The WHOLE system sounds better

[cc1091]

I remember a few years back how someone in these forums went to the ear doctor, got his ears cleaned out, and then was stunned about how much better his system sounded. I just had a similar experience, but not because of ear wax cleaning.

My 200WPC amp that drives my mains had just recently developed an annoying humm. I checked the wires leading to and from the amp. I also pulled and replaced all the fuses in the amp. No luck. My other amp was working fine from the same power source, so I was sure the problem was in the amp. I didn't want to take it to the local stereo shop where they would pack it up and send it to a local service center only to have it come back 'fixed' and sounding no better than when it left (and usually at a minimum charge of $50 plus shipping). So a friend of mine who works daily on non-audio electrical equipment at his job suggested something radical. After he checked the system to see if it was running within spec, he said something like this:

" I bet it is one of these two caps on the left side of the amp that is causing the humm. But before we think about replacing those, take the circuit board off of the cooling fins so you can get at the side of the board where everything is soldered. First clean it with Formula 409 and a soft brush (of course with no power to the amp), and then rinse it with water: Just a light spray of water to get the cleaning residue and any dust left after the cleaning formula off of it. Once that is done, let it dry over an Air conditioning vent for a few days. Then, I'm going to have you attach two wires to each of the suspect caps, one to the negative terminal, and one to the positive. Then, while you're back there, touch the soldering iron to each soldered connection for about five seconds..just enough to get the solder heated. Once you've done all this, reassemble the circuit board to the cooling fins, and then reinsert it into the chassis of the amp. Once it is remounted, put some black electrical tape over each of those wires I had you attach to the caps so that they don't touch anything. Those wires will be how we check the integrity of the caps if you still hear a humm when you plug it back in."

Well, I did what he said. I never had to use the wires connected to the caps because when I plugged the amp back into the system and turned it on, WOW! It was quieter than I have ever heard it. "Well, is it really on?" I thought, so I fired up the preamp and added a movie. Oh YES; it was working just fine. In fact, I've never heard the highs be so crisp and distinct. Nor have I heard the bass be so overwhelming and solid. It was like a new amp....or maybe like having my ears cleaned.

I don't think I would suggest this to everyone. And I will probably not try it again unless I get a similar situation. Plus, even this uneducated ear can tell the difference between a minor electrical humm and a full blown "man you really screwed up your amp" power arcing humm. So I guess you try this as a fix only when you suspect a cap or a ground is going bad and can hear it well enough that it affects your enjoyment. Of course, if you're made of money, you can buy new and sell the old on Ebay. Your choice.

Happy listening.

CC

[Blvdre]

Sounds like the problem may have been a cold solder joint, and re-soldering the connections did the trick. Just as a suggestion, if you ever have the need to clean a circuit board again, and you don't have a proper flux cleaner, use isopropyl alcohol (you can be generous) and let dry thoroughly (no rinse necessary). The problem with water is, it may contain various salts which are conductive and these will stay on the PCB as deposits (unless of course you use a good quality distilled water).

[Daddy Dee]

congrats on having a "new" amp.

It's great to redeem a piece of gear like that.

[sunburnwilly]

Now that you have done it successfully I'm sending my amps to you if they ever develop that problem .

Thanks in advance !

[WMcD]

From what you descibed, and described very well, the tech knows his stuff about the cap being the problem and the cure of heating up the solder joint. Great guy. Go to him in the future.

= = = =

Something happened today at the office which is in the same vein. The big boss showed up with a printed circuit board from his furnace and wanted to show me.

There had been some problem with furnace at home and a tech came in and put in a new board.. The tech gave the big boss the old one with the tech's hand drawn felt tipped pen arrow on the trace side of the board. It pointed to a very compromised solder joint. It was a connection to the contact side of a relay.

My thought is that the application of solder at the time of manufacture was good but maybe the metal lead sticking through the board was not tinned. But current is part of it, I think.

= = = =

There is something in common here. The cap in your amp (and the connection of course) handles high current when the amp powers up. The relay in the furnace controller I(and its connection) handles high current when a motor is switched on. It may be that over the years the solder in these connections melted and reformed until eventually the connection was compromised.

