Re: Help reclaiming the magic smoke that came out of my 50W PA #help #magicsmoke #troubleshooting


R. Tyson
 

On Sat, Apr 16, 2022 at 07:50 PM, Charles Johnson wrote:
Also, while Hans lists 85mA in the build instruction guide, on my first bias adjustment attempt, I was measuring 93mA, and in another thread, someone mentions a bias value well in excess of 100mA. Is there a common window in which the bias values usually fall?
My amps were nowhere near 93mA and as mentioned in the instructions your amp may be different... so there doesn't seem to be an ideal value and I think it will vary according to the IRF510's fitted into your particular amp. All you are looking for is the point where they just turn on and that can vary from batch to batch of IRF 510's.  Somewhere else and with a different amplifier there is a tale of woe. The guys involved blew up several IRF510's by setting the bias to a particular voltage or current (can't remember which they were using) then they had a lucky break and found out that IRF510's needed setting individually not to some standard value printed somewhere else. Once they realised that each transistor was different then they stopped blowing them up.

Reg                       G4NFR

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