Seeking assistance with an unusual Pioneer CT-F1000 rewind issue.

[Ricktptman]

I just went through one of my Pioneer CT-F1000s and I'm having a rewind issue that was very much unexpected.

It has all-new rubber and a new (donated from an FG-driven motor Technics) low-hours motor. It has GREAT torque in both directions and will rewind a tape to about 80% and the rewind TIME will be ahead of spec by a comfortable margin. And then...it slows down (instead of speeding up like one usually sees) and slowly comes to a stop. I suspect it's mechanical and NOT electronic as I can take the tape out and the rewind hub still has a LOT of torque. It does it on multiple tapes. I checked it when I first changed all the belts and WJOE-manufactured rubber replacement pieces and it worked (I thought it did anyway) perfectly. I had to travel for a couple of weeks and when I returned it started to exhibit this weird behavior with an approximately 90-minute tape (The Elton John Australia tape) and now does it with a number of tapes. Any helpful insights are appreciated. I've worked on a bunch of these CT-F's and I've never encountered this problem before including on other CT-F1000's. It's a low-hours sample (I've had it for about twelve years and it worked fine until the playback function stopped working owing to idler/motor pulley interactions, as described before now fixed) and I did NOT note any cracks in anything ANYWHERE. It's a pickle. TIA...

 

[nakmandan]

Having worked on numerous CT-F1000's and several other vintage Pioneer's that share a similar transport, there are a few areas I can suggest as to the culprit here.

The first is a cracked fast wind clutch that unloads the heavy spring inside it and causes a lot of drag in the clutch itself. It isn't readily apparent until you look closely at it. The symptom of this fault is perfect playback but fast wind struggles, as the clutch only comes into play during fast wind. Markthefixer does the clutch rebuilds that work great in the clutches that have this specific crack.

Second is cracked reel pieces. This generation of Pioneer machines plastic components have aged very badly and almost everywhere you have a metal shaft encased or enclosed by plastic, the plastic will lose the material shrinking battle every time and cracks. When these pieces crack, they lose their grip on the metal shafts and torque is not transmitted properly. I see this most often in the drive pulleys and especially the cassette drive hubs. The hubs are particularly troublesome as there is not much you can do about this since there is no glue that I am aware of that works very well with this type of plastic.

Third is a worn fast wind motor pinion. This is the rubber tipped pinion that drives the previously mentioned fast wind clutch. What happens is when the clutch lets go and starts dragging, the fast wind pinion keeps trying to drive it and grinds itself into oblivion from the fairly significant splines on the clutch which aid traction. The solution is to first fix the clutch, second, replace the pinion. WJOE makes a fantastic replacement that works very well and is a solid investment in reliability.

Those would be my guesses. As you can see, all of them are related to cracked plastic pieces that either lose their grip on the metal drive shafts or unload a heavy spring that binds the clutch. Pioneer is certainly not the only manufacturer suffering from age shrinking cracked plastic, but unfortunately they seem to be more affected by the problem due to the way they implemented those plastic pieces in the transport design.

 

[Ricktptman]

Thanks, Nakmandan. I know you have a lot of experience and I appreciate your suggestions.

As previously noted the pinion (and everything else with a rubber component) has been replaced.

I looked very closely and I don't see any cracks in anything anywhere. It might be hidden from view, though, so I can't discount it outright.

The part that gives me the biggest disconnect from the plastic pieces being the issue is how much AGGRESSIVE torque there is on the rewind hub. It matches the torque on the FF hub and it winds the tape all the way to the end every time, with that satisfying "thwack" audible cue that signals it's time to flip the tape. : - )

I know I'm going to have to go back into it again, so I'll get to undo a lot of what I've already done. Having read the threads about the cracked plastic I did pay close attention to all the plastic parts. Again, if I take the tape out of the hub it's difficult to stop and this is just a second or two after the tape comes to a stop. That's the head-scratcher for me. I suspect (?) I can put more drag on the hub than a tape can and I can't easily get it to stop. But the tape just seems to gradually drag it down just after it reaches the halfway point through rewinding. I've worked on CT-F1000s for friends, but I've never seen this particular issue before. I only own two myself and the other one is fine after I changed out all the hardened rubber parts (and belts) in it a couple of years ago. I'm studying for a Ham Radio exam for the rest of this week, but I'll post back next Monday or Tuesday after I've had a chance to look around inside it again. Could it be thermally influenced? The plastic heats up and expands? (Just spitballing...) Thanks, again!

 

[nakmandan]

One other item I forgot that could be throwing a wrench in the works is the counter and/or tape sensor box. Either one of these can throw quite a bit of drag on the take up reel if they are not behaving. If you disconnect the small belt between the tape sensor box and counter and all starts to work well than you know the counter is gummed up and needs to be cleaned. The tape sensor is another matter. Those boxes are sealed and I usually find the shaft going through the box is seriously dirty. It could easily be dragging on the take up reel. Unlike the counter, the tape sensor is required to operate the transport, otherwise it will stop within a second in any mode.