Forums :: NEW! Web Resources :: Features :: Photo Gallery :: Vintage Radio Shows :: Archives
Support This Site: Contributors :: Advertise


It is currently Oct Wed 27, 2021 7:17 am


All times are UTC [ DST ]





Post New Topic Post Reply  [ 37 posts ]  Go to page Previous  1, 2
Author Message
 Post subject: Re: V-M 1200 Changer Step-by-Step Restoration
PostPosted: Sep Thu 03, 2015 7:35 pm 
Member

Joined: Jan Thu 01, 1970 1:00 am
Posts: 16749
Location: Albuquerque, NM 87123
I can't remember the last time I had to replace a motor that was seized. Maybe never. When I see a seized shaft I just use acetone and it loosens up; it may take several applications with a swab, but it works.


Top
 Profile  
 
 Post subject: Re: V-M 1200 Changer Step-by-Step Restoration
PostPosted: Sep Thu 03, 2015 8:02 pm 
Member
User avatar

Joined: Jan Sun 06, 2008 3:28 am
Posts: 4502
Location: Richmond, VA
First time for me, too. Overnight soaking didn't free it up. The motor would work with help starting, but I don't know if the speed was correct as it may have been that the bearing was just spinning on the rotor shaft. There's not much access to the upper bearing as the stepper shaft is pressed on the rotor.

_________________
Ed


Top
 Profile  
 
 Post subject: Re: V-M 1200 Changer Step-by-Step Restoration
PostPosted: Sep Fri 04, 2015 4:35 pm 
Member
User avatar

Joined: Jan Sun 06, 2008 3:28 am
Posts: 4502
Location: Richmond, VA
Before the cycling mechanism can be re-mounted to the deck, there is one more task to be completed: installing the reject rod and retraction rod. These are actuated by the OFF/ON/REJECT knob, and the rods are connected to the cycling mechanism and motor.

The reject rod passes UNDER the cycling mechanism and connects to the control shaft assembly in the cycling mechanism through a slot in the bottom of the mechanism, so it must be installed before the cycling mechanism is re-attached to the deck.

First, install the bushing that the control lever assembly shaft fits through:

Attachment:
Cobramatic79.jpg
Cobramatic79.jpg [ 113.93 KiB | Viewed 14586 times ]


Slip the hooked end of the retraction rod through the hole in the idler arm assembly:

Attachment:
Cobramatic80.jpg
Cobramatic80.jpg [ 119.53 KiB | Viewed 14586 times ]



Attach the other end of the retraction rod to the control lever assembly as shown:

Attachment:
Cobramatic81.jpg
Cobramatic81.jpg [ 116.04 KiB | Viewed 14586 times ]


The reject rod is installed next. Fit the "S" shaped end through the control lever as shown in the photo below:

Attachment:
Cobramatic82.jpg
Cobramatic82.jpg [ 118.57 KiB | Viewed 14586 times ]


The other end of the reject rod has a small lip on the end. The rod passes under the cycling mechanism body and fits through a slot into a hole in the control shaft assembly as shown in this view from the under side of the cycling mechanism:

Attachment:
Cobramatic83.jpg
Cobramatic83.jpg [ 130.78 KiB | Viewed 14586 times ]


Attachment:
Cobramatic72.jpg
Cobramatic72.jpg [ 135.91 KiB | Viewed 14586 times ]


When fitted correctly, the lip at the tip of the reject rod fits through the hole in the control shaft assembly and keeps the rod from slipping out.

Attachment:
Cobramatic85.jpg
Cobramatic85.jpg [ 98.9 KiB | Viewed 14586 times ]


This is one of the more awkward steps in re-assembly and it may take several tries to get the reject rod properly seated. One it is in place, fit the control lever shaft through the bushing and secure from the top of the deck with the speed nut and clip.

