Sony telephone IT-B9 (15-yr old circuit board w/ Rubycon YK caps)

[windser]

I have a 15-year old corded Sony telephone model IT-B9. This phone started exhibiting some flakiness. For one thing, it developed a relatively loud background white noise. The other thing, when I punched in a phone number on the keypad, it would not consistently complete the call.

Anyway, I decided to open it up to see if there was an obvious problem.

There are 17 radial electrolytic capacitors on the circuit board (all Rubycon YK). However, none show any obvious signs of leaking or bulging.

1 x 0.22uF 50V (C91)
4 x 2.2uF 50V (C94,C95,C97,C98)
1 x 3.3uF 50V (C82)
1 x 10uF 50V (C2)
2 x 22uF 25V (C19,C21)
2 x 47uF 10V (C93,C100)
1 x 100uF 16V (C55)
2 x 220uF 10V (C13,C92)
3 x 470uF 6.3V (C58,C101,C114)

The underside of the circuit board has quite a few tiny surface mount capacitors.

It has 4 slider-type switches plus the off-hook switch.

The phone runs off the 12v supplied by the phone company so there is no PSU.

Should I suspect the capacitors, even though they are Rubycon?

Thanks

[stj]

Re: Sony telephone IT-B9 (15-yr old circuit board w/ Rubycon YK caps)

all caps fail eventually, and small ones dont bulge or leak.

having said that, look at the track-side foto - connector CN1.
see those tiny rings in the image? that's cracked soldering.

you need to resolder any joints you see like that.

[windser]

Re: Sony telephone IT-B9 (15-yr old circuit board w/ Rubycon YK caps)

Good catch! So I resoldered those 12 points on CN1. Then scanned the rest of the board with a magnifying glass for other similar faulty solder connections but no others obvious to me anyway. Reassembled the phone and it tests good! The background white noise is gone. And a few test dials on the keypad worked as they should.
Thanks.