ah . is that what is !!. great to know at last . not sure what actually melted ..or if it's just glue ..will have a closer look ,try take that clear cover off and will clean it up afterwards ...carefully . thanks for that

I would leave it alone for now. Do the trouble-shooting first.

 

I would leave it alone for now. Do the trouble-shooting first.

ok . I have the same loud distorted signal through all the points you mentioned on the RH channel.

( RIGHT channel audio goes from LPF802 pin-6, IC806 pin-1, C813, R822)
also at the LH Jumper you marked .

The new resistor at R815 has a clean signal however, slightly louder than the LH signal at the RCA output.

 

It is not conclusive where the fault lies, possibly,
IC805 = CD4053BCN
IC806 = LM833N

I would start by replacing IC806. Use IC sockets to allow ease of future replacements.
If you cannot find LM833, you can try NE5532P or TL072BCP or any such variants.
They are all dual op amps in 8-pin DIP package.

If you have never reworked a PCB before, you should practice on a scrap PCB. I requires learning the right techniques in order to avoid damaging the traces and pads on the PCB.

 

Hiya,

I have done a few op-amps before , will see if I can get one of those but not sure if I will continue after that. IC 805 looks a bit tricky with my limited gear and experience . Its an old unit ..perhaps it needs a recon job but I wont be doing that . pity its a great player.

will let you know if I have any luck with IC806 , if I get it .

Thank you for all your help once again Mr Chips . much appreciated .

Cheers
Paul

 

Hiya,

I have done a few op-amps before , will see if I can get one of those but not sure if I will continue after that. IC 805 looks a bit tricky with my limited gear and experience . Its an old unit ..perhaps it needs a recon job but I wont be doing that . pity its a great player.

will let you know if I have any luck with IC806 , if I get it .

Thank you for all your help once again Mr Chips . much appreciated .

Cheers
Paul

If you know for certain that the IC will be replaced, it is easier to cut the leads of the IC from the top side of the board using a small side cutter. Then you can remove each pin one at a time with low risk of damaging the PCB.

 

If you know for certain that the IC will be replaced, it is easier to cut the leads of the IC from the top side of the board using a small side cutter. Then you can remove each pin one at a time with low risk of damaging the PCB.

ah. ok . good tip . didnt know about that . I have IC sockets here already. is it too much heat that does the damage ?

£4 for an lm833 ...does that sound right ? too cheap ?

 

ah. ok . good tip . didnt know about that . I have IC sockets here already. is it too much heat that does the damage ?

£4 for an lm833 ...does that sound right ? too cheap ?

High temperature and lingering for too long at a pad will loosen the adhesive that holds the copper on to the PCB material.

There are altenatives to LM833 that might be lower cost. I would go that route first, especially since you are going to use sockets. There are other dual op amps to choose from:
NE5532
TL072
OPA2134
OPA2604
LM4562

Reference: https://www.audiosciencereview.com/...lm4562-ne5532-opa2134-tl072-and-lm1458.61679/

 

High temperature and lingering for too long at a pad will loosen the adhesive that holds the copper on to the PCB material.

There are altenatives to LM833 that might be lower cost. I would go that route first, especially since you are going to use sockets. There are other dual op amps to choose from:
NE5532
TL072
OPA2134
OPA2604
LM4562

Reference: https://www.audiosciencereview.com/...lm4562-ne5532-opa2134-tl072-and-lm1458.61679/

Hiya,

So I ordered a few of the NE5532 but its teeny tiny . about a third of the size of the original . not going to fit . is there an adaptor or have they sent me the wrong one? . I cant even read the print its so small but its 5532 on the pack . any ideas what happened . thanks

 

Hiya,

So I ordered a few of the NE5532 but its teeny tiny . about a third of the size of the original . not going to fit . is there an adaptor or have they sent me the wrong one? . I cant even read the print its so small but its 5532 on the pack . any ideas what happened . thanks

You got the IC in the wrong package. You want through-hole DIP-8, 8DIP, PDIP package, NE5532P, NE5532AP.

 

You got the IC in the wrong package. You want through-hole DIP-8, 8DIP, PDIP package, NE5532P, NE5532AP.

ah. ok ... thanks Mr Chips . will try again . doh!

 

ah. ok ... thanks Mr Chips . will try again . doh!

Ok . got the new op amp and the signal is still loud and distorting . do I move on to the next component or do I leave it at that ... I'm pondering .

 

Have you traced the audio signal along the signal path?
Where is it good and where is it bad?

