Tube Amps / Music Electronics
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|12/12/2003 3:07 AM|
|Frank De Salvo
||Zenith Phonograph challenge! Help!!!|
I know this is way OT, but I need someone's help locating a part. I've been all over the net and this is my last resource to explore.
The device is a 1961 Zenith console radio/phonograph with built-in speakers. You know, the old time radios that were built inside of furniture
Anyhoo, here is the model number and the number embossed into the part that I am in need of:
Model# 184T20 (Z)
Part# VM-22915 MR
also need a set of stylus'
Here's the scoop: This thing is solid state, but it is wired ptp on terminal strips! It is way cool. IT was sitting for 20 years and was assumed to be broken, but all it needed was someone to find and connect the negative wires of the speakers
After I figured this out, I decided to try my luck with fixing the phonograph which wouldn't spin. I saw that the motor's shaft was spinning and getting hot, but the turn-table wasn't moving. I then moved it by hand and all of a sudden it lurched forward and started spinning. It was making a loud, speed-dependant clunking noise, so I got back inside and had another look about.
The device that controls the RPMs is simply a mechanism that raises or lowers a shaft, graduated in diameter, that is set against and spun by a hub connected to the turn-table's motor. Really cool technology back in the day, heh? The engineers used the varying diameter to adjust the rpms!
On the output shaft's hub is a rubber surround that has been permanently indented by 20 years of spring pressure against the graduated RPM shaft. The rubber has hardened and this indentation is why the motor was freewheeling and not spinning the turntable; it couldn't produce enough torque to free itself from the indention and was practically overheating! After freeing it, the clunking sound was produced by the indented hub bumping the RPM shaft. You've got to love troubleshooting!
Can anyone help me locate this part??
|12/12/2003 3:06 PM|
|Frank De Salvo
|12/12/2003 7:46 PM|
I don't personally know anything about it, but aren't there paint-like rubber products that you could dip that thing into?
|12/13/2003 12:04 AM|
Frank, I work on that stuff all the time. I am in the phone book as the "Stereo DOctor" believe it or not.
The stepped capstan is a very common way to change speeds.
The thing you need is an idler wheel. The rubber gets hard and they need to be replaced, especially if it got stuck and wore a groove in the rubber. Depending on how it is made, you can sometimes worry the rubber off the disk and put a new tire on it. Mostly you replace the whole thing.
Obviously the hub is important since it sets the height and the shaft diameter. The actual diameter of the disk doesn't matter except it has to be large enough to make good contact but not too large that it won't fit.
I have a box of miscellanous ones, but there are replacement lines. EVGame and Pfansteil come to mind. I am not sure if they are still around. Everything and its brother uses idler wheels, so I guess phono idler would be more specific if you are doing search.
WHen I encounter an old player, I can almost promise you the lube will be dried up. Your mechanism got stuck because the poor idler and motor could not turn the big gear. CHeck the lube on the big gear, and the turntable platter itself. The platter should spin freely, and the gears, cams, cam followers, etc should have nice fresh grease.
One other thing to look out for is the rubber grommets the motor mounts with. Many motors hang from shafts through rubber grommets. If the grommets disintegrate, the motor drops, and the idler hits the wrong step, or misses the shaft altogether. Plus the motor will then no longer be mechanically isolated from the chassis so there will be a lot of motor noise transmitted to the table.
For a source for the idler, I looked in ANtique Electronic, www.tubesandmore.com They have a references page. If you do not have their paper catalog, you should order it. There were some potential references there, but I just Googled "phono idler" and BOOM, a bunch of places popped up. SO try that.
|12/13/2003 6:17 PM|
While Enzo's reply is quite accurate there is one small detail worth considering - at the time of production your turntable was designed for fairly cheap records that weren't expected to last very long - America's "new car every year - keep up with the Jones'" mentality. So the mechanism, while complicated, is pretty "sloppy" and was subject to various "jamming" type malfunctions when fairly new. So don't get too discouraged if you find that fixing one thing reveals another part to be fixed. Enzo obviously has much more patience than I do - or I should say "did" - when I worked on general electronics in the 1970s I kept a stack of old turntables around and generally just cannabalized parts until I got something that worked. These units also have a pretty high contact pressure on the needle - often in the tens of grams - and a good bit of tracking error so, once repaired, I wouldn't use it for any record that I valued. I remember literally "wearing out" albums during my teen years after 20 playings or so (the Beatles White Album and Who's Next come to mind right off). I'm pretty sure that this unit is a changer - dropping a "dead weight" record onto a spinning record can do some nice "polishing" if there is any abrasive dust around so I wouldn't use the changer.
But, have fun with it - this was my "CD deck" during my teen years.
|12/14/2003 3:15 PM|
I recently purchased two tube consoles from the early 60s(the big one's a 14-tube RCA Victor) and did some research looking for needles.
Hope this helps.
|12/14/2003 4:06 PM|
|Frank De Salvo
Hey, guys, thanks! It certainly helps to know the nomenclature of the parts in question. Haha, my "graduated-cylendar-thingy" attempts certainly wouldn't help me on the googler!
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