[ARC5] Solid State 6AL5

[Bill Cromwell]

Hi Peter,

I think the filaments/heaters in those higher power amplifiers have 
special coatings on them that require being hot *before* B+ is applied. 
The tubes used by mere mortals like me are not so finicky. We DO have to 
be aware that the parts downstream from the solid state subs are going 
to see higher voltages and if they are tubes they are going to see it, 
'ready or not'. Most likely to suffer are some of the capacitors that 
may have already been operating close to their limits. Or resistors that 
were already being abused.

Anybody is free to delay onset of B+ with appropriate means. There are 
probably any number of ways to do it. Just like my means of containment 
under an inverted washtub in cases that may be catastrophic (see earlier 
comments in this thread). Things can range from simple to exquisite, 
Rube Goldberg designs.

73,

Bill  KU8H

On 02/05/2018 06:03 PM, Peter Gottlieb wrote:
> There is also the issue of sequencing. If you replace a tube with solid
> state you are applying B+ to all the tubes before the filaments are
> warmed up. Maybe for low voltages it’s not so much of an issue but for
> something like the radar test set I was recently working on with over
> 1kV it certainly made me think hard about whether I wanted to do that,
> ultimately deciding to keep the tube rectifier.
>
> My knowledge is limited here, but I do know in larger tube amps there is
> a time delay relay to delay B+ so there must be some basis for that.
>
>
> Peter
>


-- 
bark less - wag more