Help with resistor value - UK Vintage Radio Repair and Restoration Discussion Forum

coopzone · 27th May 2020, 9:36 am

Hello, i'm currently looking at an ULTRA T401 chassis. I'm having difficulty trying to work out what the colour marking are on a resistor, Trader sheet 859, R8 "diode load". According to the sheet it should be 470k. But it measures at 1m ? However i can't make the colour on the resister match either or even close!, maybe a 520k?

I've attached a picture, it's the mostly blue one - can anybody tell me how to read the value please?

Derek

barrymagrec · 27th May 2020, 9:44 am

Body looks blue. 620K, a standard value.

These types frequently go high with age, in my experience.

Herald1360 · 27th May 2020, 9:55 am

Did I imagine a reply from StationX? Reference to body tip spot?

Lucien Nunes · 27th May 2020, 10:01 am

It seems to have a grey band on the right-hand end, in which case it's 680k and the red blob is a (red) herring.

Station X · 27th May 2020, 10:04 am

Quote:

Originally Posted by Herald1360

Did I imagine a reply from StationX? Reference to body tip spot?

No you didn't, but I deleted it within the half hour window as it contained a typo.

Had there not been follow up posts I'd have edited it giving a reason.

Herald1360 · 27th May 2020, 10:11 am

Could be the underlying body colour. A little extra scratching would confirm.

680k would be a logical E6 20% value whereas 620k would be an unlikely E24 5% one.

ms660 · 27th May 2020, 10:13 am

680k...Body, end band, middle band......no other end band so +-20% tolerance.

Lawrence.

coopzone · 27th May 2020, 10:39 am

680k sound like a plan to me!, thanks everyone.

Chris55000 · 27th May 2020, 11:45 am

Hi!

Other than in test instruments, it was exceptional to use a 5% tolerance resistor in most consumer equipment of that era - it was often called up specially in the components list or circuit diagram when needed!

Therefore, unless especially called for otherwise, you need only consider the E12 series of values (1.0, 1.2, 1.5, 1.8, 2.2, 2.7, 3.3, 3.9, 4.7, 5.6, 6.8 & 8.2 and decades up) when repairing pre-1965 valved equipment.

The red blob on it is simply a blob of locking paint that happened to fall on the resistor's body.

Chris Williams

Sideband · 27th May 2020, 2:15 pm

There was a slight variation to the old 'body tip band' coding which was 'body tip spot'. Same protocol though so the main body is the first number (in this case 6), the tip is the second number (grey so 8) and the band is the third colour (yellow so 4 zeros). Gold or silver at the opposite tip would have meant 5 or 10 percent.

Just as well that this method of coding wasn't used for the modern 5 or 6 band resistors which I find totally confusing.

27th May 2020, 9:36 am	#1
coopzone Hexode Join Date: Jan 2018 Location: Cannock, Staffordshire, UK. Posts: 268	Help with resistor value Hello, i'm currently looking at an ULTRA T401 chassis. I'm having difficulty trying to work out what the colour marking are on a resistor, Trader sheet 859, R8 "diode load". According to the sheet it should be 470k. But it measures at 1m ? However i can't make the colour on the resister match either or even close!, maybe a 520k? I've attached a picture, it's the mostly blue one - can anybody tell me how to read the value please? Derek Attached Thumbnails

27th May 2020, 9:44 am	#2
barrymagrec Octode Join Date: Dec 2017 Location: Morden, Surrey, UK. Posts: 1,557	Re: Help with resistor value Body looks blue. 620K, a standard value. These types frequently go high with age, in my experience.

27th May 2020, 9:55 am	#3
Herald1360 Dekatron Join Date: Feb 2007 Location: Leominster, Herefordshire, UK. Posts: 16,535	Re: Help with resistor value Did I imagine a reply from StationX? Reference to body tip spot? __________________ ....__________ ....\|____\|\|__\|__\_____ .=.\| _---\__\|__\|_---_\|. .........O..Chris....O

27th May 2020, 10:01 am	#4
Lucien Nunes Rest in Peace Join Date: Apr 2008 Location: London, UK. Posts: 2,508	Re: Help with resistor value It seems to have a grey band on the right-hand end, in which case it's 680k and the red blob is a (red) herring.

27th May 2020, 10:11 am	#6
Herald1360 Dekatron Join Date: Feb 2007 Location: Leominster, Herefordshire, UK. Posts: 16,535	Re: Help with resistor value Could be the underlying body colour. A little extra scratching would confirm. 680k would be a logical E6 20% value whereas 620k would be an unlikely E24 5% one. __________________ ....__________ ....\|____\|\|__\|__\_____ .=.\| _---\__\|__\|_---_\|. .........O..Chris....O

27th May 2020, 10:13 am	#7
ms660 Dekatron Join Date: Apr 2011 Location: Cornwall, UK. Posts: 13,454	Re: Help with resistor value 680k...Body, end band, middle band......no other end band so +-20% tolerance. Lawrence.

27th May 2020, 10:39 am	#8
coopzone Hexode Join Date: Jan 2018 Location: Cannock, Staffordshire, UK. Posts: 268	Re: Help with resistor value 680k sound like a plan to me!, thanks everyone.

27th May 2020, 11:45 am	#9
Chris55000 Nonode Join Date: Aug 2007 Location: Walsall Wood, Aldridge, Walsall, UK. Posts: 2,868	Re: Help with resistor value Hi! Other than in test instruments, it was exceptional to use a 5% tolerance resistor in most consumer equipment of that era - it was often called up specially in the components list or circuit diagram when needed! Therefore, unless especially called for otherwise, you need only consider the E12 series of values (1.0, 1.2, 1.5, 1.8, 2.2, 2.7, 3.3, 3.9, 4.7, 5.6, 6.8 & 8.2 and decades up) when repairing pre-1965 valved equipment. The red blob on it is simply a blob of locking paint that happened to fall on the resistor's body. Chris Williams __________________ It's an enigma, that's what it is! This thing's not fixed because it doesn't want to be fixed!

27th May 2020, 2:15 pm	#10
Sideband Dekatron Join Date: Oct 2003 Location: Croydon, Surrey, UK. Posts: 7,571	Re: Help with resistor value There was a slight variation to the old 'body tip band' coding which was 'body tip spot'. Same protocol though so the main body is the first number (in this case 6), the tip is the second number (grey so 8) and the band is the third colour (yellow so 4 zeros). Gold or silver at the opposite tip would have meant 5 or 10 percent. Just as well that this method of coding wasn't used for the modern 5 or 6 band resistors which I find totally confusing. __________________ There are lots of brilliant keyboard players and then there is Rick Wakeman.....