Attachment:
Cobramatic88.jpg
Cobramatic88.jpg [ 95.38 KiB | Viewed 14586 times ]


Attachment:
Cobramatic86.jpg
Cobramatic86.jpg [ 99.96 KiB | Viewed 14586 times ]


The final step is the install the reject spring to the control lever and the turntable deck:

Attachment:
Cobramatic87.jpg
Cobramatic87.jpg [ 130.61 KiB | Viewed 14586 times ]

_________________
Ed


Top
 Profile  
 
 Post subject: Re: V-M 1200 Changer Step-by-Step Restoration
PostPosted: Sep Sat 12, 2015 6:46 pm 
Member
User avatar

Joined: Jan Sun 06, 2008 3:28 am
Posts: 4502
Location: Richmond, VA
To re-install the slide and cycling mechanism to the deck, pass the 12" record lever and tone arm shaft through their openings and align the screw holes. Check to see that the 10" lever is properly situated. Make sure the reject rod doesn't jump out of place.

Attachment:
Cobramatic91.jpg
Cobramatic91.jpg [ 115.19 KiB | Viewed 14524 times ]


The mechanism is held in place by three screw, one from beneath and two topside. From underneath, install the screw near the rear of the slide:

Attachment:
Cobramatic89.jpg
Cobramatic89.jpg [ 146.79 KiB | Viewed 14524 times ]


Flip the unit over and install the two topside screws:

Attachment:
Cobramatic90.jpg
Cobramatic90.jpg [ 183.05 KiB | Viewed 14524 times ]


Clean the record support shaft guide assembly. Clean the record support shaft with alcohol and 0000 steel wool. Remove all traces of steel wool, than apply a few drops of oil to the shaft. Replace the shaft by passing it up through the bottom of the deck. (Photos show parts before removal and cleaning)

Attachment:
Cobramatic92.jpg
Cobramatic92.jpg [ 122.61 KiB | Viewed 14524 times ]


Attachment:
Cobramatic93.jpg
Cobramatic93.jpg [ 135.22 KiB | Viewed 14524 times ]


Re-attach the record support arm to the record support shaft. Line up the set screw holes with the old marks on the shaft and tighten then set screws.

Attachment:
Cobramatic94.jpg
Cobramatic94.jpg [ 126.57 KiB | Viewed 14524 times ]


Attachment:
Cobramatic95.jpg
Cobramatic95.jpg [ 121.09 KiB | Viewed 14524 times ]


Slip the rubber bumper back on top of the 10" record lever. I used a bit of Walther's Goo to hold it in place as it didn't fit snug. Walther's Goo is available in hobby shops. It is flexible and the bumper can be easily removed again if needed.

Attachment:
Cobramatic96.jpg
Cobramatic96.jpg [ 163.12 KiB | Viewed 14524 times ]


Finally, install the record support shaft guide assembly. This is a critical step in re-assembly, because if done incorrectly, the changer will not cycle properly. The small spring steel arm on the guide assembly must engage the shut-off lever on the cycling mechanism when the record support shaft drops down after the last record drops. Install the guide assembly as shown in the photo:

Attachment:
Cobramatic96.jpg
Cobramatic96.jpg [ 153.24 KiB | Viewed 14524 times ]


All that remains now is to re-wire the tone arm, install a new cartridge and stylus, and install the tone arm on the changer, along with the platter and bearings. Since this unit came out of a console, I won't be using the original wiring harness, so I will have to rewire the motor and pickup to operate as an external attachment to an amplifier.

_________________
Ed


Top
 Profile  
 
 Post subject: Re: V-M 1200 Changer Step-by-Step Restoration
PostPosted: Sep Mon 21, 2015 6:31 pm 
Member
User avatar

Joined: Jan Sun 06, 2008 3:28 am
Posts: 4502
Location: Richmond, VA
This Cobramatic pre-dates stereo, so the original cartridge was a monophonic cartridge using two wires. After removing the old cartridge and stylus, I removed the two wire harness and installed a four wire harness for a stereo cartridge.

Attachment:
Cobramatic201.jpg
Cobramatic201.jpg [ 40.62 KiB | Viewed 14483 times ]


Attachment:
Cobramatic202.jpg
Cobramatic202.jpg [ 47.19 KiB | Viewed 14483 times ]


I originally installed a Pfanstiehl MG55C magnetic cartridge, but I swapped it out later for a Pfanstiehl P228 so I could play 78's. I would also would have needed to add a pre-amp between the amplifier I planned to use and the Cobramatic to use the magnetic cartridge.

