Tesoro Golden µMax ground balance mod?

[porkluvr]

I just air tested the unit, it seems to be able to function in that it will pick up targets, even at the same depths, just the sound coming through is very quiet and practically non-functional.

That is strange.

Er, looks like your friend may have "Ham Fist Syndrome", or HFS.
Did he leave residual flux on the board? If it was no-clean flux, that is not a big problem. But rosin flux needs to be removed. Scrub with a soft brush and some 91% alcohol, then rinse the board with alcohol. If the flux has been on the board for more than a few hours you'll probably need to first let it soak for a while. Repeat as often as necessary. Compressed air really comes in handy for cleaning under components but that's a luxury.

Try not to get alcohol in that other potentiometer

That white box is a 33nF (.033uF) +/-10% "film" capacitor with 100V rating. I believe it's made with either Mylar, polyester, or metalized polyester - either one would be fine. You don't absolutely need the 100V rating, I think 63V or even 50V should work. I can't tell you to replace it but anywhere I ever worked had zero tolerance for solder iron dings on capacitors.

[Pinpoint]

I can't tell you to replace it but anywhere I ever worked had zero tolerance for solder iron dings on capacitors.

Well, there is definitely a ding on that capacitor. The one next to it don't look too healthy either:

Here's the ding on the capacitor on the left, highly likely it's from the solder job:


Here's the back of those capacitors, the one on the left has a mark on it at it's bottom left. I don't think it was from the job:


If the solder touched the capacitor, would you say the capacitor needs changing? You said zero tolerance right?

[porkluvr]

In reality you do not have to comply with the same standards that a large manufacturing facility would use. Use some common sense.

After I mentioned "zero Tolerance", I did recollect one stint at a place that allowed trimming rough burned edges with an x-acto and letting it go, if the damage was not too severe.

So, how deep does the burn need to go before it can cause real damage, not just cosmetic damage? The answer is this: Don't burn the darn things in the first place so you won't have to wonder about it.

The new solder joints look just plain awful. I'm thinking your friend needed some liquid flux, did not have any, and there's a simple job that got botched.

Find a professional to do the work and not some moron with a soldering iron. One thing about rework is that if you're not careful, you can wind up with more problems than you started with.

[Pinpoint]

Find a professional to do the work and not some moron with a soldering iron. One thing about rework is that if you're not careful, you can wind up with more problems than you started with.

He was not a friend, he was supposed to be a professional recommended by an electronic store. This will come back to him.

So what do I need to do? Alright, find a professional, they could be anyone, just like the last guy. But what I mean is, even if I find someone who is reliable, what do I get him to do; re-solder the two (red) wires; change the capacitor; else?

[porkluvr]

Maybe you should try to find a small general purpose electronics repair shop and explain what was done and get them to re-do it.

Either that or get ahold of either of the two gentlemen mentioned in the original modification article and see if someone would be so kind as to take a look.

#2 might be the better option.

[Pinpoint]

(I might be able to get hold of those two gentlemen, I've tried posting...)

I guess trying to get a (proper) professional to re-do would be the best option. I forgot to mention that the wire connected to the wiper makes noises whenever I move it (when the detector's turned on), even a bit.

Maybe a cold solder? The pictures suggest it might be...? The one connected to the CW doesn't make any noises when you wriggle it about.

[porkluvr]

Cold solder is a distinct possibility.

It is really hard to get good solder joints on wires on double sided boards, unless you have some liquid flux to squirt down into the joint. Just because you have rosin core solder, doesn't cut it. Thin solder, with adequate flux squirted around is the way to go.

It is also very hard to remove components and old solder, cleanly, without liquid flux.

You can buy rosin flux pens, or you can make your own rosin flux. Find a good music store or someplace that sells or repairs violins. Buy a cake of rosin and dissolve a chunk in denatured alcohol, or maybe 91% isopropyl alcohol would work.

It is nice to have a 2~3 oz. applicator bottle, preferably with a needle tip. Liquid flux can make really nasty messes if not careful.

You might be able to do some good with what I told you, just please don't use a large iron and go burning things. You would need a small tip iron of about 25W. 3Wire irons are recommended so you don't shock the components with static electricity.
Before you do anything I suggest you Google ESD safety and also "how to solder".

Whether you attempt the job or get somebody else (AGAIN) is totally up to you.