 

Have you traced the audio signal along the signal path?
Where is it good and where is it bad?

View attachment 365118

Hiya.

yes . you had me trace these points ( RIGHT channel audio goes from LPF802 pin-6, IC806 pin-1, C813, R822) and I got the same loud signal at all points ..... so are you saying I should trace it again ? the new op amp (IC 806) hasnt made a difference so the next one to replace is IC805 , correct ?

so.. I tested at the new IC806 .. still loud signal.... then IC805 ... now this has a low volume but distorted signal

 

Hiya.

yes . you had me trace these points (LEFT channel audio goes from LPF801 pin-6, IC803 pin-1, IC804 pin-1, C808, R813.) and I got the same loud signal at all points ..... so are you saying I should trace it again ? the new op amp (IC 806) hasnt made a difference so the next one to replace is IC805 , correct ?

I am not yet convinced.
I thought that the LEFT channel was working fine.
The RIGHT channel is loud and distorted, or is the RIGHT channel barely audible?

To me, that means that the RIGHT channel is overloaded and clipping. This can only happen if the gain of the stage is too high or there is a problem with an attenuation circuit.

I don't see how IC802 or IC806 would cause this.

Use the audio signal tracer and go backwards along the signal chain. Compare the good LEFT channel with the bad RIGHT channel.
Somewhere along the chain you should find when the signal is good and then goes bad.

 

I am not yet convinced.
I thought that the LEFT channel was working fine.
The RIGHT channel is loud and distorted, or is the RIGHT channel barely audible?

To me, that means that the RIGHT channel is overloaded and clipping. This can only happen if the gain of the stage is too high or there is a problem with an attenuation circuit.

I don't see how IC802 or IC806 would cause this.

sorry Mr chips . I copy and pasted the wrong info . let me start my message again . ignore last post ok .

I just tested IC806 . still loud .
IC805 has a low and distorted volume at point 16 . nothing at 6 or 1 .
signal at RH Jumper is loud and distorted .
the new resistor 822 .. is clear but slightly louder than LH channel at the output .
I'm only working with the RH channel ok .
does that make sense now ?

 

I added this at my last post:

Use the audio signal tracer and go backwards along the signal chain. Compare the good LEFT channel with the bad RIGHT channel.
Somewhere along the chain you should find when the signal is good and then goes bad.

Let me have a look at the circuit leading up to IC805.

 

I added this at my last post:



Let me have a look at the circuit leading up to IC805.

LPF 802 pin 6 loud and distorted .
C813 loud and distorted .

 

Read post #39 first.

Here is the circuit of the audio chain.

IC801 is PCM53JP which is a single channel 16-bit D/A converter.
It processes both LEFT and RIGHT channels with a single voltage output on pin-17. This must be good.
The gain of op amp IC806 is controlled by,
R815 6.8 kΩ
R816 2.2 kΩ
C810 470 pF

If there is any doubt, replace all three first, since these are easier to replace than the next IC.

If the problem is not resolved, replace IC805, CD4053BE. Clip the legs of the IC and remove one pin at a time. Install in a 16-pin DIP socket.

 

I did not follow your previous posts.

sorry Mr chips . I copy and pasted the wrong info . let me start my message again . ignore last post ok .

I just tested IC806 . still loud .
IC805 has a low and distorted volume at point 16 . nothing at 6 or 1 .
signal at RH Jumper is loud and distorted .
the new resistor 822 .. is clear but slightly louder than LH channel at the output .
I'm only working with the RH channel ok .
does that make sense now ?

Why are you testing IC805 pins 16, 6 and 1?
These are not part of the audio signal.

I'm only working with the RH channel ok .

That statement is ambiguous and misleading.

The signal at LPF802 pin-6 is loud and distorted.
What about the signal at IC806 pin-7 leading to LFP802 pin-1, or on one side of R816, C810?

 

I've had some second thoughts.

It would appear that the LPF (Low Pass Filter) is not doing its job.
We can replace it with a simple RC LPF and see if this solves the problem.

I have no idea what is the switching frequency of the IC805 mux. However, we can try this circuit.

Feed the signal from LPF802 pin-1. Cut the trace from LPF802 pin-6 to IC806 pin-3.
Connect the output of your DIY LPF to IC806 pin-3.

Edit: Just insert your DIY RC filter between LPF802 pin-6 and IC806 pin-3.

10 kΩ and 1 nF will give a cut-off frequency of 16 kHz.