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2014-07-18, 00:48
(This post was last modified: 2014-08-09, 00:29 by gadjex.)
I got my red kit in yesterday  for the Amplifier 12 Ver 3c and Controller 10 Ver 4 and I used the inventory sheets to inventory the order. I received a few extra parts and I am missing a few parts. I am missing 3 - 47 ohm metal film resistors. I have 3 extra 49.9 ohm metal film resistors and 1 1N4148 Diode. Can I substitute the 49.9 ohm for the 47 ohm? The amp needs 2 and the controller needs 1? I used a Fluke multimeter to check the value of all the resistors and double checked that I am missing the 47 ohm ones.
Edit: Found where the 6 extra 2.2k metal film resistors go. OOPs 
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Egon responded to my query about the 49.9 ohm substitution on the internal forum by verifying he had run out of the 47 ohm parts. It's fine to substitute in the 49.9 ohm parts. I've built two controllers/h-field amps with the substituted parts, and they work fine.
Best,
Don
WD9DMP
(2014-07-18, 00:48)gadjex Wrote: I got my red kit in yesterday for the Amplifier 12 Ver 3c and Controller 10 Ver 4 and I used the inventory sheets to inventory the order. I received a few extra parts and I am missing a few parts. I am missing 3 - 47 ohm metal film resistors. I have 3 extra 49.9 ohm metal film resistors and 1 1N4148 Diode. Can I substitute the 49.9 ohm for the 47 ohm? The amp needs 2 and the controller needs 1? I used a Fluke multimeter to check the value of all the resistors and double checked that I am missing the 47 ohm ones.
Edit: Found where the 6 extra 2.2k metal film resistors go. OOPs
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Ah, good. You should put the 47 Ohm thing in the title, so as to sweep up more people (like myself) who have this same problem.
I counted the parts and assumed the 49.9 was to sub for the 47s. One of them just sets the backlight brightness on the display, but the other two set the value of a low-pass filter (I think) on the amplifier board. I guess a 5% change in the filter cutoff isn't going to cause any issues.
I can get 47 Ohm resistors in town, maybe I'll try to find the right values before I start stuffing the amplifier board.
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5-6% change in value on that place, don't give 5-6% chance in filter, so 49,9 is just fine.
I don't remember exact, but I calculate a given value, perhaps 50 ohms, and then select the nearest common value, and it is/was 47 ohms.
It may seem random, but is not. Egon and I had a discussion long time ago if were to use BOTH 47 and 49.9 ohms since they were so close - the result was that the values were just numbers on a shopping list, so we kept both values.
PCB12 ver2 had the two extra 2,2k resistors ... chance in design rom ver2 to ver3
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(2014-08-07, 05:31)wiggly Wrote: Ah, good. You should put the 47 Ohm thing in the title, so as to sweep up more people (like myself) who have this same problem.
Good suggestion. Edited title.
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I don't mean to be overly critical, but when sourcing alternate resistors, it's a bit difficult to find 47 Ohm resistors, because 47.0 Ohms is not a standard 1% resistor decade value.
The standard decade values in that range for 1% resistors are 464, 475, 487 and 491.
Given it's actually a bit hard to find 1/10th Watt resistors as anything but precision values anymore and 1% are by far the most common, it would be best to select a resistor value of either 47.5, 48.7 or 49.1 Ohms.
I actually put in 46.4 Ohm resistors there (closest to 47.0) and now I regret it a bit. Oh well, I'll leave it. I have bigger fish to fry at the moment, I have to start considering my antenna options.
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(2014-08-09, 06:41)wiggly Wrote: I don't mean to be overly critical, but when sourcing alternate resistors, it's a bit difficult to find 47 Ohm resistors, because 47.0 Ohms is not a standard 1% resistor decade value.
The standard decade values in that range for 1% resistors are 464, 475, 487 and 491.
Given it's actually a bit hard to find 1/10th Watt resistors as anything but precision values anymore and 1% are by far the most common, it would be best to select a resistor value of either 47.5, 48.7 or 49.1 Ohms.
I actually put in 46.4 Ohm resistors there (closest to 47.0) and now I regret it a bit. Oh well, I'll leave it. I have bigger fish to fry at the moment, I have to start considering my antenna options.
