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Resistor substitution 20% range? - Printable Version

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Resistor substitution 20% range? - lyle - 03-02-2012

Hello,

I plan to replace most of the resistors in my Philco 60, but cannot find exact values. I figure I can choose replacement values 20% above and below the value of the resistors which need to be replaced. I was wondering if it is better to be above or below the replaced resistors ohmic value, or if it even matters?

Thanks,

lyle



RE: Resistor substitution 20% range? - codefox1 - 03-02-2012

(03-02-2012, 07:29 PM)lyle Wrote:  Hello,

I plan to replace most of the resistors in my Philco 60, but cannot find exact values. I figure I can choose replacement values 20% above and below the value of the resistors which need to be replaced. I was wondering if it is better to be above or below the replaced resistors ohmic value, or if it even matters?

Thanks,

lyle

If you are into a restoration rather than a repair, just replace all of them with the next available value plus or minus 10% of stated value. That should hold for a few more dacades. All old carbon resistors will test high. Only a a matter of time until it "matters."

RE: Resistor substitution 20% range? - lyle - 03-02-2012

Thanks for the info. A few more decades will be great.

lyle

RE: Resistor substitution 20% range? - Radioroslyn - 03-02-2012

I'll add to what Codefox sez. Back in the day alot of resistors where standard values now days not all of these older resistors are standard anymore. So you may not be able to find the exact value but bear in mind that back then 20 percent was standard.So you've got a fairly broad range to pick from. WELCOME TO THE PHORUM!!!
Terry

RE: Resistor substitution 20% range? - codefox1 - 03-02-2012

(03-02-2012, 09:56 PM)7estatdef Wrote:  I'll add to what Codefox sez. Back in the day alot of resistors where standard values now days not all of these older resistors are standard anymore. So you may not be able to find the exact value but bear in mind that back then 20 percent was standard.So you've got a fairly broad range to pick from. WELCOME TO THE PHORUM!!!
Terry

Welcome indeed, and most resistors are in fact 5% or better and only a few pennies apiece. If you have an odd value, you can order an assortment to find out which works better with your application or visit Mr. Ohm (Ohm's Las) to parallel or series what you got to what you need. Just be mindfull or lead dress if you start fooling around.

We're here.

RE: Resistor substitution 20% range? - Arran - 03-03-2012

Generally it's recommended that you go slightly higher in value if you can't get an exact value like with a power resistor. In some cases it wouldn't hurt to go bellow because the actual value will be above the marked value and close to what the schematic specifies like replacing a 500K ohm resistor with a 470K ohm. I would not go with + or - 20% though, that's too much. There are standard values of 5 and 10% tollerance, 5% is the most common, there are also ones with a 1% tollerance and precision resistors.
I've made a habit of replacing any resitor more then 10% off in value while overhauling a radio, when 1/2 watt 5% tollerance resistors are $.05 cents or less there isn't much point in not changing them. In the case of the ones found in Philco 60s many are body-end-dot code carbon resitors of the dogbone style and those are notorious for drifting upwards in value as much as 100% or more, even without being overloaded or damaged in some way. Whenever I restore a set from this era I always cound on replacing every carbon resistor as well as every capacitor in the set, it just doesn't make sense not to.
Regards
Arran

RE: Resistor substitution 20% range? - lyle - 03-03-2012

Thanks Arran,

I've checked every resistor in the set and only two are within 10%. I will replace them all as well as rebuild the Bakelite blocks. tone control, replacing all caps with the exception of the mica caps.

Where do you find resistors for $0.05? JustRadios and TubesAndMore are around $0.45 each. Do you buy them by the boxcar load? Icon_smile

I would like to ask how I can get beyond just being a mechanic. I've studied up on basic electronics and understand resistance, capacitance, resonance, etc., went through an RCA radio course on disc, so I get the theory. But, I would really like to know why a certain resistor is where it is and what it does. I would like to look at a schematic and understand what all the components do and how everything ties together. I've restored a number of nice old radios mainly by recapping. I have a couple of cheap old tube radios that I could experiment on. I've also home-brewed some crystal and one tube broadcast and SW band radios. I may not be expressing this very well, but I hope you get my drift.