[Pinpoint]

I have been practicing, but I'm not going to go anywhere near attempting to solder anything on that board, unless I have the precision of a NASA engineer!

I'll look into the rosin flux deal, thanks.

[porkluvr]

I have some second thoughts about using denatured alcohol for making flux. Ideally it would be pure ethylene mixed only with methylene, but unfortunately it will also usually have a small percentage of MEK or some other foul smelling junk that could attack plastic. Use at your own risk, Alternatively, 91% isopropyl alcohol from the drug store should be good enough.

Methylene is a general purpose electronics solvent that would work great for making liquid flux but it is not so easily available to the average hobbyist as it used to be - not since DEA and Homeland Security have their noses all over place.

[Pinpoint]

Underside

I have taken pictures of the underside:





Do you seen anything unusual?

[Pinpoint]

I think I have found what's wrong!

In the picture below, I have marked where the problem is (I think) in red. I had a friend (he has experience with soldering speakers, PAs, amplifiers) have a look and this is what we think: There is a component that fell off where it's circled red. We think it's because the guy who did the initial job heated up the pot as he was soldering it and dropped it onto the area marked red, and the component fell off. The chip that says "Gold3.hex" shows burn marks as well and that may be damaged as well. We took it out and some of the contacts ( from the gold3.hex chip) look a lighter colour, it may have gotten a surge.

The component circled green is what that missing component is supposed to be (I have purchased another Golden uMax and had a look on that one), but I might have to check again just to be sure.

My friend thinks that that gold3.hex chip may have something to do with processing the sound, which may explain why the detector still works but the sound is barely functioning.



That missing component seems to have "L 44" written on it.

[Sean_Goddard]

Oh if I had a penny for everytime I've seen a metal detector damaged or destroyed by "a mate who can solder" (most have nowhere near the skills to work on these small components )!

I can't see the pictures you posted (blocked by our network) but I can tell you it's (hopefully) nothing very serious. Most detectors are so simple in design they're quite robust.

I gave up doing repairs due to the like of Joan *****holes, Lamebin, and Rectum constantly breaking the law as regards to operating a monopoly on not supplying spares then threatening legal action or "coming round to pay me a visit" (Yeah...bring it ladies...ANYTIME)!!

Satdaveuk, detectors are not as difficult to repair as you might think. I had very little info when I started, just what I could find on this forum and I repaired MANY machines Pentechnic couldn't (or so customers used to tell me). I find this strange as I have ALWAYS had the highest respect for Dave, he's a very capable guy.

Don't forget Tesoro machines are ALL basically the SAME. New money old rope, but it keeps them in business and punters happy so it must be good, right?!?

I'll revisit this when I get home and can see the pictures, see if I can spot anything. If the PIC is fried, your as good as finished. Tesoro won't sell you a new one and will charge you a left nut to repair it......To be continued!

[Pinpoint]

Oh if I had a penny for everytime I've seen a metal detector damaged or destroyed by "a mate who can solder" (most have nowhere near the skills to work on these small components )!

My "friend who can solder" actually did a good job and added a GB to my second Golden, he did a good job. It wasn't him that did the initial stuff-up! The initial guy was supposed to be a professional and he did a disgusting job. In fact, I've gotten better at soldering myself and can do a better job than the initial guy.

The pictures which I took down from earlier in this thread are irrelevant now.

[Pinpoint]

If the PIC is fried, your as good as finished.

The detector still works, it's the sound that's not working properly.

[Qiaozhi]

In the picture below, I have marked where the problem is (I think) in red. I had a friend (he has experience with soldering speakers, PAs, amplifiers) have a look and this is what we think: There is a component that fell off where it's circled red. We think it's because the guy who did the initial job heated up the pot as he was soldering it and dropped it onto the area marked red, and the component fell off. The chip that says "Gold3.hex" shows burn marks as well and that may be damaged as well. We took it out and some of the contacts ( from the gold3.hex chip) look a lighter colour, it may have gotten a surge.

The component circled green is what that missing component is supposed to be (I have purchased another Golden uMax and had a look on that one), but I might have to check again just to be sure.

My friend thinks that that gold3.hex chip may have something to do with processing the sound, which may explain why the detector still works but the sound is barely functioning.

That missing component seems to have "L 44" written on it.

Have a look at the pins on the PIC, that go to the missing transistor pins, using an oscilloscope, and see whether there is any signal there that looks like an audio output, or might be enabling the audio.