Model 20 tuner

Discussion in 'Marantz Audio' started by thxdave, Apr 16, 2018.

  1. thxdave

    thxdave Lava Lamp repairman Subscriber

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    I have a chance to pick up a Model 20 tuner with wood case this weekend and was wondering if there were any "gotchas" I should look for. Obviously, I'd want the o'scope to be working and burn free, but are there other issues I should look for?
     

     

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  2. thxdave

    thxdave Lava Lamp repairman Subscriber

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    Wow, this thing must be rare. More than 30 views and nobody has commented. I'm hoping to have it this weekend for testing before I make a buying/trading decision so any advice will be welcomed.
     
  3. rBuckner

    rBuckner Luv 2 Restore Subscriber

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    Wish I had words of wisdom for ya bud! You have the most important criteria listed - the scope. Know where the weaker stations are on the dial and try them out. Good luck!
     
  4. thxdave

    thxdave Lava Lamp repairman Subscriber

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    Thanks for the thoughts. I'll give it a good test via my rotor-mounted outdoor FM Yagi.
     
  5. jstang

    jstang Honey,I can't hear you... Subscriber

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    Power supply diodes go bad, stereo lamp burns out, fm FETs go.... But all fixable. Scopes hard to find.
     
  6. g..v

    g..v Lunatic Member

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    Buy it because it's there. I've had one (new) since the early 70s. Had only one service call. However, aside from what has been mentioned, the RCA connections into the black box can be an issue which is easily remedied. I'm not using mine as much as I like, and I never got around to putting up an outside antenna.
     

     

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  7. bktheking

    bktheking Gitter Done!

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    My 20b still chugging along, well built tuners and worth owning as part of any Marantz collection.
     
  8. onemug

    onemug AK Subscriber Subscriber

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    It's an excellent tuner. Most of your "gotchas" have been answered.

    Unless you already know for sure, check the serial # on the back to see if it's a 20 or 20b. Both models say Model 20 on the front. The serial # will say either 20-xxxx or 20b-xxxx.

    I have and love both and personally favor the B. Good luck.
     
  9. thxdave

    thxdave Lava Lamp repairman Subscriber

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    I'm pretty sure this one is the non-B model. I should have it here for evaluation over the weekend. I'll keep you posted.
     
  10. thxdave

    thxdave Lava Lamp repairman Subscriber

    Messages:
    405
    Location:
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    Got the tuner this morning and it's in great shape. Definitely a 20 and not 20b.

    DSCN5184.jpg

    Dial pointer is dead-on accurate and tunes into Stereo despite the Stereo Indicator lamp being dead. Tuner still needs a tiny bit of cleaning with Deoxit but all front panel controls are quiet. I heard a bit of noise on the Output Level pots but rotating them several times seems to have broken up the crud. All scope functions are working and there appears to be no burns. Guy who sold it to me says he might have a spare NOS scope for it but hasn't found it yet.

    DSCN5187.jpg

    So, I'm trying to fix the usual stuff (burned out bulbs) which in this tuner appear to be bayonet-style bulbs. According to the SM, the tuner dial backlight has four GE #55 (7vAC, .41Amp). The Stereo Indicator lamp is a GE #2187D (28vAC, .04Amp) also bayonet style. The big problem I'm having is getting TO the darned bulbs. I can see the backs of the sockets from behind the panel. I disassembled the faceplate as far as I could by removing the three screws and a piece of black tape along the bottom. It appears that there are a pair of clips on the bottom of the tuner scale. I managed to swing the pointer up a bit to try to pull down the plastic scale but the clips are holding it very tightly and I'm afraid I'll break it if I pull too hard:

    DSCN5198.jpg

    Is there a trick to getting the dial scale off this thing? Also, the wood case is almost perfect but I'm curious as to what model case this is. The case is screwed to the chassis in the back and rests on the thumbtack-sized feet pressed into the wood. I see no way to attach regular Marantz feet to this thing. Anybody know if this is the right case for my #20? Also, what screws are normally used in the corners of the faceplate? They appear to screw into the cabinet to secure the faceplate into the case.
    DSCN5195.jpg
     
    Last edited: Apr 22, 2018
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  11. onemug

    onemug AK Subscriber Subscriber

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    Congrats on your "20". Looks great in wood cabinet.

