Pioneer CT-F1250 - Rebuild the take-up motor (RMX-047 or 047A)

Hi, I have a beautiful Pioneer CT-F1250. The common problem with these 40-plus year old dinosaurs is that the take-up motors go bad with lack of use or get "dead" spot on the motor then lose torque. I know that there is limited success in rebuilding these but I thought I'd try asking here. Hit me up if you have had success or willing to give it a try. The motor is the RMX-047 or 047A. Models CT-F800/850/950/1250 all use this motor. The CT-F900 uses the RMX-038. Thanks!
 

pustelniakr

Silver Miner at Large
Staff member
The motor needs to be "run in" with the deck it will be used in. This is because the belts and other aspects of the transport affect the "taking" of the rebuild. As stated in the rebuild thread, the voltage across the motor needs to be monitored while running the rebuild in. That way you will know when the rebuild "takes." If it does not take, you may have to go back in. Because of this, repeated shipping back and forth could be a problem. Shipping high end gear these days is a risky endeavor. Best to find someone local to you. Refer them to the rebuild thread, here:


Enjoy,
Rich P
 
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I can ship the entire deck, has new belts. Just need an idea of who is willing to mess with these. I have a 1000 that is starting to do the same. 72113, AR
 
Hi guys, I recently bought a used CT-F 900, and, among other issues, it was affected by the usual reel motor problem (pulley locking always in the same position, voltage going down to 7,3 V, etc..). But I saw that the motor showed a very good torque when fed with the 13V for FF/REW.

So, instead of opening it risking damage, I decided to try to increase the voltage during PLAY. I then installed a 47 Ohms resistor in parallel with the existing 30 Ohms one on the motor supply circuit dedicated to PLAY function.

And guess what... problem solved!!! Before writing here, I tested the deck for some days. After approx 20hrs of play with various cassettes it is working flawlessly. I hope my experience may be useful for old deck lovers! Cheers from Italy.
 
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Hi, I have a beautiful Pioneer CT-F1250. The common problem with these 40-plus year old dinosaurs is that the take-up motors go bad with lack of use or get "dead" spot on the motor then lose torque. I know that there is limited success in rebuilding these but I thought I'd try asking here. Hit me up if you have had success or willing to give it a try. The motor is the RMX-047 or 047A. Models CT-F800/850/950/1250 all use this motor. The CT-F900 uses the RMX-038. Thanks!
That makes two us. I have a mint 1250 also. Perfect appearance, but seeing the comments about "due to non-use" or something like that made me decide I better try mine out again for the first time in a veeerrry long time. I also have the SA 8500 and the TX 9800. All from 1980-81. The amp has only had to have a couple servicings in the past 10 years. Cleaning the function switch a few years ago, and a rebuild of thePioneer Amp SA 9800.jpgSystem is Still Cookin.jpg function switch just last week along with 4 resistors replaced at the same time. The shop I go to in L.A. told me the function switches are super scarce to replace. They found only one and then rebuilt that for my replacement. I really like this equipment and so glad I didn't feel like I needed to keep upgrading.
 
Hi guys, I recently bought a used CT-F 900, and, among other issues, it was affected by the usual reel motor problem (pulley locking always in the same position, voltage going down to 7,3 V, etc..). But I saw that the motor showed a very good torque when fed with the 13V for FF/REW.

So, instead of opening it risking damage, I decided to try to increase the voltage during PLAY. I then installed a 47 Ohms resistor in parallel with the existing 30 Ohms one on the motor supply circuit dedicated to PLAY function.

And guess what... problem solved!!! Before writing here, I tested the deck for some days. After approx 20hrs of play with various cassettes it is working flawlessly. I hope my experience may be useful for old deck lovers! Cheers from Italy.

Can anyone confirm that this is safe? I recall doing something like this on a 900 I had several years ago (though I don’t recall if I replaced the 30 ohm resistor or bypassed it or what) and burned up my control board. After very carefully reading and using pustelniakr’s rebuild guides I am confused as to why he hasn’t very adamantly trashed this idea.

What voltage are you reading across the reel motor now with the extra resistor in place? Did you use a 2W 47 ohm resistor to match the existing 2W 30 ohm resistor? Are you noticing the two transistors involved in turning on the reel motor for play mode getting unusually hot? Has your deck suffered any damage since you posted this comment in April?

I have a 900 on the bench right now with new belts, a new tire, a rebuilt transport, and a newly rebuilt reel motor reading about 8.2V in play, which I understand is not enough, and I’m considering my next move. I’m wondering if the plastic idler wheel is shrinking as some plastics do as they age, and the center hole is gripping the idler spindle tighter than it’s supposed to. I would appreciate an update on your deck.
 
Can anyone confirm that this is safe? I recall doing something like this on a 900 I had several years ago (though I don’t recall if I replaced the 30 ohm resistor or bypassed it or what) and burned up my control board. After very carefully reading and using pustelniakr’s rebuild guides I am confused as to why he hasn’t very adamantly trashed this idea.

What voltage are you reading across the reel motor now with the extra resistor in place? Did you use a 2W 47 ohm resistor to match the existing 2W 30 ohm resistor? Are you noticing the two transistors involved in turning on the reel motor for play mode getting unusually hot? Has your deck suffered any damage since you posted this comment in April?

