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Adjustment of Cassette Engine Speed in National RX-7000


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#1 Magnum

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Posted 09 January 2017 - 09:50 AM

Hello everyone!

 

Maybe someone can help me with this.

 

I have a decent National RX-7000. I noticed now, that the speed of the cassette engine needs to be adjusted just a tiny bit. Unfortunately all the tapes recorded on it run to fast on other tape decks. Tapes recorded on other tape decks run to slow on the National. It's not a big issue but quiete annoying now that I have noticed it.

 

Is there any chance I can fix this on my own? I heard that the National seems to be pretty friendly when it comes to repairs.



#2 toshik

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Posted 09 January 2017 - 10:32 AM

I use pre-recorded on Quartz capstain deck (in my signature) 4 Khz tone cassette, hook up frequency meter to line out and adjust the speed. There is a round hole on the back of the motor covered with rubber protector takes small size flat or philips screwdriver.

#3 Magnum

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Posted 09 January 2017 - 02:25 PM

Thank you toshik! I downloaded the service manual from here. It shows the procedure how to remove the front cabinet from the National. I can follow along that.

 

But you say there is a round hole on the back of the motor. How do I get to it or even see it?

 

Sorry for asking but I have never done it before.



#4 toshik

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Posted 09 January 2017 - 05:45 PM

Take the mechanism off

#5 Magnum

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Posted 09 January 2017 - 06:01 PM

Ok, and can I operate it when it is taken off? I wonder because otherwise I won't be able to listen to it while adjusting...?



#6 baddboybill

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Posted 09 January 2017 - 06:06 PM

Ok, and can I operate it when it is taken off? I wonder because otherwise I won't be able to listen to it while adjusting...?


It can be but cautiously ;-)

#7 toshik

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Posted 09 January 2017 - 06:24 PM

Based on the questions you ask I won't bother opening it, ask someone who knows what to do. Otherwise you might add more damage to the unit.

#8 Magnum

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Posted 10 January 2017 - 07:47 AM

Thanks for the answers!

 

Yes, it is my very first time of opening a boombox, that's true. Having successfully repaired a camera and a flash, I'm willing to take it to the next level.

 

I had a phone call with a repair guy who was recommended to me. And I told him I needed fixing for my "boombox", and he was like "What's a boombox?" So yeah there went my faith in him.

 

Any other things to consider before I open the RX-7000?



#9 toshik

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Posted 10 January 2017 - 10:17 AM

Get a basic knowledge on how it works (including tape transport mechanism and its speed adjustment).



#10 Reli

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Posted 10 January 2017 - 11:32 AM

If you googe search cassette motor speed adjustment you'll see many articles. There's usually a hole on the back of the motor meant for a jeweler's screwdriver.  It is usually covered with a piece of rubber.



#11 Magnum

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Posted 10 January 2017 - 02:39 PM

Thanks! Reading this forum it seems that opening and repairing those old boxes is half the fun of it. :-)



#12 BoomboxLover48

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Posted 10 January 2017 - 07:35 PM

Attached File  1ot62v.jpg   174.27K   1 downloadsAttached File  Untitled.jpg   97.38K   0 downloads

 

Use a small flat head screw driver to turn the trimmer to adjust the speed. You just introduce the tip, go straight down and feel for that slot on top of the trimmer.

 

I have marked the inside head of the trimmer for speed adjustment with a red arrow. This is the part you reach inside through the hole.

 

The width of the screw driver tip should be around 3.0mm. Tip thickness like 1.0 mm.

 

You can see the motor back side showing the black hole covered with a cross hatched rubber dust shield.



#13 BoomboxLover48

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Posted 10 January 2017 - 11:01 PM

Thanks for the answers!

 

Yes, it is my very first time of opening a boombox, that's true. Having successfully repaired a camera and a flash, I'm willing to take it to the next level.

 

I had a phone call with a repair guy who was recommended to me. And I told him I needed fixing for my "boombox", and he was like "What's a boombox?" So yeah there went my faith in him.

 

Any other things to consider before I open the RX-7000?

I am pretty sure you can do this work for the speed adjustment.

