Trouble Shooting 50s Dearmond Guitar Mike

[sys]

Hi all -

I am getting a very strange and strong distortion/buzzing specifically on and around the second and third octave A (Strongest when hitting A, but also present when hitting half step below/above) on a an old Levin with a 1952 Dearmond Guitar Mike. The noise does not appear on other notes, not even the lowest and highest octave As, but it appears on those notes everywhere on the fretboard.

The buzzing is not a million miles away from the sort of farting out that you get from a dying speaker/. I tried two different amps, with two different speakers, and same issue occurs on the same note. Tried 3 different cables also. My other guitars are fine. Which points me to the guitar.

The guitar does not show any sign of this noise when unplugged, and it sounds very much like an electronic issue. Which makes me assume it's resonating with a cold solder joint somewhere - either inside the pickup or throughout the electronics - but that's just conjecture at this point.

The noise is also always present when turning the volume knob down, but is not present when picking the note very very lightly (at any Position of the volume knob).

I got the guitar a few weeks ago and had no such issue for the first few days. Started hearing it in the middle of a gig on Saturday, though at the time I assumed it was the backline amp. Plugged the guitar in at home yesterday and there it was.

The guitar came to me with the pickup mounted on the classic monkey stick, with the wiring inside the body, through single volume pot, and out through a jack at the end pin jack. I do not currently have the tools or the know how to take the electronics apart and redo the solder joints/clean everything, which would otherwise be my next step.

Anyone ever experience something similar?

I apologize for the plethora of information - but it's the only way I know how to troubleshoot.

[sgosnell]

It's possible that it could be a faulty solder joint anywhere in the link, and there are several. That's where I would start investigating, because it's the easiest to check. There are other possibilities, and I couldn't say anything definitive from a distance.

[omphalopsychos]

I’ve replaced the lead on several of those pickups because the cables tend to deteriorate over time.

If you are not confident about your ability to do the work I’d take the pickup to a tech. If you are comfortable though it’s not a very hard job.

You can start by removing the cover and clipping an ohm meter to the end of the lead and ground. Now wiggle the lead around on the pickup and see if the circuit shorts. It could be that your lead is sympathetically vibrating with certain notes and this is causing it to touch the ground. A simple solution is to put a piece of tape around the lead so it doesn’t short. If that’s not the issue you can try simply reheating the joint and adding a bit more solder. Sometimes the joint that’s really struggling is actually the connection between the braided shield and the metal casing. This is because that joint is the one getting 100% of the tension whenever the cable gets tugged on.

you may find that while you’re working with the cable it will start crumbling. If that’s the case, you’ll likely want to replace it.


The worst case finding is that there’s actual damage to the coil. Then I’d definitely send it to a tech. There’s a guy on the east coast who is good at working on these but he takes a while to turn them around.

The hardest dearmond to work on is an 1100 because the cover is actually riveted onto the back. I don’t have the tools to remove and re-rivet.

[sys]

Very very useful information - thank you. I will keep it in my back pocket.

I am currently just after a move and therefore don't even have a soldering iron handy - all still packed.

But for what it's worth after calling 3 local techs I trust, one finally found that by applying a bit of pressure on one particular spot by the b string slot, the noise stopped. so he dropped a touch of super glue in there and, at least temporarily, it fixed it. If nothing else that stuff is easily removable if the problem shows up again and I need a better fix. Something was vibrating in there.

[omphalopsychos]

Interesting. I guess the black plastic strip must make contact with the lead somehow. Well as long as it works you're good.

I remembered the guy now. TOM BRANTLEY REWINDS He takes a couple months to do the work but if you ever need the pickup rewound, he's the guy recommended to me by the cognoscenti.

[KirkP]

… by applying a bit of pressure on one particular spot by the b string slot, the noise stopped. so he dropped a touch of super glue in there and, at least temporarily, it fixed it. If nothing else that stuff is easily removable if the problem shows up again and I need a better fix. Something was vibrating in there.

Are you talking about a nut slot or the saddle? Was the super glue used to reshape the slot?

[sgosnell]

I think he's talking about the pickup.

[omphalopsychos]

I think he's talking about the pickup.

Yeah I'm 99% sure he was talking about cutout in the pickup casing. Obviously the bridge saddle has nothing to do with the magnetic circuit.

[KirkP]

Yeah I'm 99% sure he was talking about cutout in the pickup casing. Obviously the bridge saddle has nothing to do with the magnetic circuit.

Makes sense now that I see the photo. Based on the description I’d guess something loose made the pickup slightly microphonic with mechanical resonance around a specific note. I think an intermittent electrical connection would affect a much wider range of notes. I hope the glue does the trick.