Hohner Jack noisy - shielding / grounding question

[pn_day]

Dear all,

I recently purchased a rather nice Hohner Jack from @eddbass on this very forum (thanks!)

 

Unfortunately, because I practice in a rather noisy electrical environment (solar PV inverters), I'm noticing some noise on the Jack in passive mode, through either/both pickups, which only goes away on touching the metal jack (or otherwise providing a good path to ground).

 

I'm assuming that this means that the grounding is a bit suspect - do others agree?

 

Did Hohner use the same style of grounding as Fender and others (i.e. ground wire touching the bridge, soldered to the sleeve of the jack socket), or should I be looking elsewhere to find the source of the problem?

 

I'm probably going to end up shielding the control cavity and pickup cavities anyway (plus linking all shielding together and then to ground), but wanted to find the source of this noise first.

 

Thanks for any help and tips,

Phil

Edited July 12, 2023 by pn_day

[philw]

Hi Phil,

 

Having spent some time looking inside a Honer Jack recently (https://www.basschat.co.uk/topic/481089-honer-jack-electronic-repair/) I suspect the source of your noise problem might be the decidedly messy original wiring and the lack of any control cavity shielding - it really is a huge mess of over-long wires in there.

 

To answer your specific question about bridge grounding, in "my" Jack there is what appears to be an earth wire heading off to the bridge, so I don't think un-earthed strings are your problem (although having just checked the continuity with a multimeter, there's a about 300Ω resistance between the bridge and earth, and that's a bit of a surprise - not sure if it's supposed to be like that). Anybody?

 

And while I'm on, back to my recent Honer Jack post, if you were able to take a couple of pics inside your Jack to show me where the red wire from the battery goes, that would be very much appreciated.

 

Cheers

Phil

 

 

[pn_day]

Thanks Phil (W). Good to know there is an earth connection to the bridge. I'll open it up in the next couple of weeks and give the wiring some TLC - I'm not a fan of old graphite paint for shielding!

 

I've added some photos to your other thread. 

 

Phil (D)

[Suburban Man]

Hi, I used to have a Hohner Jack and as I recall the 'earth' wire running to the bridge didn't have any specific connection, but just sat on the body of the bass, with the connection being achieved by having the bridge screwed down on top of it.  Over time its the sort of arrangement that is probably going to cause a high(er) resistance than the nice solid connection that should stop any humming.  Might be worth looking to see if there is corrosion on the end of that wire, or if it isn't making direct contact any more?

[rmorris]

The 300 Ohm measurement is too high. So check for a good connection pressure and any corrosion etc. Remove any tarnishing etc. But also check that when using the meter the tips of the probes are making good solid contact and breaking through any surface finish or oxidisation. 

Bizarrely some cheap probes don't have a great surface to the tips themselves so check that and touch them to themselves to check how near to Zero Ohm you get.

As for the OP question. Your grounding is fine. You are NOT "earthing" the bass when you touch strings, bridge etc. The bass is already earthed through the cable screen and amp. YOU are not "earthed" until you touch the bass. Ie it is the bass that is grounding you.

When you are not grounded your body / hands act as an antennae transmitting noise that is picked up by the bass.

When you touch the bass your body is held at the same potential as the bass so no noise is transmitted.

You can illustrate this by not touching the bass but by touching some other piece of earthed conductor eg chassis of grounded equipment.

Shielding / Screening will help reduce the amount of noise picked up on this situation.

 

 

 

 

[pn_day]

Updating this thread for posterity, and in case of future searches...

 

I finally got around to the shielding job - and am much happier. 

Copper tape (with conductive adhesive) in both pickup cavities and the control cavity (including the lid, with plenty of overlap to ensure good connection) plus ground wire linking them all together have resulted in a much quieter bass. It is now very usable, even with 1 pickup soloed. 

 

I couldn't get the active pre to work, so ended up getting rid of it, and throwing in a loom from KiOgon that not only had a working tone control, but also push/pull for series mode. I have the same Hohner active 2 band preamp in my black fretless Hohner (with humbuckers) and did not really enjoy the sound much, so was happy to just ditch it. 

 

Oh my. The bass sounds good now (the Hohner Jack).

 

Incidentally, I much prefer the sound of the (EMG Select?) single coil (jazz style) pickups in this later Hohner Jack 'Professional' to the sound of the EMG Select humbuckers in the Hohner B2A. 

 

Phil