds something and it works so they think it's OK to publish.
Full-blooded professional design has to account for the full tolerance spreads of all components, and has to make some hard-nosed estimates of those parameters which are never graced with actual specs. Provided all units are built from in-spec components, all units ever built had better work or the designer gets it. Some amateur designers do take this level of care, and some professional designers don't. There are many irreproducible designs in various magazines (Elector seems to be one of the safest) And a few overrun resistors seems to be the hallmark of any Quad amplifier. Sometimes, to read a magazine article and to be able to decide whether it's OK to build takes as much knowledge as designing your own thing properly in the first place. It's survivable for hardened constructors, but it can damage the confidence of beginners. David
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12th Oct 2017, 5:35 pm | #57 | |
Nonode
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Re: The perils of homebrewing equipment
Quote:
Regards, Lloyd |
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12th Oct 2017, 9:34 pm | #58 | |
Octode
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Re: The perils of homebrewing equipment
Quote:
I really enjoyed David's post. I really ought to be a lot further on with project 'if you can meet with triumph or disaster, and treat those two impostors just the same', at my age. On a good day, homebrew projects help with one's humility - one way or another |
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13th Oct 2017, 10:21 am | #59 | |
Dekatron
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Location: Leominster, Herefordshire, UK.
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Re: The perils of homebrewing equipment
Quote:
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....__________ ....|____||__|__\_____ .=.| _---\__|__|_---_|. .........O..Chris....O |
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13th Oct 2017, 1:36 pm | #60 |
Dekatron
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Location: London, UK.
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Re: The perils of homebrewing equipment
I usually use Vishay MRS25's which was actually the problem. Thing is they've got very expensive suddenly (£0.08-£0.12 each) so I switched to Royal Ohm imports from Thailand (£0.008 each) as most of my requirements are pretty modest with respect to power. I've now got an influx of 0.25W ones which are the same size. The Royal Ohm ones are really nice, with decent tempco and nice thick legs. But only if you don't smoke 'em
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