[AMPS] 811a to 572b conversion

[Lee Roberts]

Forgive my ignorance, but, what is "zsac"? It's been a long time
since I've worked with tubes but I don't recall such a term ever
being used.

Too bad you didn't give a real e-mail address because I wonder why
someone that hates spam is using Juno. Last time I used Juno there
were all kinds of advertisements that were displayed.

	73.....Lee (KI7RW - ki7rw@arrl.net)

>From: nospam4me@juno.com
>Date: 2/8/00  4:42:46AM
>To: amps@contesting.com
>Subject: [AMPS] 811a to 572b conversion
>
>
>
>: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. 
>
>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
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