In Reply to: My Fisher 500B just blew up. posted by Sidewinder on April 25, 2007 at 23:47:16:
The new 7591 won't tolerate the high value grid leak resistors fisher used. They must be made lower in value. Likely you will want to bump up the coupling cap size one notch to maintain frequency response. The limit is 0.3 megs and NOS will handle that but the new ones won't. I'd say no more than 220K. Jim McShane has discussed this before so search the archives. It is real (I promise) and don't discount it.Russ
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Follow Ups
- Important and probable cause for failure - Russ57 05:58:45 04/26/07 (3)
- Re: Important and probable cause for failure - Jim McShane 06:57:27 04/26/07 (2)
- I have 7591S (not 'A') - do these also need mods? - PeterI 21:29:10 04/26/07 (1)
- Re: I have 7591S (not 'A') - do these also need mods? - Eli Duttman 23:31:03 04/26/07 (0)