The Pfanstiehl P228 is a tad too large to use the 1/2" mounting holes, but can be installed using double-sided tape:

Attachment:
Cobramatic203.jpg
Cobramatic203.jpg [ 71.64 KiB | Viewed 14483 times ]


The next post will show the installation of the tone arm on the deck.

_________________
Ed


Top
 Profile  
 
 Post subject: Re: V-M 1200 Changer Step-by-Step Restoration
PostPosted: Sep Mon 21, 2015 7:00 pm 
Member
User avatar

Joined: Jan Sun 06, 2008 3:28 am
Posts: 4502
Location: Richmond, VA
Feed the tone arm wire down through the opening as shown, then replace the fiber washer over the tone arm shaft, which is part of the cycling mechanism.

Attachment:
Cobramatic206.jpg
Cobramatic206.jpg [ 135.8 KiB | Viewed 14482 times ]


Next, fit the hinge arm assembly, with tone arm attached, down over the shaft:

Attachment:
Cobramatic207.jpg
Cobramatic207.jpg [ 159.07 KiB | Viewed 14482 times ]


Slip the safety plate over the shaft. Note the correct orientation. The small end goes to the left, toward the platter, and the larger end, which is a pawl that rides against the needle set-down adjusting screw, goes to the right:

Attachment:
Cobramatic208.jpg
Cobramatic208.jpg [ 167.64 KiB | Viewed 14482 times ]


Secure the safety plate with the nut:

Attachment:
Cobramatic209.jpg
Cobramatic209.jpg [ 127.67 KiB | Viewed 14482 times ]


Attach the small hooked end of the safety spring to the catch on the left side of the safety plate:

Attachment:
Cobramatic210.jpg
Cobramatic210.jpg [ 114.64 KiB | Viewed 14482 times ]


Grasp the spring with needle nose pliers and slip the large end of the spring over the needle set-down adjusting screw. Make sure the hooks fits into the groove in the needle set-down adjusting screw:

Attachment:
Cobramatic211.jpg
Cobramatic211.jpg [ 118.96 KiB | Viewed 14482 times ]


Attachment:
Cobramatic212.jpg
Cobramatic212.jpg [ 131.15 KiB | Viewed 14482 times ]


Attachment:
Cobramatic213.jpg
Cobramatic213.jpg [ 121.68 KiB | Viewed 14482 times ]


After I rewire the machine, and I can make sure the cycling mechanism is functioning correctly, the needle set-down screw can be adjusted so that the tone arm sets down correctly for different sized records.

_________________
Ed


Top
 Profile  
 
 Post subject: Re: V-M 1200 Changer Step-by-Step Restoration
PostPosted: Sep Mon 21, 2015 7:55 pm 
Member
User avatar

Joined: Jan Sun 06, 2008 3:28 am
Posts: 4502
Location: Richmond, VA
The Cobramatic was originally wired for installation in a console.

Attachment:
Cobramatic219.jpg
Cobramatic219.jpg [ 230.74 KiB | Viewed 14480 times ]


I removed the original loom and installed a new AC power cord with a non-polarized plug. To make future servicing of the unit easier, I used a Molex power connector between the power cord and the motor and switch.

One lead goes directly to the motor, and the other is connected to the hot side of the switch.

Attachment:
Cobramatic215.jpg
Cobramatic215.jpg [ 165.08 KiB | Viewed 14480 times ]


Note that there are three leads coming from switch, but only two are needed, the hot lead to the AC in terminal, and the switched lead going to the motor.

Attachment:
Cobramatic217.jpg
Cobramatic217.jpg [ 150.65 KiB | Viewed 14480 times ]


Attachment:
Cobramatic224.jpg
Cobramatic224.jpg [ 127.21 KiB | Viewed 14472 times ]


The extra lead is capped with shrink tubing, and tucked out of the way. I could have removed it at the switch, but I left it in case the Cobramatic is re-installed in a console at some point in the future.

