Good show. I have a set or two of weights in low orbit.
Enjoy,
Rich P
Enjoy,
Rich P
CT-F1250 Reel Motor Rebuild (CT-F800/900/950/1250)
- Thread starter pustelniakr
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ChopperChas
Super Member
Can you tell me the order of the poly washers? I took off the white ones and put them
Aside so id know how to reassemble, but now I see two small green ones on my desk, which I didn't remove and must have been hiding.
Charles
Aside so id know how to reassemble, but now I see two small green ones on my desk, which I didn't remove and must have been hiding.
Charles
I'm sorry. I do not remember, and do not have one handy that needs opening up.
Good luck,
Rich P
ChopperChas
Super Member
Well, I guessed on the two green ones, and the motor works perfect now. My guess was that they went on either side of the bearing on the case. There appeared to be a wear pattern on the pulley that matched diameter of the washers, and when assembled without them the shaft could be pulled out and pushed in more than when I took it apart. So I put the thicker washer on the inside, the thinner washer on the outside, and it all feels the same as when I disassembled it. It works too. I went from very little torque and frequent stopping in both play and FF modes to GOBS of torque. Cleaned the black spots off the armature and the centrifugal switches with 1000 grit sandpaper, just enough to remove the high spots on the armature, and two passes in the switches (one each direction).
One very interesting thing... when I pulled it all apart, and removed the tape off the motor, one of the wires came off. It broke off just after the solder point, and was likely making intermittent contact... which may explain why the problem came on suddenly and really prevalent, instead of mildly intermittent. I was tempted to just resolder the wire and reinstall the motor, but I figured I'd do a full cleaning on it and not have to open it up again in the near future. (hopefully ever).
As an added bonus, FF and rewind speeds are ridiculously fast now.
Charles.
One very interesting thing... when I pulled it all apart, and removed the tape off the motor, one of the wires came off. It broke off just after the solder point, and was likely making intermittent contact... which may explain why the problem came on suddenly and really prevalent, instead of mildly intermittent. I was tempted to just resolder the wire and reinstall the motor, but I figured I'd do a full cleaning on it and not have to open it up again in the near future. (hopefully ever).
As an added bonus, FF and rewind speeds are ridiculously fast now.
Charles.
I'm working a CTf 950 now. What about the capstan motor . I have extra one so I went to investigate. I took the outside case off. The armature etc.. is expose but it is held in at brushes end . It doesn't come out like on FF motor(and the brushes are not holding it in ). I see that the commutator is black (dirty or burnt? don't know). I was thinking about cleaning it very carefully with a small Q tip and deoxit . This would avoid trying to remove the other end ,which has a small circuit board and other unknown parts. What do you think ?
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The old adage, "If it ain't broke, don't fix it," was created to indicate that there is significant risk to the operation. I fix things that are not broke all the time. Some things I don't mess with unless I have to. The capstan motor is one of them.
As you noted, this is a much more complicated motor (DC servo). There is a lot more going on. My recommendation is not to mess with it, if it is working correctly.
The issue with the reel motor is associated with low voltage and current being provided during tape play. This makes it intolerant of schmutz in the motor current path (switches, brush interface, etc.). I have never seen one do the intermittent stop problem during FF or REW (full voltage and current).
The capstan motor never sees a low voltage current condition during operation. It always gets nice voltage and current. I would put a drop or two of tri-flow on each end of the motor shaft and close it back up, unless it is acting badly. Do so being careful to align everything up to ensure that the motor spins freely, without any indication of binding.
Good luck,
Rich P
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ChopperChas
Super Member
Take it back apart and look for a broken wire or a busted brush.
Charles.
Charles.
Cassette decks are very sensitive to changes. If you know how to modify the drive circuitry to produce the correct take-up torque, and the motor can produce smooth, consistent torque under low voltage/current conditions, you "might" be able to get something out of the deck. The reel motor and drive circuitry is designed to produce take-up torque that is within a very specific range during play, and significantly more torque during fast-forward. If it does not do so, you will have excessive wow & flutter, as well as become hyper-sensitive to pinch roller and capstan imperfections during play. Excessive torque during fast mode and you could exceed what the brakes were designed to deal with and you could wind up with slack loops in the cassette body and tape path, resulting in the deck eating tapes, and tape snapping at the ends.
