12AX7/ECC83S Tubes

Discussion in 'Fisher' started by Jim 2018, Jan 12, 2018.

  1. Jim 2018

    Jim 2018 Member

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    I ordered some JJ Electronic tubes from Amazon and they just arrived. My Fisher uses 6 of these. They appear to work okay in the MPX and for tone but do not work at all in the pre-amp. My old tubes still work, I just wanted to get new ones and have the old ones as spares.

    So I contacted Amazon and they are replacing the order. FYI, the tubes were shipped loose in the box. There was a little packing material, and I mean little. So little you could hear the tubes rattle around shaking the box.

    I'm assuming the tubes are bad because of how they were packed. But I'm not 100% sure since they work in the tone and MPX application.

    I guess my forum question here is whether there's any possibility the tubes are fine and they are exposing a problem with the stereo? If the tubes are bad, how come they work in the MPX and tone functions? Just to be clear, my old 12AX7s work fine in the pre-amp application.
     

     

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  2. larryderouin

    larryderouin Turn it UP, POP? PLLUUEEEZZZZZEE Subscriber

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    Heater series wiring in the tone section vs. parallel wiring in the rest of the unit. Which FISHER do you have so we can look at the schematic and give you some somewhat Non Wild Ass Guesses. Series heater wiring is like the old christmas tree light so when 1 goes out the whole string dies. This series string is part of the bias circuit. Should be 4 tubes in a parallel/series setup. The 1st tube will have -24V in and -12 out. The 2nd tube in the string will have -12v and ZERO (0) volts out. It most likely won't be -24 or -12v but -22v an -11v or somewhere in that range. Anywhere in there is fine. FISHER tended to starve the heaters in the series strings a little. Also if the wiring is suspect (either crushed and separated, OR has suspect soldering at the tube sockets, you'll get no heater (Filament) voltage, and the tubes won't "glow". Loose socket leaves in pins 4-5-and 9 can leave you with a open connection and no power.

    1.) get underneath with a meter. Set to Ohms and trace the series string from one end to the other with the tubes in (probes on pins 4 and 5 on each tube then on the ends of each wire to the next tube. if you get an "OPEN" indication anywhere, your problem is there.)

    2.) once identified, either replace the faulty wire, re-solder the connections, and tighten the socket leaves that grab the pins. (I'm betting on the pins on the new tubes being just slightly smaller and not making contact. After tightening the leaves douse them with DeOxit and cycle the tubes in and out of the socket about 10 times. You can also rock the tube in a circle to get and in and out motion too. Then wipe off the pins, and put them back in their sockets.
     
  3. Jim 2018

    Jim 2018 Member

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    77
    Thanks for the response. So let me give you a bit more context. This is a Fisher D-39 with a T-290 chassis. There is no D-39 schematic however the D-29 is available and uses the same chassis.

    One experiment I just ran is to test each of the six JJ Electric tubes in just one channel, other pre amp socket empty. All the JJ Electric tubes will work for a couple seconds and then go immediately quiet. Then I tested the old Fisher branded tubes one by one, no problem. Also have one 3M tube and one Silvertone tube. Those both work. Then I tested in the other pre amp tube socket and same results. By the way, the heaters work and stay on after they go quiet.

    Mind you, if I use these JJ Electric tubes in this stereo's MPX or the tone application, they work fine, so far. Actually, they might be a tad distorted but I'm not sure. I'm going to listen to it more tonight to make that determination official (or not). Anyway, if the tubes were not damaged in transit, it's almost like there are just slightly out of spec such that they fail in the pre amp application and but function for tone and MPX.

    With that additional info...let me know what you think. Thanks!

     
  4. larryderouin

    larryderouin Turn it UP, POP? PLLUUEEEZZZZZEE Subscriber

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    Try the same scenario AGAIN, only when they start conducting (putting out sound) wiggle the tube and see if you can get them to keep going. It still sounds like loose socket leaves to me, AND/OR the pins on the JJ's are slightly undersized causing drop outs, as you are getting normal op's when NON JJ's are inserted. Tighen up on the socket leaves and see if you can get the JJ's to run consistantly.
     
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  5. Jim 2018

    Jim 2018 Member

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    Bad tube contacts was the first thing I suspected and I did wiggle them, no help. As a sidebar, weeks ago earlier in the process of getting this ol' Fishe to work, I sprayed out all the tube sockets with contact cleaner followed by a course of dielectric grease. So there is no static or trouble wiggling the tubes in this Fisher. Also, I'm working on a GE T-1007A tabletop tube stereo circa 1962 that despite cleaning, has some loose pin sockets. So from all that I have some sense of dirty socket/loose socket behavior and this isn't it.

    Anyway, while I am a still a green eared puppy at learning to fix this tube stuff, I don't think it's the sockets or dirt. I think it's the tubes. But how six tubes can all be bad in the pre amp function yet all work in other functions, I don't know. I don't get it. Mind you, if I put the Fisher/Silvertone/3M tubes in the pre-amp, it's fine. In fact as I type this I'm listening to it and I have two Fisher branded tubes in the pre-amp so it'll even work (and JJ Electric's in the MPX and tone).

