Other reasons for parallel resistors - Page 2 - Electronic Circuits Projects Diagrams Free

Roff · 23rd December 2004, 03:37 AM

Quote:

Originally Posted by TheOne

Also, any small AC signal on the input of the 7805 will be attenuated by at least by 60dB at the low end and about 40dB at 100kHz

Yeah, that should have been one of my points. Thanks.

**Nigel Goodwin** · 23rd December 2004, 07:03 AM

Quote:

Originally Posted by Dean Huster

I might temper Nigel's advice about replacing an over-dissipating resistor or resistor pair with a higher wattage assembly. Assuming the circuit was designed properly and worked fine originally, an overdissipating resistor is usually an indicator of another problem in the circuit causing excess current to be drawn.

Yes, assuming that was the case. But usually it's down to simply poor design, or at least poor manufacturing. Cost driven manufacturing often results in products with poor reliability, due to excessive cost cutting.

Also your fuse comparison is hardly relevent, a fuse is a safety device, two 3W resistors in parallel is hardly a safety device! - and certainly shouldn't be designed as such!.

Styx · 23rd December 2004, 08:03 AM

Quote:

Originally Posted by Nigel Goodwin

Also your fuse comparison is hardly relevent, a fuse is a safety device, two 3W resistors in parallel is hardly a safety device! - and certainly shouldn't be designed as such!.

Unless it was an excessive cost-saving by bloody stratigic-shopping!!! how can people with no engineering background have the authority to change a part of your design with no consoltation with some form of design team

pandaemonium · 23rd December 2004, 08:43 AM

I'm only assuming that what I had was Johnson noise. I have a remote control extender, the indicator LED would be active when the receiver was first turned on and then gradually dissipate after a couple of minutes and the remote control was very unresponsive during this time. After changing the resistor, when turning on the receiver (after letting the receiver cool) there is very little activity on the LED and it is gone after about 10-15 seconds. I don't know what else it could have been but it seems to have been temperature related.

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23rd December 2004, 08:43 AM	(permalink)
pandaemonium	I'm only assuming that what I had was Johnson noise. I have a remote control extender, the indicator LED would be active when the receiver was first turned on and then gradually dissipate after a couple of minutes and the remote control was very unresponsive during this time. After changing the resistor, when turning on the receiver (after letting the receiver cool) there is very little activity on the LED and it is gone after about 10-15 seconds. I don't know what else it could have been but it seems to have been temperature related.