Cassettes were not originally designed for high-fi. They were designed for dictation machines. Engineers have squeezed amazing performance out of the format. However, that requires most operating characteristics to be taken near to the boundaries of their envelopes, and then for each of those characteristics to be carefully balanced against all the rest. As a result, "high end" decks are sensitive to any deviation from design function, take-up torque being one of those characteristics. Wow, flutter, frequency response, tape handling, etc. are all affected when parts are not operating up to spec, or are not original parts.
If your reel motor has been damaged, what you really need is a motor from a parts unit. It is your machine. Obviously, you may do as you wish. However, unless you can do the work of a design engineer, you will not likely be able to get the deck to perform anywhere near the specs it was designed to produce, if you begin to use differing transport components. Each component has specific operating characteristics contributing to its selection, and specific circuit designs to accommodate those characteristics. Design verification, after modifications, requires very specific tools and equipment, special torque meters being needed in your case.
I have said this frequently. It is relatively easy to get a cassette deck to more or less work, but getting it to perform up to original specifications is not so easy, even with original parts. Your deck, you decide.
Rich P
Cassettes were not originally designed for high-fi. They were designed for dictation machines. Engineers have squeezed amazing performance out of the format. However, that requires most operating characteristics to be taken near to the boundaries of their envelopes, and then for each of those characteristics to be carefully balanced against all the rest. As a result, "high end" decks are sensitive to any deviation from design function, take-up torque being one of those characteristics. Wow, flutter, frequency response, tape handling, etc. are all affected when parts are not operating up to spec, or are not original parts.
If your reel motor has been damaged, what you really need is a motor from a parts unit. It is your machine. Obviously, you may do as you wish. However, unless you can do the work of a design engineer, you will not likely be able to get the deck to perform anywhere near the specs it was designed to produce, if you begin to use differing transport components. Each component has specific operating characteristics contributing to its selection, and specific circuit designs to accommodate those characteristics. Design verification, after modifications, requires very specific tools and equipment, special torque meters being needed in your case.
I have said this frequently. It is relatively easy to get a cassette deck to more or less work, but getting it to perform up to original specifications is not so easy, even with original parts. Your deck, you decide.
Rich P
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First, the motors are "not" unreliable and failure prone. Period. These decks are 40+ years old and still working. The motor is one of the weaker links, and is generally a problem due to having been left sitting for very long periods.
Second, the clutch is designed to balance out the characteristics of a specific motor, not just any motor you can get to fit. It also does not address fast mode speeds, fast mode back torque and cassette tape packing, adequacy of brakes relating to fast mode speeds and torques, or how hard the deck hits the end of the tape in fast modes. Also, if you miss the motor speed torque specs, the clutch cannot compensate in play mode (playback and record performance suffers). If motor torque is excessive, the special slack removal operation, done when a cassette is first inserted, becomes a slack insertion operation. Slack loops in a dual capstan deck is very bad news, as previously stated.
As for the motor restoration (when done carefully and correctly, and properly run in) does, in fact take. If you use a reel motor belt that is too tight, it will cause a repeat fail before the brushes get run back in. You may ask any of my countless customers that have received one of my restored decks and rebuilt motors if they have ever had a failure of the reel motor. Do you have to go back in now and then to repeat the process? Yes. Always? No. Once the rebuild takes, does it hold? Yes, generally.
Rich P
Second, the clutch is designed to balance out the characteristics of a specific motor, not just any motor you can get to fit. It also does not address fast mode speeds, fast mode back torque and cassette tape packing, adequacy of brakes relating to fast mode speeds and torques, or how hard the deck hits the end of the tape in fast modes. Also, if you miss the motor speed torque specs, the clutch cannot compensate in play mode (playback and record performance suffers). If motor torque is excessive, the special slack removal operation, done when a cassette is first inserted, becomes a slack insertion operation. Slack loops in a dual capstan deck is very bad news, as previously stated.
As for the motor restoration (when done carefully and correctly, and properly run in) does, in fact take. If you use a reel motor belt that is too tight, it will cause a repeat fail before the brushes get run back in. You may ask any of my countless customers that have received one of my restored decks and rebuilt motors if they have ever had a failure of the reel motor. Do you have to go back in now and then to repeat the process? Yes. Always? No. Once the rebuild takes, does it hold? Yes, generally.
