• The move to the new server is done. There are some software and database maintenance updates in process. This has us passing the hat around to help out. We appreciate any donations. Seriously, even a dollar helps. The payment page may be found here - https://www.audiokarma.org/support.html

Pioneer CT-F900 repair help

D

Dangernoodle

New Member
I have a Pioneer CT-F900 I have recently acquired that upon inspection has some problems. when I press play with a tape withing the transport it plays however severely out of pitch to slow and even while looking at the tape collectors it looks to be traveling way to slow. Another problem i have found with this unit is that the reverse function does not operate. when i depress the reverse switch the solenoid on the top of the transport engages but after a second or less disengages and nothing happens. When i hold down the reverse switch after a few seconds belts within will spin and the cassette will move forward not reverse. I have already changed out the belts for new ones and changed out the idler wheel which i believe facilitates the reverse fast forward action. I believe my next course of action is to repair/ replace the take up motor but would like any help on how i should move forward with this project. I am new to posting to online threads and repairing a cassette deck but am looking for a project.

Thanks!
 
Register to hide this ad
No cassette installed, and faceplate removed, hold down the presence sensor (round button on the right side of the cassette well). Watch what is happening and give more information. The reel motor drives a pulley via belt. The pulley drives the idler, which swings to contact the right or left reel, depending on direction, due to slight resistance in a clutch beneath the idler. Now describe what is, or is not, actually happening.

The reverse mode will not continue without movement of the3 tape counter. It will stop after a couple seconds.

Enjoy,
Rich P
 
OK I included a photo of what I was depressing and believe to be the presence sensor. When depressed, the metal break plate ( above the two parts that spin the cassette) moves up, and over the course of a second or so returns back to its initial non activated state all while holding the senor down. The solonoid at the top left of the transport moves in an out again over the course of a second when the presence sensor is activated. The idler with the rubber tire on it between the two parts that spin the tape moves up with the break plate and makes contact with the left drive wheel but again returns to its original state between the two drive wheels. That appears to be all that is happening. Again it all happens over about a second.

I have included a video that shows what's happening
 

Attachments

  • 2016-09-17 21.03.40.jpg
    2016-09-17 21.03.40.jpg
    88.5 KB · Views: 30
I distinctly saw a bit of rotation on the left reel. Not much, but some. The belt to the pulley, from the motor might be a bit tight. But the initial activity is to rotate gently upon pressing the sensor, to take up tape slack.

Push in and hold the presence sensor, as before, and press rewind. See if there is any rotation on the left side. It will stop right away because there is no rotation of the right side reel (motion sensor). Keep holding the presence sensor and press fast forward. The right reel should start spinning, and keep doing so, unless the tape counter isn't counting. Press stop. Then press play. The heads should move up, and the right reel should start rotating. If working properly, you can let go of the presence sensor and the right reel will continue to rotate.

Show that stuff.

Enjoy,
Rich P
 
Ok, I am attaching a video link to show what exactly is happening. It would appear that when pressing reverse it does move the left drive wheel a little bit. When in play and I release the presence sensor the mechanism shuts off compleatly.
 
First, your presence sensor switch is bad and/or out of adjustment. In play, the presence sensor should be held in by the part of the transport plate that moves up to bring the pinch rollers up. Examine the area around the presence sensor button, and you will see what I mean. It is likely the switch is bad, as are the other two of them, at the top of the transport. The switch (far right on top) has a bit of rotational adjustment. You can move it until it still sees the cassette when inserted, but does not let go when you let go of the presence button during play.

Moving on...As before, hold the presence sensor in, and go into fast forward mode. manually stop the right reel rotation and see how long before the fast forward stops.

Enjoy,
Rich P
 
Last edited:
I was able to adjust the presence sensor at the top right to operate as you described. When I hold down the presence sensor and press play it will play even when I let off of the sensor. When running the fast forward and trying to stop the right reels rotation it requires a bit of strength but I can stop the rotation and the machine will still try to turn it but eventually it does shut it's self off. Again I have included a video because they seem to help haha. (The tape over the light is to reduce glare)

 
On the control panel, select "Memory-Play." The "Memory/Repeat" indicator should illuminate. Then, hold the presence sensor in, then press and release the rewind button. Let's see what happens. I know it will lift the brakes for a moment and re-drop them again right away. I think there might be something more this time.