There are lots of things to keep in mind when you start working on this RX7000. It is one of the most sought after and beautiful Panasonic boxes ever made. So don’t take any chances working on this box. Be patient and do the work with utmost care. I have worked on so many boomboxes and other electronic gadgets. I am not an expert in anything. I am always willing to learn and made so many mistakes in the past working on boomboxes alone.
Here are some simple steps to follow
1. Read the manual carefully and identify the parts, the disassembly process.
2. Search for the same model and see if you can find pictures of the interior parts of the unit.
3. Take pictures of every step of your work, even small steps. Pictures tells a lot!
4. Work in a well lighted area and have a soft white towel to lay place the box.
5. Get some small receptacles or trays for the screws and parts you remove.
6. Take care not to get tools trapped under the box, it might scratch and damage the finish.
7. In most cases the first thing you do is to disconnect power and then remove the cassette door cover.
8. Open the cassette door and remove the cover by gently sliding upward and pulling outward. Be careful, it is easy to damage it if you use excessive force.
9. Now look and the service manual and locate the rear cover screws.
10. Use long screw Philips head screw drivers and remove screws starting from bottom and all the way up.
11. Mark the location of each screw on a Styrofoam piece and poke those screws there. This way you are using the same screws at the same location.
12. Very gently try to open the rear or front cover whatever shows in the manual.
13. When you separate the cover, watch for wire leads. IN many cases there will be connectors on the lead wires, remove them carefully without bending the PC board. Give support on the edges of the PC board and gently separate them
14. Keep your hands and fingers away from electronic components. Take care not to touch any components in the radio circuit, if tampered that might misalign the radio.
15. Take a breath now and relax for a while.
16. Now identify the mounting screws of the tape deck assembly. There is always a metal piece hanging from there to a record bar switch. Learn how it is connected. We have to put it back in the same position when you put the deck assembly back.
17. Now start removing the deck. There will be several connectors hooked to the deck section.
18. Take pictures of each connector. In some cases you don’t have to completely remove the deck and still you will be able to work on the deck.

 

 

 

 

 

70. Turn the screws back ward until you feel a click, then turn forward. This way you can make sure you are in the groove and not cross threading it. :-D

 

I would order belts for this RX7000 also before you start the work.... 

 

Good Luck! 

 

There are so many experts here... we can help you as you move forward..

 

Cheers!

~Royce



#14 Magnum

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Posted 11 January 2017 - 06:04 AM

Wow! Fantastic answers now!! Many thanks!

 

The 'operation' has started and so far all the knobs have come easily off.

 

Also the cassette panel was very easy to remove.

 

I will you keep updated!



#15 Magnum

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Posted 11 January 2017 - 07:15 AM

Image No.1 - Knobs off

 

boombox-06221.jpg



#16 BoomboxLover48

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Posted 11 January 2017 - 07:25 AM

Image No.1 - Knobs off

 

 

Your RX7000 is in fantastic cosmetic condition. I see only a small scratch under the band switch area along the edge. 

 

Don't let the knobs rub on each other, it might mar the finish. 

Be careful using any solvents on the finish. Use a moist micro fiber cloth to clean it. 

Watch the chrome around the speaker grills not to get dings or scratches. 



#17 Magnum

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Posted 11 January 2017 - 07:38 AM

Very accurate observation, BoomboxLover 48. :-)  That is the only scratch it has. And it can be hardly seen on the photo.



#18 BoomboxLover48

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Posted 11 January 2017 - 04:05 PM

Here are a few pics I found on the net for reference purpose. If you search for images for RX7000 you can find many of them. 

 

Watch the tuning cord and the axle of the pulleys through which it is run. be careful not to break it. Also cover the dial with a layer of clear plastic not to get scratched when you take the motor section out. The tape transport key button assembly with the cassette section all should come out together so that you can take it out, turn it to one side and lay it, then adjust the motor speed while it is working. I hope those connector wires are long enough to do that. You can see it all in the picture. Hope this helps! Good Luck!

Attached Files



#19 hopey

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Posted 11 January 2017 - 06:54 PM

I have rebuilt these motors before, the Brass bearing over time becomes tight due to corrosion on the main shaft. I discovered this when I replaced all the belts and was playing slow. My concern would be that even if you do manage to alter the speed (from Factory) this would end up being inconsistent.

 

Great care needs to be taken not to damage the contacts, remove the back plate (bend the tabs with a screw driver) and push the whole assembly rotor, shaft and contacts in one piece out the back. Clean the shaft where the bearing sits top and bottom apply a little oil and reassemble.

 

Go easy on me as I'm only Normal Bias, Cheers.



#20 Superduper

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Posted 11 January 2017 - 08:05 PM

Recommending a novice to disassemble a motor is simply inviting catastrophe.  To be useful, such advise should be accompanied with detailed photo step-step otherwise, it's far too easy for someone who has no clue what they are doing to find a pile of tiny parts that can't be reassembled when a brush pops out and prevents reassembly or some such thing.  



#21 BoomboxLover48

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Posted 11 January 2017 - 11:06 PM

Recommending a novice to disassemble a motor is simply inviting catastrophe.  To be useful, such advise should be accompanied with detailed photo step-step otherwise, it's far too easy for someone who has no clue what they are doing to find a pile of tiny parts that can't be reassembled when a brush pops out and prevents reassembly or some such thing.  

 

That is so correct! Words of wisdom!

 

Just to remove the pulley from the shaft in some cases needs lots of skill and technique. 



#22 hopey

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Posted 12 January 2017 - 01:26 AM


Recommending a novice to disassemble a motor is simply inviting catastrophe. To be useful, such advise should be accompanied with detailed photo step-step otherwise, it's far too easy for someone who has no clue what they are doing to find a pile of tiny parts that can't be reassembled when a brush pops out and prevents reassembly or some such thing.


