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

make believe
brinsmeads
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Re: Sony Ps-x75 Important notice re Main MicroProcessor MB8841-2

Post by brinsmeads » 11 Jul 2019 23:55

ND45 x.JPG
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correct Mike in regard to ND45x stylus..post was to indicate various accessories supplied with this assembly, this is ND45x Stylus.......
thankyou for that observation

brinsmeads
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Re: Sony Ps-x75 Important notice re Main MicroProcessor MB8841-2

Post by brinsmeads » 12 Jul 2019 09:34

Sony PS-x75 Motor Drive.jpg
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Found a Motor Drive Transistor dry joint on Q117, heat will contribute to a break down on their solder terminations ….
Check 2 x 2SC1419 ……
2 x 2SA755. ……
Q117-Q118-Q119-Q120

brinsmeads
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Re: Sony Ps-x75 Important notice re Main MicroProcessor MB8841-2

Post by brinsmeads » 05 Aug 2019 01:50

SH165 SH155.jpg
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Sony 1980 Turntable Specs .jpg
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Don’t be confused by claims these SH165 / SH155 are Magnesium or Carbon infilled Headshells.

They are Die- Cast Aluminium as shown in The 1980 Sony spec Sheet

Charc
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Re: Sony Ps-x75 Important notice re Main MicroProcessor MB8841-2

Post by Charc » 19 Sep 2019 17:43

"Bring Out Your Dead"

Hi Everyone
I have possibly found a solution to the dead MB8841's. On the theory that the Mb8841'a reset switch was not getting enough juice(voltage or current) to reset,.... AFTER RECAPING WITH HIGHER VOLTAGE CAPS..... I was able to get two dead PS-X'S a 65 and a 75, with dead, ie no lock, spins backward, to reset and function! My solution was to raise the voltage with a "variac" to around 130vac. This for my turntable raised the voltage at the reset pin(2 or 3 I cant remember) to just around 5vdc(4.98vdc,4.92vdc). On the PS-X65, I had not recapped and started to smoke various of the 16vac cap's.
Both turntables have been recapped now and are working mostly well(speed locked and keys functioning), and long process of fixing the tone arm grease and adjusting has begun.
It may be possible to directly increase this pin's voltage, I will leave that for smarter people.
jan

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