Help! JP6 piezo malfunction

[Evoker]

Hello everybody!

I have recently faced a very strange issue with the JP6 piezo system -

as I switch to piezo it's humming a lot, sound can also disappear, and then get back..

Seemed to me like a bad wiring somewhere..

I started to check everything - all the wiring, piezo preamp, etc was OK I supposed - no issues were found - but then I figured out that the sound appears and dissappears as I move the wire going from the piezo pcb to the bridge block (where a small PCB is).

After I took the bridge out of the guitar there was a small PCB screwed to the tremolo block where 6 piezo wires from the saddles were connected.

When I unscrewed the PCB and examined it it turned out that all the wiring there was OK - well, there were not many wires after all - nothing complicated..

The only thing is that when I began to screw the PCB to the tremolo block it seems like it shortens on something and the sound disappears..

It also is humming when the pcb is unscreweb from the block - but it's ok I suppose as the two screws that hold the PCB on the block are supposed to ground it as far as I understand..

That confused me a lot as now I'm lost... Don;t have any more ideas why the piezo isn't working. PCB is clear, no dents or cracks, all the traces are OK, all piezo pickups are soldered firmly as well as the wire that goes to the PCB with input jacks on it...

Magic maybe?

I need a helping hand on that Can order a new piezo bridge from MM, but it's more of an interest to me to figure out what's wrong with mine..

Seems like something obvious that I'm missing...

Maybe some of You have faced similar problem?

Thanks for Your advice!

Kind Regards,
Ilia.

 

[Spudmurphy]

When I rebuilt my JP6 I had to rebuild the PCB on the trem block - I bought 6 new saddles and resoldered the fly leads to the PCB. I had a few problems as the factory assembled PCB has very "low" soldered joints. I don't have a super fine soldering iron and found that my soldered joints were "higher". So I cut a piece of cardboard same size as the PCB and used that as in insulator. It works just fine.

When I have the inclination and time I'm going to take the trem block off and resolder the PCB around my mates workshop - he has all the right tools!!

 

[DrKev]

Hi Ilia, and welcome to the forum!

How old is your guitar? Assuming your guitar is still under warranty, bring it back to where you bought it.. If they can't do anything, you should contact Music Man customer service.

BTW, there is a forum rule - your guitar doesn't exist without pictures!

 

[Evoker]

Spudmurphy,

Thanks for Your reply -

indeed - the small PCB there has it's solder joints covered with lacquer or something for insulation - maybe I have a shorting somewhere there - thanks - will try to cover them up with more lacquer and we'll see.

Also - could you please tell me if the two screws that hold the PCB on the block has something to do with the hum? I mean - as I understand - they connect the ground on the PCB to the block - right? - but as I tighten them up - the guitar begin to crackle as if the bad contact occurs..
It there any difference of how tight these screws are, or this doesn't affect anything? Mine were a little bit loosened as I took the bridge out for the first time, not too much, but still.

But I'll definitely try to better insulate the PCB solder joints that might get into contact with the block. Tnx for the tip!

DRKev,

Thanks for Your welcome!
Guitar is 2008 - will order a new part only if I won't be able to repair this one - I like messing up with guitar electronics, it's much more interesting for me to repair it by myself then to make someone else do that for me Personal experience rules

As for the pics - no offence bro, but I really do not have time for this kindergarten stuff - need a piezo thingie to be repaired ASAP, looking for the advice here, that's all
But of course - If someone prefers to believe the guitar doesn't exist - he's welcome to %)

 

[DrKev]

Personal experience rules

Absolutely! I guess you probably already know that PCBs are easy to damage if our soldering skills are not up to scratch. Try not to over-heat them!

If someone prefers to believe the guitar doesn't exist - he's welcome to

Ha ha! Good luck fixing your imaginary guitar!

 

[beej]

Ilia-

Your best bet is to email or call the MM customer service dept. If there's an issue with your guitar, they can help you diagnose it.

What you're describing, intermittent grounding/shorting issues, are going to be extremely difficult for any of us to diagnose, without having the guitar in front of us. It's an unusual problem.

So please drop them a line.

 

[Spudmurphy]

Customer Services are by far your best route. I was intrigued to delve a bit deeper and unearthed this photo

You can see the holes in the middle of the PCB, that the screws pass through into the brass trem block.

I don't believe that this grounds the PCB but you are talking to someone who knows not too much about electronics. I also remember I had an intermittent fault but this was due to the wire from the PCB to the pre amp (remember I did have the guitar stripped down to it's last nut and bolt) Believe me when you getthe Piezo sorted out you will be VERY pleased with the results/

Let us know what CS says?

Spud