[Amps] Meter protection

[Steve Thompson]

If you're trying to protect a 'bare' meter, where FSD is likely to 
be well below 0.7V, it's worth considering big Schottky diodes as 
the voltage drop is somewhat lower. Prices aren't high but if 
you're miserly scrap computer PSUs usually yield moderate current 
diodes. In one amp where I did this, I put several in parallel to 
get 40 or 50A rating so the glitch current resulted in about 0.4V max.

Steve

> Carl wrote:
>>
>>
>>Ian, do you have any references to those diodes NOT protecting a 
>>SB-200/220 meter?  I certainly dont and have seen many failed 1N400x 
>>diodes that saved the meter. Redesigining the Heath circuits is not an 
>>option to most users.
>>
> Granted - for those particular meters in that particular amplifier.
> 
> Carl and I are approaching the problem from two different directions. He 
> repairs many examples of the same models with the same faults, so he 
> builds up a wide database of experience. But my boards sell mostly to 
> individual constructors - every amp is different, and the only way I can 
> cover that wide range of unknown situations is to aim for the maximum 
> possible protection.
> 
> The "0.5V full scale" idea can do that. Bill's method using a series 
> resistor is the simplest, while mine will work with a wider range of 
> meters.
> 
> 
> -- 
> 
> 73 from Ian GM3SEK