Vintage Asylum

RE: Recommendation for cleaning stubborn dust off old board

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ltman

A

In Reply to: RE: Recommendation for cleaning stubborn dust off old board posted by ltman on December 29, 2023 at 16:52:20

thanks guys for the ideas.

Last night I got the hum 100% eliminated by the well known upgrade of installing new jacks insulated from the chassis and instead grounded to the central grounding post already in use on the 12AX7 socket.

Worked perfectly to eliminate the hum and the tuner is sounding great in stereo, although perhaps a bit laid back in the highs. Wish I could get the PEC upgrade kit but now unobtanium I believe.

Follow Ups:

"Wish I could get the PEC upgrade kit but now unobtanium" - 1973shovel 14:47:47 12/30/23 (3)
As projects go, building David Berning's corrected 555001 (shown above, on your right) PEC is easier than most. Get yourself two pieces of perfboard, cut to size, and solder together the components shown. You won't even need extra wire.

You also mentioned the late Bill Thomas. Did you ever read this post of his regarding R11 and R13 in the FM3?

"2 W resistor FM3

"However, in most tube applications, higher wattage *is* better. On the FM3, one resistor as-supplied is 2-watts, and runs at about 1.9999-> watts. Going to 5 watts is a very good thing."

[10k, R-11 and R-13 on PC-8 are 2 watt resistors]"
- RE: "Wish I could get the PEC upgrade kit but now unobtanium" - ltman 16:42:31 12/31/23 (2)
  thank you! this will be added to my todo list for the tuner. I did the RCA jack ground fixes and that worked out great.
  
  And yep, I have copies of Bill's articles on restoring the FM3.
  
  Next will probably be tube replacements, except for the 12AX7 tubes which I think are original.
  
  And I have a brand new replacement power supply quad capacitor can waiting to go in, and some other caps.
  
  But I want to be super careful with the old fragile boards because I do not have the troubleshooting skills to find and fix a damaged trace if it happens. So I may put off the capacitor replacements until absolutely neccessary...
  
  I am very lucky I have line of sight to one of the few remaining 24x7 all classical FM broadcasts: KCNV 89.7
  - You're welcome - 1973shovel 15:28:26 01/02/24 (1)
    I wouldn't go changing tubes unless what you have test poorly.
    
    A guy in my old audio club knew his way around tube amps, preamps, etc, and did a lot of bench work. I remember him telling me that undertaking the alignment of the Dynaco FM3 was not for the faint of heart, despite the DIY instructions.
    
    I have the James Lin "Improving Dyna's FM-3" article from a January 1991 Glass Audio I can send you if you're interested. Email me via the Asylum if you'd like a copy.
    - RE: You're welcome - ltman 21:20:58 01/03/24 (0)
      Yep, others have recommended not to change the tubes unless neccessary. I will test the new ones to have a reference, then test those currently installed.
      
      I expect the pec upgrade will be a noticeable sonic improvement, and maybe all other replacements will be beneficial more for reliability. We'll see.
      
      And thank you, I think I do have the James Lin article, I will look.

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