>

I have to rant. Vintage parts and new builds...just stop it.

Discussion in 'The Workbench' started by Matthews Guitars, Apr 6, 2021.

  1. Matthews Guitars

    Matthews Guitars Well-Known Member

    Joined:
    Aug 17, 2019
    Messages:
    3,939
    Likes Received:
    5,980
    I have two B&K Dyna-Jet 707 tube testers. One is freshly overhauled and has been modded to give a much better test to 12AX7s/ECC83s. The other is going to get the same treatment.

    When I get around to it I'm going to build a noise figure test system as well. That way I can select tubes by noise figure as well as gain/transconductance.
     
  2. StingRay85

    StingRay85 Well-Known Member

    Joined:
    Aug 18, 2019
    Messages:
    1,279
    Likes Received:
    987
    I love my Maxi testers, but there a few disadvantages for the power tubes. Current is measured on a fixed plate voltage (400V) and bias supply (-36V). Transconductance is also measured. But it is still difficult to predict how well tubes match on e.g. 450V. A curve tracer would be interesting. Also, they can't measure GZ34 or EF86. Maybe one day I'll get the Amplitrex AT1000. Or sell enough tubes on ebay until my paypal account can cover the purchase. I'm close to 100 blackburn EL34, around 30 RFT, more than 200 ECC83. The Maxi Preamp measures noise, but also interesting is that you can tap tubes and listen to them. It remains subjective when a tube is too microphonic. Getting the Maxi testers made my tube hoarding a lot worse :D
     
  3. alpha al

    alpha al New Member

    Joined:
    Oct 19, 2017
    Messages:
    23
    Likes Received:
    22
    Location:
    Gastonia, NC
    I hate the newer 1% resistors. The extra color band really screws me up.

    I can look at any 2% or 5% resistor and tell you the value.
     
  4. anitoli

    anitoli Well-Known Member Gold Supporting Member

    Joined:
    Jul 9, 2011
    Messages:
    9,555
    Likes Received:
    12,997
    Location:
    Lewiston, Maine U.S.A.
    Many of these tubes test real high, gain 90+, MHo higher than data sheet spec, listened to for noise. Even then many to my ears don't sound good.
     
  5. Matthews Guitars

    Matthews Guitars Well-Known Member

    Joined:
    Aug 17, 2019
    Messages:
    3,939
    Likes Received:
    5,980
    1 percent, 5 band, established reliability band...it does get confusing. So have your handy little 20 dollar device tester on your bench and ready to clip to any questionable device on a moment's notice. When in doubt, read it out!
     
  6. william vogel

    william vogel Well-Known Member

    Joined:
    Dec 18, 2016
    Messages:
    587
    Likes Received:
    596
    Be careful with that linen phenolic board material. It’s sensitive to moisture and when it becomes conductive the amp will have some nasty behavior and terrible sound. I already went down that rabbit hole and trashed every piece I had. You can get the paxolin board material from England but it’s hard to get them to ship it to us here in the states.
     
  7. william vogel

    william vogel Well-Known Member

    Joined:
    Dec 18, 2016
    Messages:
    587
    Likes Received:
    596
  8. Matthews Guitars

    Matthews Guitars Well-Known Member

    Joined:
    Aug 17, 2019
    Messages:
    3,939
    Likes Received:
    5,980
    I'm sure it's an awesome amp but you could have made it just as awesome using current production components, and maybe even ended up with an amp with a lower noise floor. You did a very nice job making it and that's the truth. But there was literally no reason to use up rare parts when there are deserving 50 year old amps that could have benefitted greatly from getting those parts. No reason except....maybe a touch of hubris?
     
  9. anitoli

    anitoli Well-Known Member Gold Supporting Member

    Joined:
    Jul 9, 2011
    Messages:
    9,555
    Likes Received:
    12,997
    Location:
    Lewiston, Maine U.S.A.
    If you pay for the parts they are yours to do with as you wish. Looks very nice.
     
  10. Emtbreid

    Emtbreid Well-Known Member

    Joined:
    Oct 22, 2018
    Messages:
    717
    Likes Received:
    816
    Location:
    East Coast, USA
    Looking for nos piher? Just sourced a few to replace a few resistors in my JMP that got changed out. Glad to point you in his direction.
     
  11. Dean Swindell

    Dean Swindell Well-Known Member

    Joined:
    Mar 12, 2017
    Messages:
    319
    Likes Received:
    293
    Bravo.
     
  12. Gunner64

    Gunner64 Emotional Support Animal Gold Supporting Member

    Joined:
    Nov 16, 2013
    Messages:
    7,144
    Likes Received:
    9,828
    Location:
    Midwest, USA
    Who makes these? I have hundreds. NOS in bags. Many values. 16179801993493242904090544516930.jpg
     

    Attached Files:

    Last edited: Apr 9, 2021
  13. william vogel

    william vogel Well-Known Member

    Joined:
    Dec 18, 2016
    Messages:
    587
    Likes Received:
    596
  14. NSV-Andy

    NSV-Andy New Member Silver Supporting Member

    Joined:
    Apr 8, 2019
    Messages:
    18
    Likes Received:
    24
    I am curious and have a couple of questions for the folks that restore vintage amps with vintage components.

    First, are these intended to be regularly played, or are they strictly collector/museum pieces that see very little use?

