Distorted sound from speakers, but not from Aux jack. 200A

[garagebandking41]

Hey guys! It's been a while for me, I used to post on the fenderrhodes.com website back in the day, and kinda fell off when the forums moved over here. Either way, I'm back! with a new toy!

So I've had this semi-noisy 200a. I've recaped it, new transistors in, and put new a vintage-vibe preamp in it. It has made less noise, but still has this issue of distorted sound coming from the built in speakers, but not the aux output jack. I've also removed the AC light and replaced with the VV LED mod as well.

Another thing I have noticed, is how loud it is. It rattles the whole piano and can self oscillate if the vibrato and volume are maxed out. Did I mess something up? Voltages from the regulator seem okay. I'm getting about 140v at the reed bar. 10v drop through the pre-amp. Any thoughts?

[Abraham]

I have the very same issue on mine, everything is stock, my tech insists everything is between tolerance boundaries so there is no need to replace anything, apparently this piano had a fuse blown right after purchase and it never got fixed by original owner, who just left it unused for years... Its like new.

My kind-of-distorted noise become noticeable as the note decays, showing up just through speakers/headphone out, not from aux, and it ends with the note release. It reminds me that kinda 8bit downsample distortion from older computer soundcards. My tech inspected the amp output feeding a pure sine test tone and passing the output through the oscyloscope getting a clean sine wave on screen... So I don't really know what's going on. Its not the speakers as the headphone out behaves the same, so its before amp. Aux out is fine, so it is the pre-amp then. It doesn't make any sense at all....

[sharan]

Hey there,

Problems you can only observe on the speakers, but not on the Aux have to be in the PowerAmp Section.
What it is exactly has to be examined by closer observation.
Distortion only noticeable in the decay might be from an unbalanced output-stage - so called crossover-distortion.
There is a Vintagevibe-video available on Youtube. Its about crossover on an old 200A.

Hope i could help,
regards,
Korbinian

[garagebandking41]

Abraham, you've described exactly what I am experiencing. It must be the same issue. I will look into this crossover distortion. Thanks for the tip. Hopefully I can try and get it solved.

edit: http://www.youtube.com/watch?v=eBTES_smMI4

This video seems of more interest to me, since i know the transistors I put in are new. There is always that chance I damaged one of them, but I'll look at my resistances from around that section and see if they have wavered and could be responsible. It's most likely the resistors are the only things left from the Wurlitzer factory on that board now.