Crate RFX 65 RetroFex Hum

[schraedertr]

I have a 65 Watt Crate solid state amp with digital effects, which hums badly whenever I plug in a guitar. It has a muting circuit which quiets it down when nothing is plugged in.

It affects all three channels, very visible on output trace, seems to modulate with the beat of the effects. Unplugging J10 disconnects the digital effects board and cures the problem.

Ground continutity is good, and 12V power to the digital effects board is pretty clean, less than 20 mV of ripple on the scope.

There is nothing loose on the effects board (almost everything is surface mount but some caps and the crystal.).

Any suggestions other than try a new effects board?

Thanks,

[Enzo]

With the FX board disconnected, does the amp work? SOme amps route the signal through the FX board, so pulling it would kill the hum, but it would kill everything else too.

I don;t have docs on that amp, but if the DC supply to it is clean - I don't know, about 10v maybe - then pretty much its a new card.

[schraedertr]

The amp works without the board plugged in. The signal return from the FX board mixes in at the same point as the CD inputs.

Thanks,

[gp8005]

Schematic and No Solo output

Would you happen to have a schematic or a fix? I am fighting with a no output when I set the switches to run the solo mode.
Thanks
Gilbert

[schraedertr]

Gilbert,

I have attempted to attach a PDF of the schematic.

Tom

[gp8005]

Schematic and No Solo output

Thanks Tom, that really helped. I was able to get my Solo channel back. Shorted Solo switch (solder piece).

Now I am stuck with the AC Hum problem.

[gp8005]

Crate RFX 65 Hum

Tom, Did you ever get rid of your hum problem?

Gilbert

[schraedertr]

The hum was caused by the digital effect sboard. After providing the serial number to Crate, they said the effects board was no longer available for that amp. Evidently the board was changed sometime in production.

Fortunately, simply unplugging the jumper cable to the board takes it out of the circuit, leaving a basic amp with no effects.

Tom

[jasonguitar]

I know this is an old thread but I recently acquired one of these amps from a student and it was doing the same horrible hum thing which went away when the effect board connector was unplugged as you described. Seemed to me that the connector cable was behaving intermittently so I directly soldered the connections to the board and the hum was virtually eliminated. I believe these effects boards are inherently noisy (more hiss than hum) but the noise level is now totally acceptable and even studio worthy.

[AdrianBass]

Ok I know this is an old thread and like Jasonguitar (above) I too purchased one of these amps recently only to discover the loud hum/buzz. My solution was almost identical but instead of re-soldering, I disconnected the FX board... this is the red wire loom that goes to the circuit board at the back) and sprayed the contacts with WD40 (did this for both ends of the wire). This solved the problem reducing the noise to about 90-95% of what it was. Acceptable noise levels for on stage, rehearsals and maybe studio.
I guess the area between the contacts has some sort of dissimilar metal corrosion going on and cleaning the contacts does the job. Hope this helps anyone.

[TeeVeeFixer]

Just had one come through our shop today also ( 2/17/2020)

Hardwiring BOTH ends of the 5 pin red harness restored a perfectly quiet amp.

[Rick Ferrell]

Given a crate rfx65 amp andwhen turned on it will only hum loudly and begins picking up on effects surge sound.
Amp came with no on off switch and was partially disambled. Stops when pedalboard loom is unplugged but no sound.
See one componet looks overheated and it is a blue and has a series of numbers. Sn85deg 0442 (v) 13 at base and np10vr. Could this be the problem.
Thanks for any input in advance

[Enzo]

Hi Rick, please start a new thread for your amp. We don't like mixing repairs within a thread.