Attachment:
Cobramatic218.jpg
Cobramatic218.jpg [ 138.76 KiB | Viewed 14480 times ]


The leads from the motor are attached with wire nuts and the wires routed away from the slide mechanism:

Attachment:
Cobramatic216.jpg
Cobramatic216.jpg [ 172.78 KiB | Viewed 14480 times ]


For audio, I removed the original terminal strip and cable, and replaced it with two RCA phone jacks mounted in a piece of styrene plastic:

Attachment:
Cobramatic220.jpg
Cobramatic220.jpg [ 164.42 KiB | Viewed 14480 times ]


Attachment:
Cobramatic221.jpg
Cobramatic221.jpg [ 120.73 KiB | Viewed 14480 times ]


I then soldered the four leads of the cartridge wiring harness to the terminals on the RCA jacks. Gary Stork at Voice of Music recommended that I install a ground loop as I was originally planning to use a magnetic cartridge. Although I later decided not to use a magnetic cartridge, I left it in place.

Attachment:
Cobramatic222.jpg
Cobramatic222.jpg [ 127.11 KiB | Viewed 14480 times ]


Attachment:
Cobramatic223.jpg
Cobramatic223.jpg [ 157.68 KiB | Viewed 14480 times ]

_________________
Ed


Last edited by Ed Morris on Sep Mon 21, 2015 11:44 pm, edited 1 time in total.

Top
 Profile  
 
 Post subject: Re: V-M 1200 Changer Step-by-Step Restoration
PostPosted: Sep Mon 21, 2015 8:29 pm 
Member
User avatar

Joined: Mar Tue 04, 2014 3:29 am
Posts: 2090
Location: Long Beach, CA 90808
Really enjoying this detailed step-by-step tutorial Ed!

It will be a great help to me in the near future as I have one of these units in a nice little Zenith Console that I'm restoring for my parents.

_________________
Aloha, Ken

No Console Left Behind!
Come join us @ http://vintagehifi.net/


Top
 Profile  
 
 Post subject: Re: V-M 1200 Changer Step-by-Step Restoration
PostPosted: Sep Mon 21, 2015 10:49 pm 
Member
User avatar

Joined: Jan Sun 06, 2008 3:28 am
Posts: 4502
Location: Richmond, VA
Thanks, Ken. Not too much more left to do.

_________________
Ed


Top
 Profile  
 
 Post subject: Re: V-M 1200 Changer Step-by-Step Restoration
PostPosted: Sep Tue 22, 2015 7:19 pm 
Member
User avatar

Joined: Jan Sun 06, 2008 3:28 am
Posts: 4502
Location: Richmond, VA
The turntable rides on a bearing assembly consisting of an upper and lower washer, and a set of bearings in a retainer. The bearings and retainer should be cleaned in alcohol. I then use a toothpick and apply a bit of Phonolube to each bearing.

Attachment:
Cobramatic225.jpg
Cobramatic225.jpg [ 133.81 KiB | Viewed 14450 times ]


Attachment:
Cobramatic226.jpg
Cobramatic226.jpg [ 100.85 KiB | Viewed 14450 times ]


Then drop the lower washer over the spindle, followed by the bearing retainer, and the upper washer:

Attachment:
Cobramatic227.jpg
Cobramatic227.jpg [ 61.3 KiB | Viewed 14450 times ]


Attachment:
Cobramatic228.jpg
Cobramatic228.jpg [ 159.77 KiB | Viewed 14450 times ]


Before attempting to replace the turntable, lift the record guide at the top of the spindle, and wrap a bit of tape around it to hold it up, otherwise, the turntable will never slip down over the spindle.

