Sony CD-P 750 player static noise
 

I've got a Sony CD player, model CD-P 750, which from one second
to the next developed a loud static noise on one channel (and a tiny
bit on the other) when playing a CD.
Changing audio cables made no difference. No bulging caps or other
"burnt-up" components visible. Any ideas anyone before I throw it out?
Thanks.

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Sony CD-P 750 player static noise
 

In article , says...

I've got a Sony CD player, model CD-P 750, which from one second
to the next developed a loud static noise on one channel (and a tiny
bit on the other) when playing a CD.
Changing audio cables made no difference. No bulging caps or other
"burnt-up" components visible. Any ideas anyone before I throw it out?
Thanks.


Cracked solder joint?

You shill could have a cap shorting, just not permanent.

Bad IC or semi.



Take a can of component cooler, it to make some noise and
start freezing IC's, then caps etc..


Jamie

Sony CD-P 750 player static noise
 

On 04.Aug.14 8:39 PM, Maynard A. Philbrook Jr. wrote:
In article , says...
I've got a Sony CD player, model CD-P 750, which from one second
to the next developed a loud static noise on one channel (and a tiny
bit on the other) when playing a CD.
Changing audio cables made no difference. No bulging caps or other
"burnt-up" components visible. Any ideas anyone before I throw it out?
Thanks.
Cracked solder joint?
You shill could have a cap shorting, just not permanent.
Bad IC or semi.
Take a can of component cooler, it to make some noise and
start freezing IC's, then caps etc..

Jamie

Gave the circuit board a good workout, and tried the component cooler,
but no luck.

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Sony CD-P 750 player static noise
 

On 05.08.14 2:28, Bert wrote:
I've got a Sony CD player, model CD-P 750, which from one second
to the next developed a loud static noise on one channel (and a tiny
bit on the other) when playing a CD.
Changing audio cables made no difference. No bulging caps or other
"burnt-up" components visible. Any ideas anyone before I throw it out?
Thanks.

---
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Broken down DA converter or its input data??
Try heating/cooling locally, to see if there
is a broken solder connection somewhere.
Bending the print in various places, to see if
there are bad connections.
Last resort, buy a new one.

Sony CD-P 750 player static noise
 

"Bert"

I've got a Sony CD player, model CD-P 750, which from one second
to the next developed a loud static noise on one channel (and a tiny
bit on the other) when playing a CD.

** By static noises you mean the sound of heavy rain or surf - right ?

Changing audio cables made no difference. No bulging caps or other
"burnt-up" components visible. Any ideas anyone before I throw it out?

** Likely to be in the digital filter, DAC or audio circuits, since it is in
one channel.

Shame to toss well built gear like those old Sonys.

I still have a CDP101 ( bought new in 1983 ) in good working and cosmetic
order.



..... Phil

Sony CD-P 750 player static noise
 

If the problem is not the actual D/A converter, I would suspect the buffer transistor at the outputs. For this vintage of player, there sould be a couple of to-92 transistors just prior to the audio output jacks. Check/replace those.

Dan

Sony CD-P 750 player static noise
 

On 5/08/2014 8:40 PM, wrote:
If the problem is not the actual D/A converter, I would suspect the buffer transistor at the outputs. For this vintage of player, there sould be a couple of to-92 transistors just prior to the audio output jacks. Check/replace those.

Dan


**VERY unlikely to be buffers (without looking at a manual). In most
budget machines, the To-92 devices are muting transistors. In higher
quality units, relays are most often used. VERY few CD players used any
discrete components after the last OP amps (apart from the muting
transistors).

--
Trevor Wilson www.rageaudio.com.au

Sony CD-P 750 player static noise
 

Too many things going on at once. You are correct, I was referring to the muting transistors. Working on a buffer problem elsewhere at the moment and have buffers on the brain...

Sorry for the confusion. I have had these muting transistors cause odd behavior in the past though.

Dan

Sony CD-P 750 player static noise
 

Too many things going on at once.
You are correct, I was referring to the muting transistors.


** Famous Chinese service tech "Confucius" say:

Muting transistor = silent but deadly......



..... Phil

Sony CD-P 750 player static noise
 

** By static noises you mean the sound of heavy rain or surf - right ?

The noise sounds like holding a small DC motor with bad brushes next to
an AM radio.

There is an 8-wire ribbon cable going from the CD unit to the circuit board,
close to a Sony 7M01/CXA1081 chip. When holding my finger near the cable,
WITHOUT TOUCHING IT, the noise diminishes, and the audio/music starts to
crackle and break up.
Touching 4 of the insulated ribbon wires lightly will instantly stop the
player.

When I ground my hand and THEN touch the same insulated wires, the noise
stops also, but the audio - while continuing to play - becomes very
distorted,
and eventually stops as well.




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Sony CD-P 750 player static noise
 

"Bert = Troll "


** By static noises you mean the sound of heavy rain or surf - right ?

The noise sounds like holding a small DC motor with bad brushes next to
an AM radio.