= = = =

Just an aside about power supplies. If I may be pedantic.

The transformer steps down the plus and minus voltage of the 60 Hertz sine from the a.c. mains. The rectifier essentially flips over the negative portion of the sine to create the same "bumps" of voltage always going plus. Then the capacitor is like a very fast acting rechargable battery. It evens out the bumps to a constant level which is called direct current or d.c. Actually, constant voltage. By the standards of music, it is silent.

The amplifier, fed by the d.c., turns on and off in time to the music so that we are really listening to that "battery" d.c. as switched by the "valves" of the amplifier.

When a capacitor or its connection is bad, the bumps from the a.c.mains line, and transformer are not evened out (not silent) and so we hear the hum of the a.c. line. Your tech friend knew this.

- - -

It is good to hear that the boss had a good tech, and you did too.

Wm McD.

[Marvel]

There had been some problem with furnace at home and a tech came in and put in a new board.. The tech gave the big boss the old one with the tech's hand drawn felt tipped pen arrow on the trace side of the board. It pointed to a very compromised solder joint. It was a connection to the contact side of a relay.

Did you tel him you would clean the connection and resolder it for him so he could have a spare board to putback in the next time it failed.?

Or was it not repairable? I used to work at a business that repaired three phase motor controllers, and I made some rather messed up boards work a whole lot better and not fail.

Bruce

[WMcD]

Marvel,

No I did not. In my experience, doing professional work for free for a friend or co-worker creates too many problems.

It is one thing when we exchange notes as fellow tinkerers or work on a hobby project together with a friend. That is basically what we do here.

The following are too weird to be made up.

= = = =

I had a real bad experience years ago when a co worker asked me to look at his car. He claimed to not know or understand anything about the grinding noise from the front end.

What is the problem? A: I don't know.

What is the noise? A: I don't know.

Where is it coming from? I don't know.

I thought the guy was just mechanically challenged. But as we will see, he is manipulating me.

I eventually was invited over for a nice lunch and then took the car out for a trip around the block. Applying the brakes caused a strong pull and gringing noise. Alarming.

I jacked it up and found that the nut on the right front axle stub had backed off and there was no cotter pin at all. The brake caliper was holding the wheel in place. Very fishy.

So I said: "Someone has been working on this recently, right?"

A: "Oh yeah, my cousin did a brake job. Could that be the problem?" (Little Mister Innocent.)

So I say, "Take it back to your cousin, there could be other damage". The guy says he can't, because the cousin lost his job at the repair shop because (implied) he screwed up on too many jobs.

So I say, "Bring it back to the shop, demand that things be set right, and the heck with your cousin's problem."

A: "I can't do that because then the cousin will not get a good recommendation for the next job, or he'll have to pay for the cost."

I tightend up the nut, put in a wire, and told them to go directly to a professional auto shop.

Grrr.

= = = =

While I'm telling stories.

There was a very nice couple in the apartment up-stairs. Professor of English etc. They want me to take care of the mail and the cats' litter box while they're on vacation. And they say, "We'll leave out a bottle of Scotch, So please have a tot after cleaning the litter box." Makes sense. They are tidy, generous, and proper.

Anyway, they get back from vacation and we're talkng over the bottle of Scotch.

They say they have this canister vacuum cleaner which doesn't work right. They had brought it (taken it?) to a shop and paid the man. But still it is not working right. So I turn it on and the motor-air pump is running fast like the hose is clogged.

I take the hose to their immaculate bathtub and stick one end of the hose up to the faucet nozzle and run water into it at full pressure. There is a big back-up of water and no flow-through for a while . . . . . and then an enormous blob of wet cat hair blasts though, making a big mess of their very clean tub.

The Prof looks at the wife, they both look at the ugly tub full of water and cat hair, and they both look at me. The cats are hiding somewhere.

Professor of English asks: "Do you thnk that was the problem all along and we should ask for our money back?"

===

I just don't want to get involved anymore. Smile.

Wm McD.

[Marvel]

The following are too weird to be made up.

= = = =

I had a real bad experience years ago when a co worker asked me to look at his car. He claimed to not know or understand anything about the grinding noise from the front end.

