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slightly slow Sharp GF 9494

sharp gf 9494

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#1 KeyserSoze

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Posted 07 September 2018 - 04:02 AM

Hi Guys,

I just thought I would see if anyone can help with a particular quandary that I have with a Sharp GF 9494 that I recently acquired.
I have been looking for one for a while as I love the styling of the 9494/9696.

The one I bought had a (surprise surprise) non-functioning tape deck, it had the usual problem with the molten capstan tyre, and also a dried up pinch roller, I replaced them both as well as the belts, re-lubricated some of the moving parts and used electrical cleaner on the various sliders and pots.

Now I have it working but it runs very slightly slow, now as some of you will know, these Sharp decks with the rubber capstan tyre usually come with motors without a screw hole in the back to make slight speed adjustments, so something that could have easily been tweaked is now driving me mad, I've disassembled and reassembled the cassette deck so many times looking for possible points of friction that I can now do it in my sleep, the only thing I can think of now is to simply replace the motor with one that can be adjusted.

Does anyone here have any experience with this?  Is getting a new motor the best option? If so has anyone got a recommendation for a motor that would be good to use?

 



#2 Ceestarrs

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Posted 07 September 2018 - 04:42 AM

That's funny- just got my 9494 tape deck serviced and working a week or so ago and it too is playing slightly slow. I've had a quick look around and not found any mention of a way to adjust am following this thread in hope of a solution.



#3 KeyserSoze

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Posted 07 September 2018 - 04:51 AM

Yeah, I was really happy to find my 9494 in great condition with everything else working but the tape deck, I have worked on a 9090 before which has almost exactly the same deck (and same problems), these decks without the speed adjust on the motor need to be set up with a high level of precision or they won't play at the correct speed, and the service manual is no use as it just tells you to put a screwdriver in the back of the motor, which of course you cant do.



#4 Hisrudeness

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Posted 07 September 2018 - 10:39 AM

Have you tried a slightly tauter belt?

#5 Fatdog

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Posted 07 September 2018 - 11:01 AM

Have you tried a slightly tauter belt?

In my experience, tighter belts are the cause of slower speed.

 

Keyser, are you sure you got the right belt sizes on there?



#6 KeyserSoze

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Posted 07 September 2018 - 11:06 AM

I have several lengths of flat belts and have been experimenting, the one I have on now is the loosest of the bunch, it is the closest to creating the correct speed, I could spring for a larger belt before I commit to changing the motor.



#7 Fatdog

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Posted 07 September 2018 - 01:21 PM

The exact belts needed for the GF-9494 are:

 

FBS10.2

SBS7.0

SBS7.4

 

Click here if you need help deciphering the codes.



#8 KeyserSoze

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Posted 09 September 2018 - 10:13 AM

Well after tweaking the belts some more, re-measuring and making sure they were the correct length I've improved it but it is still out by a fraction of a second, it's almost imperceptible... almost.



#9 jimmyjimmy19702010

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Posted 09 September 2018 - 11:38 PM

So no adjustment hole on the motor?

#10 KeyserSoze

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Posted 10 September 2018 - 02:22 AM

Alas no, oh how easy it would have been to have an adjustment hole in the motor, as far as I know, many Sharps with this kind of tape deck were fitted with motors without an adjustment hole.



#11 KeyserSoze

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Posted 10 September 2018 - 04:36 AM

Another strange problem has surfaced, when I first got the deck it was pulling tape off the spindle inside the cassette, usually a sign that the pinch roller needs replacing, I did so but now it is just pulling the tape off my Maxell tapes, but not my TDK's

Has anyone else experienced this? I'm guessing its the cheaper Maxell tapes that are more sensitive to underlying problems with the deck, But I've changed the pinch roller and the capstan tyre, and have made sure that the capstan tyre is not catching against the housing.  



#12 Fatdog

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Posted 10 September 2018 - 11:07 AM

What lengths are the TDK and Maxell tapes?  Tapes longer than 90 minutes (total length) become much thinner to accommodate the extra length.



#13 KeyserSoze

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Posted 10 September 2018 - 01:27 PM

All the tapes I use are 90 minutes, the Maxell's are all ferric while the TDK's I have are a mix of ferric and chrome, I did notice that the spindles inside the cassette that feed the tape back in are smaller on the Maxell's and have a smaller lip, so would be more sensitive to the tape travelling on the capstan, could this travelling be caused by a lack of tension in the pinch roller spring?



#14 KeyserSoze

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Posted 11 September 2018 - 01:53 PM

Ok, so it seems like I've solved the problems, I noticed that the cassette door was protruding more than it should when shut, so I looked at the latch mechanism and found that it was broken, should have noticed earlier but ah well. :-/ 

The post that holds the latch in place and allows it to pivot was completely gone, so when the cassette door was closed the opening spring was pushing the door out slightly, and so the tape wasn't aligned correctly with the deck, causing it to pull the tape off the capstan and run slightly slower than normal.

I glued a small peace of plastic over the pivot arm of the catch, and replaced the post on the other side by drilling out the plastic and putting a spare pinch roller pin in to it.

41736286_10155577870206646_8974006446102


Anyway, it now works perfectly! I knew once the door was realigned that it would make a difference, I have to give a shout out to my poor Judas Priest album for taking the brunt of the mangling  :rock: 

Here it is in its now functioning glory!

41520595_10155577870331646_1983533364648

Thanks for all the help guys, Ceestarrs, I hope some of this might have helped you too.

 



#15 Fatdog

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Posted 11 September 2018 - 02:13 PM

Most excellent!  Great job in determining the cause of the problem - and then being able to fix it.  :rock:



#16 hopey

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Posted 11 September 2018 - 08:07 PM

I have found that the spring for the pinch roller can fatigue and not put enough pressure on the capstan shaft. This will also give you a slow performance. Remove and replace or try bending the spring to get maxmium pressure as this is the point where the tape speed is generated.



#17 Ceestarrs

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Posted 12 September 2018 - 03:29 AM

Nice fix KeyserSoze, I'm not near my box at the moment, but don't think that's the cause with mine. Will double check there's nothing causing pressure/friction on the cassette. Thinking about it, as I still have some work to do inside, I haven't screwed everything back together properly yet- the tape deck's only got its bottom screws, the whole PCB assembly's only held in with 2 screws and the whole thing's only held together with 3 screws- maybe I should tighten everything up!

 

When I changed the pinch roller I did retension its spring a bit, but will give this another go if nothing else works.

 

My belts are from Nikonfoo, so I'm pretty sure they're the correct lengths.





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