In over my head... hifi / am fm phono player restoration

Discussion in 'Amp Tech Center' started by MrCoolGuy, Oct 17, 2020.

  1. MrCoolGuy

    MrCoolGuy Tele-Meister Silver Supporter

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    I am trying to help a friend restore an old record player/ am fm radio. Does anyone know a good forum for discussing this type of thing? My questions are many, but we'll start by asking... this vintage machine has 4 speakers, two 6" (5.5"?)
    Woofers and two 3" tweeters with big crossover caps in series with the tweeters... which I understand, but...
    They are all blown.

    Is it necessary to replace all 4 speakers or could I use 2 speakers (correct impedance) to do the work of the 4?

    My question is not in regards to power handling or impedance. I'm capable of understanding that. I'm asking is it necessary to have woofers and tweeters?
    Guitar amp speakers seem to produce a broad range of frequencies just fine...
    Am I missing something?

    By the way, it's a 1965 Air Chief 13R10. received_348692529799087.jpeg received_740542846526916.jpeg received_684020642244719.jpeg

    Thanks!
     
  2. CaptainCrunch

    CaptainCrunch TDPRI Member

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    I am far from an expert on any of your questions, but I can say that overall, guitar amps/speakers are pretty midrangey. It can have a lot of grunt or a ton of chime, for a guitar amp, but it’s pretty apples and oranges from our amps to hi-fi.
     
  3. NTC

    NTC Tele-Meister

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    ...which is to say you will need tweeters if you want it to sound good.
     
  4. BelairPlayer

    BelairPlayer Tele-Afflicted

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    If the phono hasn’t been used much/recently, expect hardened grease in the mechanics, and deteriorated rubber on the idler wheel or drive belt. We used to have the idler wheels “re-rubbered” since they don’t make many (most) of the serviceable parts anymore. I can’t even remember where we used to send them. You can throw most of the mechanical parts in an ultrasonic sink to get the old grease off of them.
     
  5. elpico

    elpico Tele-Afflicted

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    Like the other guys said, guitar speakers can't reproduce the top two octaves or the bottom two octaves but to be fair these old console stereos were often pretty limited too.

    Hifi drivers meant to work alone are called "full-range" drivers. You can certainly go that route if you want.

    A 2-way or 3-way design will generally have more extension at the extreme highs and lows and a smoother frequency response... at the expense of increased complexity, driver costs, and crossover costs.
     
  6. dogmeat

    dogmeat Tele-Afflicted

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    its a Firestone. I looked quickly at my best source but didn't find anything. betting someone there can help though, try

    https://www.radiomuseum.org/dsp_schaltplanubersicht.cfm

    they have a forum too. I've revived old rubber drive drums to serviceable condition with wintergreen oil. it will soften hard rubber by reintroducing a natural plasticizer into the rubber. I've used it on a number of vintage motorcycle parts too. it can be rubbed on straight or mixed with alcohol or xylene or other carriers. threes stuff on the net. it won't fix cracks though


    heres another couple sites

    https://antiqueradios.com/forums/index.php

    https://www.tuberadioforum.com/
     
    Last edited: Oct 18, 2020
  7. MrCoolGuy

    MrCoolGuy Tele-Meister Silver Supporter

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    Thanks everyone, but thank you, @elpico ... that is what I was hoping to hear.
    I didn't mean to actually use guitar speakers, I was asking if there are single "full range drivers" the could replace a woofer + tweeter pair.

    And yes, @BelairPlayer ... I'm not looking forward to cleaning all that grease on the mechanical bits... but I am aware of it. Thank you. I suppose I'll start looking for speakers, whether full range or otherwise. Any good places to check?
     
  8. BelairPlayer

    BelairPlayer Tele-Afflicted

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    You might look at two way car speakers. They integrate tweeter and mid-range driver. Bass performance varies depending on size. They have the added benefit of integrated crossover circuits, so you wouldn’t even need to fool with crossovers. It’s an option.
     
  9. BelairPlayer

    BelairPlayer Tele-Afflicted

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  10. avspecialist

    avspecialist Tele-Meister

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    Is this a tube amplifier in the console, if it is then you have to match the output impedance. If it’s solid state, then do not go below 4 ohms. You can call parts express and give them the make and model number of the speakers, they usually can help you find a good replacement match. They also have crossover parts. Also Madisound is a good resource for crossover parts and drivers. If you have pictures of the drivers and caps your are looking for I might be able to help with that also.
     
