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Reviving 50+ year old Wire Recorder

Discussion in 'General Electronics' started by Chris Cooper, Nov 10, 2003.

  1. Chris Cooper

    Chris Cooper Guest

    My father has "bestowed" upon me the old family wire recorder, a Silvertone
    Model 8170. He claims that the last time he ran it (a year or two ago) it
    worked for a while and then smoke came out of it.

    And now I have it.

    I opened it up, blew all the dust out, reseated the tubes, plugged it in,
    and it ran fine - except that the only sound out of the speaker was a strong
    60 Hz hum.

    For $20 I've ordered replacement tubes for it, seems like that's got a good
    chance of solving the problem.

    If not, do people have suggestions on how to "debug" this problem? I've got
    an old oscillscope I can use.

    It's got a schematic printed on the bottom of the case, but only about half
    the schematic remains, and it's the half dealing with the microphone and
    phono input, not the speaker output.

    The only idea I have, is to take beast apart even more, and try to re-create
    the schematic, or at least the speaker amplifier portion.

    And then the next question - if I get this thing working (or even if I
    don't), is there anything reasonable to do with it? It has some mild
    sentimental value, not much, on eBay some of these are going for a whopping
    $10, are there museums that might be interested in such a piece?

    Thanks all!
    Chris
     
  2. James Sweet

    James Sweet Guest

    The tubes are probably fine, you have some audio and tubes rarely just fail
    unless the heater burns out, usually they gradually get weak. Any
    electrolytic capacitors are likely dried out and will need to be replaced,
    switches should be cleaned, and everything carefully inspected.
     
  3. [snip]

    You can also ask on rec.antiques.radio+phono. Wire recorders are
    discussed from time to time.

    Frank Dresser
     
  4. Eric Vey

    Eric Vey Guest

    If smoke came out, you should see some charring.
     
  5. Ken Taylor

    Ken Taylor Guest

    I'd actually suspect filter cap('s) in the power supply, or if it happens to
    use selenium rectifier(s) in the ps, then those.

    Ken
     
  6. GPG

    GPG Guest

    Selenium rectifiers make a very distinctive smell when they fail
     
  7. Or dripping if the filter cap. :)

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  8. James Sweet

    James Sweet Guest


    Blech! Yeah they do! Is there anything that smells more horrible?
     
  9. Oh yeah! If you've ever smoked one of these there's no way you're *ever*
    going to forget that smell...

    I wonder how many of you guys have worked on stuff that uses these?
     
  10. Jason D.

    Jason D. Guest

    What about those aka stinky rotten fish cans (caps) when soldering?
    This made me really go oooh! snorting & hands waving trying to get
    stink out of my nose every time. Is this like that for smoking
    selenium rectifiers? Yes I did seen them but not ones that blew.

    What about the blue disk caps that let out pall of BIG thick pink
    smoke, somewhat stinky?

    Cheers,

    Wizard
     
  11. Robert Baer

    Robert Baer Guest

    Old tube circuits should be powered up slowly with a variac, so that
    the electrolytics have a chance to reform.
    Failing that, all electrolytics should be replaced before power on, as
    it is extremely likely they are bad; that is why you heard hum. New
    tubes will not fix that.
    My questions are (1) do the e-bay recorders *work*, (2) are those you
    found actually wire recorders?, (3) if they had been repaired, were as
    orginal parts as possible used? (4) case, panel, knobs, etc in
    semi-pristine condition?
    I dare say *no* to most of that criteria.
    You have a possible collectible, and the better the condition, and
    original-type parts for repair used, the higher the value.
    Oh, yes i forgot - any wire spools for recording? And what is recorded
    on those you have? Any documented provenance concerning those recordings
    (historical interest).
     
  12. Yeah, *real* slowly, if you have the patience for that. And they may end up
    turning out to not be any good anyway...
    That "original parts" bit got my attention.
    How can you even *get* "original-type parts" for a lot of this stuff? And why
    would you want to, assuming that you wanted something to work?

