When I turn the volume up past 3 it starts this

I suggest you try Ebay.Unfortunatle I see this kind of problem a lot where parts for not really that old products are unobtainable.

Please see my previous anwser re cleaning your bright switch and input jack.

1974 s=seventy 4= the year

Guitar Info This guitar is from the U.S. Vintage Series
made at the Corona Plant (Fender), USA
in the Year(s): Cannot be determined from serial number,
however you can consult this chart showing the
corelation between serial numbers and dates found on the neck
Fender MIA RI Serial Number vs. Neck Date


Fender: Corona Corona factory was opened in 1985, Corona California, with major guitar production starting in 1987. With the addition of a custom shop in 1987 the plant currently employs about 700 workers. Apart from general and Custom Shop Fender instruments and amplifiers, it also encompasses Guild acoustic & electric guitars.

Verify the footswitch with an ohmmeter. You should find that each of four pins should have continuity to pin 2 of the connector when the switch associated with the pin is pressed.

Note the pin numbers on the connector seem to have a weird layout. Here is a link to your amp schematic. The Footswitch interface is shown on page 3 of 12.

http://elektrotanya.com/fender_cyber-twin_sch.pdf/download.html

Use the ohmmeter to check each wire in the cable is good. SOme cables, unless the official one for the unit, may lack some wires.

The amp "reads" the footswitch state into a register which is then read serially. The inouts are pretty well protected from user mistakes. With the schematic you should be able to analyze the failure.

Realize that the number on the volume control is only relative... it means nothing regarding what the amp can produce. With a high level output guitar you can easily drive the amp into distortion at very low volume control level settings... what counts is the actual output sound volume and specifically the voltage output going to the speaker. Once the amp reaches saturation, any further input just pushes it into distortion or "flat topping".
An oscilloscope on the output will quickly show when amp starts to flat top.

From the manual... is THIS the proceedure you are using to save the settings?


T o SAVE:
1) Press the SAVE key once and a prompt displays the PLAYER’S
LOUNGE preset about to be replaced, (example prompt shown).
2) Rotate the DATA WHEEL to select a PLAYER’S LOUNGE preset to
overwrite with the currently active amp design
(last chance to press EXIT, cancelling the save).
3) Press the SAVE key a second time to complete the save.

First make sure you have the TRIM knob positioned correctly. When playing loud the Red Led should just blink a bit so you know you're not overloading the preamp and Digital sections. The Twin Reverb Patch is a clean place to start so select that first. On this amp it's a good idea to set the MASTER to 5 and use the VOLUME control at as low a setting as you can. The GAIN control should be set under 4. You better sound crystal clear on this setting. Try turning up the volume to see how loud you can get without breaking up. It's a guitar amp so there will be some grainy distortion but it should be very light. I bet you get through this test without much trouble. After that you need to be very careful about what settings you're using since many of the presets may not mesh with your guitar pickups. You should concentrate on tweaking one highgain setting and learn about how the controls interact. The amp is so much more complicated than a 10 knob standard guitar amp. Most people need to put in some time to get a handle on it.

As far as the tubes go, typically they can get microphonic which was a problem with versions 1.1 and 1.0 of this amp so check that. Fender had a Cyber twin upgrade kit way back to fix this but if you have version 1.2 or 1.3 that's not it. Problems with this amp are typically caused by control setting more often than an electronic problem but this reponse should get you started figuring it out.
MYREL

Here is a test you can do at home for the sound. Test out the speaker. To do this you will need two alligator clips with wire about ft. long. Remove the speaker wire clips under the speaker magnet and attach the alligator clips . Take a C size battery and touch both ends of the battery. You should here a scratching sound . If you do you know your speaker is OK. Then you have a problem that needs a Technician. A good music shop should be able to give you a idea of the repair cost. Don't go to a big music change, find a small full service shop that deals with Fender. I don't think this will cost a lot. Fenders play for years, Its truly worth the bench fee. Good luck DFD , please rate me thanks