Mosrite Mark I Ground Issue

[Texasbob]

I just bought a Mark I USA Standard from Ed Roman and it's a thing of beauty, however I've been having a couple problems:

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This is the major one!

I noticed a popping sound, like a static crack, when I first got the guitar. When I tapped on the pick guard next to the switch you could hear it. This was not a hum or buzz. I removed the pick guard and thought I traced the problem to the ground leads that connect the pickups to the switch and re-soldered them. The popping would disappear when I touched the casing of the volume pot, which to me indicated a ground issue.

The popping no longer happens when I tap on the pick guard, but still happens, occasionally when I'm strumming. This is not an amp or cord issue, I've checked all that.

At first I thought it was the switch, but now I'm wondering if it could possibly be the capacitor or the ground that connects to the Vibramute or maybe a weak ground connection from the switch to the volume and tone pots.

Help!

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This is a string issue

I've been setting the Mark I up with heavy 12-54 D'Addarrio strings, which I've used for years on my other guitars. I've had two sets on where the high E string has failed at the ball end. The last one actually didn't break, but unwound at the ball! You got it right, it simply kept slipping and came unwound where it raps around the ball. I've never had this happen before and I've been playing for over 40 years.

Anyone ever run into this problem before?

Thanx

I've had this happen on my doubleneck. With the heavy guage string your pulling the arm down lower. Therefore, the string hole on the tailpiece is acting like a guillatine when the tremelo is used. Shim the spring or get a thicker guage, heavier tension spring to bring the arm up and in doing so put the string at the bottom of the string hole.

[surfdude2000]

Okay everybody... This popping thing just won't seem to go away and it's driving me nuts! I'm at the point where I'm ready to hard wire the pickups to the output jack to make sure it's not coming from them and check every pot, one at a time. I don't trust any of the Fillmore electronics at this point.

I swapped out the switch and that didn't fix it, but while I had it apart, I discovered that the tone pot would make intermittent contact because it's lead was directly bridged (no wire) to the volume pot lead. It looked solid, but the tone control completely stopped working on me. The stuff looks American, but now I just don't know.

Anyone have an original wiring diagram?

joe

[dubtrub]

Anyone have an original wiring diagram?

viewtopic.php?f=20&t=85

[Dennisthe Menace]

Okay everybody... This popping thing just won't seem to go away and it's driving me nuts! I'm at the point where I'm ready to hard wire the pickups to the output jack to make sure it's not coming from them and check every pot, one at a time. I don't trust any of the Fillmore electronics at this point.

I swapped out the switch and that didn't fix it, but while I had it apart, I discovered that the tone pot would make intermittent contact because it's lead was directly bridged (no wire) to the volume pot lead. It looked solid, but the tone control completely stopped working on me. The stuff looks American, but now I just don't know.

Anyone have an original wiring diagram?

joe

Joe, did you swap out the switch with another 'box type' switch, or did you replace it with a Switchcraft? I don't own any Japanese Models, but I have heard from time to time, that the switches can become intermittent......On the other hand, I once had a Celebrity that the switch (Switchcraft) had so much play in it (the actual contacts were loose), that when I had both P'ups on, the weight (believe it or not!) of the switch lever would sometimes lean towards the Bridge P'up, creating a 'light' popping noise, which actually was the bridge P'up turning itself on against my will. LOL! Not sure if that's what you are experiencing or not.....
As for the tone control, although everything looks OK, you might want to 'tug' on the wire assembly and check for a dry solder connection. I think I saw someone else had mentioned this on another thread.....Definitely check the Wiring Diagram that Danny just posted

[surfdude2000]

Problem solved! (This is almost embarrassing)

I swapped out the switch, the pots, re-soldered connections, and was still getting the occasional popping while playing. Even when disassembled, I could get a popping by tapping on the pickguard, next to the switch, which is why I always suspected the switch.

When I removed the switch from the pickguard (still wired) and tapped on the pickguard where the switch was mounted, there was no popping while I held the pickguard 5 or 6 inches away from the switch, BUT if I moved it closer to the switch, I would. In fact, if I just rubbed my finger on the pickguard, I could hear static crackle!

Note: The pickguard was not fully shielded. This one had shielding under the output jack and volume and tone pots, but nothing under the switch.

I got some more copper foil and lined the rest of the pickguard, over to where the switch is and the static crackle an popping has gone away!!! Someone might explain to me why this happens.

Note: You really couldn't hear any of this annoying popping if you were running through a Tube Screamer, but straight into a clean amp, it was very noticeable.

I'm curious if anyone else has shielded the entire cavity or done any other wiring tweaks to help keep things clean.

Thanx to everyone for their feedback!!!

-joe-

[dubtrub]

I'd be interested in seeing a photo of the wiring of your pick guard. The original Mosrite's did not have any grounding/shielding foil and did not have these issues.

Here's a peek under the hood of an original '60s model.

[Dennisthe Menace]

It must be a different wiring configuration for the export??

[MWaldorf]

I don't have any pictures, but if I remember correctly, my Excellent had foil under the pickguard from the switch to the pots and jack.

Glad to hear you've got it handled,
Mel

[dubtrub]

Here's a photo from Ed Romans web site. Apparently they use a different wiring and grounding layout than an original.

[GattonFan]

I shield all cavities - pickups and control cavities, but will say that if the any of the electronics come into contact with the shielding, it will produce a pop .... I do it primarily just to quiet everything down ...