Unusual resistors?

[Ian - G4JQT]

Can anyone suggest what the figure after the 1 % means on these resistors?

eg: 56 ohm 1% 36; 27k ohm 1% 56; 180k ohm 76

Do these resistors have any particular properties apart from tolerance?

Thanks.

Ian

(Incidentally, how do I type the omega symbol on the forum? [alt 234] doesn't work.)

[Radio Wrangler]

Not unusual, they're quite common in 50's/60's test equipment. Carbon film precision resistors, 1% tolerance. Different makes might be black or pink. They went out of use as metal film and metal oxide types took over.

After coating and capping a ceramic rod, a spiral cut was made in the coating allowing the resistance to be changed, and stopped automatically to get the tight tolerance.

Interesting to measure them and see haw far they've drifted.

David

(Incidentally, how do I type the omega symbol on the forum? [alt 234] doesn't work.)

I wouldn't bother, ohm spelt out always works, some fonts have something different, and ohm is one less key press than alt 234 !

The original question, is it temperature coefficient?

[Radio Wrangler]

No, tolerance of resistance value at time of manufacture and room temp.

David

[yesnaby]

Hello,

I still don't get what the extra numbers mean!

Michael

[Nickthedentist]

Nor me. The main question posed has been ignored, presumably because nobody knows.

N.

[Refugee]

Temperature drift rating in parts per million perhaps.

[paulsherwin]

I would just measure them. I do this with any NOS resistors before using them.

[AC/HL]

Several posts moved to a new thread: https://www.vintage-radio.net/forum/...d.php?t=108843

[Radio Wrangler]

I think those could be series or batch codes. The digits certainly don't correspond directly to common temperature coefficient ranges.

Welwyn used a pinker sort of coating and used to stick their name on everything unless forbidden by contract. I'd go looking for old Philips data first.

David

[Jac]

These certainly look like Philips resistors to me, and the code is a production code. Nothing to be determined from it I fear.

Jac

[Maarten]

Philips seems about right, the triangle rings a bell for that as well. The numbers are most likely batch numbers or encoded date codes.

[Radio Wrangler]

Paul's advice in post 8 is important. The resistance of many older types of resistor are known to change with time, even without them being used. So, despite being unused and despite the 1% marking, check them before using them.

Philips components were always better than average quality. A lot of information on the technology behind them as well as recommended circuits was printed in 'Philips Technical Review' if I remember the name right. It was distributed to major customers and would make good reading nowadays. The editor was C M Hargreaves, famous for his book on Phillips' Stirling engines.

HP has made the HP journal archive available on-line. Does anyone know if Philips has done the same?

David

[Ian - G4JQT]

Thanks for all the ideas and thoughts. So it appears the 'odd' numbers may be batch data.

I have measured about half of them (ranging from 330R to 470k) with a meter of claimed 1% accuracy, and as far as I can tell they're all more or less within spec.

Ian

[Radio Wrangler]

Then you might want to use them in period equipment for appaerance sake. I wouldn't use them for building anything new because they will be a bit noisier than metal film types.

Might be worth advertising them in small quantities and with the batch numbers declared, because they may have hitherto unsuspected audible properties like the mustard capacitors.

David

[Ian - G4JQT]

Originally Posted by Radio Wrangler

Might be worth advertising them in small quantities and with the batch numbers declared, because they may have hitherto unsuspected audible properties like the mustard capacitors.

I don't have a vast number of these resistors, just what was in the original photo and not a complete selection of values.

What's the story regarding the mustard capacitors and their audio properties? I always thought they were amongst the 'good guys' in the cast of old-ish capacitors in most of our type of work...

Ian

[m0cemdave]

David was making a tongue-in-cheek reference to them having become popular with the audio fraternity and the inevitable consequent price inflation...

They are definitely amongst the good guys, very high quality and not prone to going leaky like the contemporaneous paper types. No need for a "replace on sight" policy with those!