How can I make the tremolo on my Ampeg Jet II footswitchable?

[robertbp]

I have an Ampeg J-12T (reissue, not vintage) that I like a lot, except for the lack of a footswitch to control the tremolo function (which sounds great). Basically it has speed and intensity controls, if you don't want tremolo, you turn the intensity down...there's no switch at all. Pretty useless for a live situation, unless you want the same amount of tremolo for the whole song...I would be happy with a regular on/off footswitch like fenders, or I was thinking I could drill a hole in the chassis and put in a female 1/4 jack, I guess it would have to be a stereo jack, right? Then I would connect the two terminals of the intensity pot to the jack and use an expression pedal in place of that pot? Would this work?

I'm really not an expert on this stuff, but I've tinkered around a bit...the schematic says the pot is 1M audio single...so I guess that means I would need a volume/expression pedal with that same resistance, right?



Any help is appreciated...

[robertbp]

Here's the schematic:

http://www.schematicheaven.com/ampeg...12t_jet_ri.pdf

[Enzo]

Insert a footswitch between R6 and ground. Open kills the trem. Look at most any Fender amp trem circuit.

[robertbp]

thanks, I will give it a shot...

[upstairsdave]

Jet II footswitch mod

Hi Robt.
How did you make out with the addition of the tremolo foot switch. Did you check out the three wire connection that is the feed for the heater of the one tube. The connector is white and has a rectangle terminal going onto a pin type connector on the board. It will cause a whole lot of noise if loose. If I keep my Jet I'm going to solder the wires to the connector. Who needs the excess resistance in the circuit. The beauty of point to point wiring.
Dave

[upstairsdave]

Has anyone figured out what creates the buzzing sound when you hit a chord or hit a g note. It sound sort of metallic but more electric.

[aaroniouscharge]

I had that same rattling sound. I fixed the problem by changing out my crappy Sovtek preamp tubes. The sovteks that I used had loose metal components inside the tube.

[upstairsdave]

How can I make the tremolo on my Ampeg Jet II footswitchable?

Howdy,
I did some research on line and a site called guitar nuts mentioned the screen resistors as the problem. After looking at a schematic, the two power tubes have a screen circuit that have a resistor controlling current flow through them.
The one resistor had way too much resistance reducing the current flow through the tube. The tube didn't get hot like the other power tube. This was the power tube on the extreme left. I changed the two resistors, R22 and R23 to the correct 100 ohm value and bumped the wattage up to one watt. I also moved the resistor up about 1/4" off the board and bent it away from the tube so it wouldn't get so hot and break down again. The amp sounds great now.
I also removed the three wires from the connector J25 which is in front the other left power tube and hard wired it to the terminals to prevent the loose connection it had. The connector is a square shaped connector pushed onto a round terminal. It is loose and vibrates and causes a crackling sound as well. It's an intermittent open circuit to the tube header. I also put rubber insulators between the chassis stands and the tube circuit board to further cut down on vibration to the board from the rest of the amp. And one last thing i did was add rubber feet to the bottom of the reverb tank to take up the excess room the stock extra long screws and help insulate the tank from the chassis. These are all minor mods/repairs that will make the amp come alive. I tried the tube swap and speaker swap thing and no difference.
Take care.
Dave