NSM Juke - distorted audio

[strobey]

I've got an ESV with distorted audio on both channels. I was sure it must be the the power amp so I've just hooked the line-out up to an external amp but it's the same.

Are there any usual suspects?

On the central board I can see VR1-5 and D1 which are TO style devices on a heat sink but the naming doesn't sound like a preamp stage.

I can also see a TDA4390 socketed chip. Is that an integrated preamp?

Thanks for any pointers!

Tim

 

[ronnie63]

I had similar but only one channel, I thought amp but no it was the central board, guessing the pre amp on that

 

[Paul]

@Pick Holder

 

[strobey]

Cheers. I've dug out a donor... fingers crossed!

 

[strobey]

Swapped central board.

Exactly the bloody same!!

Line-out and amp o/p both distorted, so I assume this rules out the PA board.

So unless they're both kaput, what else can it be?

 

[ronnie63]

Bummer! There is 2 boards in the top of the changer , if not the amp or central must be one of them right side I think handles the audio from memory? Or could be the optical unit maybe?

 

[strobey]

Thankfully I think I've ruled that out... (?)

Just tried the line-in (background option) and it's still distorted on the amp and the line-out.

Need to find a schematic but it sounds like both boards have the same issue

 

[ronnie63]

Ah ok must be the central like you said, not sure what might have gone faulty I just swapped my board and not looked at the faulty one

 

[Pick Holder]

I can not see both the boards having the same issue.

Totally disconnect the CD changer - should be two ribbon cables on the back and an audio cable - then try the background music input - if it is clear from distortion it is in the mech.

Then try the line out into another amp - see if it is distorted.

You can download the manuals easily.

MAKE SURE YOU HAVE THE AMPLIFIER SWITCHED TO STEREO. If you have it on mono you will get any fault on both channels.

Also I would look on a scope at your DC power rails. The capacitors do go on these.

Burn a CDR with a test tone. Put the supply directly out of the CD player into a scope and check for clipping.

Next up trace it thru the audio stage (keeping in mind that the switch should be on stereo).

Distorted sound on this technology (CDM3 or CDM4) usually points to a bad encoder inside the mechanism itself.

IMPORTANT - Make sure you have not lost one of the power lines. From memory one is a + and - rail that if you loose one it sounds awful.......

 

[Pick Holder]

The usual suspect is this:

x2 Nsm CD Jukebox DECODER / PICK UP UNIT, Fire CD Fire Heritage Firebird, Galaxy | eBay

X2 Nsm CD Decoder & Pick Up Driver Units. #1 - when tested the cdm3 laser swings oveer to one side and the laser head is spinning backwards constantly, even when not playing it is still spinning backwards.

www.ebay.co.uk

The board on the left hand side - I do have a spare one from a sound leisure but it is identical. Just needs to be installed 'as per the old one'.

Are you using the external amplifier with the same speakers you have on your juke ? Could you have blown speakers ?

 

[strobey]

Great stuff, thanks. I'll go through and try all of this.

The speakers are fine, it's the bass which is completely missing and there's clipping noise when low bass is present. Top and mid seems ok.

Thanks again, will report back

 

[Pick Holder]

Great stuff, thanks. I'll go through and try all of this.

The speakers are fine, it's the bass which is completely missing and there's clipping noise when low bass is present. Top and mid seems ok.

Thanks again, will report back

Sounds like it is the encoder board to me. Or a bad audio cable.