MXR 129 pitch transposer

sadrew · Post by **sadrew** » 06 Dec 2015, 18:06

I am trying to repair a pitch shifting rack unit from MXR, the model is M-129 pitch transposer

I am desperately trying to find the schematics

I am trying to tackle some weird distortion that is happening in the pitch shift section but I can't really operate without a schematic, all the ics have been sanded and the circuit is very complex with 2x dual sided boards

Anyone has the documentation for this one ? Also the calibration info would be great

Thanks

Dirk_Hendrik · Post by **Dirk_Hendrik** » 06 Dec 2015, 20:45

How much resemblance is there to be found between the MXR you have and the ART (Since ART came from MXR)?
http://www.modezero.com/mxr-psd-art-pitch-trans.htm

And a bulkload of sharp photo's by you "might" help a lot.

As well,
Spend hours finding schematics....

or spend 4 minutes:
http://www.ronsound.com/index.php?main_ ... cts_id=812

After that, watch a movie, grab a beer, go out to the gym, bang the missus..... or whatever. All time that you outherwise would have spend searching for free schematics.

sadrew · Post by **sadrew** » 06 Dec 2015, 21:38

that is some wise advice mr Hendrik ! Indeed I purchased the schematic

Then.... where can i get the calibration information ?

Thanks,
Giacomo

Dirk_Hendrik · Post by **Dirk_Hendrik** » 07 Dec 2015, 07:46

probably not....
I can only hope the functioning of the circuit is so evident (for you) you can figure out yourself what calibrates what. I cannot help you. I do jnot have that schem.
As well, what makes you sure something is out of calibration? Did someone play around with trimmers?

sadrew · Post by **sadrew** » 07 Dec 2015, 09:35

unfortunately this is a tad more complex than a fuzzface, so I don't fully understand this circuit

but hopefully i will succeed in troubleshooting the noise at least

the trimpots are old metal type and they have been soldered ! you can't really turn them anymore
I hope the machine will stay in calibration after the repair, I have already changed all the polarized caps so maybe that already made a difference?

uncleboko · Post by **uncleboko** » 07 Dec 2015, 09:48

A poster here may be able to help you,

https://www.gearslutz.com/board/so-much ... lease.html

rlg42fs · Post by **rlg42fs** » 26 May 2016, 23:26

Hi,

Schematics and calibration info are now available for the MXR 129 at tauntek.com

Bob

Dirk_Hendrik · Post by **Dirk_Hendrik** » 27 May 2016, 06:23

Thanks.

Linking is allowed.
http://www.tauntek.com/MXR129.htm

rlg42fs · Post by **rlg42fs** » 27 May 2016, 11:49

The trimpots used in at least some of the MXR 129's have a round metal
part on the top that turns and a small vertical post right next to it. I think they
are actually meant to be soldered to prevent them from moving after being set.
The factory calibration instructions at the very end say "Solder all trimpots".
I have never seen this before, but the good part is that you don't need to worry about
someone having messed with the trimmers trying to make it work.

I was able to remove the solder using solder wick, and then I performed the
calibration. Don't think I will re-solder them.

Bob