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CT-F950 intermittent problem

Tripqzon

Tripqzon

AK Subscriber
Subscriber
Are there any cassette deck techs on AK?

My cassette deck stops intermittently when in Play mode.

I've replaced all belts, idler assembly, and have had the pinch rollers resurfaced with rubber rejuvinator. Also the deck has been cleaned and lubed as required.

You may ask why I have not replaced the pinch rollers? well, let me tell you. I ordered a set of pinch roller assemblies about a year ago and they were not quite right for my deck so I got rid of them. I do have a set on order now from a different retailer.

Anyway, after having the rollers "rejuvinated" the deck worked fine up until last night. It stopped playing on me twice within a 15 minute period. Could there be something wrong other than the rollers? I noticed last night that after the unit stopped, there was a small amount of loose tape (maybe an inch) between the heads and the take-up roller assembly. The rollers are pretty shiny and hard.

Also, what about the spring tension on the roller assemblies? I have no way to measure it as I do not have a spring tension gauge. Is this really an issue? Should I just put the new roller assemblies in when they arrive and put the springs in the same adjustment position as they were originally? Does anyone know where I can get such a gauge?

FYI, I've tried different cassettes and the problem still exists.

I've attached an image from the service manual.

Any help would be great.

 
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It looks like a critical adjustment. I just got the manual and belts for my 900/950's, I think I have a spring gauge around and planned on checking that when I go in. I don't remember where I got it, used to use it to adjust belt tension on daisy wheel printers. How bad was it replacing the belts?
 
you guys find out anything useful about this, i wanna know, because my recently 'overhauled' ct-f950 is doing EXACTLY THE SAME THING!! i've already got too much $$ in this otherwise gorgeous machine....

shrinkboy
 
Did you replace the intermediate idler behind the back plate between the take up reels?
 
Wardsweb said:
Did you replace the intermediate idler behind the back plate between the take up reels?
Click to expand...

Is this what you mean. If so, Yes. This pic is of the original.
Part # RNK-561
 
Strawman said:
It looks like a critical adjustment. I just got the manual and belts for my 900/950's, I think I have a spring gauge around and planned on checking that when I go in. I don't remember where I got it, used to use it to adjust belt tension on daisy wheel printers. How bad was it replacing the belts?
Click to expand...

It takes some patience and little disassembly. I remember having to remove the Plunger Chassis Assembly screws and gently pulling back on the assembly plate just enough to get in to replace the flywheel/capstan belt. If you run short on patience, I would recommend letting someone who's done it before replace that belt. The other three belts I was able to replace without much difficulty. Although I did need a belt removal/insertion tool (looks sorta like a dental pick. One end has a hook, the other end has an "S" shaped hook). How I like a challenge!!

Would you consider loaning me your spring gauge if I can't find one? I would pay for shipping to me and back to you and a reasonable deposit also. Just something to think about. In the mean time I will continue looking.
 
Tripqzon said:
It takes some patience and little disassembly. I remember having to remove the Plunger Chassis Assembly screws and gently pulling back on the assembly plate just enough to get in to replace the flywheel/capstan belt. If you run short on patience, I would recommend letting someone who's done it before replace that belt. The other three belts I was able to replace without much difficulty. Although I did need a belt removal/insertion tool (looks sorta like a dental pick. One end has a hook, the other end has an "S" shaped hook). How I like a challenge!!

Would you consider loaning me your spring gauge if I can't find one? I would pay for shipping to me and back to you and a reasonable deposit also. Just something to think about. In the mean time I will continue looking.
Click to expand...
I have a lot more patience than money for the hobby. I repair computers and printers and stuff, so taking things apart is no problem. I also have picks, spring hooks, etc. Just got the service manual for the 900, but the exploded views are like ass. Let me see if I can find the gauge and you are welcome to borrow it.
 
Thanks Strawman. Hopefully you'll find it. I had no luck finding one last night either. I'm sure if I do, it will probably cost an arm and a leg.

By the way, I am in the same boat as you. I also have more patience than money for this hobby. It's definitely a "love" thing.
 
Tripqzon said:
Are there any cassette deck techs on AK?

My cassette deck stops intermittently when in Play mode.

I've replaced all belts, idler assembly, and have had the pinch rollers resurfaced with rubber rejuvinator. Also the deck has been cleaned and lubed as required.
Click to expand...

It's been about 30 years since I've worked on this stuff, and I have not worked on your particular model, but I would find out how the deck detects tape motion and start there. Frequently, in the old days, tape motion was sensed by watching the tape counter. The tape counter belt also spun a multipole magnet which, in turn, continuously actuated a reed switch. If the reed switch stopped switching, the decks would stop. Reed switches were notorious, as well as the counter belts. The tape motion chain probably begins with the take-up spool, so I guess, the take-up idler (if any) could be suspect.

For what y $.02 is worth...

Rich P
 
pustelniakr said:
The tape counter belt also spun a multipole magnet which, in turn, continuously actuated a reed switch.
Click to expand...

I've also come across magnets that loose their magnetic properties enough not to trigger the reed switch. I've seen this happen in tape decks before. I've come across it most often in Motorola cell phones like the V60 and StarTAC series..
 
