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

Posted: 11 Jul 2019 23:55
by brinsmeads
ND45 x.JPG
(293.07 KiB) Downloaded 69 times
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

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

Posted: 12 Jul 2019 09:34
by brinsmeads
Sony PS-x75 Motor Drive.jpg
(244.46 KiB) Downloaded 72 times
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

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

Posted: 05 Aug 2019 01:50
by brinsmeads
SH165 SH155.jpg
(204.72 KiB) Downloaded 59 times
Sony 1980 Turntable Specs .jpg
(257.04 KiB) Downloaded 66 times


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

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

Posted: 19 Sep 2019 17:43
by Charc
"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

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

Posted: 15 Feb 2020 09:44
by cristi68p
brinsmeads wrote:
17 Sep 2013 03:28
Also absent in the display will be the word ‘Locked’
And ‘33’ will not change
Question : it is confirmed 100% that missing word "Locked" means a dead MB8841-209 chip?
I have a PS-X65 in very nice condition with motor don"t spinning , no other function at all , but lights are OK , "33" is present also (but no "Locked").
Didn"t checked yet voltages on mainboard and PS.

Regards,

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

Posted: 18 Feb 2020 02:36
by lherbal
Rob,
You are my guru for the PS-X75 and I have a new issue: without power my table balances perfectly. Once the power is turned on, the arm moves strongly to the post and any effort to manually move it toward the disc just pulls it back to the post. The pull is so strong that the start button can't overcome the pull to the outside. All of the other functions work but this is making the turntable inoperable. Any good suggestions?