Fisher 500b crackle issue

Discussion in 'Audio Hardware' started by Guy Gadbois, Apr 23, 2015.

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  1. Analogman

    Analogman Well-Known Member

    You will be wasting your time
    The mains AC has absolutely nothing to do with this problem
    Nothing
     
  2. Analogman

    Analogman Well-Known Member

    It is not the gain pot if the noise is present regardless of where you adjust it
    The pots do track poorly, make nose at times and the mains switches are weak, but the problems these give rise to are not what you are suffering; "steady state"

    If you have a working power switch (and I assume you do) there are some simple steps you can take to preserve it (you can do yourself if you are decent with a soldering iron)

    The switches are still available but expensive (read: gouge) and ancient NOS not any better than the one you have if it's working

    Even after I "overhauled" and protected mine electrically I do still turn my Fishers on and off with a power strip; just a good idea and not that difficult to become accustomed to
    (the switches won't be available/repairable forever)
     
  3. chervokas

    chervokas Senior Member

    Like Analogman says by far the moat like cause of the problem and the easiest to check for is a noisy preamp or phase inverter tube or a poorly seat one or one otherwise make poor contact with a tube socket. In an old amp it's impossible to discount the failure of another part like those PI pots or a cap or something, but I agree that spending a lot of time trying everything but checking for noisy tubes is barking up the wrong tree.
     
    McLover likes this.
  4. Analogman

    Analogman Well-Known Member

    That, and those inverter pots; have had it happen exactly as his problem has been described, and more importantly, more than once
    Easy, but need to be delicate, fix
    The little plastic tits are easy the break
    That's why I suggest the "wiggle test" first
    The inverters can be adjusted with a DVOM if need be (best to avoid)
    Not that big of an issue; just don't go grabbing and twisting them as if it were a new amp
    I can help you with the fix if that turns out to be the problem spot
     
  5. Ken Clark

    Ken Clark Forum Resident

    Location:
    Chicago Suburbs
    The Adcom I use is an ACE-515 AC Enhancer (power conditioner). I leave the Fisher on and turn power on/off with this unit, so no additional power is consumed. I like the Adcome because it's good quality but not expensive; I bought two for around a hundred dollars each several years ago. Obviously there are many similar offerings available but some are crazy expensive and my system is not going to know the difference.
     
  6. Ken Clark

    Ken Clark Forum Resident

    Location:
    Chicago Suburbs
    Analogman I would have to respectfully disagree. Although I know little about electronics, the volume control and power switch are the same device. I could rotate volume up & down after switching on and hear crackling. Cleaning it did nothing, but eliminating the need to actually switch the unit off solved my problem. The tech who restored my unit had suggested this to me.
     
  7. Analogman

    Analogman Well-Known Member

    You didn't read my post, or the OP's very carefully
    The problem you are describing is a TRACKING problem; the OP's problem is "steady state"

    These two distinct forms of transient noise are easily identifiable (and differentiated)

    As for the gain control/mains switch on the Fishers I am intimately familiar, I have serviced repaired and replaced at least a dozen or more
    They are two separate components cobbled together, a traditional mid-quality Centralab carbon dual gang STEREO pot with a tap, crimped and soldered (via a sheet metal shield) to an AC mains switch and coupled via the center shaft (the shaft on the end of the volume control engages a little tit inside the mains switch) to function as a singular device
    The noise you hear from these pots (turning the control "up" and "down") when the track(s) becomes dirty, worn or damaged has NOTHING to do with the burn out from arching inside the mains switch (AFTER the unit has been turned on)

    Nothing

    There are plenty of Fishers floating around, still using their original volume control (functioning fine) with the AC mains switch either jumpered, by-passed to another switch, hacked in some other way or simply being used with a switched power strip

    The noise I hear in his video is NOT a tracking problem
     
    Last edited: Apr 24, 2015
    The Pinhead likes this.
  8. Analogman

    Analogman Well-Known Member

    That make no sense unless your "tech" replaced the gain pot (or it's "elements") while at the same time providing you with whatever means or advice (alternative deviation from the original design) he gave you to use for turning your receiver on and off (see my next to last comment above regarding this common practice)

    No disrespect, but it SOUNDS like a hack job; that or he didn't want to fool with tracking down the appropriate "factory style" parts to repair your unit

    Maybe he simply installed a new dual gang 500K pot, disabled/re-routed/re-located the old mains switch and called it a day, I have no way of knowing..........it doesn't matter
     
  9. Guy Gadbois

    Guy Gadbois Chief Inspector Thread Starter

  10. Analogman

    Analogman Well-Known Member

    You don't need that (clearing throat) fine piece of quality engineering to fix your problem

    If you simply want to preserve your AC mains switch, any decent power strip with an "ON/OFF" switch will be just fine

    I buy nice ones ($50 dollar and up list price types ) all the time at thrift stores..........Belden, Tripp-Lite etc
    Just go to the hardware store and buy a decent strip, $20 bucks tops; you can even catch them on sale for less
    Then your problem is solved and you can be on the hunt for a "deal" if you feel the need
     
  11. Analogman

    Analogman Well-Known Member

    Here is an EXCELLENT strip for $20 bucks
    http://www.amazon.com/Monster-MP-PowerCenter-Discontinued-Manufacturer/dp/B00003CWDL
    I own the larger model, the HTS-2000
    It really is a nice strip and the filtering is honestly evident with video
    Only reason I bought it was I talked them out of it (Good Guys) when it was a discontinued model ages ago

    Spending a fortune on power strips and "in-line" conditioners is an enormous waste of money unless you know what it is you are buying (looking at)
     
  12. Steve G

    Steve G Senior Member

    Location:
    los angeles
    I know less about electronics than anyone else on this thread but if you swap all the tubes between channels and and the noise stays on the same side I would look at the caps. I do have Fishers and when one of mine was making noise it was a cap. It wasn't the same exact noise but it wasn't from a different universe either. You can even look at the caps and see if there's gunk around any of them. Don't do that when it's on.
     
