Sony ST-S730ES Tuner Start-up Issue

[Mohan Siribadda]

Hi Friends,

Can any one help me to overcome the issue pertaining to my Sony St-S730ES vintage tuner.

Recently, I noticed that when the tuner is a switched on after long period of idle ( say after 4-5 hours), the red stereo mode indicator on the display panel including the SST (green light) and the signal strength indicator on the display panel do not light up. When this happens no sound is heard from the amplifier (which is connected to).

When I keep the tuner on for about 5 minutes, all the indicators and the stereo signal strength light up (after brief blinking) and the tuner attains the normal operations.

When this happened, I checked the tuner by intermittently switching off the power. It operates normal.

This problem occurs when the tuner is switched off and kept for more than 4-5 hours switched off and later when I need to start the tuner from the cold start (in the morning).

Kindly advise me how to get over the problem,

Have a nice day!

Cheers

[DF96]

Faulty power supply? Soft start circuit, or overzealous overcurrent trip?

[Mohan Siribadda]

Dear Friend,

Can you send me your e-mail address, I could upload the service manual of this tuner, then I could diagnose it if you tell me the area to be checked.

Thanks for the support.

Have a nice day!

Cheers

Mohan

[DF96]

See post 2. If that is not sufficient information to get you started, then you need to take it to a competent repairer or do a whole lot of reading.

[indianajo]

Mostly, in equipment over 20 years old, every electrolytic cap needs replacing before one wastes time analyzing the circuit. I gave up on using my Sony TC250 tape deck as a preamp because it had about 100 e-caps, and bought a disco mixer instead. After the caps are replaced, those that were shorted might have blown diodes, resistors, or other parts supplying current. I usually check the gear after every few caps I replace to see if I made it better, or worse. If the latter, my most recent solder joints might have been cold, or the cap backwards, or some similar fault.

[Mohan Siribadda]

thanks for your reply. Only alternative I have to take it to competent technician.

Thanks

Mohan

[indianajo]

If it still sort of works it might be a very mechanical process, like changing sparkplugs in a car. I recapped a 197? 6 band radio last year that I inherited from my father. I didn't have a schematic, and I don't have a scope suitable for alighning a radio front end. When I got it, it was a fuzzy distorted radio with no sensitivity. After I replaced the electrolytic caps , it is a crisp sensitive good sounding device that I remember in my father's house. No adjustments were made- I just replaced the electrolytic caps one for one with similar sized and rated ones.

[Mohan Siribadda]

Dear Indianajo,

Thank you for your kind suggestions, when I contacted a one of experienced electronic tech locally, he said me exactly the same. He said one of the capacitors in powering circuit may be sluggish when charging. I think your suggestion is exactly the case why?.

When I keep the Tuner ( switched off) plugged on to the live power outlet, the it powers up normal after prolonged hours of idle. Other case is, as I said, the Tuner operates normal after long hours of use and used without long hours of idle (without use).

Thanks for your support.

Cheers

[indianajo]

Electrolytic caps are aluminum cans full of water and chemicals, sealed with rubber, most often. At 20 years plus the rubber cracks, allowing the water to evaporate. Thus the temperature sensitivity of performance before they completely fail. Cheap caps can leak and fail at 4 - 6 years, or less if run very hot. I like to buy the ones rated >3000 hours service life.

[Mohan Siribadda]

Dear friend,

Noted with thanks. I will be getting the tuner checked shortly based on your suggestions.

Thanks very much for the kind support.

Have a nice day!

Cheers