Mitsubishi TV model CS35MX1 weird audio problem

[[email protected]]

I got this set in for a picture problem. I bypassed the PIP and
restored the pix but before doing this I noticed that the right
channel audio was out. I initially concentrated on the PIP and after
bypassing it and testing the set I noticed a humming sound from the
right channel. The humming slowly increases in amplitude and after
awhile it would occur in about one second bursts. The duty cycle, (for
want of a better term) of these bursts eventually speeds up and after
perhaps 30 more seconds short bursts of sound are then heard, (hum,
sound, hum, sound, etc), until the sound stays on permanently.
I found three caps in the audio circuit with somewhat high ESR and
replaced them. Two were 100uf 10V and the third was a 22uf 50V. This
however didn't seem to make much difference. There are two RCA outputs
on the back of the set and they are both good. Has anyone seen this
problem on one of these sets before? Thanks for any assistance. Lenny
Stein, Barlen Electronics.

 

[David Farber]

I got this set in for a picture problem. I bypassed the PIP and
restored the pix but before doing this I noticed that the right
channel audio was out. I initially concentrated on the PIP and after
bypassing it and testing the set I noticed a humming sound from the
right channel. The humming slowly increases in amplitude and after
awhile it would occur in about one second bursts. The duty cycle, (for
want of a better term) of these bursts eventually speeds up and after
perhaps 30 more seconds short bursts of sound are then heard, (hum,
sound, hum, sound, etc), until the sound stays on permanently.
I found three caps in the audio circuit with somewhat high ESR and
replaced them. Two were 100uf 10V and the third was a 22uf 50V. This
however didn't seem to make much difference. There are two RCA outputs
on the back of the set and they are both good. Has anyone seen this
problem on one of these sets before? Thanks for any assistance. Lenny
Stein, Barlen Electronics.

I know you mentioned the audio problem is in the right channel but maybe
this tip will let you think outside the box, no pun intended.

From an old Mitsubishi tip file:
Symptom: Int.distorted left audio.

Check for continuity of the grounding points on the heat sink of IC3A2
located on the main-pcb.

Good luck.

 

[Leonard Caillouet]

Nothing weird about this one at all. It is very typical in this set. Start
looking for more caps. You will find 1-2 dozen bad ones. Look in the 5 and
12 volt supplies, vertical circuit, power supply, etc.

Leonard

 

[[email protected]]

Thanks for the help guys. I'm going to have another look at this one.
Thought it might be easy. I guess not. Lenny.

 

[[email protected]]

Thanks for the help guys. I'm going to have another look at this one.
Thought it might be easy. I guess not. Lenny.

Grounding the input to the audio output chip eliminates the hum so I
have chased the problem to an area before the output circuit but with
the chassis up on end and very short wire lengths it gets very
difficult at this point. Does anyone by chance have a schematic for
this set? Thanks very much. Lenny.