Attachment:
Cobramatic229.jpg
Cobramatic229.jpg [ 62.07 KiB | Viewed 14450 times ]


Apply a small amount of Phonolube to the splines of the turntable hub:

Attachment:
Cobramatic230.jpg
Cobramatic230.jpg [ 94.77 KiB | Viewed 14450 times ]


Make sure the control knob is in the OFF position to move the idler wheel out of the way, then slip the turntable down over the spindle:

Attachment:
Cobramatic231.jpg
Cobramatic231.jpg [ 100.67 KiB | Viewed 14450 times ]


Remove the tape:

Attachment:
Cobramatic232.jpg
Cobramatic232.jpg [ 94.88 KiB | Viewed 14450 times ]


Make sure the turntable has settled completely on the bearings and has not trapped the idler wheel.

Attachment:
Cobramatic233.jpg
Cobramatic233.jpg [ 123.17 KiB | Viewed 14450 times ]

_________________
Ed


Top
 Profile  
 
 Post subject: Re: V-M 1200 Changer Step-by-Step Restoration
PostPosted: Sep Tue 22, 2015 8:36 pm 
Member
User avatar

Joined: Jan Sun 06, 2008 3:28 am
Posts: 4502
Location: Richmond, VA
The tracking force on the tone arm should be adjusted for the cartridge installed in the tone arm. The tracking force, or stylus pressure, is adjusted by moving a spring either closer or further away from the head of the tone arm.

Attachment:
Cobramatic 304.jpg
Cobramatic 304.jpg [ 80.33 KiB | Viewed 14446 times ]


To adjust the tension, grab the spring clip across both legs with needle nose pliers, and move it closer or further away from the end of the tone arm, depending on whether you need to increase or decrease tension. For some reason, I had a lot of problem moving the spring clip from one setting to another, and ended up launching it into parts unknown. I had to make a replacement, which actually was easier to use than the clip and provided more precise adjustments:

Attachment:
Cobramatic 305.jpg
Cobramatic 305.jpg [ 97.57 KiB | Viewed 14446 times ]


The tracking force for the Pfanstiehl P228 cartridge is 4 - 8 grams. I adjusted the tracking force on the Zenith to 6 grams. You will need a stylus pressure gauge, but if you don't have one, borrow your wife's food scale and set it to grams.

Attachment:
Cobramatic 306.jpg
Cobramatic 306.jpg [ 139.83 KiB | Viewed 14446 times ]


Attachment:
Cobramatic307.jpg
Cobramatic307.jpg [ 113.74 KiB | Viewed 14446 times ]


There are different views on tracking force. Some set the tracking force to the maximum recommended for the cartridge to improve tracking and tripping reliability. Others prefer setting it at the minimum needed. If the tracking force is too light, the stylus may jump out of the grooves on loud passages, which can happen when modern LP's are played on vintage equipment, and the tone arm may fail to trip the reject mechanism at the end of a record. On the other hand, lighter stylus pressure is easier on your records. I have not noted any problems with tracking or tripping with tracking force as low as 4 grams on the V-M changers.

Two more adjustments may be needed for proper operation. The V-M record changers are designed to play 7", 10", and 12" records. The needle set-down adjustment requires a 10" record. A 10" LP record is probably best, but I would guess a 10" 78 RPM record could be used as well if it has a lead-in groove.

To adjust the needle set-down, place a 10" record on the spindle and secure it with the record support arm. Then turn the control knob to reject. Assuming everything has been properly reassembled, the record will drop and the tone arm will move over and set down to play the record. It may set down too far in or it may miss the record completely. Be on guard to prevent damage to the stylus.

Attachment:
Cobramatic234.jpg
Cobramatic234.jpg [ 134.23 KiB | Viewed 14446 times ]


Lift the tone arm and use a screw driver to turn the needle set-down adjustment screw at little bit in one direction or the other. Then repeat the process above. Note where the needle sets down, and re-adjust the screw accordingly. It took me about four tries to get the needle to set down correctly.

Attachment:
Cobramatic235.jpg
Cobramatic235.jpg [ 173.35 KiB | Viewed 14446 times ]


Attachment:
Cobramatic236.jpg
Cobramatic236.jpg [ 119.64 KiB | Viewed 14446 times ]


Once you have adjusted for a 10" record, the set-down point will be correct for 7" and 12" records. No further adjustment should be necessary.

