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.

View attachment 365131

apologies for ambiguous statements .

sorry, I dont understand . just follow yr edited msg? : 'Just insert your DIY RC filter between LPF802 pin-6 and IC806 pin-3.'
so you want me to test each pin between 3 and 6 ? I can tell you that 6,4 and 1 give me the loud , distorted signal .

do you still want me to cut the trace ?

I guess , I could swap the two filters ?

was just wondering , that blown resistor R822.... do you think that it failed first or was it blown due to another component issue ?

 

I missed where in this thread you said that R822, 560Ω was blown. I don't see any reason why it should blow.
R815 6.8kΩ was blown and replaced. That one also should not blow.

LFP802 is an active filter. It requires power to operate. I would leave it alone. Don't do any swapping.
Cut the trace leading from LPF802 pin-6, close to pin-6. This will make it easier to repair if you need to do so. Only a small 0.5-mm wide cut is required.

Insert a 10 kΩ resistor from LPF802 pin-6 to IC806 pin-3.
Connect a 1 nF capacitor from IC806 pin-3 to GND.

 

I missed where in this thread you said that R822, 560Ω was blown. I don't see any reason why it should blow.
R815 6.8kΩ was blown and replaced. That one also should not blow.

LFP802 is an active filter. It requires power to operate. I would leave it alone. Don't do any swapping.
Cut the trace leading from LPF802 pin-6, close to pin-6. This will make it easier to repair if you need to do so. Only a small 0.5-mm wide cut is required.

Insert a 10 kΩ resistor from LPF802 pin-6 to IC806 pin-3.
Connect a 1 nF capacitor from IC806 pin-3 to GND.

View attachment 365137

msg received and understood. will get on it asap . thanks

 

msg received and understood. will get on it asap . thanks

Note that this is just experimental at this stage. It might require some fine tuning.

 

ok. installed 10K resistor and 1nf Cap . cut the trace to pin 3 .

no change at rca outlet. still distorted and loud .

 

ok. installed 10K resistor and 1nf Cap . cut the trace to pin 3 .

no change at rca outlet. still distorted and loud .

To cut the voltage in half, put another 10kΩ resistor in parallel with the capacitor.
Increase the value of the capacitor to 10 nF or higher.

You can also try ganging two RC low-pass filters. Experiment with different values.

 

To cut the voltage in half, put another 10kΩ resistor in parallel with the capacitor.
Increase the value of the capacitor to 10 nF or higher.

You can also try ganging two RC low-pass filters. Experiment with different values.

View attachment 365163

ok. will try that Mr Chips . I may be a while though . have to order parts . thankyou

 

ok. will try that Mr Chips . I may be a while though . have to order parts . thankyou

ok I tried a 20 nf Cap in there and added a 20k resistor in parallel ( didnt have a 10k) . no difference . still a loud distorted signal from RH channel .

Do you think I would be able to buy a low pass filter like this one . ?

 

ok I tried a 20 nf Cap in there and added a 20k resistor in parallel ( didnt have a 10k) . no difference . still a loud distorted signal from RH channel .

Do you think I would be able to buy a low pass filter like this one . ?

What value resistors and capacitors do you have? We can try a different 2nd order low-pass filter and attenuator to see if we are on the right track.

 

What value resistors and capacitors do you have? We can try a different 2nd order low-pass filter and attenuator to see if we are on the right track.

not much Im afraid . I have boards I salvage stuff off and some packs of resistors and diodes . about how many components would I need ?

 

You need a voltage divider to attenuate the signal.



Vout = Vin x R2 / (R1 + R2)


1st order low pass filter



Use this online calculator to set the cut-off frequency somewhere around 8 kHz - 16 kHz.

https://www.omnicalculator.com/physics/low-pass-filter


2nd order low pass filter

 

You need a voltage divider to attenuate the signal.

View attachment 365569

Vout = Vin x R2 / (R1 + R2)


1st order low pass filter

View attachment 365571

Use this online calculator to set the cut-off frequency somewhere around 8 kHz - 16 kHz.

https://www.omnicalculator.com/physics/low-pass-filter


2nd order low pass filter

View attachment 365570

so could I hook up a pot ...then work out values later ?

 

so could I hook up a pot ...then work out values later ?

Yes.

 

just taking a break for a while Mr Chips . will get back to work sometime soon I hope . just wanted to let you know , I havent run to the hills yet.

Im going to be gone for two months looks like . Hope we can continue then . thanks for your help once again.