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| Thread ID: 59459 | 2005-07-03 07:01:00 | Resistor Colour Code | B.M. (505) | PC World Chat |
| Post ID | Timestamp | Content | User | ||
| 368944 | 2005-07-03 07:01:00 | I’ve got a cordless phone that wasn’t going 100%. Investigation shows a resistor connected to the Aerial with one leg broken off. No big deal, but the colour code is Brown – Green – Gold – Black, that’s it. What the devil should that be? I would have guessed 1.7 Ohms but what is the black? A reading with my Multimeter, taken by poking a probe in where the leg was attached comes up 0.7 Ohms. What should it be and what use is it???? At 0.7 ohms can I just by-pass it? :) |
B.M. (505) | ||
| 368945 | 2005-07-03 07:11:00 | www.google.co.nz | ILikeLinux (1669) | ||
| 368946 | 2005-07-03 07:15:00 | It may be an inductor or a choke, which just happens to look like a resistor. Strange it should be in an aerial lead unless its actually part of the tuning. That code suggests 15 microH Or 0.51 microH if read the other way (more probable if a tuning component) Gold designates a decimal point in a choke, appearing only in the first or second position. It also means no multiplier should be attributed |
godfather (25) | ||
| 368947 | 2005-07-03 08:03:00 | It sure is an oddball GF. I’d swear it was a common 1/8 watt resistor but I can’t for the love of me work out its value or its role. Incidentally, it’s in the base unit of an old Panasonic (Telepermit PTC-206/90/003) in case there’s any serviceman out there that has a workshop manual. |
B.M. (505) | ||
| 368948 | 2005-07-03 11:15:00 | At 0.7 ohms can I just by-pass it? :) Provided it goes to the aerial, yes you can just bypass it. It may be a base loading inductance to improve the efficiency of the antenna on transmit, but provided it works ok and still gives adequate range I wouldn't worry about it. Cheers Billy 8-{) |
Billy T (70) | ||
| 368949 | 2005-07-03 21:53:00 | Yes Billy I thought about base loading but I’m positive it’s just a resistor. I have seen resistors used as a former for a small inductance but that is not the case here. Anyway, bypassing it didn’t upset things at all and the phone is now working perfectly. I’d still like to solve the colour code though. It isn’t a new code because the phone is a 1990 model. :D |
B.M. (505) | ||
| 368950 | 2005-07-03 22:51:00 | I have a "heap" of small inductors and some not so small, that look exactly like resistors, really the only one way to tell is to measure the inductance. Then there are others that look like small capacitors with coloured dots to denote the values. But I have many in all shapes and sizes with many different styles, there is no consistent pattern to inductors. I havent quite worked out the gold and silver dot/bands codings though. For example I have some marked from one end with these coloured bands: Silver, Red, Red, Red, Silver, and they are 2200 microhenries, as one would expect from the red bands, I suspect if gold or silver bands/dots occur at the end of the colour coding, then it will denote tolerance as for a resistor, if gold occurs in the middle it will be a decimal point as GF suggests. |
Terry Porritt (14) | ||
| 368951 | 2005-07-03 22:59:00 | Well, you wouldn't put a resistor in series with an antenna feed, not even a low ohms value, and the resistors used as formers for small inductors are usually high value jobbies. An inductance with a winding resistance of .7 ohms would also have a reasonable winding size so that seems a bit odd too. The phone is probably in the 30-40 MHz range, so that much inductance in series with the antenna would be a bit odd. I'm not sure exactly what band they inhabit but I have a 10 year old Panasonic in that general range and I'd expect a value in the low microhenries range, possibly to suppress any higher-order harmonics. Unless you find the odd jumbo jet homing in on your QTH during long conversations, best you just settle for a working phone. Cheers Billy 8-{) :) Just saw Terry's post. Try reading it as a low value inductor and see what you get. Could be 1.7 µH and that plus about 8-10 pF would make a 500 ohm impedance at around 40 MHz (rule of thumb guesswork though). It could be an inductance wound on a capacitive former. |
Billy T (70) | ||
| 368952 | 2005-07-04 01:00:00 | Here's a pic of an assortment of inductors that look like resistors or capacitors: inductors.jpg (www.sal.neoburn.net) You can see the 2.2mH to the right with silver bands each side of the red. |
Terry Porritt (14) | ||
| 368953 | 2005-07-04 02:04:00 | An aside, perhaps Terry and others remember this pneumonic, bigger better resistors make your grid bias voltage go west ie black brown red etc etc |
bonzo29 (2348) | ||
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