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Re: [Amps] SB 220 Exploding Resistor

Subject: Re: [Amps] SB 220 Exploding Resistor
From: George <>
Date: Tue, 19 Jan 2016 09:33:34 -0600
List-post: <">>
Have you ever looked at Surface Mount Power Film Resistors? A 25 ohm/ 25 watt is available from Mouser at around $6. I used one of these as the input resistor on a tetrode amp several years ago and it has work without any issues.

73, George

On 1/18/2016 3:13 PM, John Lyles wrote:
If you get a strong enough wirewound resistor, this can suffice as the surge current limiting resistor for a spark over in a tube. With 250 amps at the beginning of the overcurrent (2500 V/10 ohms) spike, there is enough magnetic field to break a wirewound R as the windings have mechanical force between turns. I have always used bulk carbon for series R, like Kanthal Globar makes. They are exactly the right part for this.

Finding them through distribution might be a problem, though. Has anyone else used these?


Date: Sun, 17 Jan 2016 13:19:20 -0500
From: "Carl" <>
To: "Tom Hellem" <>, <>
That blown resistor may have been underated and blew during a tube arc. The idea of a surge suppressor is to not fail and allow the milliseconds for a
fuse/breaker to open.
A 10-15 Ohm 20-25W Real wirewound resistor will cure that problem. Look for
Vitreous Enamel in the description.

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