Sony PS-X700 Biotracer arm doesn’t auto balance

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DualJon
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Sony PS-X700 Biotracer arm doesn’t auto balance

Post by DualJon » 11 Feb 2019 02:26

Hi Sony Squad,

I’m hoping to find someone here with the right arcane knowledge of these esoteric tables.

I recently dropped by PS-X700 off at my local audio equipment service center to get the record size selector bulb replaced (it had gone dark about a month before). When I got it back, the bulb was working but the arm was not.

Here are the symptoms:
1. Arm balance: often the arm will not move toward the record at all... it raises, tries to balance, then blinks “L” no matter what weight is on the headshell. I do have the additional counterweight but on, off, doesn’t matter, always L.

2. Very rarely, by removing the headshell, turning off the table, turning it back on, then putting the headshell back on after the arm tries to auto balance, I can get the arm to balance and start playing the record. However, in these situations, the arm lift/move L/move R during play functions don’t work

3. Disk size select from platter mat doesn’t work. Sometimes the arm sets down at 7, sometimes 12.

4. Not positive about this, but I think the Start/stop mute doesn’t pop on as fast as it used to.

I’ve heard that the bulb could act as a fuse, and when it burns out it means that something bigger is going on... but anyone have advice on what to look for or replace here?

It really was working just fine before replacing the bulb (other than size selection).

I can solder and follow instructions. Please help

fscl
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Re: Sony PS-X700 Biotracer arm doesn’t auto balance

Post by fscl » 11 Feb 2019 16:09

Professor Bizzt has not posted for a long time, however, he has been kind enough to not delete his presence, HTH with the zero balance:

viewtopic.php?t=28975

You will have to study the schematics for the X700 and the X800, they should be very similar in logic and operation.

Regarding the automatic size selection. I know the circuit responds to an LED flashlight, ie if the bulb is out, you can shine an LED flashlight and the sensors will not allow the tonearm to cue on a naked platter, I've got to replace a tower bulb on an X555es myself that I haven't gotten around to....... :? #-o Does your X700 perform correctly with the replacement bulb taped over :-k :?:

Good luck and welcome to VE...... :)

Hate it when the turntable comes back with more problems after "servicing"...... :-k :-k :-k #-o ](*,)

If they are competent, make them make it right..... :twisted:

Fred

goldorak
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Re: Sony PS-X700 Biotracer arm doesn’t auto balance

Post by goldorak » 12 Feb 2019 02:18

Sorry for your turntable. I have the same, works perfectly. Don't mean to highjack your thread but would you be king enough to measure the weight of the 2 auxiliary sub weights as I am missing those parts.
Good luck making your Sony work properly.

DualJon
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Re: Sony PS-X700 Biotracer arm doesn’t auto balance

Post by DualJon » 12 Feb 2019 02:45

That is something I can answer, at least partially!

I know that the manual lists two counterweights, but mine only came with one and I’ve never had a problem either using it or not using one at all.

Mine is 5/8 oz, or about 17.5g.

goldorak
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Re: Sony PS-X700 Biotracer arm doesn’t auto balance

Post by goldorak » 12 Feb 2019 03:07

Thanks a lot, I have searched a lot to find the information. Do you think you have the small or large one? Dimensions?

DualJon
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Re: Sony PS-X700 Biotracer arm doesn’t auto balance

Post by DualJon » 12 Feb 2019 19:13

My guess is there could be a larger one out there somewhere, because I haven’t had a situation where my cartridge was too heavy for counterweight-less balance, but too light for balance with the weight. Does that make sense?

The dimensions are roughly: 18mm in diameter, 19mm tall including screw height, threaded screw height about 5mm.

Now, back to the issue at hand... I will take delivery of my non-functional X700 today and try to troubleshoot. I’ll give covering the light a try to see if that makes a difference too.

Any other advice would be really helpful.

goldorak
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Re: Sony PS-X700 Biotracer arm doesn’t auto balance

Post by goldorak » 08 Mar 2019 03:23

Was wondering how your situation ended up. Is it working?

DualJon
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Re: Sony PS-X700 Biotracer arm doesn’t auto balance

Post by DualJon » 08 Mar 2019 04:35

Thanks for asking! I wish. I am going to have to open it up and start testing resistors, but I haven’t yet because I’m nervous about all the work it’ll take.

DualJon
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Re: Sony PS-X700 Biotracer arm doesn’t auto balance

Post by DualJon » 30 Oct 2019 03:42

Update:

After letting the turntable sit for a few months, I decided to go ahead and try to diagnose the underlying problem. Before opening her up, I decided to turn it on and check operation again.

Interestingly, the bulb had burnt out again. And the tonearm still didn’t autobalance. It flashes L continually and sinks slowly down. The symptom reminds me of when the arm is locked into the tonearm rest and can’t balance itself freely; it also flashes L in that case. This makes me wonder if there’s an issue with the vertical sensor mechanism not registering the location of the arm, or not being able to control it. Turns out that there is another bulb attached to the vertical sensor—it may also be burned out.

So I started exploring the PCBs with the service manual schematics guiding me, and initially I couldn’t find any obvious signs of damage to the components. No bulging capacitors or clear soldering issues.

Then I checked the auto size PCB that has the problem bulb on it. I was shocked: the bulb was completely missing, and there was what looked to be a bit of charring on the curved metal reflector piece that cradles where the bulb should sit. Very strange.

If the bulb popped twice, to me that means that it’s getting too much voltage from the circuit somehow. A resistor isn’t resisting, or something else is happening.

There are a few resistors marked on the service manual with a “!”, meaning they are very important and must be replaced with the exact part listed. Interestingly, one of them (R250) is near the area that powers the auto size bulb that had originally burned out. When I looked closer, the resistor installed was a 42ohm 1/4w resistor (it tested normally) but the schematic calls for a 47ohm 1/4w resistor. Was this a game time sub at the factory? Or did someone install an incorrect replacement at some point down the line? There’s no way for me to tell, but I decided to put in a 47ohm 1/4w resistor just to be safe.

Today I checked voltages. There are hundreds of voltages listed in the service manual, some with oscillator readings. No way am I going to check them all, so I chose some places to check along the circuit from the transformer to the auto size and vertical sensor boards. Power supply PCB voltages were all in range. The main board voltages looked good too, except I found one leg of a transistor (Q203) that should read 5v but was basically at 0v. Hmm. The transistor looks to be directly tied into the problem circuit.

Tracing the circuit back, it connects with the IC202 chip at the 14th pin. That pin should also read 5v, but instead reads 0v. Double hmm. The other pins read out correctly. Just this one is problematic.

So now I’m wondering if I have a bum chip. If you guessed that I can’t find a replacement for it online, you’re right.

I still need to disassemble the tonearm in order to look at the vertical sensor board to see if that bulb is still there. But if any of this prompts you all to give me some suggestions of what to try next, I’m all ears.

dkonsta1974
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Re: Sony PS-X700 Biotracer arm doesn’t auto balance

Post by dkonsta1974 » 02 Dec 2019 08:07

I have a similar problem with my Ps-x700.
It wont autobalance and i get "H" light blinking constantly.
It was working fine for a few weeks.i did not change the cartridge or headshell and noemw it wont balance.
If i leave the lock on it will blink "L" which is correct.
Where do i start?
Cheers Dimitrios

DualJon
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Re: Sony PS-X700 Biotracer arm doesn’t auto balance

Post by DualJon » 02 Dec 2019 14:46

Is there anything you can change to get the arm to autobalance? Different headshell, larger counterweight, leveling the table, etc.?

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