Duo Op Amp Upgrade?

[nick3092]

I recently started having audio issues on my TG Duo, and thanks to this forum I was able to learn about the capacitor issue.  So I re-capped the entire thing, and outside of having to work around a few solder pads/traces that got removed when taking off the old caps, I managed to get it working again.

While I was in there poking around, I started pondering replacing the 4558 op amp in the audio circuit.  I don't know much about this op amp, but the general consensus after doing a Google search is that it's not that great, and it's somewhat common for people to replace them.  So, my question is, has any one tried to replace it with something else?  If so, what, and was it worth the trouble?

Thanks,

-Nick

[nat]

I've always wondered about that, with one question: why?

The amp functions fine, gives a perfectly viable audio level. My motto is: if it's not broke, don't fuck with it.

BTW, I've re-capped and modded my fair share of Duos and never saw fit to replace the op amp. I've never seen any instance where it's failed. So unless it does, I would say "don't bother."

[nick3092]

Yeah.  You're probably right.  I just have this nasty habit of always trying to make things that are working fine, work better.  Even though the change I'm making is probably minimal, if at all really doing any good.  And will probably inevitably go wrong on me.  I guess I'm just a sucker for punishment.

[Duo_R]

Turbokon does an op amp upgrade. I replaced 95% of the caps on the entire board, but unfortunately I have a little scratchy sound that is intermittent. It isn't really bad but a little annoying. I wonder if the op amp is bad on my Duo.

[nat]

No, it's definitely a cap. Or the residuals left over from bad caps.

It's always a good idea to dishwash the PCB after a cap swap to remove those residuals. They are conductive and cause random shorts which can cause that audio static. I had a case once where I replaced every cap on the entire board and the sound still didn't work. A good soak and dry later and it was good as new. Often times the residuals aren't visible, even under extremely close inspection.

[Duo_R]

Nat, thanks for the reply. I have seen your post on the dishwashing method. I saw that you ran it several times through the wash (and used 7th generation soap). Is it best to run it a few times, and skip on the drying cycle? I searched on the internet and saw that sometimes people don't use soap when doing a PCB wash. I am going to take a look at my PCB (I wonder if my ohmeter can find a spot where this residual is left over). I know the specific locations where a cap leaked so I probably should start there before doing an entire wash.

Also - after doing a wash would it be a good idea to run the wash a couple of times empty? I don't want to contaminate my plates with flux/solder residue.

No, it's definitely a cap. Or the residuals left over from bad caps.

It's always a good idea to dishwash the PCB after a cap swap to remove those residuals. They are conductive and cause random shorts which can cause that audio static. I had a case once where I replaced every cap on the entire board and the sound still didn't work. A good soak and dry later and it was good as new. Often times the residuals aren't visible, even under extremely close inspection.

[nat]

Nat, thanks for the reply. I have seen your post on the dishwashing method. I saw that you ran it several times through the wash (and used 7th generation soap). Is it best to run it a few times, and skip on the drying cycle? I searched on the internet and saw that sometimes people don't use soap when doing a PCB wash. I am going to take a look at my PCB (I wonder if my ohmeter can find a spot where this residual is left over). I know the specific locations where a cap leaked so I probably should start there before doing an entire wash.

Also - after doing a wash would it be a good idea to run the wash a couple of times empty? I don't want to contaminate my plates with flux/solder residue.

Do two runs, consecutively, with no drying in between. Disable the dry cycle on your washer altogether if it has one, and let the board air dry after the second run.

People sometimes worry that detergent will harm the PCB, which is a myth, because in actuality PCBs are subjected to much harsher detergents in a dishwasher-like device at the end of the manufacture process.

You don't need to worry about running your dishwasher on empty, either, unless you're extremely paranoid. Any small bits of stuff that gets broken loose gets washed down the drain with the water. Consider this: do you run your washer on empty a couple times after every load of dishes? Because the rotten food chunks the washer cleans from your plates is a whole lot more gross to contemplate consuming opposed to a flake of flux.

[Duo_R]

the main thing is my wife is pregnant, I don't want to put her at risk with toxins in the dishwasher. Maybe to be safe I could run the dishwasher on empty 1-2 runs with soap after doing the Duo scrub???

[nat]

Sure, if it makes you feel better.

[Duo_R]

Nat - 2 runs, and the board was much cleaner. There was some white residue stuck in areas that there was alot of that gunk. I dried the used alcohol and toothbrush to loosen up. Did one final run with just water and no soap. Now drying it again.

Back on topic - i know there is a direct replacement for the op amp, but like Nat says no point doing unless there is a problem. We will see if the dishwash fixes my issue.