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Salvaging used components - Good idea?

Discussion in 'General Electronics Chat' started by Ratchit, Jan 11, 2015.

  1. dr pepper

    dr pepper Well-Known Member

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    The 1936 ekco has only had 2 caps replaced by me, all other bits look original, I did align the if strip but I couldnt improve it, truely an amazing old radio, thye must be best quality components.
    I have a 1942 hmv table top that the owner had used every day from new till 2011 when they unfortunately croaked, it has never needed repair.
    Also I've a weimar from the late 60s, I gave up testing when I got about 1/3 of the way through, everything seems to have failed, even the if transfo's are open.
     
  2. Honduras

    Honduras Member

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    (Way off topic.) Reminds me of a funny story. I grew up in Saudi Arabia when Israel was still not recognized as a country. The school ordered paper globes, and Israel would be scratched off in Customs. Solution? We bought inflatable globes.
     
  3. Honduras

    Honduras Member

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    That happens. The quality ones were HIGH quality. The mid grades were built with components that might last a few years. Kind of like Kleenex. Use it for a while, then get a new one out. The new one may be higher tech and have the same functionality, but a handkerchief works for a LONG time. (properly cared for, of course)

    During the early years of radio, the manufacturers were trying to decide which way to go. Fortunately, some went for quality and long life. Everything under-stressed and made with the best parts available. Some manufacturers decided to go the other way.

    I've found out that, most of the time, you can get a good idea of the manufacturer's intent from the case. Polished solid hardwood is a good sign. Veneer and pressed fiberboard is a bad sign.

    Then open it up. If the guts in a real wood case look like the original installation, and don't have any signs of sloppy, but well intentioned modifications, the radio will probably require minimal repairs to have it operating correctly.

    There is the tube issue, but many people, including me, are working on replacing tubes with modern components that are readily available. Most audiophiles say they can tell the difference between a matched pair of 12AX7s and a semi-conductor replacement, but 12AX7s aren't made any more.

    It is not a good thing to have a favorite radio become unusable due to a worldwide shortage of tubes. I guess no one ever thought this type of dinosaur would still be in use now.
     
  4. dave

    Dave New Member

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  5. dr pepper

    dr pepper Well-Known Member

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    I have no interest in audiophilery.

    Tubes radios are on the other hand very interesting, my philosophy is similarish, I dont do any mods that cant be undone, on valuable sets I will restuff caps that have failed so they look original.
    The majority of tubes are available, allthough ok maybe not audiowhatsit grade.
    The only time I've replaced a tube with a semi is in a tv that loads its rectifier heavily.
     
  6. Honduras

    Honduras Member

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    I agree about audiophelery. I can't hear the difference.

    Restuff caps? Please explain.

    A lot of tubes are still available, but they are expensive, and you pay a premium to have them tested first. That's how I got into repairing tube testers.

    I have about a year of research to do before I will feel comfortable replacing a tube any more complicated than a diode. :)
     
  7. granddad

    granddad Active Member

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  8. dr pepper

    dr pepper Well-Known Member

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    12ax7 I think here in the uk is a ecc83 or similar.

    Restuffing caps, simple really take a 0.1uF hunts wax coated cap, split the case, empty out the guts, take a new polyprop cap put it inside the hunts case then reseal it up and pour some of the wax over it after you melted it, looks like an old cap but theres a new one inside it.
    On sets from the uk jubillee era fitting the caps back in the set with the date code showing seems to be popular, the jubilee is significant here as thats when a lot of folks bought their first telly.

    For audio valves groove tubes are marked as to their hardness, which essentially is the vacuum level in the tube, this does make a diffrence for people like guitarists that want a particular sound, the vox ac30 guitar amp that doesnt use negative feedback responds to diffrent hardness output bottles sound wise.
     
  9. Honduras

    Honduras Member

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  10. Honduras

    Honduras Member

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    TYVM on 're-stuffing caps'. I've never had anyone ask for true authenticity. If I do, now I know.