    It's these JJ Electrics that don't work in the pre amp function. This is just weird. My fear is when Amazon replaces them the same thing will happen. And then what do I do? I guess try some Chinese tube or some NOS somewhere. Ugh.
     
    Last edited: Jan 12, 2018
  6. fred soop

    fred soop Super Member

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    Also consider that these tubes, not being up to the same standards as the originals, may also draw a slightly different heater current. With heaters in series, this would affect the voltage across the individual heaters.

    I once repaired a really POS TV (no, not a Muntz but just as bad if not worse) where the tube heaters were configured in a series/parallel network so as to avoid a power transformer. Replacing a few tubes resulted in a game of juggling tubes to get close to proper voltage on all of them.

    The Muntz game was similar but worked with plate current rather than heaters. They divided the small signal tubes into 2 groups and put those 2 groups in series so they could run from the same B+ as the higher power tubes. This saved a large resistor and lowered the total power supply current. Fine until they started going weak and the mid point B+ line started changing value.
     

     

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  7. Jim 2018

    Jim 2018 Member

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    Hey Fred. Well, I don't think these tubes are in series. In fact, while testing this afternoon, I didn't have the tone tube in. And I could faintly hear sound but it was ultra faint with the volume cranked. Then I discovered, duh, no tone tube. And all the tubes glowed and nominally worked without the tone tube. Also, I tested the pre amp with only one tube installed and everything worked. And I also unplugged the MPX. Can't say whether the RF tubes might be in series or the output tubes as those were installed during the tests. Otherwise, I don't think anything else is in series with this particular stereo...
     
  8. larryderouin

    larryderouin Turn it UP, POP? PLLUUEEEZZZZZEE Subscriber

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    I just looked at the philharmonic and diplomat P-290 schematics. None of the heaters are in series. Phono is ceramic so no phono preamp. All signals go thru S1 1st and then to V9 (Tone Amp) then to V8 and V11 (P.I. and Voltage Amps) then to outputs V7 and V10. Output's are ELL80's V8-V9-V11 are 12ax7's.
     
    Last edited: Jan 14, 2018
  9. larryderouin

    larryderouin Turn it UP, POP? PLLUUEEEZZZZZEE Subscriber

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    Gadget73 might be the guy to go to as he has a couple of these chassis and knows them better than I do.
     
  10. Jim 2018

    Jim 2018 Member

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    I just wanted to copy and paste here a review of JJ Electronic 6V6 tubes from musicansfriend.com. This is not the same tube as mine but the complaint is very similar to what I'm experiencing. Ironically, while this guy had bad luck with JJ Electric output tubes he mentions having had good success with their pre amp tubes.

    By Telewrangler
    from Lexington, SC

    Comments about JJ Electronics 6V6 Power Vacuum Tube:

    I purchased 2 separate JJ 6V6's for use in my single ended class A amplifier. The stock Ruby tube sounded OK and I tried EH tubes which sounded even better. I decided to try JJ's because I'd heard they were better built and more robust than the others. WRONG. Both JJ's failed within 10 minutes of use. The amp is new and biased correctly for 6V6 tubes. The JJ's each made a crackling sound and fizzed out in the same manner. I won't buy JJ power tubes again. I've had good success with their preamp tubes.
     
  11. gadget73

    gadget73 junk junkie Subscriber

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    Just so we're all on the same page here, are we talking about a 290-T chassis in a Diplomat, and the spot these tubes don't work in is V9 ? Or do they work in V9 but not V8 and V10? I'm a little confused about which spot you're calling the pre-amp tube since Fisher doesn't label any of them that way.

    V100-102 are all MPX.

    The only real preamp function this chassis has going on is V9, and its not a particularly involved arrangement. 6.3 vac power, one triode per channel. Unless the tube was completely dead you'd get output from at least one side. If the tubes work in the MPX spot, I'd say they are probably not all dead.

    V8 and V10 are the voltage amp / phase inverters for the output stage. Nothing really complex here either, except the voltage amp is direct coupled to the phase inverter. If the tubes behave significantly different than old production 12AX7's its possible that the phase inverter bias is so far off that it can't pass signal.

    If its V8 and V10 that the JJ's don't work in, I'll just guess and say its a difference in tube characteristics vs old ones, likely not so much a bad tube as they simply aren't a 12ax7 in terms of how they behave. If thats the case there isn't much to be done for it other than using different tubes in that spot. I suppose you could re-design that stage to get it working but then it would only work with that specific tube type. Not the route I'd go honestly.

    Mine runs random mixed used 12ax7's that came from various places. I doubt I've even tested them, but its possible I screened them for duds before putting them in the bin of mixed tubes to pull stuff from as needed. It works fine. I'm too cheap to buy NOS, but not too conservative to take a gamble on used tubes at the right price. I've probably never paid over 15 bucks for a 12ax7 and rarely have I gotten something that was just used up.
     