I did not need to adjust tone arm height, but if the tone arm strikes records on the spindle or the tone arm rest, the height can be adjusted by turning the screw shown in the photo below clockwise to lower the arm or counter-clockwise to raise it.

Attachment:
Cobramatic308.jpg
Cobramatic308.jpg [ 145.67 KiB | Viewed 14446 times ]


I installed the changer in a cabinet I purchased from Voice of Music Audio Enthusiasts. At present it is playing through a 1955 Bell Sound amplifier I restored a few years ago. Well, that should be it.

Attachment:
Cobramatic200.jpg
Cobramatic200.jpg [ 142.9 KiB | Viewed 14446 times ]


You can see and hear this Zenith Cobramatic play on You Tube:

https://youtu.be/SX2y38p8LLI

_________________
Ed


Top
 Profile  
 
 Post subject: Re: V-M 1200 Changer Step-by-Step Restoration
PostPosted: Jun Sun 04, 2017 7:22 pm 
New Member

Joined: Jun Sun 04, 2017 5:13 pm
Posts: 2
This whole thread is going to be a life saver. I tried following the guide provided to me by Gary at VoM, but without accompanying visuals, I was completely lost with 2 dozen cups of random parts. I took lots of pictures but it didn't help. I almost purchased a second player just so I could see it all together again.

Thank you so much for take my the time to do this! Gary should pay you for these detailed instructions and pictures and include it in his materials.

Thanks again!


Top
 Profile  
 
 Post subject: Re: V-M 1200 Changer Step-by-Step Restoration
PostPosted: Jun Mon 05, 2017 3:25 am 
Member
User avatar

Joined: Jan Sun 06, 2008 3:28 am
Posts: 4502
Location: Richmond, VA
Thanks and let us know how your Restoration turns out.

_________________
Ed


Top
 Profile  
 
 Post subject: Re: V-M 1200 Changer Step-by-Step Restoration
PostPosted: Jun Wed 07, 2017 2:14 am 
New Member

Joined: Jun Mon 05, 2017 4:22 am
Posts: 12
Holy cow this thread was amazing...


Top
 Profile  
 
 Post subject: Re: V-M 1200 Changer Step-by-Step Restoration
PostPosted: Jun Wed 07, 2017 5:03 pm 
Member

Joined: Feb Wed 04, 2015 12:26 am
Posts: 1648
I bought one of those bases for my mid 60's VoM, I then had a woodworking shop make an exact copy in maple and polished to a high shine. No comparison. Much much nicer.


Top
 Profile  
 
 Post subject: Re: V-M 1200 Changer Step-by-Step Restoration
PostPosted: Aug Tue 31, 2021 11:33 pm 
New Member

Joined: Aug Mon 30, 2021 6:53 pm
Posts: 6
This is invaluable. Was going to buy a new turntable but know I can return the VOM 1200 to its past glory due to your help! Thank you for the time and effort to provide this resource.


Brandons2185 wrote:
This whole thread is going to be a life saver. I tried following the guide provided to me by Gary at VoM, but without accompanying visuals, I was completely lost with 2 dozen cups of random parts. I took lots of pictures but it didn't help. I almost purchased a second player just so I could see it all together again.

Thank you so much for take my the time to do this! Gary should pay you for these detailed instructions and pictures and include it in his materials.

Thanks again!


Top
 Profile  
 
 Post subject: Re: V-M 1200 Changer Step-by-Step Restoration
PostPosted: Sep Mon 27, 2021 5:37 am 
Member

Joined: Nov Mon 11, 2013 6:37 am
Posts: 226
Location: Maple Grove, MN
great job and thank you.

i just completed a VM 560A and could not do it without this detailed precice documentation.
thank you very much.
Rich


Top
 Profile  
 
Post New Topic Post Reply  [ 37 posts ]  Moderator: Alan Voorhees Go to page Previous  1, 2

All times are UTC [ DST ]


Who is online

Users browsing this forum: No registered users and 6 guests



Search for:
Jump to:  


































Privacy Policy :: Powered by phpBB