Vintage Asylum

RE: Fisher 500C Up and running again

24.27.41.140

Triode_Kingdom

In Reply to: RE: Fisher 500C Up and running again posted by Daveslater on July 21, 2023 at 10:24:53

Glad it's OK. Those aren't safety resistors. They're installed to allow measuring the idle bias at each tube.

Follow Ups:

RE: Fisher 500C Up and running again - Daveslater 22:03:12 07/21/23 (9)
When I refurbished the Fisher I installed the resistors on the advice of member smglaw. He suggested installing low wattage 10 ohm so they could be used both for measurement and also to act as a fuse to protect the output transformers. They have performed the fuse role very well for me.
- RE: Fisher 500C Up and running again - Triode_Kingdom 08:40:30 07/22/23 (0)
  Are they fusible resistors? I'm not a fan of relying on standard resistors to burn up and go open. Instrument amp manufacturers used to install a B+ fuse for this purpose. Oh well, I guess any protection is better than nothing. Glad your unit is working well. I used to perform factory service for Fisher (and many other brands).
- RE: Fisher 500C Up and running again - Uncle Mike 03:09:46 07/22/23 (7)
  smglaw....A long missed inmate that was so knowledgeable of all things Fisher, especially the tube receivers.
  - He was an incredible resource about Fisher gear - gonzo 07:41:02 07/22/23 (6)
    Any idea what happened to him? Norm
    - RE: He was an incredible resource about Fisher gear - Uncle Mike 14:32:16 07/22/23 (5)
      I saw he was posting on another forum, Audio Karma maybe, but that was quite awhile back.
      - RE: He was an incredible resource about Fisher gear - sony6060 02:13:41 07/23/23 (4)
        
        In Reply to: RE: He was an incredible resource about Fisher gear posted by Uncle Mike on July 22, 2023 at 14:32:16
        
        The Fisher 500C has superior audio transformers vs the 500B model. Install Russian K40Y-9 coupling capacitors to clean up the sound. JJ E83CC available at Amazon are best sounding. Beats any NOS 12AX7 including Mullard long plate.
        
        RE: He was an incredible resource about Fisher gear - Daveslater 08:31:48 07/23/23 (3)
        
        In Reply to: RE: He was an incredible resource about Fisher gear posted by sony6060 on July 23, 2023 at 02:13:41
        
        After a disastrous experience with JJ 7591s in my Fisher I will never put another JJ tube near it.
        
        RE: He was an incredible resource about Fisher gear - Triode_Kingdom 16:03:09 07/23/23 (2)
        
        In Reply to: RE: He was an incredible resource about Fisher gear posted by Daveslater on July 23, 2023 at 08:31:48
        
        The JJ 7591s had a reputation for that. Jim McShane wouldn't sell them after it was realized they were so prone to failure. Their preamp tubes seem to be holding up pretty well, though.
        
        RE: He was an incredible resource about Fisher gear - Daveslater 00:04:16 07/24/23 (1)
        
        In Reply to: RE: He was an incredible resource about Fisher gear posted by Triode_Kingdom on July 23, 2023 at 16:03:09
        
        Apart from the JJ debacle I have always used ElectroHarmonix 7591s. The large bottle always reminds me of Mullard EL34s. Have you any experience with other small bottle 7591s like Tung Sol?
        
        RE: He was an incredible resource about Fisher gear - Triode_Kingdom 06:50:27 07/24/23 (0)
        
        In Reply to: RE: He was an incredible resource about Fisher gear posted by Daveslater on July 24, 2023 at 00:04:16
        
        I don't have direct experience with 7591 reissues. However, Jim continued to sell all the Russian brands up until the Ukraine invasion. That tells me they were/are much better than JJ and not prone to failures.

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