[ARC5] Solid State 6AL5

[Richard Knoppow]

     FWIW, when I got one of my SP-600-JX's it had a solid state 
rectifier in place of the 5R4. I removed it because I found all 
the voltages were too high. This was not from high line voltage, 
I checked that, it was the rectifier. When replaced with a 
standard 5R4 all were OK. This is a molded case made of resin of 
some sort on a standard tube base. I forgot about this until this 
thread and have no idea where to look for it but it had a label 
and was not home made.
     As fare as using solid state diodes for AVC, I think perhaps 
the difference in minimum voltage and effects of contact 
potential might require a change in the bias for AVC delay. I 
have not tested this. You may be aware that it has been standard 
practice since about the mid-1940s to put a dropping resistor in 
the filament of 6H6 and I think also 6AL5 tubes when used as 
noise limiters. This affects the contact potential and reduces 
the effects of hum from heater to cathode leakage. Obviously it 
would have no effect on solid state diodes. BTW, I have never 
found any technical paper about the filament resistors but all 
receiver manufacturers began to add them about the early to 
mid-1940. You would think the standard engineering texts would 
have something. Maybe I missed it but if anyone knows please tell 
me.

On 2/7/2018 12:29 PM, J Mcvey via ARC5 wrote:
> I'm curious...
> 
> 
> On Wednesday, February 7, 2018 12:39 PM, John Watkins 
> <jpwatkins9 at yahoo.com> wrote:
> 
> 
> I have the metal case off of one of my mil 6AL5s, it is encased 
> in an amber colored epoxy.  I could remove enough to see exactly 
> what is in there and provide a few pictures if it would be of 
> interest.
> 
> John WD5ENU
> 


-- 
Richard Knoppow
1oldlens1 at ix.netcom.com
WB6KBL