    Going back a couple of decades, I spent some time helping a guy get a number
    of antique radios working. He was interested in anything that wasn't
    plastic, most of it going back to WWII or before. I'd take the guts out and
    work 'em over, get it working well.

    For electrolytics a number of those sets had cans that had a *big* nut going
    around a threaded bushing. I'd never seen those prior to working with those
    sets. At that time, I had a few of those mounting plates for the twist-tab
    type cans (and probably still have a couple) and I ended up drilling screw
    holes, putting one of those in, and putting a twist-tab can in there.
    These days I'm not sure those are even available.

    And those old wax-coated paper caps! I always end up yanking them out and
    replacing them with mylar types. There's little likelihood of them still all
    being good after all those years.

    Now, assuming that you could even _find_ original-type parts for these
    things, would you really want to use them? Seems to me that would be just
    asking for trouble...
     
  13. Rich Grise

    Rich Grise Guest

    Yes. When they fail inside a sealed, pressurized power supply housing,
    and the dimwit pilot or EWO leaves it on for the whole mission (i.e.,
    continuing to burn), and you open the power supply case in the shop.

    It clears the room. :) (how do you do a yucchy-face with punct. marks?)

    Cheers!
    Rich
     
  14. Dennis Davis

    Dennis Davis Guest

    sounds like a paper capacitor smoked, could of caused a resistor or 2 to
    burn as well,replace all the paper caps and check for bad resistors. a
    schematic probably will be nessasary as the values on the parts will be
    hard to read,might get lucky with schematic if its on inside of the cover.
    the tubes are also a good idea, most are probably weak and in need of
    replacement.
     
  15. N. Thornton

    N. Thornton Guest

    Hi. Sounds probably like a bad capacitor, or possibly a dud connection
    on the input end of the audio chain. I'm not sure if youve got the
    knowledge to do it but we can see.

    Forget new valves, keep the old ones in there if poss. And keep the
    scope off it as you may make the scope case live and get electrocuted.
    Place to start is work out which valve does what, and try the unit
    with different valves pulled out to locate the problem area.

    Next move would be to replace any bad caps. But since this is a
    valuable museum piece I wouldnt replace them, I'd open the caps up,
    fit well rated modern ones inside and reseal exactly as per original.
    And only on caps that test bad.

    Dont dismantle unless you know what youre doing. Live voltages may
    appear where you least expect them, eg on heads, knob spindles,
    chassis, and stored in reservoir caps when the things unlpugged. I
    would do as assessment of its safety before plugging it in, theres
    some truly stuipid stuff around from back then.

    Really though I'd give it to a specialist to assess if possible.


    Regards, NT
     
  16. Robert Baer

    Robert Baer Guest

    AFAIK this is an *old* and maybe repeated posting, and has been
    answered numerous times....
     
  17. Bill Chaplin

    Bill Chaplin Guest

    A serious 60~ hum is wonderful,tells you a near guaranteed filter capacitor in
    power supply was the source of smoke being they were almost always electrolytic
    (oil filled) and had a shelf life,value is printed on each one (just replace all
    big metal cans or cardboard tubes,to use scope on tube audio eqp just connect both
    chassis and probe away using right hand only,enjoy Bill
     
  18. Robert Baer

    Robert Baer Guest

    An oil-filled capacitor is *completely* different than an
    electrolytic!
    In tube equipment, the 250-450V plate supply is filtered with
    electrolytic capacitors, which can age when not used.
    Best way to try "re-juvenation" is to put the equipment on a variac
    and s-l-o-w-l-y turn the voltage up from zero to full line voltage; some
    will not recoup so need to be replaced.
     
  19. N. Thornton

    N. Thornton Guest


    Sounds like a good way for the inexperienced to electrocute
    themselves. Cant recommend it.

    A much more minor point - reservoir cap failure will in most cases
    produce 100 or 120Hz hum. 50 or 60Hz more likely means a problem at
    the audio input end.

    Regards, NT
     
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