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Resistor Substitutions

misterguitar

misterguitar

Active Member
So I have a question for you guys. I have come across a couple of ceramic encased resistors I'm planning to replace to increase relaibility. They seem to be resistors cemented or potted in rectangular ceramic cases. There is one in the power supply section and the other 4 are emitter resistors in the output stage. The question I have is are these wirewound resistors or standard metal oxide or metal film? Also what is the typical tollerance of these? The one on the power supply is a 3 watt 220ohm and the emitter resistors are 2 watt .33 ohm.

I was planning to replace these with metal foil at the correct wattage in flameproof cases with 230C operating temp at 5% tolerance. woud those be suitable? Its the ceramic brick cases that has me wondering. No idea what is inside! And the service manual just says Ce. R. lol
 

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The K after the ohm symbol is your tolerance code - 10%. Those wirewound resistors are pretty reliable so if they're still reading their rated value you can probably leave them. If they're running close (or even like half) their wattage limit it might be worth upgrading them though.
 
Brian1970 said:
The K after the ohm symbol is your tolerance code - 10%. Those wirewound resistors are pretty reliable so if they're still reading their rated value you can probably leave them. If they're running close (or even like half) their wattage limit it might be worth upgrading them though.
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OK I wondered about that if it meant Kohms or what! Thanks for the information. The cement in a few of them is cracking and loose. I assume just deteriortation from heat from near half century of use lol.
 
If they're cracking, you're probably right. Heat cycles over a long time can do that to those cement resistors especially if they're running near their watt limit and getting really hot. It won't hurt anything to increase the watt rating. A higher watt rating will run cooler. Just make sure what you get will still fit.
 
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