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Components and Circuits For discussions about component types, alternatives and availability, circuit configurations and modifications etc. Discussions here should be of a general nature and not about specific sets. |
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27th Jan 2010, 9:44 pm | #1 |
Hexode
Join Date: Oct 2006
Location: Edenderry, Republic of Ireland.
Posts: 428
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Type of resistors to use in valve radios
Hello again,Firstly I hope it is alright to ask this question, Why is there such a difference in prices of resistors. For .6watt resistors I have been quoted from 2 pence to 20 pence each. Is there a difference in quality. Regards Dick.
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27th Jan 2010, 10:26 pm | #2 |
Dekatron
Join Date: Jan 2004
Location: Newcastle upon Tyne, Tyne & Wear, UK.
Posts: 8,173
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Re: Type of resistors to use in valve radios
Hi Dick, it is the type of construction; carbon film, metal film, power oxide, bulk carbon or wirewound that determines the cost. These vary by application.
Try looking at the Welwyn resistors website and this may give you an insight into what the various technologies are used for Ed |
27th Jan 2010, 10:55 pm | #3 |
Nonode
Join Date: Jun 2004
Location: Norwich, Norfolk, UK.
Posts: 2,543
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Re: Type of resistors to use in valve radios
Hi Dick,
Although not always stated, resistors have a voltage rating and modern 0.5/0.6W resistors may not have a voltage rating high enough for valve radios. Personally I buy 2W metal film ones from Maplin or I get the multipack 1W carbon types from China, via ebay hth David |
28th Jan 2010, 12:02 am | #4 |
Retired Dormant Member
Join Date: Nov 2009
Location: Lancashire, UK.
Posts: 67
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Re: Type of resistors to use in valve radios
Also caution to be given to wirewound resistors, some parts of the circuit may not be compatible with wirewound types (if the original is non wirewound) due to the inductance of them, this is even more likely with sets that have vhf.
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29th Jan 2010, 1:40 am | #5 |
Retired Dormant Member
Join Date: Jan 2010
Location: Hertfordshire, UK.
Posts: 8
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Re: Type of resistors to use in valve radios
I haven’t had anything to do with valves since my teens but generally its best to calculate the power required and consider heat and stability / accuracy needed.
In some cases you may want to over-rate the wattage in others it may make sense for the resistor to be the weak link in case of a fault condition cheep and easier to replace a resister than other components. if its a repair then I would think best to replace "like for like" where posible. |
29th Jan 2010, 11:19 am | #6 |
Rest in Peace
Join Date: Mar 2006
Location: N.W. Oxfordshire(Chipping Norton)
Posts: 7,306
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Re: Type of resistors to use in valve radios
I have often used the Maplin 2W resistors, and also 3watt types, the latter available from(amongst others) Savoy hill publications and CHS(Charles Hyde). The CHS ones are usually green bodied, whilst those from Savoy Hill are brown with conventional colour code bands, and are similar in size to the old 0.5W Carbon types found in '50s radios.
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29th Jan 2010, 11:42 am | #7 |
Dekatron
Join Date: Jan 2003
Location: Bradford on Avon, Wiltshire, UK.
Posts: 3,301
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Re: Type of resistors to use in valve radios
Most resistors I have seen are rated at 600-1000v. I use those grey metal film 1/2 watt ones for most radio repairs, simply because I have piles of them. If a greater power is needed then a rummage is required! Most high wattage applications will be in power stages anyway, where WW types will be fine.
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