CRATE FXT 120 No Sound Output??

[hughz]

Hi, I figured I would give this forum a try to resolve an issue I have with my Crate FXT 120 Not giving any sound... It powers up and stays completely Mute?? The onboard Tuner reads correctly and works but that's it..

I am not a guru amp tech but have dealt with DC audio amp repairs and stereo installations successfully and I do have some entry level knowledge of components and solder skills however I have a lot to learn no doubt..

So hopefully Maybe there is a few electronic techs here that could point me in a good trouble shooting direction...

I did all the obvious with using multiple cables and a different outlet and its still mute..

I pulled the board out and did a basic over check to see if there was any burnt areas or blown parts etc.. And it looks new on the board..

Also prior to it not producing sound it had been very noisy in the speakers and seemed over whelmed with a shaky odd noise that was sublte but noticeably annoying in the background of the guitar sound ------if that makes any sense-----..

Maybe the speakers?? The caps or Transistors internally shot?? Any insight to this mute amp and tips that I could apply to trouble shooting my Crate would be very well appreciated..

[52 Bill]

Any insight to this mute amp and tips that I could apply to trouble shooting my Crate would be very well appreciated..

Hey, welcome to the place.

There are three things that come to mind, the loop jacks, the extension speaker jack and the internal fet turn on mute.

Try a spare patch cord from the send jack to the return jack. Try connecting a second speaker to the amp or try cleaning the extension speaker jack with some DeoxIt contact cleaner. Test the mute fet and the mute control voltage at the gate of the fet.

[g1]

schematic:

[hughz]

Thanks for quick reply.. I will update as I go along this trouble shooting process---Thanks for the intel!! Hughz

[hughz]

Hello again... To 52 Bill,,, Its' been some months but I just finally decided to fix this crate no sound output issue just a couple weeks ago sense I had a backup amp I figured why not just back burner this FXT until I have to fix it,,,,,,,, Well I did fix it a couple weeks ago but I went ahead and swapped out the FETs which were TIP 142 And TIP 147---- 2 each being 4 fets altogether..

The install went smooth and clean.. The amped jammed for a couple weeks for maybe 2 hours a day..

However I run my own effects unit and I run it on the clean channel for this.. I have had the volume on the amp at notch 3 only.. Which is beastly loud at that...

Overall the amp didn't smell hot or burnt but it just kicked off again and before doing so made a weird jingly noise in the speakers as it went mute...

Real subtle though and then silence... This time I did jump a patch cord from the front 1/4 inch with the speaker symbol next the jack and then plugged the tip only touching the first contact into the back of the DSP 1/4 and had full sound again????

If I plugged it all the way in it made a real faint scratchy noise and seemed to make popping noises.. I did this to both 1/4 inputs on the back and only the tip could touch the first part of the jack to produce sound again.. The front jack was Again at the other end of the cord and was plugged all the way in on the front side of the 1/4 inch input with the speaker symbol next to it.. The insert jack on the front does nothing in any combination which is next to the front 1/4 inch input I am plugged into..

Note I do have my input plugged in with my guitar all the way as well which is by the on off switch.. Guitar to input jack then patch cord from front speaker jack all the way inserted to the rear DSP with that end only touching the first contact of the cable and 1/4 DSP or channel gain select jack input..

As long as I touch any one contact of those rear inputs with a patch cord it produces sound at full power sounds like..

Hope this makes sense and is understandable.. Any Ideas as to what may be the problem???? I did check contacts and fresh solder repairs and all looks good for the 3rd and 4th time of inspection.. I am at a loss and would greatly appreciate some more help as it helped the first time.. So thank you for taking the time to read this...

Hughz