I would be happy to hear from anybody on this subject.

Thanks for replying to my resistor question.

lyle



RE: Resistor substitution 20% range? - lyle - 03-03-2012

(03-02-2012, 09:56 PM)7estatdef Wrote:  I'll add to what Codefox sez. Back in the day alot of resistors where standard values now days not all of these older resistors are standard anymore. So you may not be able to find the exact value but bear in mind that back then 20 percent was standard.So you've got a fairly broad range to pick from. WELCOME TO THE PHORUM!!!
Terry

Thanks,

This Phorum and you folks are great.

Thanks for your reply.

lyle

RE: Resistor substitution 20% range? - lyle - 03-03-2012

(03-02-2012, 10:45 PM)codefox1 Wrote:  
(03-02-2012, 09:56 PM)7estatdef Wrote:  I'll add to what Codefox sez. Back in the day alot of resistors where standard values now days not all of these older resistors are standard anymore. So you may not be able to find the exact value but bear in mind that back then 20 percent was standard.So you've got a fairly broad range to pick from. WELCOME TO THE PHORUM!!!
Terry

Welcome indeed, and most resistors are in fact 5% or better and only a few pennies apiece. If you have an odd value, you can order an assortment to find out which works better with your application or visit Mr. Ohm (Ohm's Las) to parallel or series what you got to what you need. Just be mindfull or lead dress if you start fooling around.

We're here.

Thank you. I can't believe how great you guys are. I really love radios that glow. Don't know why, and don't care. I just want to rescue as many as I can from the dump. Oh sorry, today it's a landfill.

lyle



RE: Resistor substitution 20% range? - codefox1 - 03-04-2012

(03-03-2012, 12:52 PM)lyle Wrote:  
(03-02-2012, 10:45 PM)codefox1 Wrote:  
(03-02-2012, 09:56 PM)7estatdef Wrote:  I'll add to what Codefox sez. Back in the day alot of resistors where standard values now days not all of these older resistors are standard anymore. So you may not be able to find the exact value but bear in mind that back then 20 percent was standard.So you've got a fairly broad range to pick from. WELCOME TO THE PHORUM!!!
Terry

Welcome indeed, and most resistors are in fact 5% or better and only a few pennies apiece. If you have an odd value, you can order an assortment to find out which works better with your application or visit Mr. Ohm (Ohm's Las) to parallel or series what you got to what you need. Just be mindfull or lead dress if you start fooling around.

We're here.

Thank you. I can't believe how great you guys are. I really love radios that glow. Don't know why, and don't care. I just want to rescue as many as I can from the dump. Oh sorry, today it's a landfill.

lyle

You can often find resistor assortments of 1000 or so pieces 1/4 or 1/2 watt at very low unit cost from suppliers or on Ebay. Then add a few 10 packs of 2 watt types for typical voltage dividers, etc... and you're all set.

RE: Resistor substitution 20% range? - lyle - 03-05-2012

(03-04-2012, 12:42 PM)codefox1 Wrote:  
(03-03-2012, 12:52 PM)lyle Wrote:  
(03-02-2012, 10:45 PM)codefox1 Wrote:  
(03-02-2012, 09:56 PM)7estatdef Wrote:  I'll add to what Codefox sez. Back in the day alot of resistors where standard values now days not all of these older resistors are standard anymore. So you may not be able to find the exact value but bear in mind that back then 20 percent was standard.So you've got a fairly broad range to pick from. WELCOME TO THE PHORUM!!!
Terry

Welcome indeed, and most resistors are in fact 5% or better and only a few pennies apiece. If you have an odd value, you can order an assortment to find out which works better with your application or visit Mr. Ohm (Ohm's Las) to parallel or series what you got to what you need. Just be mindfull or lead dress if you start fooling around.

