problem with AKA Nippon FS 2420

[stevenrob]

Hello,
I have cleaned all pots and contacts but I have a strange problem : with tape deck or radio the sound cuts when volume is max or near the max, but in half position it is OK. The sound is ok on max when the boombox is plugged with DC transformer. Do you have an idea ?

Best regards

 

[caution]

Sounds like a bad pot if that's what you're fiddling with to create the sound cuts

 

[floyd]

I would check the ac\dc switch, it might have intermittent contact causing it to lose full power.

 

[stevenrob]

I have changed tha AC/DC switch but no result. I would like to change the rectifier.

 

[Superduper]

No, Floyds suggestion makes more sense. Rectifier is only an array of 4 diodes. It either works or doesnt. On the other hand, if there is a poor solder connection, at the rectifier, then that is possibility. Otherwise, switching the rectifier with these symptoms will be 98% a wasted effort.

Unfortunately I don't know of the existence of schematic but I have seen similar symptoms on the Wheely's when a zener diode goes out. But the problem is that without reference, it is often hard to know what zener spec to stuff in there.

Why don't you start by checking system voltage during operation, both at normal and max (cut out) conditions.

 

[stevenrob]

Hello,

I have verified the voltage of the tape deck engine : volume 0 (14.4v) volume 7 the voltage is not stable (12.. 13...14...12...) like the sound.
There is another part not shown on the first photo (T3B1K).