The DSP board in this Crate looks different from the ones I can find on ebay. I found a photo:



Why should I jumper the Send and the Return of the DSP board? What is that Send and Return?

I'm not a real technician, nor an engineer. But I build pedal effect, so I have some experience, but no much in big amp like that.
Anyway, I'd say it's impossible to repair because the issue, I think, is in the DSP board. Change a cap, a potentiometer... is ok, but if the problem is in the microprocessor (if I can call it like that) I just can change the board, but I can't find it.
Actually, the fact I have to wait some minutes to warm it up to make it work could be a soldering or bad contact problem. But I'm not sure.

I don't say I won't try to fix it anymore, but I want to wait to have some clue about this problem. I read somewhere about another guy with this amp with the same problem here: I turn it on, I hear loud pops even with volume at zero (this is the reason I have to disconnect the speakers).
When I disconnected the DSP board, taking away the ribbon wire between the tuner and the DSP board I "solved" the problem, but it was stuck in the second channel, with volume at zero (but I can hear it, because in this amp, the volume, is never mute!), and of course no effects and no tuner worked (maybe the loop effects, too).
(Actually, I don't know why taking away that wire changes all this, because the DSP board is soldered directly on the main PCB, I just separated it form the tuner interface. Maybe the wire makes some jumper on the DSP board itself?)

It was enough for me if I can get even only the clean channel, no matter about the distortion channels, the effects and the tuner.
But to make this I should know how to do it.

Hello.
I have a problem with my Crate FX212 120w, probably it's impossible to repair, it's no matter now. For the moment, to makes it work somehow, I have to turn it on for a while without speakers, and I did it twice, but I want to be sure it won't damage the amp. Generally, the solid state are ok with it, but I want to be sure about this amp.

This are the schematic:




Can you help me with this?

Thanks!

Hi, I'm sorry for the long pause.
This project, the power amp section at least, it's became enough hard.

Ground noise: Attaching the ground wires with the clip alligator in the same spot I reduced the hum and cancelled the oscillating. I also tried to shield the circuit with a tin foil.
PSU: I tried an alternative 12v PSU, that of my external hard drive for test, this more than else it's been what is really reduced the hum. But I still got distortion.
Then I tried another PSU of 15v. Slightly more volume, but still distortion.
Gain resistor: I encreased the R8 (if you look the schematic above) from 2.2R until 10R. I got a sound enough clean, finally, but I reduced the volume. (I even lost some treble, but I guess I can encrease the high acting on R7).

Now the problem is the PSU.
I want to use a 18v PSU for more headroom and volume, and the speaker is 8 Ohm, the only one I can use. I didn't find out how much will be the current draw though I read the datasheet. It's really hard for me to find a right PSU, 18v, a lot of Ampere, the right jack, low noise.

The PSU of a laptop could be really really good, theorically, because usually work at 18-19v, them can have even 4-5 Ampere, but I don't have a my own to test, I should to found one with a Boos pedal style plug, and I can know just after I bought if it's silence beacuse, of course, the PSU laptop are made for laptop and not for audio.

My only hope is a 18v PSU, apparently made for pedals (and I hope low noise), right plug, 2000mA. So this is the reason I want to ask about the consuption about whole amp. I predict that the two channels, the relays, and a buffer in front and a 78L09 regulator will be no more than 300mA.

Thank you!

I don't have 12v battery. Can I use a 9v as well? At least about the noise.

Update: Tried the 9v battery. No noise, just a bit of hum, but it still oscillate when the pot is over the half and when the volume guitar pot is to zero. Because the flying connections of the clips and wires I didn't shielded it with the tinfoil this time.

Tried to put in front of it a Fetzer Valve or a Woody Acoustic Simulator. No changing about oscillating. It still too much distorted at half volume.

Hello guys, my first post here.
I want to realize a big little amp for practice for my electric guitars.
After some mini amp I would like to build something louder. I found this mini amp:
http://www.hotoneaudio.com/products/nanolegacy/Amplifier1/2016/1114/183.html


None schematic, but I know it based on TDA2003. I already built a Triple Wreck to use as hi-gain channel, but also a Tonemender to use as clean channel. I like both when I tested them with the guitar and my main guitar amp.

Now I built the TDA2003 power amp taken from the last part of this schematic:
http://www.redcircuits.com/Page145.htm

Of course, I have omitted the input stage.

But, testing the TDA2003 circuit I have many problems. I partially shielded with tinfoil.
I connected the circuit with a cheap homemade cab with a guitar speaker 8", 8 Ohm, 15w.
The PSU is a 12v 3A.

1. Too much hum when I increase the volume.
2. Some ground problem, I guess, I feel through my fingers a kind of... tingle? when I touch the hardware of the guitar as well as the strings.
3. I wanted a clean amp, but this start to clip too soon. At max I got about the distortiom of a LM386, and not more volume then my Noisy Cricket (LM386 based).

Need help.

Thank you!