    I have changed the dial bulbs on my 20. I did not need to deal with faceplate removal. If you remove the top lid of the metal cabinet, you can pull the "light holder" backwards (the holder slides on to the shelf below it). Then it's just a simple push and twist to remove the bulb from it and replace with a new one. I can get at 3 of the 4 easily with just my hand but for the 2nd one in from the left, it took some agility and patience on my part. I have found it much easier to unscrew the rectangular box behind them to get at that one.

    Re faceplate screws...originally came with antique brass wood screws (Phillips). I needed some for one of my 20/20b's and bought some brass ones at my local Hardware store. You may have to settle for regular brass if they don't have antique ones. It looks better than empty holes. BE FOREWARNED...It "secures" the cabinet a little. but when you actually screw them in you will see they are pretty small and tapered and might not stop a large jolt. The bottom screws are for that. Phillips head are the correct type and be VERY careful screwing them in. One slip of the screwdriver and you will have a scratch on that beautiful faceplate.

    Good luck.
     

     

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  12. thxdave

    thxdave Lava Lamp repairman Subscriber

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    Thanks onemug. I see what you mean about that one bulb holder in the middle. I was able to get mine out without loosening the box (tuning capacitor) and pulled the Stereo indicator bulb, too. I peeked down inside the tuner faceplate and it appears that the diffuser in this unit is plastic instead of the usual vellum. I can only see the edge of it. Do you know if the plastic yellows the way the paper does? When you relamped yours, did you stick with incandescent or did you go LED? Finally, do you know how to get the faceplate out? Do I have to bend those two clips at the bottom of the dialface?
     
  13. jstang

    jstang Honey,I can't hear you... Subscriber

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    The 20 is Solid State Sex....
     
  14. jstang

    jstang Honey,I can't hear you... Subscriber

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    Do I obsess?

     
  15. thxdave

    thxdave Lava Lamp repairman Subscriber

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    Hey, I live alone so I hope you're not suggesting.....um.....gotta go.
     
  16. jstang

    jstang Honey,I can't hear you... Subscriber

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    Just the 20 and only the 20....
     

     

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  17. onemug

    onemug AK Subscriber Subscriber

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    I don't think so. The only thing I see is the blue gets a little lighter from fading but nowhere near the greenish turquoise that I've seen on some of their receivers. Trivia...the very first 20's did have a green dial.

    Stayed with incandescent. If you do go LED, I'd like to see a picture of it when your done.

    No. Never had to take it off.
     
  18. thxdave

    thxdave Lava Lamp repairman Subscriber

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    Location:
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    I'm buttoning up the front panel today while I wait for dwojo's LEDs to arrive. Dave's sending me Cool White and Warm White to try so I might shoot both samples for comparison. The Stereo Indicator lamp will be replaced with incandescent due to no LED equivalent. One ham-handed thing I did was snap off the dial pointer so I'm reattaching that, too.
     
  19. thxdave

    thxdave Lava Lamp repairman Subscriber

    Messages:
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    Location:
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    I thought I had ordered Cool White and Warm Whte, but I screwed up and ordered CW only. But, to help show the difference, I replaced the burned out #55 bulb and shot one photo with nothing but incandescent bulbs, seen here:

    IncandescentOnly.jpg

    In the next shot, the right half has Cool White LEDs and I left the other two incandescent bulbs in place so you could see the difference. I locked the exposure and white balance so there should be no drift between shots:

    LEDonRightSide.jpg

    Here's one I shot in the dark to accentuate the color difference even more:

    DSC_5998.jpg

    Honestly, I'm not sure which I prefer. I'd be willing to swap out the Cool Whites for something more Light Blue just to make it more of a Marantz blue but that may be later on. I'm anxious to button it up and start enjoying it!!
     
  20. jstang

    jstang Honey,I can't hear you... Subscriber

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    Also the early and later 20s displayed different colors even with the standard bulbs.
     

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