MXR A/C Transformer Replacement

[seanm1234]

Hi Everyone,

I have an old A/C MXR Stereo Chorus in need of a new transformer (orig. was bourns pw-0205 (m8110)). I posted in the sale and trade to see if anyone has this as NOS they might sell me but in the meantime I'm looking for any advise on fixing this pedal. I've pulled to old transformer after testing it under power on the board (~115v in -> 0v out ).  Also has no signal across the leads off the board and the pcb shows serious gunge where transformer was.

I'm wondering if anyone has found a suitable replacement transformer or knows of a current transformer that I could use as a replacement (same in/out v and size, etc). Otherwise, I did find an earlier post about bypassing this to use an external power supply, but it would be nice to restore this to it origninal state. Thanks for reading.

Sean

[Mark Hammer]

The pedal has an LM340 regulator in it. Assuming the regulator, and the 400uf cap ahead of it are in decent shape, do yourself a favour and replace the grommet with a jack. 

At that point you have several choices.  You can simply feed the jack with a 15-18vdc wallwart, and run hot and ground from the jack to the + and - sides of the 400uf cap.  The onboard regulator will then regulate that 15-18v down to the 12 the pedal wants.

Or, you can feed the jack a regulated 12vdc and bypass the regulation circuitry on the pedal entirely.

Or you can feed the pedal 12VAC, run the jack to the diodes, and let the regulation do its work.

[seanm1234]

Thanks for the reply, Mark.

You make a good point esp. since I know that this is a reversable mod. If I come across a transformer, I can pop it in but keep using my pedal in the meantime.

There is another upside to this as well ... I can put the now unused A/C cord on my flanger that had it's original cord replaced before I bought it.

BTW, I'm new to this forum and I'm glad to find you guys. I'm a long time player with a little electronics experience. I've built a Shaka Tube a while ago (and it even works) but right now I'm looking at getting what I have working including a mxr phase 100 that seems to have a low output issue. Sounds fine going into a solid state amp (no signal drop) but the volume cuts out when it is engaged and I run it into my old marshall.  A forthcoming post perhaps ...

Thanks again.

Sean