  11. schmee

    schmee Doctor of Teleocity Silver Supporter

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    "it depends". Some old mono and stereo's had woofers and tweeters but just used a simple crossover to divide lows from highs for them. There are good full range speakers out there and many (not all) guitar speakers are fine for that. But there are places that sell speakers for this stuff and they can be cheap.
    6" Stereo full range speaker $12:
    https://www.parts-express.com/grs-6...rYE-1YTPkuFSrBsoZgT2Y52Zv36whiIBoCv2UQAvD_BwE
     
  12. ArcticWhite

    ArcticWhite Tele-Afflicted

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    Have you thought about the amplifier yet?
    All of the electrolytic capacitors (and there will be many in a tube amp) will need to be replaced.
    Speakers can be replaced, but you will need new crossovers if you're going from three speakers to two.

    I recommend audiokarma.org
     
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  13. BobbyZ

    BobbyZ Doctor of Teleocity

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    Had an old solid state one kinda like that in my old house. When I still though I'd restore the house I'd use the radio in it, sounded great and filled the whole place with sound. One day I thought there must be a thunderstorm coming because it sounded like close lighting strikes on AM radio.
    Then it dawns on me, I'm listening to FM!
    I suspected the old electrolytic caps or something were breaking down inside but never pulled it apart for a look, ment to do that but it's gone now anyway. Lol
     
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  14. MrCoolGuy

    MrCoolGuy Tele-Meister Silver Supporter

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    Yes, I'm very familiar with working on amplifiers... I've fixed/ replaced most of the caps and components that need to be replaced... the voltages look good... everything is looking good except all 4 speakers are blown... and phono works, AM works great, but FM doesn't work (zero sound at all)...

    Yes, @avspecialist , it is a tube amp...
    I know I have to match impedance...
    That's why I'm the original post I said that "My question is not in regards to power handling or impedance."
    But thanks.

    I was thinking of getting two 6" full range speakers... but these type of speakers (as opposed to guitar amp speakers) seem to be pretty cheap... so maybe I will stick with original setup with crossovers.
     
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  15. avspecialist

    avspecialist Tele-Meister

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    Also in most cases, you will need at least a piece of wire a couple of feet long, to try and pull in any strong local FM station. Connect the wire to the 300 ohm antenna terminals. Also, if the fm muting is on, try switching it off and you could also try to connect a FM dipole antenna for slightly better reception. In a lot of cases all but the strongest stations will come in, mostly they are in the middle of the dial, like the 96.5 to 100.5 stations.
     
  16. MrCoolGuy

    MrCoolGuy Tele-Meister Silver Supporter

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    Yeah, I don't see any kind of "fm muting"
    It has an antenna that wraps half way around the console... it doesn't seem like an issue of not having signal... it sounds like you're turning the whole thing off when you switch it to fm.
    Meaning when it's on am or phono there is a very slight hum in the speakers, just enough to know it's on... but when you switch to fm, silence.
     
  17. avspecialist

    avspecialist Tele-Meister

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    on the FM are there any tuning meters or mono stereo indicator lights when you turn to a know strong fm station?
     
  18. MrCoolGuy

    MrCoolGuy Tele-Meister Silver Supporter

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    I'm not home at the moment, but no I don't belive so.
     
  19. avspecialist

    avspecialist Tele-Meister

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    MrCoolGuy, I looked through the internet, I couldn’t find your model, I found others. I tried to zoom in on the 3rd knob down in you photo but couldn’t make out what that knob points to. i’m thinking it’s an input selector. Also looking at the back panel it does show a folded dipole FM wire on the 300 ohm terminals. Some times there are RCA cables going from the tuner section to the preamp input. Perhaps if there are some, you could plug in another line level device to see if that input is functioning. Sometimes you could find the lead wires going into the line level tuner input. If at all possible you could attach a different line level device to the radio input just see if that input is working. Also if there are actual tuner outputs, perhaps you could run that Firestone tuner into a different stereo line input.
     
  20. BobbyZ

    BobbyZ Doctor of Teleocity

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    I'm not sure how these things work, but if it sounds like it shuts off when switched to FM, could it be the switch?
    I have messed with old radios, just not a heck of a lot.
     
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