MXR M78 Badass Distortion

[Shamus71]

Looking for info on what U4 is. Markings on top are IG123. Diode Maybe? It is burnt on my pedal. Can't seem to post pictures, but here is a link with pics and sort of a schematic, although they never answer what u4 might be.
https://www.freestompboxes.org/viewt...hp?f=1&t=13121

[Helmholtz]

Typically U designates an integrated circuit (diodes are Dxy). Looks to have 5 terminals. Maybe a voltage regulator IC.

[vintagekiki]

https://www.freestompboxes.org/viewtopic.php?f=1&t=13121&start=80

https://www.freestompboxes.org/download/file.php?id=33267
U4 = IG123 Maybe SOT-23-5L, adjustable 1.23V LDO Regulator

[Shamus71]

https://www.freestompboxes.org/viewtopic.php?f=1&t=13121&start=80

https://www.freestompboxes.org/download/file.php?id=33267
U4 = IG123 Maybe SOT-23-5L, adjustable 1.23V LDO Regulator

Ya, Thanks. I read that. Just looking to see if anyone has any further info as to what it may be for certain.

[Jazz P Bass]

MXR - Custom Badass '78 Distortion - Page 6 - freestompboxes.org
The last page of that post seems to confirm the IC as a 1.23V low drop out voltage regulator.
And the schematic of the power supply.

[vintagekiki]

https://www.freestompboxes.org/viewtopic.php?f=1&t=13121&start=80

U4 = IG123 Maybe SOT-23-5L, adjustable LDO, ~1.25V
IG 123, 1.23V (as per 123 marking), maybe Richtek
Could be Richtek RT9167/A wired abnormally
but this regulator is not adjustable.
Calculate: 1.23V + 240k (R30) +38.3k (R32) give +V = 8.94V.

https://www.richtek.com/assets/product_file/RT9167=RT9167A/DS9167A-29.pdf
Richtek RT9167/A

[Shamus71]

When I read it, all I saw where a bunch of Maybe's and some Could Be's. Alrighty gents... will try this https://www.digikey.ca/en/products/d...5-TRPBF/960068

[Helmholtz]

When I read it, all I saw where a bunch of Maybe's and some Could Be's. Alrighty gents... will try this https://www.digikey.ca/en/products/d...5-TRPBF/960068

If the schematic is correct, I doubt that chip will work. The LT1615 is a switched mode regulator that needs an external inductor, typically used to step up voltage (boost converter), see application examples.
The schematic shows a linear voltage regulator.

[Shamus71]

If the schematic is correct, I doubt that chip will work. The LT1615 is a switched mode regulator that needs an external inductor, typically used to step up voltage (boost converter), see application examples.
The schematic shows a linear voltage regulator.

Would this work? https://www.digikey.ca/en/products/d...DJ-NOPB/483015

[Helmholtz]

Would this work? https://www.digikey.ca/en/products/d...DJ-NOPB/483015

Now that looks really promising. It seems advisable to add a 2.2” tantalum cap at the regulator output.

[Shamus71]

Now that looks really promising. It seems advisable to add a 2.2” tantalum cap at the regulator output.

Awesome. Thanks Helmholtz. Will let you know how it goes.

[Helmholtz]

There's something else you could do in the meantime.

The unit doesn't need the regulator when powered by a battery. So remove the bad IC and use a battery with positive lead connected to the output pad (pin 5 ) of the IC, top of RŽ30, V+ in the schematic and see if the unit works.

[Jazz P Bass]

Hello China.
RT9167-33PB regulator
https://www.ebay.com/sch/i.html?_fro...-33PB&_sacat=0

[Helmholtz]

RT9167-33PB regulato

I checked that earlier. It's not suitable for the application.
The RT9167 is a fixed output regulator with a max input voltage of 7V. Max available output voltage seems to 5V.

[Shamus71]

Success! Parts used from Digikey: LP2980IM5-ADJ/NOPB and a 2.2” tantalum cap across Pin 5(+) and Pin 2 (ground).
Thanks for the help.