    On another note, a friend of mine and I are working on the 'Ultimate Vacuum Tube (Valve) Tester. You have added a whole new dimension to the project. How do we determine the 'Hardness' without drilling into the tube?
     
  11. dr pepper

    dr pepper Well-Known Member

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    I'll check my amp book and get back on that one I cant remember now, I think its emmision or impedance related.
     
  12. throbscottle

    throbscottle Well-Known Member

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    At a random guess, stick HV between the anode and cathode, turn the lights out and see if you see a plasma glow - would indicate a soft tube. You could do a colour scale... Or a better guess, do the same thing but measure current. More accurate than judging shades of purple...
     
  13. Honduras

    Honduras Member

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    TYVM. Another great idea. No wonder I try to hang around places like this, :)
     
  14. throbscottle

    throbscottle Well-Known Member

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    Dammit! I said "soft tube". I should say "soft valve" - I'm British, darn it! Too much time spent reading American, grumble grumble
    (huh, and I nearly said "dagnabbit". Rapidly abandoning hope)
     
  15. throbscottle

    throbscottle Well-Known Member

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    Just having great success re-using some SMD components I removed using a heat gun a couple years ago, been keeping them in a little pot. And now I have a soldering iron with a bit that has a long straight edge I can desolder individual devices from scrap boards, to use. I'm using Mr RB's small cap meter to find the cap values I want. Made myself a tweezer probe so I can find the caps I want in situ on the scrap boards.
    One good thing I've discovered about using scrap smd's compared to new ones is that they are easier to solder, because they have enough solder on them to initially tack down (with a bit of flux on the track). I'll post a photo when it's done.
     
  16. dr pepper

    dr pepper Well-Known Member

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    Apparently its done by measuring the impulse response of the tube, a hard vacuum gives less harmonics, in other words a high vac gives more power before distortion.
    Guitar players are exceptionally fussy about the ratings, groove tubes are in numbers, mesa boogie have their own system too, theres are rated in colours.

    I'm guessing a little here but I'd assume that a soft tube would emmit less electrons from the cathode (well the same but more would collide with contaminants within the tube and therfore wouldnt reach the anode) thefore at the same dc or ac conditions a softer tube would have less anode current and mu.

    Noise is also increased by soft vacuum, but thats going out of my knowledge, I spose shot noise would be caused by electrons bouncing of contaminants.
     
  17. Honduras

    Honduras Member

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    I had a British friend in Germany. We decided to split the difference and speak Syrian. :)
     
  18. Honduras

    Honduras Member

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    TYVM. At this time we have more than a year of research to do, but most tube (valve) testers included a test for gassy tubes. I don't feel like re-inventing any more wheels this year.
     
  19. throbscottle

    throbscottle Well-Known Member

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    Just finished building SMD side of this board. Still got holes to stuff. Anyway, there is a 4066 on there which came from a Sky box, and all the R's, C's, T's and D's are board pulls. It is supposed to have 2x 6.8v zeners at the top right, but I could only find one so I'll have to put a wire ended one there for now. The orange thing at bottom right of centre is wire link I had to put in because the pcb symbol for the voltage regulator was wrong, had tab connected to gnd when it should be to o/p. Didn't realise until I started checking connections when building. Had to take reg off again carve around tab. Grrrr.
     

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  20. Honduras

    Honduras Member

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    I would love to do Surface Mount, but I have not found a way. (Old and creaky. Poor eyesight.)

    I had thought to change to Brooklyn Style, but It's hard to find 'islands' small enough.

    Suggestions?
     
  21. throbscottle

    throbscottle Well-Known Member

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    I use a big illuminated magnifier so I can see what I'm doing, hold the components down with the tip of a small craft knife so they don't shift easily. Soldering would definitely be easier with more spaced out parts and larger lands, so you could over-size your pads. (eg, I've been making boards for 0805, but occasionally have to use 0604, so there is a lot more room on the pads!)

    By Brooklyn style, I take you mean "dead bug with islands"? I've seen diamond coated mini hole saws, a few mm across, so you could use one of those.
     

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