>
>
>: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.
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