Un responsive sony ps-x75

[TrevorBarten]

I bought this defective sony biotracer one ebay and it's completely unresponsive. I have been reading around a bit and it seems that it's most likely an ic that's broken. However before I go around and look for a replacement I would like to cross out all the other possible defects and confirm that it's indeed the ic. I already cleaned thee buttons internally and that didn't help much. Only thing that does work use the pot meter for the anti skating. Any tips?

 

[stratokaster]

First things first - check all the power rails.

If they test OK, check pin 3 of the MB8841 IC - it's the reset pin. It should be at 5V, otherwise the CPU will not function. (It is held at 0V for about 0.5 seconds after turning the turntable on, this resets the CPU.) If the reset pin stays at 0V, the problem likely lies in the reset circuit (IC111, C112, D108).

The buttons are directly connected to the CPU inputs, so there is nothing else that would cause it to be completely unresponsive.

 

[TrevorBarten]

J

First things first - check all the power rails.

If they test OK, check pin 3 of the MB8841 IC - it's the reset pin. It should be at 5V, otherwise the CPU will not function. (It is held at 0V for about 0.5 seconds after turning the turntable on, this resets the CPU.) If the reset pin stays at 0V, the problem likely lies in the reset circuit (IC111, C112, D108).

The buttons are directly connected to the CPU inputs, so there is nothing else that would cause it to be completely unresponsive.

Just checked the third pin and that switches to 5 volts like it should. With power rails you just mean the path from the wall plug to the rest of thee board?

 

[stratokaster]

No, I mean the output of the voltage regulator circuit. There should be -15V at the emitter of Q106, +15V at the emitter of Q101 and +5V at the output of IC101.

and while you're at it, download the service manual from vinylengine.com, you won't get very far without it

 

[TrevorBarten]

No, I mean the output of the voltage regulator circuit. There should be -15V at the emitter of Q106, +15V at the emitter of Q101 and +5V at the output of IC101.

and while you're at it, download the service manual from vinylengine.com, you won't get very far without it

Yep was already looking at the service manual. Q106 and q101 measure correctly ic 101 does aswell. Any other possibilities?

 

[TrevorBarten]

No, I mean the output of the voltage regulator circuit. There should be -15V at the emitter of Q106, +15V at the emitter of Q101 and +5V at the output of IC101.

and while you're at it, download the service manual from vinylengine.com, you won't get very far without it

Also since Idk what to look for I checked to see if the buttons do something and they do work as they should according to my multi meter.

 

[stratokaster]

The service manual says the buttons are disabled until it can be assured that the tonearm has been on the tonearm rest for at least 0.5 seconds - check the voltages at their respective points as detailed on page 11 of the service manual (IC110: -0.4V at pin 3, -2V at pin 7, 0V at pin 6; -5V at the base of Q124/Q125).

if they check out, that's definitely the CPU.

 

[stratokaster]

This is probably the best service manual I have ever seen, very detailed descriptions of what the CPU should do when various buttons are pressed. Check if it actually does what it is supposed to (e.g.: when pressing the "Back" button, pins 17 and 18 should go high). But so far all signs point to the CPU.

 

[TrevorBarten]

The service manual says the buttons are disabled until it can be assured that the tonearm has been on the tonearm rest for at least 0.5 seconds - check the voltages at their respective points as detailed on page 11 of the service manual (IC110: -0.4V at pin 3, -2V at pin 7, 0V at pin 6; -5V at the base of Q124/Q125).

if they check out, that's definitely the CPU.

I am getting 14 at the base of both q125 and q124 and the ic 110 is only giving me the -0.4 v on pin 3 and not the other 2.