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malgo jack splat
MUFF WIGGLER Forum Index -> The Harvestman  
Author malgo jack splat
boramx
Hi-
since scott dips in here semi-often i thought i'd try to catch him (or someone else helpful) for some "tech support".

my malgorithm (several years old, i think i bought the first run from AH) recently developed a dodgy jack. the audio ouput now seems to short with a plug fully inserted. the signal shows up fine if a plug is left "sitting" in the jack (i.e. inserted until it first stops, but not pushed through until clicking).

obviously not ideal to have the cable not "clicked in place".

it has worked fine until recently. seems like i should replace the jack...yes? if so, is there a part number? this jack is soldered to the PCB. perhaps a brief tutorial? i understand that i need to unscrew all the surface components to seperate the PCB from the faceplate. i noticed the common ground wire on the audio jacks. seems like a *pretty* easy fix.

maybe a method to diagnose and repair the jack itself? the plastic casing makes the actual contact seem inaccessible.

while i'm at it.....

i'd love to make (or buy?) a breakout box in which the switching "bends" are operable via gate/trigger signals. the malgo is real go-to module for CV processing. i love it for this purpose and use it as a CV processor more than audio. some voltage trickery whith the switches would make it really fun when making wild sequences etc.
Nuuj
My HD has this problem with one of the jacks.
The problem is not the jack, but the PCB under the jack.
Early TipTop cables had an abrasive tip which scratched the PCB mask to the point where the tip of the cable makes contact with part of the circuit, which I assume is ground. I keep meaning to try and fix this with a bit of paint but I never get to it. I hear some early Cewjman have the same issue.
boramx
ok.

but to "paint" the pcb mask back to it's virginal "masking" state, i need to un-solder the jack, "paint", then re-solder it?
Kent
Maybe not. Take it out of the case and shine a flashlight in there.

You could roll ghetto-stylee (if what has been described is truly the cause) and just dab some rubber cement on the spot.
boramx
Kent- i'm not sure i follow you....drip model cement into the jack? Not sure how to do that with possibly gluing the contact for the plug tip - with a syringe maybe.

From what i can see, it doesn't appear that any circuit traces go under the jack, though peering down into it i see just the red pcb.

I'll xperiment a little more.
Nuuj
Another possibility might be to drill a hole underneath the jack, so that a cable tip would hit air instead of the pcb.
boramx
^that seems easy and reasonable, but why would having the tip contact the PCB be a problem? Is the PCB material itself shorting the signal?
Nuuj
The problem on my HD is that the area right bellow the tip of a cable has had the paint rubbed off and the tip of a cable now touches a part of the circuit, which I assume is ground. You need to look down the barrel of the jack with a flash light to see if this is the same problem you have or not. If it is just a large area of ground and their are no components or traces on either side of the PCB it should be possible to drill a hole in that area. This is essentially a design change that Cwejman adopted some while back.
boramx
since it's the "jack and pots" pcb there aren't many traces at all. all the traces just go right to the pin header that jumps the signals down to the other PCB with the ICs and such.

there is nothing at all under this jack but (from what i can tell) bare PCB. I wouldn't think the tip of the cable could be touching ground, because it just looks like that plasticky PCB material, not even one of those wide ground areas you see on many PCBs (at least as far as i can tell, i could be wrong).

obviously the contact on the jack still works, just not with the cable "locked", as it should.
Nuuj
If you have a multimeter you could check if the tip get's connected to ground when it's fully inserted or not by checking for continuity between the tip and sleeve at the other end of the cable when fully inserted.
boramx
Good idea. I'll do that as soon as i get a chance.
governor blacksnake
The Malgorithm's control PCB has no signals under that jack, so I guess the jack itself has gone bad. It is a kobiconn 16PJ138 (available from mouser), the fix is very easy. Or, you could just send the thing to me.

-Scott
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