Sony Ps-x75 Important notice re Main MicroProcessor MB8841-2

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twhtalm
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Re: Sony Ps-x75 Important notice re Main MicroProcessor MB88

Post by twhtalm » 18 Jan 2014 23:44

Status update. Today I spent maybe an hour working on the table. To make testing easier I jumpered the MB8841 socket in the turntable to a breadboard to break out the pins. After about half an hour of playing with a very basic program all major functions are working. The motor locks in at either 33 or 45 and the arm moves in every direction. Things are looking very promising for the table to be brought back to life completely. More updates to come.

Cobra2
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Re: Sony Ps-x75 Important notice re Main MicroProcessor MB88

Post by Cobra2 » 19 Jan 2014 15:50

Good work!

Arne K

twhtalm
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Re: Sony Ps-x75 Important notice re Main MicroProcessor MB88

Post by twhtalm » 23 Jan 2014 20:52

Last night I was able to control the table via the buttons, all except for the start button (not ready for auto play). All of it is a bit rough right now, the program for the table is evolving on a nightly basis. Tonight the arm position sensing will be worked on along with tweaking the button performance and overall startup behavior.

twhtalm
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Re: Sony Ps-x75 Important notice re Main MicroProcessor MB88

Post by twhtalm » 27 Jan 2014 14:46

Spent more time over the weekend and made some nice progress. The buttons now work reliably when pressed. The tone arm moves up and down nicely, firmly down and back up. Zero zone is being registered along with absolute arm position. Adjusting the stylus force works when and where it should. The tone arm lifter works but discovered that my lifter is partially seized, will not lower or raise all the way without assistance. The only remaining function that is giving me trouble is the tone arm forward and backward, it works but I can't figure out how to stop on a dime. Will continue working on the arm movement and will update come the weekend.

Cobra2
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Re: Sony Ps-x75 Important notice re Main MicroProcessor MB88

Post by Cobra2 » 27 Jan 2014 14:57

Would it not be easier to reverse-engineer the chip than the hardware?

Arne K

twhtalm
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Re: Sony Ps-x75 Important notice re Main MicroProcessor MB88

Post by twhtalm » 28 Jan 2014 18:49

Yes and no. Yes reverse engineering is the correct way to do things but it is also the most expensive and technically challenging way. Right now I have about $30 dollars into the repair with hardware that is readily available worldwide and easy to work with.

TurboSound
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Re: Sony Ps-x75 Important notice re Main MicroProcessor MB88

Post by TurboSound » 05 Mar 2015 17:56

Any updates on either a source for the processor chip or twhtalm's processor conversion project?

I have the "no buttons work" problem with my PS-X75 and although I've not checked the power supply voltages yet, it probably is a bad processor. I'm very interested in the processor conversion especially to the ATmega family.

Dennis

sterzi
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Re: Sony Ps-x75 Important notice re Main MicroProcessor MB88

Post by sterzi » 05 May 2015 21:34

Hi,
found this in my workshop.
Probably 20 years in stock :shock:
If it's useful for somebody, contact me

Markus

http://fs2.directupload.net/images/150505/a87m3b3b.jpg
http://fs2.directupload.net/images/150505/8hcniu5n.jpg

Vinylberry
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Re: Sony Ps-x75 Important notice re Main MicroProcessor MB88

Post by Vinylberry » 08 May 2015 17:22

twhtalm wrote:The tone arm lifter works but discovered that my lifter is partially seized, will not lower or raise all the way without assistance.
I had the same problem with the operation of the arm lifter of my PS-X75.
After full dismantling the bottom of the arm,
I found dried and thickened grease on the axle of the coil holder that raise and lower lifter.
Sony 01.jpg
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Also I found out there some cracks, which probably formed due to old age.
Sony 02.jpg
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I removed the old grease and lubricate the axis.
After mounting of all parts it was required to make a serious adjustment of the coil plate position and drop point adjustment.
For those who wants to repeat my actions - be careful with the coils, they can be damaged during assembly, because the design uses a very strong magnets.
It also requires considerable effort to loosen the old screws.

brinsmeads
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Re: Sony Ps-x75 Important notice re Main MicroProcessor MB88

Post by brinsmeads » 19 May 2015 05:28

Very good job, step by step would be great

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Re: Sony Ps-x75 Important notice re Main MicroProcessor MB88

Post by brinsmeads » 13 Jun 2015 02:17

Supplied Original equipment with the Sony PS-x75 : Sony SH165 Headshell fitted with Sony MM XL25 cartridge
Attachments
Sony SH165 Headshell fitted with XL25 Sony MM cartridge.jpg
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brinsmeads
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Re: Sony Ps-x75 Important notice re Main MicroProcessor MB88

Post by brinsmeads » 13 Jun 2015 02:20

Supplied Original equipment with the Sony PS-x75 : Sony SH165 Headshell fitted with Sony MM XL25 cartridge
Attachments
b .Sony SH165 Headshell fitted with MM XL25A Sony Cartridge .jpg
(827.8 KiB) Downloaded 1683 times

brinsmeads
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Re: Sony Ps-x75 Important notice re Main MicroProcessor MB88

Post by brinsmeads » 29 Jul 2015 04:28

In addition to the above repair on the PS-x75, if the arm lifter pin had seized , take the bottom cover off and rotate the cam at the base of the arm and at the same time lubricate the lifter with standard WD40 with a push pull action until the lifter pin until free. Do not rely on WD40 to finish the repair, use a super lubricate with ptfe like Slick50

brinsmeads
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Re: Sony Ps-x75 Important notice re Main MicroProcessor MB88

Post by brinsmeads » 01 Sep 2015 00:09

Still many Sony PS-x75 are failing because of faulty MB8841-209L. Long years of turntable inactivity are exacerbating the failures and decay of this IC.
We really need to get a substitute programmed, Why has this featured replacement stalled ?

pivo1
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Re: Sony Ps-x75 Important notice re Main MicroProcessor MB88

Post by pivo1 » 26 Sep 2015 20:01

Hi,
After reading this thread I decided to look a bit closer into main PCB. In my '75, originally (seems originally) is MB8841-327L but... what I saw makes me thrilled.
C110 (100uF/6.3V) on 5V line (near 78L05) was bulging at the top. There was a few cold-solder point visible, including GND of 78L05 (!). I resolded whole area, also replaced all elecrolitics caps in power supply section. Also 78L05 0.1A was replaced with 1A 7805 - take care of pins !.
Please check this above at your's TT - it can save microcontroller. No doubt - one of it's fault reason is poor/bad 5V line.
VBR,
Voytek