We're here.

Thank you. I can't believe how great you guys are. I really love radios that glow. Don't know why, and don't care. I just want to rescue as many as I can from the dump. Oh sorry, today it's a landfill.

lyle

You can often find resistor assortments of 1000 or so pieces 1/4 or 1/2 watt at very low unit cost from suppliers or on Ebay. Then add a few 10 packs of 2 watt types for typical voltage dividers, etc... and you're all set.

Sounds like a plan. Thanks lyle

RE: Resistor substitution 20% range? - Arran - 03-06-2012

(03-03-2012, 12:40 PM)lyle Wrote:  Thanks Arran,

I've checked every resistor in the set and only two are within 10%. I will replace them all as well as rebuild the Bakelite blocks. tone control, replacing all caps with the exception of the mica caps.

Where do you find resistors for $0.05? JustRadios and TubesAndMore are around $0.45 each. Do you buy them by the boxcar load? Icon_smile

I would like to ask how I can get beyond just being a mechanic. I've studied up on basic electronics and understand resistance, capacitance, resonance, etc., went through an RCA radio course on disc, so I get the theory. But, I would really like to know why a certain resistor is where it is and what it does. I would like to look at a schematic and understand what all the components do and how everything ties together. I've restored a number of nice old radios mainly by recapping. I have a couple of cheap old tube radios that I could experiment on. I've also home-brewed some crystal and one tube broadcast and SW band radios. I may not be expressing this very well, but I hope you get my drift.

I would be happy to hear from anybody on this subject.

Thanks for replying to my resistor question.

lyle

Well for starters Mauser Electronics sells quite a variety, not sure why common 1/2 watt resistors would be $.45 each that is more in line with what a 1 watt or higher resistor would cost. I would also try WJOE.com and Bob's Old Radios and Radio Daze for comparisons but Mauser has the largest selection. Quite often a more local parts jobber would carry most of what you would need as well but the price would be higher although still not $.45 each.
Regards
Arran


RE: Resistor substitution 20% range? - lyle - 03-07-2012

(03-06-2012, 12:47 AM)Arran Wrote:  
(03-03-2012, 12:40 PM)lyle Wrote:  Thanks Arran,

I've checked every resistor in the set and only two are within 10%. I will replace them all as well as rebuild the Bakelite blocks. tone control, replacing all caps with the exception of the mica caps.

Where do you find resistors for $0.05? JustRadios and TubesAndMore are around $0.45 each. Do you buy them by the boxcar load? Icon_smile

I would like to ask how I can get beyond just being a mechanic. I've studied up on basic electronics and understand resistance, capacitance, resonance, etc., went through an RCA radio course on disc, so I get the theory. But, I would really like to know why a certain resistor is where it is and what it does. I would like to look at a schematic and understand what all the components do and how everything ties together. I've restored a number of nice old radios mainly by recapping. I have a couple of cheap old tube radios that I could experiment on. I've also home-brewed some crystal and one tube broadcast and SW band radios. I may not be expressing this very well, but I hope you get my drift.

I would be happy to hear from anybody on this subject.

Thanks for replying to my resistor question.

lyle

Well for starters Mauser Electronics sells quite a variety, not sure why common 1/2 watt resistors would be $.45 each that is more in line with what a 1 watt or higher resistor would cost. I would also try WJOE.com and Bob's Old Radios and Radio Daze for comparisons but Mauser has the largest selection. Quite often a more local parts jobber would carry most of what you would need as well but the price would be higher although still not $.45 each.
Regards
Arran

Actually I need to read more carefully. JustRadios sells 5 packs of 1 watters for 59 cents. Which works fine for me. Apologies to Dave at JustRadios.

Now attending Remedial Reading,

Regards,

lyle