Enjoy,
Rich P
 
Ok, I pressed the play button under the memory tab (light comes on) and held down the presence sensor. When pressing rewind it acts as you described with the breaks moving up and back down right away with the left wheel moving slightly. Nothing else seems to have changed but if you think there might be something I am missing I can include a video of it.
 
We are now to a place where casual knowledge, ability, and equipment is insufficient. What kind of electronics knowledge and equipment do you have?

Enjoy,
Rich P
 
Not much to be honest I took an electronics circuits class last semester but most of my knowledge to this point has been looking through your past posts on rebuilding the transport and motor of this same unit. I also have been doing research on other forms but this is the first time I have undertaken a project like this. As far as equipment goes I have access to basic tools and can get my hands on a dremel, multimeter, files, and my father who is helping me has acess to an aircraft machine shop and more tools than I can decribe.
 
Did you assess the unit before replacing belts and idler tire? If so, how did it act then?

Enjoy,
Rich P
 
I did I plugged it into a pair of powered speakers and loading in a cassette. The unit powers on fine and the play function plays the cassette (although out of tone by running slow). Fast foward with the cassette in also appears to work, pause works but I did not test record. When testing rewind the break plate moves up and back down as it did when you had me test the rewind function without a cassette. My pre belt replacement assessment had the machine play out of tone and the rewind function not working.
 
I did I plugged it into a pair of powered speakers and loading in a cassette. The unit powers on fine and the play function plays the cassette (although out of tone by running slow). Fast foward with the cassette in also appears to work, pause works but I did not test record. When testing rewind the break plate moves up and back down as it did when you had me test the rewind function without a cassette. My pre belt replacement assessment had the machine play out of tone and the rewind function not working.
 
OK I will get my hands on one hopefully within the day or so and get back to you thanks for helping me to this point it's much appreciated
 
You will need leads with clip ends and also very sharp and pointy ends.

You need to prepare yourself for the possible need for a part of two from a parts unit. Your reel motor works, so for now, rule that out. For rewind the polarity of voltage applied to it changes. It works forward, it will work backward.

The issue is that the deck immediately drops out of rewind mode. It lifts the reel brakes, and starts to rotate the reel, as indicated by the shift of the idler to the left side. It immediately drops out of rewind mode, as indicated by dropping the brakes. This is a control logic problem. transport control is handled by a dedicated logic chip. It responds to a variety of input signals, from buttons and special circuits. Some input line to the logic chip may be telling it to drop out of rewind, or the chip itself may be bad.

The circuit board with the control logic chip is the one immediately behind the transport. Check every wire that connects to it, and follow it back to where it comes from. Make sure that it is not pinched, or broken. Make sure that the connectors on the board are properly installed and oriented. Remove and reinstall the two connectors a few times, to make sure that they are making good contact. Check all of the components on the board, and make sure that they are not bent over to make short circuits, or have broken leads.

The affect upon rewind only indicates that the problem is in the memory stop/repeat logic functions, where the deck is supposed to exit rewind mode in response to reaching the end of the tape or 999 on the tape counter. So, there is a microprocessor chip on the indicator amp board (for the meters and counter). This processor chip, or the control logic chip on the transport control board could be bad. For replacements for either of these chips, you will need a parts unit. The chips are no longer manufactured. One or more transistors, or other components, may be bad. Those can be obtained, or modern replacements can be sourced.

Enjoy,
Rich P
 
Last edited:
Ok so I looked over the circuit board behind the transport to see if there was any unplugged or damaged connections or wires and I found nothing that jumped out at me and I also followed then to there source like you said and found nothing. Now I was not to sure about where the indicator amp board was but I checked the two up right boards at the back right of the unit by the left right inputs and again saw nothing that jumped out at me. If I where to purchase a donor parts unit what price should I be looking to spend, ie could I go too low?
 
You are not ready for a parts unit. CT-F900s are pretty rare, and un-restored units are commanding stiff prices lately. Maybe a fellow AK'r has a parts unit on hand.

You need the multi-meter with leads I previously mentioned. You might need access to an oscilloscope, but I'm not sure yet.

With your limited electronics knowledge and experience, you might be over your head on this one. But we have not hit a brick wall yet.

Where are you located? Maybe a fellow AK'r is in your neighborhood with some equipment and expertise. A little remote troubleshooting might prove fruitful.

Enjoy,
Rich P
 
Last edited:
You must log in or register to reply here.
Back
Top Bottom