[AMPS] 811a to 572b conversion

[Mark S Graalman]

Zero Signal Anode Current


Mark  WB8JKR

On Wed, 9 Feb 2000 09:23:19 -0700 "Lee Roberts" <ki7rw@scottsbluff.net>
writes:
>
>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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>
>
>
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________________________________________________________________
YOU'RE PAYING TOO MUCH FOR THE INTERNET!
Juno now offers FREE Internet Access!
Try it today - there's no risk!  For your FREE software, visit:
http://dl.www.juno.com/get/tagj.

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