What is the problem? A: I don't know.

What is the noise? A: I don't know.

Where is it coming from? I don't know.

I thought the guy was just mechanically challenged. But as we will see, he is manipulating me.

I eventually was invited over for a nice lunch and then took the car out for a trip around the block. Applying the brakes caused a strong pull and gringing noise. Alarming.

I jacked it up and found that the nut on the right front axle stub had backed off and there was no cotter pin at all. The brake caliper was holding the wheel in place. Very fishy.

So I said: "Someone has been working on this recently, right?"

A: "Oh yeah, my cousin did a brake job. Could that be the problem?" (Little Mister Innocent.)

So I say, "Take it back to your cousin, there could be other damage". The guy says he can't, because the cousin lost his job at the repair shop because (implied) he screwed up on too many jobs.

So I say, "Bring it back to the shop, demand that things be set right, and the heck with your cousin's problem."

A: "I can't do that because then the cousin will not get a good recommendation for the next job, or he'll have to pay for the cost."

I tightend up the nut, put in a wire, and told them to go directly to a professional auto shop.

Grrr.

= = = =

While I'm telling stories.

There was a very nice couple in the apartment up-stairs. Professor of English etc. They want me to take care of the mail and the cats' litter box while they're on vacation. And they say, "We'll leave out a bottle of Scotch, So please have a tot after cleaning the litter box." Makes sense. They are tidy, generous, and proper.

Anyway, they get back from vacation and we're talkng over the bottle of Scotch.

They say they have this canister vacuum cleaner which doesn't work right. They had brought it (taken it?) to a shop and paid the man. But still it is not working right. So I turn it on and the motor-air pump is running fast like the hose is clogged.

I take the hose to their immaculate bathtub and stick one end of the hose up to the faucet nozzle and run water into it at full pressure. There is a big back-up of water and no flow-through for a while . . . . . and then an enormous blob of wet cat hair blasts though, making a big mess of their very clean tub.

The Prof looks at the wife, they both look at the ugly tub full of water and cat hair, and they both look at me. The cats are hiding somewhere.

Professor of English asks: "Do you thnk that was the problem all along and we should ask for our money back?"

===

I just don't want to get involved anymore. Smile.

Wm McD.

I can understand that. Does sound like the first one knew what was wrong all along, and the second sounds like Epanimondas. Although a stereotype, his momma tells him, "Epanimondas, you ain't got the sense you was born with."

Bruce

[Blvdre]

There is something in common here. The cap in your amp (and the connection of course) handles high current when the amp powers up. The relay in the furnace controller I(and its connection) handles high current when a motor is switched on. It may be that over the years the solder in these connections melted and reformed until eventually the connection was compromised.

That's a good point. A solder joint will eventually become oxidized, and if it continually reheats without a flux being applied to clean the oxidized layer, the solder will degrade as it is continually re-flowed (just a guess). The other issue is temperature. I believe solder will flow at <400 F, but you really need ~700F to create a proper shiny joint. A joint that is heated due to current flow might not be at an optimum temperature.

Of course the other scenario is that the joint isn't heating enough to cause the solder to flow, but the uneven expansion and contaction of the two dissimilar metals of the lead and solder eventually cause the joint to fail.

[cc1091]

The tech person that told me to clean and resolder is someone working at a company that supplies avionics to the military. He has a house (and soon a garage) littered with small projects in some state of repair/rebirth. Most of the projects are for himself. Not all are electronics. He's a regular Doc Brown (Back to the Future) wanna-be.

I'm sure the reason why he gave me the step by step instructions was because he didn't want the responsibility himself or the chunk taken from his time. That's fine, I'm always up for learning.

Now I know I remember him saying why he preferred Formula 409 and a water rinse over Isoprophyl alcohol, but I can't remember what he said. Good point about the salts though.

CC

[Blvdre]

The problem with Isopropyl alcohol is that often times the version sold in drug stores is isopropanol "mis-labeled" as isopropyl alcohol. Isopropanol will leave a lot of residue on the PCB. Sounds like your friend has a tried and true method . My favorite was trichlor (anyone remember trichloroethane? but you had to be careful not to breath too hard around it.