MXR 6-band EQ surgery

[jubal81]

Picked up an MXR 6-Band EQ off Craigslist yesterday for $30 and found it to be a hiss monster. Some quick google-fu revealed this to be a common complaint and someone offers a modding service to replace the opamps, which their demo video shows to be an appreciable improvement.


I just ordered a pair of SMD quad opamps from Mouser  - OPA1664 like in this blog (link).


Anyone have a preferred method for removing SMD opamps without a hot-air station? I've tried it with a regular wide-mouth heat gun before and it didn't go so well.

[mmlee]

Solder wick each pin...?

Edit: tbh don't know why I replied, I've never done it. Far more knowledgeable folk about.

[jubal81]

Went at it with the heat gun and needle-nose pliers.

[RobA]

Nice work on the IC-ectomy. It does make sense that changing out the IC's to some low noise type would improve the hiss. When I've been playing with the GEQ circuits, it's pretty easy to get a lot of noise in there. It really helps to use low noise op-amps. There's a bunch of gain in each of the bands and the whole circuit seems to be pretty sensitive to noise.

[jubal81]

The surgery was a success, but not without a few hairy moments. The traces/pads on this PCB are microscopically thin. Just positioning the opamp on there would scoot a pad or two around and I'd have to set it back in place with the tweezers.


The change is pretty dramatic, though. It's much quieter and actually usable now.

[rullywowr]

Excellent surgery, and nice modification!  I should do this to my MXR 10 band...

Another method (without using a heat gun or SMD hot air station) would be to nip each leg off the chip and then use tweezers and your iron to remove each leg from the pad.  Of course, this is only if you don't give a f@@k about the part you are removing.

PS....this is my 2000th post.

[jubal81]

Excellent surgery, and nice modification!  I should do this to my MXR 10 band...

Another method (without using a heat gun or SMD hot air station) would be to nip each leg off the chip and then use tweezers and your iron to remove each leg from the pad.  Of course, this is only if you don't give a f@@k about the part you are removing.

PS....this is my 2000th post.

I thought about doing it that way, but I'm glad I didn't. The traces and pads are so thin, I don't think they'd have handled the stress.

[GrindCustoms]

Glad it fixed the noise problem, nice execution on that!

[chuckbuick]

Nice work, Jason.  I just saw this thread so it's a little late.  But for anyone dealing with this in the future I swear by Chip Quik.  I have removed all 5 of the OTA's from my MRP-8 board 3 times each and all the pads are still fine.  I've also used it to remove board-mounted 16mm pots with much success.  Should work well for through-hole IC's or sockets, too.

My guerrilla method is to lay down a bead of solder across all the legs on both sides of the IC.  Heat up one side making sure the solder is molten across all legs and slowly start prying up the IC from underneath.  Do a little at a time alternating sides of the IC until it is elevated off the board enough to wick away the solder under one side.  Once the first side is completely free of the board you can grab it with your tweezers, heat the legs on the other side of the IC, and pull it free.  Wick up the solder and install the new IC.

This 2nd method has much more of a chance of lifting pads.  For the $15 bucks I really recommend Chip Quick.  In total I've removed about twenty 14 or 16 pin IC's and would estimate I have enough left over to do another 50 IC's.

[RobA]

Great work on the IC replacement. It's interesting to hear how successful it was too. It makes me wonder why companies do this though. The cost differential in the IC's in the quantities they are using is tiny. I can't figure out the logic in messing up the design by cheaping out on a couple of IC's where it really is critical.

Nice work, Jason.  I just saw this thread so it's a little late.  But for anyone dealing with this in the future I swear by Chip Quik.  I have removed all 5 of the OTA's from my MRP-8 board 3 times each and all the pads are still fine.  I've also used it to remove board-mounted 16mm pots with much success.  Should work well for through-hole IC's or sockets, too.

My guerrilla method is to lay down a bead of solder across all the legs on both sides of the IC.  Heat up one side making sure the solder is molten across all legs and slowly start prying up the IC from underneath.  Do a little at a time alternating sides of the IC until it is elevated off the board enough to wick away the solder under one side.  Once the first side is completely free of the board you can grab it with your tweezers, heat the legs on the other side of the IC, and pull it free.  Wick up the solder and install the new IC.

This 2nd method has much more of a chance of lifting pads.  For the $15 bucks I really recommend Chip Quick.  In total I've removed about twenty 14 or 16 pin IC's and would estimate I have enough left over to do another 50 IC's.

That went straight into my cart at Mouser. Thanks for pointing it out! I think I'll have to mess something up just so I can try it out. Actually, I've got some test boards with IC's on them that I'd like to recover without damaging them. So, this should prove pretty useful to me right away.

[jubal81]

Here's the comparison video by that company that does the mod. I got the same results with the 6-band.


I really don't understand the cost analysis these companies do on components and circuits - especially when it comes to something like noise.