There is an 8-wire ribbon cable going from the CD unit to the circuit
board,
close to a Sony 7M01/CXA1081 chip. When holding my finger near the cable,
WITHOUT TOUCHING IT, the noise diminishes, and the audio/music starts to
crackle and break up.
Touching 4 of the insulated ribbon wires lightly will instantly stop the
player.

When I ground my hand and THEN touch the same insulated wires, the noise
stops also, but the audio - while continuing to play - becomes very
distorted, and eventually stops as well.


** OK - your Sony is obviously possessed by demonic creatures form Hell.

Or you are.

Take your pick.



..... Phil

Sony CD-P 750 player static noise
 

Shame to toss well built gear like those old Sonys. I still have a
CDP101
( bought new in 1983 ) in good working and cosmetic order. .... Phil

I had more than a dozen Sony units from that era - a fabulous Trinitron TV,
lots of high-end Beta and VHS VCRs, including a nice SLV-R5U SVHS VCR.
Except for a rarely used Hi8 EV-S7000, they and that CD-P 750 player are
all history now.

OTOH, I also still have a number of JVC units (high-end stereo, dual
cassette,
CD player...) from that same time period, and every single one still
looks and
functions like out of the box...

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Sony CD-P 750 player static noise
 

Phil Allison wrote:

"Bert = Troll "

No troll. It's a factual description of the symptoms.
You can check it out and play with it any time you like.


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Sony CD-P 750 player static noise
 

"Bert" wrote in message ...

Except for a rarely used Hi8 EV-S7000 ... all history now.

If it's still in working order, consider yourself lucky.

Sony CD-P 750 player static noise
 

On 05.Aug.14 12:45 PM, William Sommerwerck wrote:

"Bert" wrote in message ...

Except for a rarely used Hi8 EV-S7000 ... all history now.

If it's still in working order, consider yourself lucky.

Yes, particularly since parts are likely not available any longer now -
but what do you do with them, even when in perfectly working condition?

They were great for linear editing by providing a separate audio channel
that could be edited without affecting the video, however while the EDIT
switch was supposed to kill all on-screen text, you still ended up with some
unwanted text on the finished video when pressing certain buttons while
editing. Installing a small switch to shorten the on-screen dialog when
editing fixed that.

Regardless, they still look very impressive just sitting there on the shelf
taking up space...




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Sony CD-P 750 player static noise
 

On 5/08/2014 11:11 PM, wrote:
Too many things going on at once. You are correct, I was referring
to the muting transistors. Working on a buffer problem elsewhere at
the moment and have buffers on the brain...

Sorry for the confusion. I have had these muting transistors cause
odd behavior in the past though.

Dan

**No argument from me. The best place for muting transistors is in the
bin and replaced by a decent relay.




--
Trevor Wilson www.rageaudio.com.au

Sony CD-P 750 player static noise
 

On 05/08/2014 01:28, Bert wrote:
I've got a Sony CD player, model CD-P 750, which from one second
to the next developed a loud static noise on one channel (and a tiny
bit on the other) when playing a CD.
Changing audio cables made no difference. No bulging caps or other
"burnt-up" components visible. Any ideas anyone before I throw it out?
Thanks.

---
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protection is active.
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With this sort of fault you can often zero in to where the fault is
,with a crystal earpiece connected between ground and a probing pin

Sony CD-P 750 player static noise
 

"Bert" wrote in message ...

On 04.Aug.14 8:39 PM, Maynard A. Philbrook Jr. wrote:
In article , says...
I've got a Sony CD player, model CD-P 750, which from one second
to the next developed a loud static noise on one channel (and a tiny
bit on the other) when playing a CD.
Changing audio cables made no difference. No bulging caps or other
"burnt-up" components visible. Any ideas anyone before I throw it out?
Thanks.
Cracked solder joint?
You shill could have a cap shorting, just not permanent.
Bad IC or semi.
Take a can of component cooler, it to make some noise and
start freezing IC's, then caps etc..

Jamie

Gave the circuit board a good workout, and tried the component cooler, but
no luck.

---

Have you tried percussive maintenance on it. Sometimes all they need is a
good whack or smash with your fist.

BTW: I used it fix medical electronics...... scary huh?

Sony CD-P 750 player static noise
 

On Tue, 05 Aug 2014 11:04:26 -0400, Bert wrote:

** By static noises you mean the sound of heavy rain or surf - right ?

The noise sounds like holding a small DC motor with bad brushes next to
an AM radio.

There is an 8-wire ribbon cable going from the CD unit to the circuit board,
close to a Sony 7M01/CXA1081 chip. When holding my finger near the cable,
WITHOUT TOUCHING IT, the noise diminishes, and the audio/music starts to
crackle and break up.
Touching 4 of the insulated ribbon wires lightly will instantly stop the
player.

When I ground my hand and THEN touch the same insulated wires, the noise
stops also, but the audio - while continuing to play - becomes very
distorted,
and eventually stops as well.

Offhand, i would say that you have put your finger right on the problem.

?-)