That is so correct! Words of wisdom!

Just to remove the pulley from the shaft in some cases needs lots of skill and technique.

I said go easy. Happy to post a step by step guide but we're to post?

#23 Superduper

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Posted 12 January 2017 - 10:07 AM

I said go easy. Happy to post a step by step guide but we're to post?


Sorry Hopey, wasn't trying to be hard on you. This WAS me going ez lol. The OP is obviously a novice based on his questions, so just trying to avoid a situation where we are giving him just enough information to walk him off a cliff. Knowledge is always welcome so it would be great if you can post the step by step here, but it's probably best to start a new thread in the tech section and if you do, if possible, please include detailed step/step accompanied with images so that the reader doesn't have to guess or imagine or maybe misinterpret the instructions.

#24 BoomboxLover48

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Posted 12 January 2017 - 11:40 AM

Magnum don't have to do this. 

 

This is just some additional info:

 

There is an easy way to remove the brass pulley from the steel shaft of a motor.

 

Cover the face of the motor just to expose the pulley with flexible card board with a cut on it, and direct hair drier on it. The cut is to slide the shaft through it.

 

While the brass pulley is slightly hot, direct compressed air cleaner on the steel shaft and pull the brass pulley out. 

 

It worked for me when I wanted to replace a deck motor. 

 

To put the brass pulley back, heat the brass pulley and quickly slip it in. Keep a spacer in between the motor face and the pulley, or else it will go and hit the motor cover.

 

In some cases by applying force you can slide it out without any heating!



#25 Superduper

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Posted 12 January 2017 - 12:05 PM

Hopey was talking about exposing the shaft at the bearing location to clean and polish it. Removing the pulley alone won't expose the shaft where it rides on bearing.



#26 BoomboxLover48

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Posted 12 January 2017 - 04:14 PM

Hopey was talking about exposing the shaft at the bearing location to clean and polish it. Removing the pulley alone won't expose the shaft where it rides on bearing.

That is correct! I'm so sorry if I misunderstood!

 

That is is not an easy process.   :yes:  

 

Very complicated... so easy to make many mistakes! 

 

I won't even attempt, unless I have another working motor with me.



#27 caution

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Posted 12 January 2017 - 04:48 PM

What's the make/model of the motor? Perhaps someone has an extra.



#28 hopey

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Posted 12 January 2017 - 05:55 PM

 

I said go easy. Happy to post a step by step guide but we're to post?


Sorry Hopey, wasn't trying to be hard on you. This WAS me going ez lol. The OP is obviously a novice based on his questions, so just trying to avoid a situation where we are giving him just enough information to walk him off a cliff. Knowledge is always welcome so it would be great if you can post the step by step here, but it's probably best to start a new thread in the tech section and if you do, if possible, please include detailed step/step accompanied with images so that the reader doesn't have to guess or imagine or maybe misinterpret the instructions.

 

 

Cheers

 

Magnum don't have to do this. 

 

This is just some additional info:

 

There is an easy way to remove the brass pulley from the steel shaft of a motor.

 

Cover the face of the motor just to expose the pulley with flexible card board with a cut on it, and direct hair drier on it. The cut is to slide the shaft through it.

 

While the brass pulley is slightly hot, direct compressed air cleaner on the steel shaft and pull the brass pulley out. 

 

It worked for me when I wanted to replace a deck motor. 

 

To put the brass pulley back, heat the brass pulley and quickly slip it in. Keep a spacer in between the motor face and the pulley, or else it will go and hit the motor cover.

 

In some cases by applying force you can slide it out without any heating!

 

Good info, but if you do it carefully; I have successfully removed Brass and Plastic pulleys without any heat! I have seen reports of damaging the motor by removing the pulley however this is not my experience. 

 

 

Hopey was talking about exposing the shaft at the bearing location to clean and polish it. Removing the pulley alone won't expose the shaft where it rides on bearing.

That is correct! I'm so sorry if I misunderstood!

 

That is is not an easy process.   :yes:  

 

Very complicated... so easy to make many mistakes! 

 

I won't even attempt, unless I have another working motor with me.

 

 

I understand your concern, I would conclude that the motor requires a service or replacement. Your current motor isn't going to get any better so if you have a crack at fixing it there is little to loose.  

 

Did you change the Pinch roller as this is crucial to obtaining the correct tape transport speed, this could make you think the motor is too slow?

 

Despite comments I have read about these Japanese motors, they are very reliable and most are serviceable; as long as you can remove the back plate!



#29 BoomboxLover48

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Posted 12 January 2017 - 05:57 PM

What's the make/model of the motor? Perhaps someone has an extra.

That makes sense to me...unless it is something else !

 

Good suggestion Eric! :yes:  :-D



#30 baddboybill

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Posted 12 January 2017 - 08:54 PM

Something I noticed that was said by Magnum in first post was that when he records on Panny the speed is fast on other machines but when he has recorded on other machines that are slow on Panny. That seems kinda fishy!!!!