Any radio techs? help!

[expat]

We have a Tivoli model 1 that has been a great radio, it looks good and sounds fantastic.

Recently,we started using it in the kitchen to stream music radio from an Ipad (the radio has an aux input)

Problem is, after playing, sometimes for minutes, sometimes for hours, sound will suddenly cut off, or at times go very faint and scratchy.

Turning the radio off momentarily and back on, or pulling the plug to the power and putting it back will normally restore the sound until it happens again.

Sometimes just as the power plug is pulled, there will be a short burst of normal sound.

I did take the radio to a repair shop, but as might be expected, it worked perfectly :-(

Any ideas?

 

[Kiwi_ME]

Have you cleaned the AUX plug connections?

Tried the radio in different power outlets around the house?

 

[expat]

Originally Posted By: Kiwi_ME
Have you cleaned the AUX plug connections?

Tried the radio in different power outlets around the house?


I have the same problem weather it's set to aux, am or fm.
I have also tried different outlets (the power led light stays lit even when there is no sound)

There is a 12vDC power jack, I wonder if I will have the problem if running on 12v?

 

[sleddriver]

perhaps it's heat-related. First thing to check is the power supply.

 

[expat]

OK, So now the radio is quite ALL the time, the problem is no longer intermittent.
Which, I guess makes the diagnosis a little easier.

I have tried running it on 12v DC through an input jack on the back of the radio, but it makes no difference. The sound is still very faint, it gets a little louder when the volume is turned up,but is nowhere near normal.

Sound through the headphone jack IS normal.

Not knowing anything about radios, I guess it's the Amp, but the pre amp must be OK for the headphones to work.

The problem is, where to go from here?

Tivoli do not make schematics available, let alone parts.
Perhaps I can work my way through the amp circuit and look for a dry joint or something?

Any ideas please!

 

[Lubener]

You mentioned you have a headphone jack, there are contacts within the jack to send audio to your main speaker when there is no plug inserted, could be dirty. Does the volume control sound scratchy when rotated? You may have a cold solder joint which acts up with temperature.Could also be a dried up electrolytic capacitor in the audio section. You can purchase freeze spray in a can and spot spray components when the radio is acting up.

Nice radio.

 

[HerrStig]

My bet is on dirty contacts on the headphone jack. The only additional part in the headphone circuit is a resistor which is supposed to keep the amp from blowing up headphones, which require a very small amount of power. In the good old days one used to see the headphone jack in the higher impedance driver circuit which matched headphones better but not today. Contact cleaner might fix it, if you can get to the jack. Sometimes the contact which switches the speaker back in when the phones are unplugged loses tension and doesn't make a low resistance connection. That radio probably has a chip output stage and they are usually very trouble free.