Ross Big Mouth Bass Amp

[yodaeatsfishstx]

Hello,

I'm posting this here because I haven't been able to find much online, so this is a bit of a shot in the dark. A buddy of mine has a Ross Big Mouth bass amp. One day after leaving it in a shared rehearsal space for a long time, he found that the speaker jack had fallen in, or so he thought. Upon opening up the amp it seems that the non-metal parts of the jack are simply gone, leaving the metal lugs. See the link to the pictures below. Strangest thing I've seen in a while. He suspects someone may have stolen the jack out of it, but who knows.

He's asked me to replace the jack, which is normally trivially simple, except there is a red and black section of cut wires on the remaining pieces of the old jack, as shown in the pictures. I'm assuming the black wire is just a shared ground point, I'm poking around but I don't see any obvious opposite end where it may have been cut. What I'm more worried about is the remaining bit of red wire on the tip lug of the old jack. Not sure where that could have gone. I know it's just a jack replacement, but at this point, I'm hesitant to do anything and risk missing two critical connections.

The pics can be found here: https://ibb.co/album/wZnM7b

If anyone knows anything about this amp or has a schematic, or advice, it'd be greatly appreciated. Thanks all.

[Kevina]

Attached is an old Kustom amplifier schematic, most probably designed by Bud, showing the input connections.

[g1]

Is it a head or a combo?
You can't 'steal' a jack like that. They don't even really disassemble. So to leave those bits in there it has to have been broken.
Likely someone went inside to remove the broken bits and solder some wires to connect to a speaker. Then they just snipped off the wires to disconnect. If it's a combo, you might find more snipped wires at the speaker end.

[yodaeatsfishstx]

Is it a head or a combo?

It's a head. Someone connecting directly to a speaker that way isn't a bad theory though.

I may try just replacing the jack, using the two connections that are there now, and trying it out. Maybe I'm overthinking this.

[g1]

I may try just replacing the jack, using the two connections that are there now, and trying it out. Maybe I'm overthinking this.

I think you should be good doing that. The schematic shows only those connections.

[J M Fahey]

Nobody "stole" anything, that amp got hit, hard, on thespeaker out jack, typically by falling on its back with a speaker cable plugged in, and the smack *disintegrated* the output jack, which is made out of shaped bits of sheet metal assembled together by being riveted and insulated from each other using thin phenolic paper disks.
Thin and brittle, a sharp knock crumbles them to pieces, leaving behind the metal bits.



This one is different, the stereo version, I show it only because it shows it from the back, the threaded tube is visible and its internal lip riveted out to hold everything together:



SO: that speaker jack has basically 2 connections:

* HOT which is probably the white cable still attached to the remaining metal contact which you will recognize in these pictures
* ground, which *may* have a dedicated (black?) wire or simply metallic jack was grounded by screwing it to chassis with its own nut (now missing).

So you mount a new metallic jack in the hole and resolder necessary wires in the proper way.

*Probably* White is the HOT wire. bringing speaker signal from the amp board to jack, and cut Red and Black *were* connected to an external speaker or even an unmounted jack dangling outside.

I bet if you mount a new metallic jack ,solder white wire only to hot terminal and let chassis do the grounding thing, a speaker plugged into that jack will work properly.

And yes, the amp looks "very Kustom" indeed.

[nosaj]

I had a hartke brought to me. The plastic on the jacks just crumbled. replaced them no problem. Was the oddest thing I'd seen in a while.

nosaj