[AMPS] 811a to 572b conversion

[measures]

>
>
>:From: Lee Roberts <ki7rw@arrl.net>
>:I have heard of a rumor about a mod for this amp that involves 
>:changing the tube to an 572 and changing a tap on the 
>:transformer. Is it true? If so, anyone have any details on this 
>:and/or experience with this?
>
>An 811a to 572b conversion requires some of the following 
>considerations: 
>
>The 572b is often larger in size.
>The zsac bias voltage will have to be reset. If it's a zener 
>diode, you'll have to replace it. Often the "string of diodes" 
>method becomes unwieldy when higher bias voltages 
>are required. 24 volts is much more practical to obtain with 
>one hefty zener diode. 
>
What would be a situation where 24v of operate bias is required to obtain 
normal ZSAC for a 572B/T160L?
thanks.

>There have been reports of stability problems with 
>"higher gain 572b's."   The conversions I've done gave no 
>indications of parasitics because Nichrome Suppressors 
>were installed during the retrofit. 
>I used NOS Jan tubes...
>
>cheers
>skipp

-  Rich..., 805.386.3734, www.vcnet.com/measures.  


--
FAQ on WWW:               http://www.contesting.com/ampsfaq.html
Submissions:              amps@contesting.com
Administrative requests:  amps-REQUEST@contesting.com
Problems:                 owner-amps@contesting.com
Search:                   http://www.contesting.com/km9p/search.htm