Rich P
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I have had to go in a couple of times on individual motors (a couple of times, even more), when I first started doing them. They take a bit of finesse, but they are do-able. You want to modify the brush to commutator contact points as little as possible, so you have more than tiny contact patches to deal with. Also, you do not want the little belt that connects right to the motor pulley to be too tight. Those from one of my sources tend to run a bit tight (I carefully stretch them, before use and there is a risk of breaking, so be careful). You also do not want to put the motor into regular service right away. A loaded motor will conduct too much current for tiny contact points to handle. You want the brushes to fit nicely to the contacts on the armature. Also, you want to have all the little spacers and washers to go back where they belong, so the motor slop is not excessive, and so the brushes ride in the right path.
If you have only contact "points" (misfit between brushes and contacts), you will arc and mess up contact conductivity near the gaps. Also, the motor spins pretty slowly during play (lower voltage, current and torque), rotational momentum is lower, so if the brushes don't bridge the slots (w/associated low spots), the motor will stop. That is the original problem. Hence, you want to modify the contact patches as little as possible, and you want to run the motor in real good before putting it under significant load (regular service). Brush to contact interface should be across the entire contact faces of the brushes.
Once the motor is done and reinstalled, you depress the tape presence detector button (the associated micro-switch must have less than 1 ohm of on state resistance when actuated), and put the unit into play without a tape in it and let it run for a day or two. The only load will be the belts, pulleys, clutch & reel. In play, motor voltage and current is lower, so you won't arc so badly while running in. If you did well in the rebuild, the rebuild should take and hold. Once you have restored good contact patches, the brush wear will drop to nil, and the brushes should keep their contact paths clean and un-corroded.
Rich P
If you have only contact "points" (misfit between brushes and contacts), you will arc and mess up contact conductivity near the gaps. Also, the motor spins pretty slowly during play (lower voltage, current and torque), rotational momentum is lower, so if the brushes don't bridge the slots (w/associated low spots), the motor will stop. That is the original problem. Hence, you want to modify the contact patches as little as possible, and you want to run the motor in real good before putting it under significant load (regular service). Brush to contact interface should be across the entire contact faces of the brushes.
Once the motor is done and reinstalled, you depress the tape presence detector button (the associated micro-switch must have less than 1 ohm of on state resistance when actuated), and put the unit into play without a tape in it and let it run for a day or two. The only load will be the belts, pulleys, clutch & reel. In play, motor voltage and current is lower, so you won't arc so badly while running in. If you did well in the rebuild, the rebuild should take and hold. Once you have restored good contact patches, the brush wear will drop to nil, and the brushes should keep their contact paths clean and un-corroded.
Rich P
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PioneerShawn
Active Member
Would not a dremel with a cutting wheel if carefully used, be a good way of getting out the divets in the outer case clamped onto the inside motor or does one need to reclap the same area when putting it back together. And why not just use some epoxy dabbed on the ends to hold it back together? Just bought a CT-F1250 off Ebay three weeks ago. Seems to be fine.
You could cut away the swaging divets. Epoxy "might" do the job. However, I am the type that likes to leave as little indication of my presence as possible, and stay as close to original as possible. I also do not recommend such operations. Anything that might be construed as a kludge by a subsequent tech will not generally be an option for me. I don't like coming along behind folks that do kludges. You may, of course do as you wish with your own gear.
This post is not intended to be snarky. It is just a statement of policy and personal recommendation.
Enjoy,
Rich P
It sounds like you have an intermittent connection in there. When it opens, the voltage goes up. Running at 9v shows that the motor rebuild wants to take. If you can clear up the intermittent connection (broken wire at a solder joint or some such), definitely run it for a nice while, without a tape. Running in the rebuild is a good idea. Also, make sure that the little belt that is directly on the motor pulley is not overly tight. That gives a better shot at the rebuild taking.
Enjoy,
Rich P
Enjoy,
Rich P
Chris Lloyd
New Member
Thank you for the step by step guide to rebuilding the RXM 047 in my CTF950. Followed the steps, was easier than I had imagined, and it worked like a charm. I am listening to Neil Diamond on BASF Chrome II tape on the now functioning deck that I got as a gift 37 years ago. Brilliant outcome.
Thanks for the reply Rich. Took the motor apart one more time. Re polished the armature with 1200 grit since it showed evidence of a low spot. Burnished the speed control contacts and cleaned the brushes again with a round wooden toothpick and alcohol. Didn't find any broken wires. Ran it in FF with no tape for 15 mins at 13V. Ran it in play mode with no tape, 10V. Put a tape in and 9V constant. Amazing, seems to be working. Played a whole 60 minute tape without stopping. Thank you so much for all the great information and Happy New Year.
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