Philips 42PFP5532D 'mushy' sound

[kenji]

Hi guys, I got given a Philips 42PFP5532D/05 and trying to save it from the skip!
Reported fault was 'no sound', but when I got to powering it up today the picture was great and, in fact, sounds works, but it's very muddy/mushy especially at lower volumes.
I've tried messing with the sound menu equaliser settings, changing sound menu options, ie normal, cimena, personal, etc, but to nothing changes this sort of distorted 'muddy' sound from the speakers.
If anything, it's a bit less mushy when turned up to higher volume. It sounds a little like blown speakers, but I couldn't say this is the root cause.
Have had a look inside and seen two caps on the power board looking 'high-domed' and a bit weepy - one 3300uf and one 100uf - but I wouldn't think the power board would affect the sound?
Any suggestions gratefully received.
Ken.

[tom66]

Re: Philips 42PFP5532D 'mushy' sound

Low voltage to sound amplifier would cause poor sound quality. Bad caps could cause low supply voltage.

[kenji]

Re: Philips 42PFP5532D 'mushy' sound

Thanks Tom...I was wondering, is there any test voltage on the PS output I could check? Unfortunately my DVM doesn't measure up 3300uF....20uF is its max!, so couldn't check the two bad-looking caps, but they don't look happy.

[johnboy1313]

Re: Philips 42PFP5532D 'mushy' sound

I wouldn't even bother testing, I would change those two caps at the least. Most folks would change all of the caps on the PSU.

[tom66]

Re: Philips 42PFP5532D 'mushy' sound

I believe (might be wrong) this main board uses +12V and -12V for audio, which is rare these days. Check that both rails are stable. It's possible that the plasma version of this set does it differently, but I know the LCD version does this.

[kenji]

Re: Philips 42PFP5532D 'mushy' sound

Thanks guys. I will change the two caps on the power board.

Tom, you're right about the +12V / -12V on this one.....shown on the attached diagram. PS connector 1C01 carries the two voltages at pins 1 & 2. I'll check these also for stability before and after caps change.

[kenji]

Re: Philips 42PFP5532D 'mushy' sound

UPDATE: Checked those two lines +12V & -12V (for the audio) off the PS board connector 1C01 (to the SSB). They are measuring +17.05V / -17.05V !!

So, PSU is putting over-voltage into the audio side on the SSB. Supposedly this is due to the bad caps I can see.....I'm hoping anyway. I'll swap these today and hope it restores the voltages to the +/- 12V.

Could this be the reason for the poor sound? I'm guessing it's not helping!

I'm hoping that the over-voltage hasn't caused any faults down line with the audio circuits.

[freakaftr8]

Re: Philips 42PFP5532D 'mushy' sound

Not to sure about that but I have had the preamp channel ICs go bad in Philips plasmas. I repaired a few but not cost effective.
Is the output IC getting extremely hot?

[tom66]

Re: Philips 42PFP5532D 'mushy' sound

That could certainly cause harm - you would need to check datasheets of the chips connected to see if they are at risk of damage. Also, check stability while playing program audio, see when sound is "mushy" if supply voltages drop.

[kenji]

Re: Philips 42PFP5532D 'mushy' sound

FURTHER UPDATE:
Well, I feel a bit of a fool.....in not seeing the fix for this mushy sound earlier!

After checking Vsnd voltages off power supply board for the audio....thinking they should be +/-12V.....replacing the 'pregnant' caps on board....re-checking Vsnd...still +/-17V.....finding out, after much research, that Vsnd SHOULD be 17V....I finally (whilst the lower back speaker cover panel was off and the TV on) thought, 'I know what that is....it's just a blown speaker'!!

And, sure enough, substituting 'bad' side speaker leads to good-sounding speaker proved, in all that time, it was just one side blown speaker!! Something I should have done right at the start! Arghhh!

So, currently running tv on mono, on one speaker, balance cranked over to good speaker side, and tv sounds fine. Found a good pair of s/h speakers (plus tweeters) on fleabay for this model for £6 and ordered them.