Actually, 47 ohms (and 4.7, 470, 4.7k, etc.) is a very standard decade value -- at least in the U.S. market.
http://www.mouser.com/Passive-Components...joZ1z0z819
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(2014-08-09, 15:42)Jonathan.Williams Wrote: (2014-08-09, 06:41)wiggly Wrote: I don't mean to be overly critical, but when sourcing alternate resistors, it's a bit difficult to find 47 Ohm resistors, because 47.0 Ohms is not a standard 1% resistor decade value.
The standard decade values in that range for 1% resistors are 464, 475, 487 and 491.
Given it's actually a bit hard to find 1/10th Watt resistors as anything but precision values anymore and 1% are by far the most common, it would be best to select a resistor value of either 47.5, 48.7 or 49.1 Ohms.
I actually put in 46.4 Ohm resistors there (closest to 47.0) and now I regret it a bit. Oh well, I'll leave it. I have bigger fish to fry at the moment, I have to start considering my antenna options.
Actually, 47 ohms (and 4.7, 470, 4.7k, etc.) is a very standard decade value -- at least in the U.S. market.
http://www.mouser.com/Passive-Components...joZ1z0z819
These are 1% resistors.
http://www.digikey.com/Web%20Export/Supp...directed=1
http://logwell.com/tech/components/resistor_values.html
The values you give are for non-precision (5%) resistors, E24 scale.
Some companies make the 5% E24 in 1% also, but the standard for 1% resistors is the E96 values in those tables.
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2014-08-10, 04:00
(This post was last modified: 2014-08-10, 04:06 by Jonathan.Williams.)
(2014-08-10, 01:33)wiggly Wrote: (2014-08-09, 15:42)Jonathan.Williams Wrote: Actually, 47 ohms (and 4.7, 470, 4.7k, etc.) is a very standard decade value -- at least in the U.S. market.
http://www.mouser.com/Passive-Components...joZ1z0z819
These are 1% resistors.
http://www.digikey.com/Web%20Export/Supp...directed=1
http://logwell.com/tech/components/resistor_values.html
The values you give are for non-precision (5%) resistors, E24 scale.
Some companies make the 5% E24 in 1% also, but the standard for 1% resistors is the E96 values in those tables.
Hmmm, I linked directly to 1% tolerance, thin film 47 ohm resistors available from Mouser, in multiple case sizes (41 options found). The link works for me.
Best,
Jonathan
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Yes, I know you linked to Mouser and found some 47 Ohm resistors in 1%. But again, 47 Ohms is not a standard value in 1%.
See how I said this:
Some companies make the 5% E24 in 1% also, but the standard for 1% resistors is the E96 values in those tables.
EIA makes the spec, and for 1% resistors the standard values are the E96 values. And 470 is not an E96 decade value.
So while you can get 47 Ohm 1% resistors at Mouser, digikey or whatever, as I mentioned it would make it easier for others to source resistors more widely (and locally) if the specified resistor values were a proper E96 standard value and not an E24 value.
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I thought this a bit strange. After >40 years of squinting at color codes the number 47 seemed familiar to me.
So I looked in my resistor rack and found 47Ohm 1%. And I this is a standard assortment rack.
Then I checked with one of my preferred suppliers.
Axial leaded, 50Ohm, <250mW, 1% or better: 6 products found.
Axial leaded, 47Ohm, <250mW, 1% or better: 6 products found.
For a BO kit either you get just that: a kit. And it probably could be in the build instructions that if you don't find the exact value, use the closest there is in the kit.
For most of those buying the components, Anders comment above is good reading.
When designing something I don't specify a % on the value unless it need to be. Even if that have become the standard component. That is a way of telling that it is a chosen value rather than an exact calculated value. Again: ref. Anders post.
If parachuted into the most remote corner of the world to build a kit, and having to beg the parts from the local radio shaman, you would most likely be getting E24 parts.
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2014-08-18, 08:40
(This post was last modified: 2014-08-18, 08:41 by RichoAnd.)
Even if a component is not standardized with an international standard, it may well be standard if sufficiently widespread.
E24 series is available across Europe, available in 1% metallized, and is cheap
Whatever you ask for 5%, you risk getting 30-40 year old components that are difficult to solder on.
I use mainly values of the E12 series, but expect to use 1%, not because it's necessary, but because they are cheap enough to have lying around.
http://www.logwell.com/tech/components/r...alues.html
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