Pioneer RT-909 tape slack after serviceing

[raffie]

Hi all, I've had this Pioneer RT 909 for a couple of years now, and the main drive belt finally needed replacement, so I ordered one together with 2 new pinch rollers. Now, I have installed everything and theres a problem. Tape slack appears in between the 2 pinch rollers. In other words, the tape comes off of the heads and so no sound after just about a second. That is, at 19cm/s. At 9.5cm/s only the left channel gets muffled, untill I increase tension by holding my hand on the left reel. The tape slack appears in both playback directions.

So, could this problem be the belt setting, dissappearing after a couple of hours of play? I'm goint to try this anyway, but does anyone here have any experience with this? I hope it's not going to be a bad belt or anything like that... As I had planned to order a 2nd one for my 2nd 909. I trust the seller, bought many other belts/pinch rollers from him, all without a problem.

thanks for your comments

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Allright, after keeping busy on trying to solve this problem, I have a theory as to what is the cause of the tape slack between the 2 pinch rollers. I'll start of with this: the used pinch rollers' surface have an inward curve, like so: http://users.telenet.be/warpmedia/diagram_01.jpg whereas the brand new pinch rollers have a slightly outward curve, looking like so: http://users.telenet.be/warpmedia/diagram_02.jpg .
Now, with the used pinch rollers, there is 100% surface contact between the capstan and the pinch roller provided there a tape is inbetween them. With the new ones there is only little contact in the middle of the tape. Now provided there is tension between the feeding reel and the 1st pinch roller, the tape "zig-zags" over the small contact point between pinch roller and capstan, making the tape "slack" just after the 1st pinch roller.
http://users.telenet.be/warpmedia/diagram_03.jpg

Now if my theory is correct, hours of play should flatten the pinch rollers out... Or so I hope :scratch2:
Well, it must be eather this or its just bad rubber that makes the tape skid off its course.
I'd still be curious to hear other ppl's experiences with new pinch rollers on 909's

[Sansui Louie]

I don't know if this will help, but I know that I'm always a little slack after a good servicing...

[Stanga]

I can't remember this deck personally, but I need some bits of information from you in order to find out which of the mechanisms is fitted in it.
1. Is this a multiple motor machine? i.e. except for the main motor that also turns the flywheel, are there other motors controlling the FF and REF spindles?
2. Have you got a C30 or shorter that you can play to see if the problem is just as bad as say with a C90?
3. When you switch the machine off and use your thumb and pointing finger to turn the left and right spindles, is there any movement on them? If there is, is it a lot?

[jblmar]

It's possible that you put the left pinch roller on the right side and the right on the left side. Common problem with Dual Capstan/Pinch roller decks.
Another possibility is, similar issue as PR/Capstan is that the belts are reversed. I would double check these two areas.

Ron

[raffie]

Left and right pinch rollers are identical, I've switched them around anyway, but no change. And there is only one belt driving both capstans.

Stanga, I believe you are talking about a cassette deck? The RT-909 is a reel to reel.

[Ozric]

The reel back tension may be out of adjustment if it's not the belts or pinch roller. Unfortunatly I have no idea how this is done on a Pioneer. I have done it on various Teac machines which use a variable resistor to adjust tension.

[raffie]

It seems the problem would be with the pinch rollers, I've tried the old ones again and it doenst happen anymore.

[Tinman]

Did you re-install the capstan motor from the top down on the belt or from the bottom up? It must be installed from the top down so the belt runs under it.

The tape tension usually drifts on these decks as well. Putting your old pinch rollers back in may only mask the fact that the deck needs aligning.

Your "new" pinch rollers don't make sense... they should be flat. Are you SURE they are for the RT-909???