Sony 6800SD speaker relay intermittent fault

[EspenJ]

Hi all. This is my first post on Audiokarma.
I currently own a Sony 6800SD, wonderful piece of audio gear.

I am experiencing some intermittent speaker relay fault. Some times the relay will click on and off making a "popping" sound in the speakers. Turning the receiver on and off can some times solve this problem.

I have replaced the relay and allmost all of the capacitors on the amp board. And allso some resistors and diodes. The issue with the relay was there before i did this.
I am suspecting a IC to be the problem.

Is there anybody here with the knowhow to help please?

Kindly

Espen, Norway

 

[ryuuoh]

It sounds like there is DC voltage on the speaker outputs, causing the protection to trigger.

 

[avionic]

Welcome aboard EspenJ

It sounds like there is DC voltage on the speaker outputs, causing the protection to trigger.

Sounds more like a solder connection in the power supply/protect circuitry or intermittent relay driver transistor.

 

[EspenJ]

Thank you

I have measured dc offset :
Right channel: 45mV
Left channel: 11mV

It is a bit off but not alarming.

I was hoping that someone had this issue before and had some firsthand knowledge about where to look.

I have inspected the solder points but cant see any faulty ones. Maybe resolder anyway?

 

[EspenJ]

I allso need to mention that the i have experienced that the relay did not click on as it should one time. After a restart it clicked on. Is there maybe a capacitor in the relay circuit that Is causing this behaviour? Typicaly the relay clicks on 1 sec after powering on the unit. I suspect this Is a bit too fast?

 

[EspenJ]

Here is the schematics for the power board with the relay . Notice the affected area on the board that has been quite warm.
R914 and R912 has not been replaced yet. Have measured them and found them within spec.

 

[EspenJ]

Update. I inspected the solder points on R914 and found that it had loosened from the printboard. It had connection to the copper conductor on the print , but i soldered a piece of copper wire allso to the respective points on the board.
I do not know if this was the isssue but i have tested the unit for a couple of hours now and no relay clicking so far. Keep my fingers crossed. U never know about these old dinosaurs.