[Amps] 47 Ohm 5 watt

Bryan Swadener bswadener at yahoo.com
Mon Aug 13 18:02:43 EDT 2018

The 2W CC resistors sold by eBay seller 'bigsmythe74' are Allen-Bradley RCR-series. IMO, that's as good as they get. The exact value isn't terribly critical -- between about 27Ω and 100Ω is OK (to kill the Q of the inductor). Sorting on price, he has 56Ω/±10%/2W for $1.00/each + $3.50/order shipping (see http://www.ebay.com/itm/400880759592). 
The cause of soaring CC resistor value is related to moisture absorption over time. In a past life, I was doing production test/repair of aviation electronic CCAs. A certain board used a 1MΩ/¼W CC resistor in two places. In-circuit pretesting invariably showed them to be around 1.4MΩ. Except for soldering, they were never above room temperature. The resistors were alternates to the first choice (metal film). I expect they were trying to use the CC resistors up. They were... we changed them to the MF before they saw power. 
vy 73, Bryan WA7PRC 
Date: Sun, 12 Aug 2018 14:36:44 -0400
From: Carl
Subject: Re: [Amps] 47 Ohm 5 watt

Yeah, it might take another 30+ years for that to happen if they are good 
----- Original Message ----- 
From: Bill Turner
To: Amps group
Sent: Saturday, August 11, 2018 3:01 PM
Subject: Re: [Amps] 47 Ohm 5 watt

> I strongly recommend against using carbon composition resistors for
> anything except restoring antique equipment to its "original"
> condition. They are notorious for changing value over time, especially
> when hot. Either metal film or metal oxide type is far superior in
> terms of stability.
> 73, Bill W6WRT   

More information about the Amps mailing list