Sharp Twin Famicom AN-505 Repair Log

[chimyfolkbutter]

Well folks, I received a dead Twin on Famicom.  NOt the sellers fault as he sold it as is.  The first thing I noticed was that it was dirty so I cleaned it.  That's the first step!

I will post pictures of the Twin as I dismantle the beast and delve into the electronics.

You can view my repair of a red one http://www.nesworld.com/cgi-bin/yabb/YaBB.pl?num=1138038082 however, you have to sign up at nesworld to view it.  Sorry

This new log will be exclusive to Famicom World.  It's Famicom Reality Forum at it's best!

-CFB

[Doc]

AWESOME! I LOVE these!

[chimyfolkbutter]

Upon further diagnosis, I determined that the Sharp Twin was working with regular cartridges.  Great.  However, I loaded a disk into the drive and I can hear the Famicom disk go round and round.

Here is the first look:




Next I systematically disassembled the internals of the Sharp Twin.  Not surprisingly, I found dirt, cobwebs, insect larvae, dead insects, crumbs, and dust.

Here is the sharp twin in its primitive and dirty form:




So, I first concentrated on the Famicom Disk.  As I suspected, the FDS belt snapped and it turned into a sticky, rubbery paste.  Which is a pain to clean but must be done.  This can be accomplished with a small sloted screw driver to scrap the belt of the wheel and motor.  Next, use some alcohol to clean remaining residue.

Here is the Famicom drive.  Notice in the lower left hand corner.  The belt is snapped.



Next, proceeded to identify the drive controller chip.  If the drive contains the IC7201 drive controller, then this drive can be used to read/write disks with FDS copy programs,  Otherwise, it will contain the IC3206 which is an evil chip that prevents copying of FDS disks.

Here are the results (sorry it is blurry):



In case you cannot see it, it is an IC3206.  Bummer!

After some cleaning of the Power board and the CPU, the Sharp Twin is starting to be restored to its former glory.

Here is the cleaned audio-video-power board.  The solder connections look great.



Here is the the CPU, I got rid of the cobwebs and dead bugs:




After more cleaning and even more cleaning, I reassembled the Sharp Twin minus the Disk drive.  Look how shiny and clean it is.




So what is next?  I have to replace the drive belt.  I have an extra one in my workbench shop,  This will take a some time and effort to fix.  Not difficult but tedious. 

Stay tuned.  Let me know if you have any questions!

-CFB

[chimyfolkbutter]

OK, I replaced the belt.  I didn't document this as it has been documented in other sites.  Plus it is really tedious.

Here is the Sharp Twin ready for a disk.




Now the Sharp Twin is successfully reading a disk.  Cool.



Wow!  Rally 3D ready to play!



But wait, I still have to test the cartridge.  I loaded my pirate cart into my Sharp.  Ahh. You noticed! What is on top of my Sharp twin?  It's a honey bee cartridge extender.  I use it for my regular famicom when I use my game doctor.  In this case, I was too lazy to take it off the twin.




The pirate cart is ready to play.




So, the Ebay Sixty-Five dollar Sharp Twin is fully operational.  If you notice in my picture above, the Sharp Twin is next to the Red Sharp Twin I fixed last year.  That repair job is documented in the Workshop section of Famicom World. 

Don't get intimidated.  You can fix one too!

Thanks for this tuning in to this edition of FamicomWorld DIY.


-CFB

[Doc]

Simply amazing.

[Nickv]

  Awesome! 
I know my next purchase 

[Doc]

When JC comes back, I'll make sure he also looks at this as well.

[flyingducky]

HI I replaced the belt in my disk drive with a factory replacement, however now I keep getting error messages #21, 22, or 27 is there anyway I could fixed this problem?

[Nickv]

ive got the same problem. I tried re aligning the gears from jfgoods.net web site but it still doesnt run anything. Does anyone know of any other things to tweak to get the games running??? I can only work on it for about 30 min a day before i get frustrated 

[chimyfolkbutter]

JFgoods site only helps with putting on the belt. 

You need to adjust the record/play head on the drive.

Error 21 Disk Header block is wrong
Error 22 Disk header block recognition isn't read and can't be ignored
Error 27 Block end mark seen and ends prematurely.

Shoot, the phone just rang.  I'll write a more technical explanation.

-CFB

[chimyfolkbutter]

OK, if you look at a dump of the FDS game, you can look at the FDS header in a hexidecimal editor.   The first 16 bytes contain the Identifier, NINTENDO-HVC.  When the game is loading, the RAM cart is looking for this header.  If the head is out of alignment, then the get the errors 21, 22 and 27.  The trick is to align the heads precisely to read the header block correctly.  Another factor is the speed of the motor.  From best practices, the speed of the motor should be set to 5 before adjusting the head.

So, how do you adjust the speed?  By using utilities like Bung Copymaster. There is a function that allows the technician to adjust the motor.  However, getting a Famicom Doctor and CopyMaster is hard to come by.

So, you have to wing it in terms of adjusting the speed.  I just turn the screw to clockwise to its slowest speed.  Then I turn the screw half way.  If you look at the FDS drive motor closely, you will see a positve and negative sign etched into the motor case.  Use that as your guide for increasing or decreasing the speed.

Once you adjust the speed, start adjusting the head screw and keep turning the screw until the errors go away.  This is by trial and error. 

1.  Note the position of the head!  This will allow you to know the original point of the the head.
1.  Load the disk and see what error comes up.
2.  Adjust the screw an 1/8 counter clockwise or clockwise.  This depends on the position of the head.  If it is to far up, you may have to turn the screw the opposite direction to move it down.  Again, remember the original position of the head.
3.  Load the disk and see if the error goes away. 
4.  Repeat as neccessary. 

PLEASE, PLEASE be careful when adjusting the head!  If you strip the screw, then you Drive is toast!

Just a disclaimer, I am not responsible for any screw ups.  Please do this at your own risk.

I don't have my camera so I can't take pictures of the screw that you need to adjust. 

I hope this helps.  I will post pictures when I get back home.




-CFB

[chimyfolkbutter]

OK, here is a photo of the FDS head.  It is the silver square in the middle.  Note the position.  You can also see the adjustment screw to the left.  Notice the red wax around the screw.  This was placed on the screw at the factory to hold its position.  You have scrape it off to loosen its grip on the screw.




The next shot shows the adjustment screw.  It is the brass screw  in the middle.  This is the screw that you adjust.  Please use a philips head screw driver.  You can buy the small screw driver sets at radioshack or even home depot.



That's it.  Good Luck.

-CFB

[Juggalo/Hulkamaniac]

Awesome job.

[madman]

I've tuned a number of FDS drives and was able to get rid of the 21/22 and 27 errors by another method that doesn't involve adjusting the head, but rather the spindle position as briefly detailed on the jfgoods site.  From what I can gather, the spindle uses an index pin, similar to how old 5.25" floppies had an index hole to allow the drive to determine the beginning of tracks.  By adjusting this, you can have the drive work perfectly.  Too far to one side, you get 21/22 errors, too far to the other, you get 27 errors.  Right in the middle and your drive will work like a charm.

The head adjustment that chimy is describing seems it would be more for radial alignment than indexing.  There's a lot of unknowns with these drives, but I've gotten 100% success rather by adjusting the spindle properly.  I'll try to write something up when I get home. 

[chimyfolkbutter]

Cool.  I do that as well but It never works for me.  However, I could be doing something wrong so your methodology may provide more details.  So, maybe as a best practice, do your methodology first and if that fails then do the radical procedure that I outlined above.

Overall, we are capturing and documenting the repair process which is a good thing!

-CFB