    Second, are things such as the mustard caps tested for value, leakage and ESR? Are the carbon composition resistors tested for value, and what about noise? These things change characteristics with age - just sitting on the shelf unused, which affects the sound. A .022 uF mustard cap may have tested within tolerance back when it was new, but what about 20 or 30 years later? What about leakage? Even if they are within spec now, how about 5 years down the road?

    I saw a YouTube video from a self-proclaimed amplifier "expert" that insisted on keeping old "bumblebee" caps in amplifiers because their tone is, in his opinion, superior. Anyone who has been on the business end of a soldering iron knows that these should be replaced immediately. They are off value and leaky, using them as coupling capacitors to output tubes could cause those tubes to red-plate. This is just an unaccountably stupid thing to say and anyone who follows his advice will suffer.

    I'll conclude this by saying that although I can't prove it because I don't have a time machine, using modern caps may very likely return an amplifier to its original sound. They're closer to the correct engineering-specified value than original caps were when new (and have the benefit of lower leakage and better ESR).

    Vacuum Tubes are a different story, of course, provided that they are in good condition, stored properly, under full vacuum and contain no exotic materials that degrade or change composition over time. They are under vacuum - not exposed to air, acids or electrolytes like in paper capacitors or other such things. If they're not rattled to death or something, they should last for an indefinite amount of time.

    I get the point of restoring something to absolute original condition as a museum or collector piece - I respect history and provenance. For everyday use, maybe modern polypropylene caps and metal-film resistors would be a better choice?
     
  15. junk notes

    junk notes Well-Known Member

    Joined:
    Dec 10, 2018
    Messages:
    2,438
    Likes Received:
    2,614
  16. StingRay85

    StingRay85 Well-Known Member

    Joined:
    Aug 18, 2019
    Messages:
    1,279
    Likes Received:
    987
  17. Derrick111

    Derrick111 Active Member

    Joined:
    Jun 26, 2020
    Messages:
    112
    Likes Received:
    144
    There are parts today that sound just like the old parts and are equal in quality. It does seem a shame to use up NOS parts for new builds that could be used for restoration of vintage amps, but if you can afford them, they're yours to do what you want with them. Everyone wants the real McCoy but not everyone can't afford a plexi. I think using old parts makes people feel better about that.
     
    Matthews Guitars likes this.
  18. herbvis

    herbvis Active Member

    Joined:
    Jul 8, 2010
    Messages:
    178
    Likes Received:
    183
    Using nos and expensive parts makes us feel better about our lack of talent on the fretboard :lol:
     
  19. Matthews Guitars

    Matthews Guitars Well-Known Member

    Joined:
    Aug 17, 2019
    Messages:
    3,939
    Likes Received:
    5,980
    There are ways...and they don't necessarily cost much...to check ESR and leakage on capacitors and of course check the value of resistors as well.

    In fact I just got a 20 dollar component tester off ebay that is really an amazing little gadget that tells me everything I'd want to know about any device with two or three legs on it. It tells value, ESR, and leakage. It identifies diodes and their conduction voltage. It identifies transistors, both bipolar and FETs, with their essential parameters. I could spend more to get a "professional" ESR meter, but this little thing seems to know what it's doing. It agrees well with my other meters on transistor, diode, and resistor measurements.

    I'll check an NOS part before using it. If that mustard cap is on value and has no signs of physical deterioration and has in spec leakage and ESR values, it's going to be used. I have yet to find a bad one, but I haven't worked with very many as of yet.

    The '69 Plexi I restored cost me 600 dollars to buy it in its original (butchered yet running) form. I'm sure that if I totalled up all I spent to bring it up, I spent more to restore it than I paid for it. But it was still a bargain. The thing just sounds great even when it's ME playing it. I play it every couple of days and I'll run it at full output without a moment's hesistation. I stick in my good Etymotic earplugs and try to make the critters in my attic (if there are any foolish enough to still be up there) explode from the sound level. I've played it fully dimed out a couple of times and it performs like a champion.


    I ended up setting it up for KT66s and it has enough bias range to run EL34s as well, without exchanging any resistors for other values. Why KT66s? Why not?
    I like their sound and I had a set to put into SOMETHING so might as well give it a shot.
     
  20. Ivan H

    Ivan H Member

    Joined:
    Jan 17, 2021
    Messages:
    18
    Likes Received:
    42
    Then do what Marshall did back in the day when Radio Spares was out of stock of certain components & use an alternative type component. If you think that Marshall only used the Philips/Mullard C296 (mustard) type coupling capacitors exclusively, then you know a lot less about the older Marshalls than you "think" you do.
    Among the capacitor types seen in totally original plexis are 0.68uf/100V Wima MKA's, 0.022uf/400V Wima TFM's, as well as other types (Ducon's??? etc etc).
    I have an original component plexi ('67/'68 JMP50) that has C296 mustard coupling caps & 0.68uf/250V Philips "yellow block" type cathode bypass caps. Now I do have a handful of 0.68uf/160V C296 mustard capacitors (not Bianchi's or Dutch or Australian Miniwatt's, actual Mullards). Should I, by your reasoning, be yanking the yellow block type cathode bypass capacitors (disturbing the original red lacquered solder joins in the process) to replace them with C296 mustards, because you think that JTM's & JMP's were only built using mustards?
    Or what about builders like, say, Chris Merren??Are you going to get on your soap-box to rant & whine at him for using mustards in his builds also??
    Who are you to tell me what I can do with components that I own. Cheers
     
    anitoli and shredless like this.

Share This Page