Well, I took the cover off last night to check the tape motion sensor. Discovered that is is a "photointerruptor" type switch. Anyway, it appears to be working fine. But , I also discovered that the two belts on the flywheel have basically no tension. I can slide them side to side on the flywheel without any effort at all. Not Good. I ordered a new set from Vintage Audio instead of ebay this time.

Has anyone else purchased belts from ebay? If so, what was your experience?

Paul
 
I've dealt with the seller minnie_maxie a few times, pretty helpful. btw, still looking for the spring gauge, I know I saw it, still have a few boxes to check.
 
Tripqzon said:
Well, I took the cover off last night to check the tape motion sensor. Discovered that is is a "photointerruptor" type switch. Anyway, it appears to be working fine. But , I also discovered that the two belts on the flywheel have basically no tension. I can slide them side to side on the flywheel without any effort at all. Not Good. I ordered a new set from Vintage Audio instead of ebay this time.

Has anyone else purchased belts from ebay? If so, what was your experience?

Paul
Click to expand...
Does the motion sensor get its drive from the flywheel? If so, you've most likely found your problem. Good show! :thmbsp:
 
Strawman said:
I've dealt with the seller minnie_maxie a few times, pretty helpful. btw, still looking for the spring gauge, I know I saw it, still have a few boxes to check.
Click to expand...

I'm not too sure about minnie_maxie. They sold me a idler tire that was way too small for my unit. Wasn't worth the hassle of returning it, so I think I threw it out. I ended up buying an idler wheel from Pioneer.

Definitely still interested in the spring gauge. You can PM me when you find it and I will give you my address.

Thanks,
Paul
 
pustelniakr said:
Does the motion sensor get its drive from the flywheel? If so, you've most likely found your problem. Good show! :thmbsp:
Click to expand...

Actually the motion sensor belt connects to the take-up reel.
The take-up reel is controlled by the idler wheel. It takes imo a lot of pressure for me to stop the take hub from spinning by grabbing it with two fingers when in Play mode. I have no way to measure exactly how much pressure though.

The flywheel turns the take-up and supply capstans via 2 belts. These 2 belts just seem to rest on the flywheel. No tension at all on them as stated in my previous post.
 
Update

Deck is stopping frequently now. Enough so that I can sit and watch what is going on just before it stops playing. It appears that the capstans are not stopping and no belt slippage. The problem seems to be in the idler region.

I took the faceplate and brake assembly off so I could get at the surfaces that come into contact with the idler tire. Cleaned all surfaces. I've played a tape more than six times now and it's running flawlessly. :banana: :banana: YEAH!! YEAH!! :banana: :banana:

If anything changes I will let you know.

Please continue to send me ideas or comments/suggestions in case this does not work.

By the way, Pinch rollers are on back order. I figured that would happen. They say demand for them is extremely high. :dammit:

Paul
 
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Tripqzon said:
Update

Deck is stopping frequently now. Enough so that I can sit and watch what is going on just before it stops playing. It appears that the capstans are not stopping and no belt slippage. The problem seems to be in the idler region.

I took the faceplate and brake assembly off so I could get at the surfaces that come into contact with the idler tire. Cleaned all surfaces. I've played a tape more than six times now and it's running flawlessly. :banana: :banana: YEAH!! YEAH!! :banana: :banana:

If anything changes I will let you know.

Please continue to send me ideas or comments/suggestions in case this does not work.

By the way, Pinch rollers are on back order. I figured that would happen. They say demand for them is extremely high. :dammit:

Paul
Click to expand...


I have a CT-F900 that I am working on right now with the same problem.

The best I can tell, the tape motion sensor is in fact driven by the takeup spool (very common). Don't worry about capstan drive for your stopping problem. Concentrate on the takeup spool or drive table. It has 2 clutches (a tight one associated with the front drive surface for fast modes and a looser one associated with the rear drive surface for play mode, allowing more slip). Sometimes the clutch wears out (you'll know what I mean when you disassemble to deal with the idler. In fast mode, the idler is supposed to hit the front drive surface. In play mode, the idler moves to drive the takeup spool by its rear drive surface.

A clutch is generally a cloth disk inside the takeup spool assembly with an internal spring to keep the clutch engaged while allowing it to slip as needed.

On the front of the mechanism that the idler is mounted on, there is a spring wire that is to contact the idler shaft from underneath. In play mode, with the faceplate off, the idler moves into the machine far enough to allow the spring wire to slip out from under the idler shaft, lessening the pressure of the idler to its drive. Check the spring wire position (it puts its tension in the up direction), the takeup clutch (it should be able to slip, relative to the takeup drive table, but not to loosely), and the idler drive surface it (should not be hard or glazed). Especially make sure the spring wire is under the idler shaft and not just hanging in front of it. If not positioned properly you will have very little takeup torque in either mode (fast or play), or either direction.
 
Hello pustelniakr,

Thanks for the wonderful tutorial.

I did notice that the idler does move from the front to the rear drive surface in play mode.

Anyway, the idler only seems to contact about half of the rear drive surface. Should the idler move back further so that the entire idler wheel comes in contact with the rear drive surface? Seems to me it should.

In fast mode, the idler does come in complete contact with the front drive.

Also, what do you recommend for cleaning the drive surfaces?

Paul
 
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