Non grounded output jacks

[Garydean]

I just repaired the output jacks on a Hartke 3500. There 2 enclosed plastic, jacks for the 8ohm output on a small circuit board, mounted to the back of the amp case. Both were not making contact therefor no signal to the speaker. I disassembled the plugs and I was able to repair one of the 2, 1/4" jacks. I considered replacing the jacks with nice solid Switchcraft jacks but they would be grounded to the chassis, and I think this is a no-no. There are only 2 leads coming from the OT section, hot(white) and yellow(ground). Is there a trick to wiring shorting style, Switchcraft jacks that ground to the chassis. Can I not use those at all. Or what is the correct wiring for 2 non-shorting 1/4" output jacks? Both jacks are labeled 8Ohm on the outside of the chassis.

thanks!!

Gary

[Amp Kat]

Follow the wire where the jack ground on the pcb board went to and ohm it out to ground. If you get continuity then it is going to chassis ground anyway and your fine . If it's not they do make insulator spacers that the jacks fit in to keep them from touching the chassis but I would think they are going there anyway but not 100 % sure.

[drewl]

Or use a switching jack and wire the neg. signal to the jack connection that makes contact with sleeve, but is not connected to the gnd part of the jack.

[Enzo]

Y'know, a lot of folks like to gripe about plastic jacks, but really they work well and unless you abuse them, they don't break. Why not just replace the jack with what was originally in there? it will fit the pc board, drop right in place, and will work another 10-20 years.

If you want to wire shorting jacks in there, just don't wire the shorting contact. it is a solid state amp, so there is absolutely zero reason to ever ground the speaker outs.

The output is referenced to ground and one of the wires will be grounded - your ohm meter will tell you which. Not grounding to the panel itself likely helps avoid return current problems.

Are these jacks the square ones with the one bevelled corner? Are they not Switchcraft already?

[Garydean]

They are square with one beveled corner. I cannot identify them. I considered just replacing them but the board is cracked. I'm sure I can just omit the board and use a plastic jack that uses solder style lugs. I just don't know weather to wire them in series or parallel. Looking at the PCB it looks like it's parallel.

[Enzo]

Oh they are in parallel, there would be no point to making them in series. The square ones with bevelled corner might not be Switchcraft, but the Switchcraft ones ought to drop right in.

SImple jack is type 111 for metal bushing and N111 for plastic bushing. Ones with cutout contacts or TRS types follow the same number system as the type 11 series, as in 112, 114, etc.

I only stock the pc board mount versions, I have no trouble soldering wires to the pc tabs when i need to. So I don't double stock. of course if you are ordering, then get whatever you need.

If they are Switchcraft, the Switchcraft name will be embossed on the top of the shoulder, running around the bushing. They probably are asian knockoffs.

[Garydean]

Great info Enzo. Thanks once again for the education!!

On another note, you may remember a few threads back where I had a Mesa Boogie with a questionable OT issue. I removed the OT this morning, took it apart and found the blue and red wires were sliced and shorting to the case, That explained why the signal was intermittent. I ordered up a new OT as the removal of the old one left me with a few short wires. I could not cut the ties under the board without removing the board. I've decided to change the electrolytics while everything is open (original 1990). Any tips on working on top mounted Mesa boards? Seems like I can work from the top of the board with double plated pads.

Thanks again,

Gary