Need to replace output jack and plate

I once used uART & some latches to decode & hold the difference between "odd & even" midi program changes. Then used the output to switch a relay in a twin necked guitar to change between necks as it were in response to a midi pedal. Perhaps you could do something similar? Else get a Studiomaster MA-36 midi analyser & hack into it to use one piece of midi data (from across an LED?) to switch channels on your amp? Good Luck!

On the back of your 6505 there are two jacks that are labeled speaker outputs. For mono function, use either one of those outputs and run a SPEAKER cable from your amp to one of the input jacks of your 1960a cabinet. I assume it is a 4X12 cabinet. Either input will work. Make sure you match the ohm selector on your 6505 (right next to the output jack, 4/8/or 16 ohms) to the ohm rating on your 1960 cabinet. It is likely labeled on the plate that houses the input jacks. You should be good to go. NOTE: Never turn your amp on unless it is hooked up to a speaker cabinet and never use instrument cable to hook your amp to your speaker cabinet. Bad for a nice tube amp like yours.
Rock on and hope it helps.

If the truss rod has broken loose, it is not user serviceable. This needs to go to a repir shop. The fretboard has to come off to fix this. The repair may be more than the value of the guitar.

Might want to rethink that....to raise the action is to have the strings higher off the fretboard....if you shim the neck in relation to the body, you'll actually lower the action. To raise the action you need to raise the height of your bridge/saddles. If you want to lower the action and the bridge/saddles are as low as they can go you could remove the neck and insert some card - might have to do some trial and error but to my mind...to shim enough to significantly lower the action, would take a thick shim and you might not get a good tight fit between neck and body. You might actually need a truss rod adjustment - not an amateur adjustment.

fret buzz can usually be cured by adjusting the tension rod, unless the neck is permanently warped from excessive heat/humidity (from, say, being left in a car on a summer day).


hold the headstock up to your face, and look down the neck. you should see that the neck is uneven around the frets that buzz. if the neck appears straight when viewed from the headstock, down toward the body, then the strings are just too low, and the bridge should be raised. if you see unevenness in the neck, however, when viewed this way, you should attempt to use the tension rod to straighten the neck.

the tension rod can be adjusted with the hex bolt that pokes out at the base of the headstock, right from under the top of the fretboard. use an allen key to gently turn the tension rod either way until the neck begins to straighten out. if the tension rod cannot straighten the neck, then the neck is warped from heat/humidity.

That high a voltage MIGHT indicate the output tubes are NOT loading the supply enough. You don't mention the voltages andthe tubes used in the unit. I have a schematic for a AH100 but I don't know if it is close to your unit. That schematic shows four output tubes.
Remember if you put matched tubesas pairs, the pairs need to be on opposite sides of the output transformer.

It is NOT clear what configuration you have set up and what you consider the MONO output is, whether it is the power amp MONO side output or the line level MONO 1/4 inch jack on the top of the unit (this jack is NOT speaker output). If you can run normal stereo speakers using both sides of the power amp in the AB mode, the problems you are having is pilot error.

REMEMBER the main out 1/4 inch jacks are BALANCED TRS jacks... DO NOT put mono plugs into these.

A WARNING: If you use Speakon to 1/4 inch speaker cables, remember that the BARREL of side A is HOT, not the tip!!! You can fry the amp if you inadvertently ground that barrel someplace. (Side B has the barrel grounded) This information is NOT readily available in the manual and results in many a blown amp. They do this to implement the "Bridged" mode easily.

I have schematics and can unravel most any problem you are having.

Raise the saddles on the FR to help take away the fret buzz. Check the neck for curve. If the neck has a VERY slight bow on the fretboard side the strings will be able to vibrate better without buzz. Also might want to step up to a heavier gauge string set if you play in lower tunings.

The way you troubleshoot this is to divide and conquer. Run KNOWN clean signal into the "Power AMP IN" jack (note that it is a balanced TRS type input).

Verify the power amp downstream is clean. If not, then confine testing to power amp portion.

I would also check that the voltage across R66 is near correct IFpower amp portion is at fault.

I AM suspicious that the voltages on the scjhematic are AC peak to peak values rather than DC...

I think things in ovals are AC and rectangles are DC.

Ensoniq zr-76 no output signal on the main and aux, but i have output on headphone jack?