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Vintage Test Gear and Workshop Equipment For discussions about vintage test gear and workshop equipment such as coil winders. |
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15th Oct 2021, 12:30 pm | #1 |
Hexode
Join Date: Feb 2011
Location: Newcastle upon Tyne, Tyne and Wear, UK.
Posts: 280
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Help identifying a resistor please
Resistor connected to the inductor on the anode of V3 ecc88 vertical amplifier telequipment D52
This resistor looks like a wirewound but the manual states that it is metal oxide 3.25 watt? 4.7K 5% has a "W" inside an ohm symbol and 27F Mv on the side. The inductor is 39 - 129 uH 100 turns |
15th Oct 2021, 3:41 pm | #2 |
Octode
Join Date: Jul 2009
Location: Carmel, Llannerchymedd, Anglesey, UK.
Posts: 1,498
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Re: Help identifying a resistor please
Looks like a bit of burning on the left of the picture, so it could be that it has been hot enough to strip any colour bands. I'd go by the manual for a replacement.
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15th Oct 2021, 3:44 pm | #3 |
Octode
Join Date: Jan 2003
Location: Guildford, Surrey, UK.
Posts: 1,958
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Re: Help identifying a resistor please
The resistor logo is for Welwyn Electric Ltd. There is the F70 series of axial leaded 'METOX' power resistors, of which the F75 is a 3.25 watts rating at 70 degrees C component. The insulation is of a grey silicone cement. Dimensions are L 0.75", D 0.36". Temperature Coefficient less than 500ppm/degree C.
This information was taken from page 116 of the 1970-71 Welwyn Electric Limited Component Catalogue. Ron Last edited by ronbryan; 15th Oct 2021 at 3:51 pm. |
15th Oct 2021, 6:10 pm | #4 | |
Hexode
Join Date: Feb 2011
Location: Newcastle upon Tyne, Tyne and Wear, UK.
Posts: 280
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Re: Help identifying a resistor please
Quote:
I'm uncertain if a carbon film equivalent would suffice in this situation. |
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15th Oct 2021, 9:22 pm | #5 |
Nonode
Join Date: Dec 2012
Location: Kirk Michael, Isle of Man
Posts: 2,346
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Re: Help identifying a resistor please
Is it faulty? If it just looks as if it has been hot, that is normal and OK.
You should have asked the other day, I MAY have loads of these. I certainly have a load of TQ metal oxides of that size, and a few wirewounds from early scopes. Les. |
16th Oct 2021, 1:42 pm | #6 | |
Hexode
Join Date: Feb 2011
Location: Newcastle upon Tyne, Tyne and Wear, UK.
Posts: 280
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Re: Help identifying a resistor please
Quote:
Y2 is 3.9K and 3.3K, given that the amplifiers won't reach the calibration height I am assuming that these lower readings may be contributing to the low amplification, but I would like an opinion on this. |
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16th Oct 2021, 3:29 pm | #7 |
Dekatron
Join Date: Oct 2003
Location: Croydon, Surrey, UK.
Posts: 7,548
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Re: Help identifying a resistor please
Well 5% suggests that they are out of spec since the low-end value should be within 235 ohms limit which makes 4.435K. Similarly the high-end value would be 4.935K limit.
Whether resistors above or below those limits would greatly affect calibration remains to be seen....
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16th Oct 2021, 4:33 pm | #8 |
Nonode
Join Date: Aug 2007
Location: Walsall Wood, Aldridge, Walsall, UK.
Posts: 2,853
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Re: Help identifying a resistor please
Hi!
Are these any help? Despite the seller's description they are a metal–oxide/metal film type – I'm familiar with this sort in Japanese CRT monitors! https://www.ebay.co.uk/itm/QTY-6-4K7...-127635-2958-0 Chris Williams
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16th Oct 2021, 7:17 pm | #9 | |
Hexode
Join Date: Feb 2011
Location: Newcastle upon Tyne, Tyne and Wear, UK.
Posts: 280
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Re: Help identifying a resistor please
Quote:
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16th Oct 2021, 7:42 pm | #10 |
Dekatron
Join Date: Aug 2016
Location: Colchester, Essex, UK.
Posts: 4,081
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Re: Help identifying a resistor please
I can't find that value amongst my spares, but i do notice very similar looking resistors with high wattage ratings made by RS...so don't restrict searching to 'Welwyn'.
Dave |