Cheap Resistors...an issue???

[Chris K]

I heard Shango recently commenting on cheap metal film resistors and how they should be avoided because of voltage issues etc. I've been getting the large packs of very inexpensive 1% 1 and 2 watt Chinese resistors available through Amazon. I've never found one that's out of specification or has gone bad after installation in a vintage TV. I used to buy resistors through DK and Mouser and I stuck with the better known suppliers but so far I've not seen a difference between these and the more inexpensive resistors. I'm not talking about the ceramic, dusty 1.0kOhm resistors that come loose in a bag. These are on tape, glossy finished and within the advertised 1% specification.

Does anyone think I'm risking long term reliability by using these resistors?

[Alex KL-1]

All those cheapo ones (carbon and metal film) I used are surviving well for years since I first adopted them. Of course, low power metal film ones (the small physical ones, like 1/8W) indeed will have issues with higher voltage.

[Electronic M]

I typically buy 1W and 2W resistors (most 1W are the same size or smaller than the 1/4W -1/2W carbon they typically replace) from mouser or digikey and I haven't had issues despite only sometimes bothering to spec high voltage. The place to be careful is B+ boost (600-1500V) focus dividers, and electrostatic deflection sets that divide 6KV with multiple resistors. The higher 100k-10M parts I try to spec higher voltage for.
Another possible issue is if the film is an inductive spiral and your using it in tuner or IF circuits.

[Chris K]

Wow…induction in the IF never occurred to me. What should I use instead? How can you tell, or can you tell, if a metal film resistor contains an inductive spiral?

[bandersen]

I'm pretty sure all metal and carbon film resistors are spiral cut. Unless you're in the GHz, the inductance shouldn't be an issue.

Use carbon comp if you think it might be.

Personally, I use Vishay PR01, PR02 and PR03 metal film 5% series resistors for everything up to 1M ohm. I buy the common value 100 at a time to get the cost down to a few cents each.
VR37 resistors above 1M. Rated for 3,500 volts - handy for those electrostatic sets.

BTW standard voltage ratings are
1/4 W = 250 volts
1/2W = 350volts
1W = 500 volts
2W = 750 volts

[Chris K]

Thanks Bob...Vishay is what I used to buy off Mouser. I know it's overkill to buy 1% resistors but I can get 3 times as many as the more mainstream brands and every resistor I've tested prior to installation has been spot on in value. I guess the proof will be in the longevity.

They're about 6 cents per resistor and I think I used to pay 30-40 cents each for the Vishay

[bandersen]

The PR01 series are about 8 cents each / 100 or 10 cents / 25. I'd rather go with reputable, name brand when were only talking about pennies.

The color stripes are vibrant and easy to read. The bodies and redish brown rather than bright blue.

[Chris K]

[bandersen]

All that being said, I've used plenty of the cheap, bulk, blue 1% resistors as well without any issues. I made sure to use 1/2 and 1W which should be able to handle the higher voltages.

[Chris K]

I haven’t used a less than 1 watt resistor in any restoration I’ve done. Probably overkill but it just makes me feel more comfortable that the circuitry is more robust. Is there a negative to using a 1 watt resistor when the parts list describes it as 1/2 watt?

[bandersen]

Not that I know of.

[MuzzcoVW]

Originally Posted by Chris K

I haven’t used a less than 1 watt resistor in any restoration I’ve done. Probably overkill but it just makes me feel more comfortable that the circuitry is more robust. Is there a negative to using a 1 watt resistor when the parts list describes it as 1/2 watt?

There shouldn't be. I was taught to replace 1/2 watt with 1 watt etc. and never had any issues. Of course years ago you could still find carbon comp everywhere. I feel the modern resistors are in general far more robust...but for the few cents or dollars they cost I'm not buying unknown Chineesium off the jungle website, I stick with Mouser or Digikey in general and have had no issues with Vishay brand

[Chris K]

Originally Posted by MuzzcoVW

There shouldn't be. I was taught to replace 1/2 watt with 1 watt etc. and never had any issues. Of course years ago you could still find carbon comp everywhere. I feel the modern resistors are in general far more robust...but for the few cents or dollars they cost I'm not buying unknown Chineesium off the jungle website, I stick with Mouser or Digikey in general and have had no issues with Vishay brand

Thanks. I have to admit, the reason I get the Chineesium ones is Amazon and the option of overnight delivery on most of the parts I've ordered. I have an issue with delaying gratification!

When I first began doing this, I had an attitude that anything made today...resistors, capacitors, diodes...even if they were cheap imports would be many times more reliable than what was installed in these units 70 years ago. I used to buy film caps in those variety packs for $10 and no name electrolytic filter caps by the dozens. Then I restored one of those art deco RCA 8" portables and could not get the horizontal to lock in no matter what I did or what I tested. Eventually, I traced the issue to one of these brand new pieces of junk...





That was it for using film or electrolytic mystery caps in a serious restoration as a permanent replacement. I have a few restored radios I did years ago that never worked right that I need to go through and replace the garbage I put in them. I haven't had that kind of experience with resistors yet but...I seem to learn electronic lessons the hard way!

[Electronic M]

If you do a significant amount of restoration work it might be worth keeping stock of various values. My initial resistor stock were parts I scavenged off boards and an assortment of NOS carbon comps...I got sick of the NOS carbon comps being as far off tolerance as the ones I wanted to replace so I got a ~$40 1W Yaego or Vishay resistor kit off of Digikey that had 5 each of a ton of resistance values between 6.8K and 1M...I originally meant to order a 2W kit but somehow goofed. They have other kits in both 1W and 2W that cover 62 ohms to ~6K. Eventually I had 4 of those starter kits sifted into drawer cabinets and whenever I would do a cap order depending on how few of a given value remained (actual demand) and how commonly I think I need a value (perceived demand) I order 10-100 of a given value/power to restock.
I don't have to worry about the long gratification of next day or next week shipping, my instant gratification is being able to blindly reach over to the side of my bench the drawers are on and grab what I need without pausing for a parts order.
On resistors my re-order point was initially when I had 3 left...On some common values 1k, 10k, 100k, 1M if I hit 10-20 I buy more.
Caps I allow to reach "0" in my main stock and are usually the trigger for an order (I try to only order 1-2x a year and anticipate what I need to save on shipping... unless doing client work where parts and shipping are on their dime) and I allow them to reach 0 in my main stock because I have a glorified pill sorting box with about 5 of each value I use that I bring on vacations to do on the fly recaps of things I buy...I can usually use that as a buffer for the main stock. I need to make a resistor travel kit too. I should probably also keep a small box of most commonly needed tubes at the cabin too (there are spares for the radios that live there hidden in said radios) but that's a big undertaking cross referencing subs and guestimating what I'll find...

[Chris K]

You are ready to go Tom! I bought a Chineseum metal film 1 and 2 watt assortment box of resistors, 1% and everything from 3 ohms to a megaohm. So far, they have all been spot on in value and have been fine in service. I've been using the mystery caps, both film and electrolytic for diagnosing and testing since I got educated by the 100uF capacitor.