  13. indy mike

    indy mike Forum Pest

    JJ is a brand of tube that's available at places like Guitar Center. If you can get your tubes checked out, you might find that some need replacing.
     
  14. The Pinhead

    The Pinhead KING OF BOOM AND SIZZLE IN HELL

    Guy; did you ever feel like switching to solid state ? Really. Those tubes seem to be making your life miserable.
     
    Ken Clark likes this.
  15. Steve G

    Steve G Senior Member

    Location:
    los angeles
    I thought of another thing: I do have a tube socket on a mac that makes a sound like that. I would like to get it replaced but I tried once - sent it to TDW and when he checked it out it wasn't making the sound but I swear it makes that exact sound. Not sure what you have to do to get a tube socket switched out on a Fisher 500 though - but it really sounds like that. I just live with mine - if I tap the tube in that socket the noise stops so I put up with it.
     
  16. Guy Gadbois

    Guy Gadbois Chief Inspector Thread Starter

    @Waxfreak I had a solid state for years, then heard a tube. No going back now! @Steve G I can't live with it. I feel like it's getting worse.
     
  17. Guy Gadbois

    Guy Gadbois Chief Inspector Thread Starter

    @indy mike The tech used the original Telefunkin tubes on mind. I think JJs would compromise the sound quality, right?
     
  18. chervokas

    chervokas Senior Member

    Not compared to constant noise. A tube that's not making constant noise -- if in fact the problem is a noisy tube -- would be a sonic step up.
     
  19. chervokas

    chervokas Senior Member

    Living with tubes is really not any more problematic that living with light bulbs for the most part. But living with vintage gear can be like living with vintage cars -- takes a more in the way of maintenance to keep 'em running sometimes.
     
    showtaper likes this.
  20. Guy Gadbois

    Guy Gadbois Chief Inspector Thread Starter

    I'm pretty sure he has more Telefunkins stocked, so it should be easy to replace
     
  21. The Pinhead

    The Pinhead KING OF BOOM AND SIZZLE IN HELL

    Yeah; I of all people should know. Touché:laugh:
     
  22. EasterEverywhere

    EasterEverywhere Forum Resident

    Location:
    Albuquerque
    Here is my recent experience,albeit a little different,but sort of similar.

    I have a Fisher X-101.I had it restored in late 2011,and did not get around to using it until late last year,because I could not get anybody to work on my Thorens.I was very suspicious because the guy that restored the amp took out all the Fisher and Telefunken branded tubes that were in the amp,and replaced them with what were literally no name tubes.

    The first couple of months it worked great,then I began to get very loud static,just as you describe in the OP,only much louder.I bought some deoxit,and cleaned the speaker connections,the pots,the tube sockets,and the tube pins.This did no good.I have two tube amps,the other is a HH Scott LK-48 that I am having restored by a local tech I just found in the last couple months.He looked the X-101 over,and he told me there was nothing wrong with the amp.Wiring,caps,switches,pots,all good,except every single tube had crapped out on me.The local tech confirmed that guy that restored my Fisher had put in all bad tubes.

    I just happened to have a spare complement of mismatched EL84s sitting around.Telefunken,Sylvania,RCA,and Zenith made in Holland.I replaced the EL84s,and then what I got was a 60 cycle hum,very much like this,from the bad 12AX7s.



    I am now saving up money to buy a good set of 12AX7s.
     
  23. Analogman

    Analogman Well-Known Member

    I just noticed "JJ" being mentioned and am not 100% certain the context, regardless:
    I do NOT want to get into a tube debate or hear "well I've used them for a hundred years and have had no troubles"
    Take it on good authority, authority far more important than my .02 cents (and I've got quite a few "JJ" stories I could tell)
    DO NOT USE "JJ ELECTRONICS" 7591A POWER TUBES FOR ANY REASON
    In they are in the receiver now, remove them
    Guys, if you have any amp that runs 7591As and you've got "JJ"s in them, GET THEM OUT NOW
    Go for the Electro-Harmonix or the Tung-Sol re-issues, but AVOID "JJ" POWER TUBES
    EVEN IF THEY ARE FREE
    (I don't know about the guitar amp crowd; if y'all dig 'em then that's your buisness)
    "JJ" power tubes SUCK out loud

    As for their 12AX7, some love them, some not, but at least that tube can't (isn't in a position) to destroy your iron
    Keep the Telefunkens in the phase inverter spots if nothing else
    (actually, keep the two strongest 12AX7s you've got in the phase inverter spots regardless of brand)
    They work very hard in a Fisher
     
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  24. Analogman

    Analogman Well-Known Member

    And just exactly which one(s) would you suggest he "look at"?

    I agree with you, BUT one should ALWAYS start from the most simple and work back, not skipping anything......................and it's a heck of a lot easier to "wiggle test" those inverter pots and clean and tighten socket pins than it is to change out coupling caps (or worse) on this receiver
    Don't ever jump to conclusions when diagnosing any piece of machinery; the practice will eventually bite you
    I also doubt that the OP has a scope or a cap tester
     
  25. Analogman

    Analogman Well-Known Member

    I am sorry this happened to you
     
    AndrewS likes this.
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