Marantz Model 28 with built-in turntable repair

Discussion in 'Marantz Audio' started by dirtman, Jun 9, 2018.

  1. dirtman

    dirtman The Dirtman Subscriber

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    A friend called to tell me about a Marantz they had stumbled across at a thrift store so I shot over and found this odd ball. It was in great shape. A little dirty but no scratches or smoke and was in the original box. So I grabbed it and quickly dug in to see what was needed. It sounded dull, lights were out and the needle was bent. It also had the usual dried up grease issues.

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    Keep in mind this is an after photo. I couldn't find the "before" one I had taken.

    I did a complete recap except for the tuner section and replaced the troublesome 458 transistors. A good cleaning of the controls and it was sounding pretty good. Added some blue LEDs for effect. It's actually in surprisingly good condition for it's age. One small crack in the lid in the back that is barely noticeable.



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    I also "upgraded" the speaker terminals since one of the push caps was missing and it was painful to attach speaker wires.

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    Next was the turntable...
    IMG_1643.JPG So the gear was seized to the shaft and the whole thing was spinning. It is riveted on so I had no choice but to drill it out of the chassis, then drill, tap it and reattach with a small bolt. If someone attempts this repair, I recommend being very careful hammering the stuck shaft out of the gear. I used a deep well socket to support the gear and a small, flat tipped punch to carefully drive the seized shaft out. If your not careful you can crush the groove that the C-clip slides into, resulting in real problems. Also notice the rubber isolating bushings on the spindle were melted as well.
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    I ended up using a different bolt than this due to clearance issues.

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    Back in. I'm thinking this is a fairly common problem that eventually trashes a lot of these tables. It really wasn't that hard to fix. Now for the melted rubber bushings problem. I thought a couple o-rings would be a good solution but they ended up being too thick and the platter didn't line up with the gear properly. The solution was to sandwich them between 2 stainless spatulas on the electric stove to heat and flatten. Once they got hot enough, I kept the pressure on and had my son put an ice cube on the top spatula to cool it quickly. I worked well and they stayed somewhat flat and were still flexible. If someone were to attempt this, I'd get some extras to practice on. Unfortunately I didn't get any flattened pics .

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    I took lots of pics as I disassembled. I used rubbing alcohol to clean off the old grease. For lubricant I used a long lasting 3 in 1 oil in some places and in others I sprayed lithium grease into a small cup and applied with a "Q-tip". I'm not sure this was the best choice for lubes but it's what I had on hand. I'm sure there are many post regarding cleaning/re-lubing turntables with much better advice. I really just wanted to share my gear and bushing fixes. It played slow and I ended up disassembling the motor and giving it a good clean and lube. A light sanding on the idler wheel rubber with 220 grit and the speed was correct again. I put a new Shure stylus on the original cartridge. It sounds OK but is very bright. I'm thinking it could benefit from a new cartridge but I've taken it as far as I'm willing to go. I'll let the next person deal with that. I doubt there is any profit left in this one but it was certainly a fun project!
     

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  2. Dingman

    Dingman Do you know where your towel is? Subscriber

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    Well, this whole thing is interesting and great work on the TT. Gah, that's why I shy away from turntables, skills needed for repair like that.

    Is this from early Superscope era then?
     
  3. dirtman

    dirtman The Dirtman Subscriber

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    Thank you Dingman. There’s not much info to be found about it. “The Model 28 was the BOTL from Marantz's first line of Receivers made in Japan by Standard Radio.” This is a quote I found while researching. Based on this I’m thinking 1968-69 maybe. It sounds pretty good but not as good as my 2215. It’s unique, looks cool and sounds good enough for causual listening. I actually thought about keeping it just because it’s so different but I’ve no place to put it.
     
  4. Dingman

    Dingman Do you know where your towel is? Subscriber

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    Ya, unique is good, I agree. And don't you hate it when you have something cool like that and nowhere to properly display\use it.

    If it's that early, late 60's, then I think that is still from Marantz, right?

    Heh, unique, if I can find that pic... Look at this thing I found and had to get because it's dingin' different..
     

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  5. sregor

    sregor AK Subscriber Subscriber

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  6. dirtman

    dirtman The Dirtman Subscriber

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    Dingman - that truly is a wild looking turntable. If it sounds even half as good as it looks, it must be a real treat. So far I’ve avoided the slippery slope of turntable upgrades. Based on my history; however, it’s only a matter of time and will likely get ugly ($$!). Lately I’ve been experimenting with Dyi phono preamp kits which has been a lot of fun and is relatively inexpensive.

    Sregor - I remember looking at that site when I first got the 28 but had completely forgotten about it. That is the exact one I have and it’s in pretty much the same condition. Thank you.
     

     

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  7. Dingman

    Dingman Do you know where your towel is? Subscriber

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    I'm sorry - my pictures are crap. That's a radio\CD player with built in amp - but no turntable. It is really cool looking, it has crazy joystick controls.
     
  8. dirtman

    dirtman The Dirtman Subscriber

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    Ah yes. I see it now. Was looking at it on my phone before. Checked it out online. Very nice indeed!
     
  9. llwhtt

    llwhtt Super Member

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    The big gear on many of those changers is frozen due dried grease, try using a heat gun to soften the grease and the gear will come right off, next time that is.

    Craig
     

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