UK Vintage Radio Repair and Restoration Powered By Google Custom Search Vintage Radio and TV Service Data

Go Back   UK Vintage Radio Repair and Restoration Discussion Forum > Specific Vintage Equipment > Vintage Test Gear and Workshop Equipment

Notices

Vintage Test Gear and Workshop Equipment For discussions about vintage test gear and workshop equipment such as coil winders.

Closed Thread
 
Thread Tools
Old 15th Oct 2021, 12:30 pm   #1
pentoad
Hexode
 
Join Date: Feb 2011
Location: Newcastle upon Tyne, Tyne and Wear, UK.
Posts: 280
Default 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
Attached Thumbnails
Click image for larger version

Name:	grey resistor photo.jpg
Views:	216
Size:	79.8 KB
ID:	243459   Click image for larger version

Name:	grey resistor.jpg
Views:	147
Size:	42.2 KB
ID:	243460  
pentoad is offline  
Old 15th Oct 2021, 3:41 pm   #2
lesmw0sec
Octode
 
Join Date: Jul 2009
Location: Carmel, Llannerchymedd, Anglesey, UK.
Posts: 1,498
Default 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.
lesmw0sec is offline  
Old 15th Oct 2021, 3:44 pm   #3
ronbryan
Octode
 
Join Date: Jan 2003
Location: Guildford, Surrey, UK.
Posts: 1,958
Default 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.
ronbryan is offline  
Old 15th Oct 2021, 6:10 pm   #4
pentoad
Hexode
 
Join Date: Feb 2011
Location: Newcastle upon Tyne, Tyne and Wear, UK.
Posts: 280
Default Re: Help identifying a resistor please

Quote:
Originally Posted by ronbryan View Post
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
Thank you for that I can ascertain that they are indeed metal oxide, however I am finding it difficult to source that value at that wattage or above.

I'm uncertain if a carbon film equivalent would suffice in this situation.
pentoad is offline  
Old 15th Oct 2021, 9:22 pm   #5
MotorBikeLes
Nonode
 
Join Date: Dec 2012
Location: Kirk Michael, Isle of Man
Posts: 2,346
Default 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.
MotorBikeLes is offline  
Old 16th Oct 2021, 1:42 pm   #6
pentoad
Hexode
 
Join Date: Feb 2011
Location: Newcastle upon Tyne, Tyne and Wear, UK.
Posts: 280
Default Re: Help identifying a resistor please

Quote:
Originally Posted by MotorBikeLes View Post
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.
They have decreased in value, they should be 4.7K 5% but Y1 is 4.1K amd 4K
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.
pentoad is offline  
Old 16th Oct 2021, 3:29 pm   #7
Sideband
Dekatron
 
Sideband's Avatar
 
Join Date: Oct 2003
Location: Croydon, Surrey, UK.
Posts: 7,548
Default 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....
__________________
There are lots of brilliant keyboard players and then there is Rick Wakeman.....
Sideband is offline  
Old 16th Oct 2021, 4:33 pm   #8
Chris55000
Nonode
 
Join Date: Aug 2007
Location: Walsall Wood, Aldridge, Walsall, UK.
Posts: 2,853
Default 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
__________________
It's an enigma, that's what it is! This thing's not fixed because it doesn't want to be fixed!
Chris55000 is offline  
Old 16th Oct 2021, 7:17 pm   #9
pentoad
Hexode
 
Join Date: Feb 2011
Location: Newcastle upon Tyne, Tyne and Wear, UK.
Posts: 280
Default Re: Help identifying a resistor please

Quote:
Originally Posted by Chris55000 View Post
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
How long are they?
pentoad is offline  
Old 16th Oct 2021, 7:42 pm   #10
The Philpott
Dekatron
 
The Philpott's Avatar
 
Join Date: Aug 2016
Location: Colchester, Essex, UK.
Posts: 4,081
Default 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
The Philpott is offline  
Closed Thread

Thread Tools



All times are GMT +1. The time now is 1:52 pm.


All information and advice on this forum is subject to the WARNING AND DISCLAIMER located at https://www.vintage-radio.net/rules.html.
Failure to heed this warning may result in death or serious injury to yourself and/or others.


Powered by vBulletin®
Copyright ©2000 - 2024, vBulletin Solutions, Inc.
Copyright ©2002 - 2023, Paul Stenning.