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  12. larryderouin

    larryderouin Turn it UP, POP? PLLUUEEEZZZZZEE Subscriber

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    They work in V9 (tone amp) but not in V8-V11(Voltage Amp/P.I.) stages. OP states they start to sound for a second or 2 and then sound fizzles out. Heaters are still lit.
     
  13. gadget73

    gadget73 junk junkie Subscriber

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    v8, v11, sorry. yeah, voltage amp / phase inverter. I'll go with the JJ tubes don't perform like old stock and its biasing the inverter stage to cutoff. Voltage readings on those sockets would tell the tale for sure.

    That said, the phase inverter used here is not fixed bias like the stock arrangement in a 400, 500, 800, so it will be somewhat sensitive to tube variables. An interesting check might be to try these out in a 400, etc that has had the "noose" removed since it would become similarly sensitive to tubes that behave themselves.
     
  14. Jim 2018

    Jim 2018 Member

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    Thanks a ton for the response. Just to be geeky, I wouldn't mind taking a voltage reading and posting back but I would need to know what pin #s. Would you know off hand? And I would test for AC voltage and not DC, right? Also I assume I would remove V11 and V8 and turn on the stereo and measure but should I let the rest of the tubes warm up for an accurate reading or would that not matter?

    Anyway, my concern now is if manufacturers of newly manufactured tubes play fast and loose with specs such that tube behavior is not reliable for some applications, what can one do? Is there a cheap currently manufactured 12AX7 that I can buy that I know will work? I was leaning towards trying an Electro-Harmonix next. If any suggestions on inexpensive brand recommendations for these console stereos, I'm all ears.

    FYI...Amazon delivered my replacement order today (even though its Sunday) and despite customer service's assurances that the tubes would not be packed loose again, they were in the exact same oversized box loose and rattling around. So I didn't even bother opening it and initiated the return process on this order as well.
     
  15. CJVx

    CJVx AK Subscriber Subscriber

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    Which JJ tubes were they? I've seen two kinds, the short plate and long plate that look like the classic 12AX7 design. I have one of the long plates (ECC803S) around still and it has works in anything I've put it in, (it's my go to test tube) including different areas of a fisher Electra stereo console I used you have, and also series D.C. heater amps, and does sound quite good too. BUT!!... I've noticed the pins are thinner than the vintage tubes I am used to and some sockets in one Japanese receiver I've tried it in wouldn't bite the pins to get reliable operation out of it.

    Make sure you put the original Fisher 12AX7's for sale here in bartertown, there's a few of us would like to get their hands on them lol.
     
  16. Jim 2018

    Jim 2018 Member

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    Hey CJVx. The one's I have are the ECC83S (and not an ECC803S) and mine are of a short plate variety as well (I think). The million dollar question is whether the tubes are made out of spec or are they in spec (but yet slightly different than my original/old stock tubes) or is my Fisher out of spec somehow by just enough to cause the JJE tubes to take a nap but not the old stock.

    Earlier in this thread I copied and pasted a post from another forum about someone with JJE 6V6 output tubes that had similar trouble. So I don't know.

    And I don't know how much life is left in the original Fishers which is why I wanted new ones and have the Fishers as spares since these 12AX7/ECC83s are relatively cheap and newly made.
     

     

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  17. gadget73

    gadget73 junk junkie Subscriber

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    DC voltage.
    On the bottom side, from the gap going clockwise its 1 - 9.
    9 is one side of the heater winding, so it will be a wire going somewhere else.
    4 and 5 will be tied together and have the other side of the heater circuit.
    Pins 2 and 6 will also be connected together, so voltages will be the same there.


    voltages on pins 1, 2, 3 and 6, 7, 8 will show whats going on.


    If you feel like sending me a pair of them I can check them in my own 290-T chassis and then return them to you. I doubt I can tell you anything about it that a voltage measurement won't though. All I'd do is flip the thing over and poke the meter in there to see what its doing.

    and its not impossible i'm dead wrong on this, but its my best guess.
     
  18. larryderouin

    larryderouin Turn it UP, POP? PLLUUEEEZZZZZEE Subscriber

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    EH 12ax7's, Sovtek 12ax7LPS (very good for phono sections), Tung-Sol 12ax7 ReIssues are the ones I use, I stay away from JJ Tubes like the plague! Most of them are junk AFAIC.
     
  19. Jim 2018

    Jim 2018 Member

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    I hear ya. I think this is just like going to the doctor where they do their best with the information they have and the nature of the complaint but may or may not be on the right track with diagnosis. Right now, you're the only doctor in town for my poor D-39. :)

    As far as the JJE tubes go, UPS will be here tomorrow to take them all back to Amazon so I won't be keeping any.

    As far as this test, do the tubes have to say in the socket? For some reason I was assuming that I could leave the chassis in the cabinet, pull the tubes, flip the stereo on, and stick the probes in the tube socket. If I have to leave the tubes in and take the chassis out, that's more of a project than I want to get into tonight. Might be able to do it tomorrow though.
     
  20. Jim 2018

    Jim 2018 Member

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    Thanks Larry! I'll try one of those and will post back results once I get them.
     

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