I have a 900 on the bench right now with new belts, a new tire, a rebuilt transport, and a newly rebuilt reel motor reading about 8.2V in play, which I understand is not enough, and I’m considering my next move. I’m wondering if the plastic idler wheel is shrinking as some plastics do as they age, and the center hole is gripping the idler spindle tighter than it’s supposed to. I would appreciate an update on your deck.
Hi, I am reading around 10V at the reel motor (it depends on motor temperature, amount of tape on the take up reel, etc..., also because most probably the internal resistance of the motor is varying during use). I used a 47 Ohm resistor in parallel with existing 30 Ohm resistor, soldering two wires directly on the 30 Ohm resistor pins on the top side of the board, without disassembly anything. I, too, was worried for the transistor dedicated to play (if I well remember the other one is also used during FF or RW, so it already supports the full amperage at the 13V for FF/REW, so no worries for this one). However, the temperature didn't rise to risky levels (I checked with the finger, I have to confess). However, if you are worried, you may easily install a small heat radiator on the transistor. The deck is still running perfectly fine. After a 3 weeks holyday, I turned it on and the reel motor started immediately without any hesitation.

Regarding the idler wheel, there is a felt shim that creates a certain amount of friction to allow the idler to move and position correctly on the take up / supply reels when tape drive direction changes, so it is normal to see some friction. My suspect is that, if you replaced the idler pulley hub drive belt, it may be a little too tight and cause excessive friction on the idler pulley drive axle. Try delicately to loose it by stretching it with your fingers. Or the friction on the take up reel brake may be too much. If everything is ok, the idler pulley must rotate with no slip with the driving hub nor the take up pulley. Instead, slipping must be present between the two parts of the take up reel (the two sections between which the felt brake is present).

Hope this helps... Warmest regards....
 
Hi, I am reading around 10V at the reel motor (it depends on motor temperature, amount of tape on the take up reel, etc..., also because most probably the internal resistance of the motor is varying during use). I used a 47 Ohm resistor in parallel with existing 30 Ohm resistor, soldering two wires directly on the 30 Ohm resistor pins on the top side of the board, without disassembly anything. I, too, was worried for the transistor dedicated to play (if I well remember the other one is also used during FF or RW, so it already supports the full amperage at the 13V for FF/REW, so no worries for this one). However, the temperature didn't rise to risky levels (I checked with the finger, I have to confess). However, if you are worried, you may easily install a small heat radiator on the transistor. The deck is still running perfectly fine. After a 3 weeks holyday, I turned it on and the reel motor started immediately without any hesitation.

Regarding the idler wheel, there is a felt shim that creates a certain amount of friction to allow the idler to move and position correctly on the take up / supply reels when tape drive direction changes, so it is normal to see some friction. My suspect is that, if you replaced the idler pulley hub drive belt, it may be a little too tight and cause excessive friction on the idler pulley drive axle. Try delicately to loose it by stretching it with your fingers. Or the friction on the take up reel brake may be too much. If everything is ok, the idler pulley must rotate with no slip with the driving hub nor the take up pulley. Instead, slipping must be present between the two parts of the take up reel (the two sections between which the felt brake is present).

Hope this helps... Warmest regards....
I appreciate your reply. 10V is probably more than you need at the reel motor. 30 and 47 ohms in parallel makes 18 ohms. I tried this for just a minute or two on my 900 with no ill effects, but the motor was drawing almost 180mA during playback and almost 300mA when waiting to auto-stop at the end of the tape. I found that adding a 100 ohm resistor in parallel with the existing 30 ohm R553 only drops it to 23 ohms, which in the case of my particular deck brings the voltage across the reel motor up to approximately 8.8V, which is right where it’s supposed to be according to pustelniakr’s motor rebuild guide (though I still imagine he would advise against this entirely). With a 23 ohm resistance in place, the motor was drawing approximately 160mA in play mode. But it was drawing 150-155mA without it, so I consider that a win.

While I did not notice Q517 heat up during my very short tests, I looked up the datasheet (it’s a 2SC2060) and unless I’m reading it wrong, the datasheet says it’s maximum power dissipation is 0.75W. 8.8V x 0.16A = 1.408W, almost double the power Q517 is designed to handle. I wonder if Q521, which is a 2SA934 but has the same power dissipation, being in series with it means that both are only dissipating half of the power. Still, I’m right up against the maximum of each transistor if that is true, and I’d suggest you see if your deck works okay with a 100 ohm resistor instead of the 47 ohm resistor, in parallel with R553, as it may delay the time it damages the deck or the motor.

I haven’t decided if I’m going to install this mod yet as my deck appears to be working properly with 8.2-8.5V across the reel motor, but I’m glad to understand why it works and appreciate the suggestion. I would still love to hear others’ opinions on this being an option after a motor and transport rebuild. I am also not a purist and I am not reselling my deck so I welcome any information that (safely) keeps it running even if it doesn’t fall under the heading of “this is the ONLY correct way to do it.” Remember, I had to remove a washer that the service manual clearly shows is supposed to be there to get a rebuilt motor to work in play mode with no cassette, so clearly there’s forces at work here that not even following the instructions keep at bay.

I have not yet stretched the belt as I am not keen on spending $24 for a new belt kit (and waiting another two weeks) every time I stretch (and break) one belt.
 
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