Fender Vibro Champ XD DSP issue

[gbono]

The amp has an issue with the DSP - some of the voice features will squeal and feed back and FX features ( delay, reverb) don't work. I chop sticked the DSP sister board but no change to output. Is there a way to reset the DSP - reload the config code? Also - where is the +3.3V supply on the schematic?

https://www.thetubestore.com/lib/the...-Schematic.pdf

[Jazz P Bass]

Not sure if this will help: Champ 30 DSP.
Champion 30 DSP .zip
The XD schematic does not have the DSP card included.
The 30 schematic has the DSP.
You will have to decide if it is close enough.

The 3.3Vdc is derived from a LM1117 voltage regulator on the DSP board.
http://www.ti.com/lit/ds/symlink/lm1117.pdf

[glebert]

Found this thread that indicates sometimes the digital chips need to be reseated. https://forums.fender.com/viewtopic.php?f=13&t=106491

[gbono]

I checked several locations on the board for the +3.3V bias and only measure +1.27V even at the LDR on the DSP board. so there is either something wrong with the regulator on the DSP board (did they load the wrong part?) or something is loading down the +3.3 supply.

[xtian]

Or failed filter caps for the 3.3 supply.

[gbono]

I will scope the +3.3V supply to see if there is excessive ripple but this DSP board only has tantalum capacitors on it - these are usually very reliable.

[g1]

this DSP board only has tantalum capacitors on it - these are usually very reliable.

Maybe the new ones are better, but I'm not sure I'm ready to agree with this statement. The are very easy to check for low resistance, which seems to be their most common failure mode.