MXR Carbon Copy need to know some voltages

[rodrigomarília]

Hey everbody

This is my first topic here.

I have a Carbon Copy and recently something odd start to happen. The MIX (and repeats) seems too faint. I read about exactly same problem many times and nobody found a definitive solution. So i opened mine and start to figure out what would be.
When i set trimpot TR8 all the way to the right, i can get more Mix/Repeats. Checking what this trimpot could adjust in circuit, i realize that it decrease/increase positive voltage across C41 and this voltage here is 3v with TR8 maxed out.

I cannot find where the C41 negative terminal is going! Only found the positive that is going to TR8

Please, any could get this voltage across C41 to compare them?

And did anybody repair this problem actually finding/replacing some part? Cause i'm firmily thinking there is some culprit comp in this PCB

Thanks

[r080]

Welcome to the forum!

I have also seen several different threads with the CC repeats low. I have not been able to find a schematic for it.

You will probably have your best success looking for a calibration procedure for a deluxe memory man (maybe some good info on the madbean forum). I believe those processes are not actually looking to get to a specific DC voltage, but rather an amount of distortion, and therefore an oscilloscope is the recommended tool, but it can apparently be done by ear.

The hardest part might be figuring out which trimmer controls what.

[rodrigomarília]

Thanks!

Messing around with those little ( trimpots, i found 4 biasing the 4 BBDs, 1 for adjust delay time, that one which add more repeats and other 2 seems not doing so much difference in any position

What leads me to thinking there is some smd part taking overall voltage down. If i power it with 9.6v i can hear it a little better. So i assume the circuit is underpowered because of something defective. I will power it with 12v soon to see.

[rodrigomarília]

Anyone with MXR CC on the shelf ?

[percyhornickel]

Rodrigo I thing first you need to check the version have, Carbon Copy V1 is reported to have some issues and the MXR guaranty is working on it. A few months ago, a friend sent his carbon copy V1 from here (Venezuela) to MXR and they sent back a brand new unit V2. Even they said MXR would cover the shipping.

You can see the contact in the web site.


Saludos.