loud buzz after bypassing selenium rectifier with diode

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loud buzz after bypassing selenium rectifier with diode

Postby jerkbag » Sun Jan 31, 2010 8:08 pm

hi all,

i posted this over at the dynaco doctor forums as well, but. . . i just did my first "mod" which was the basic soldering of a 1n4004 diode to the selenium recitifer. when i hooked everything back up, i got a LOUD buzz in both channels when the amp was turned on, regardless of volume setting or what preamp inputs were selected. after panicking for awhile (i'm new to soldering) i opened it up again and resoldered the diode. to my suprise, everything sounds fine now.

so what happened there? was a bad solder connection causing stray voltage to be all over the place? should i be worried about other damage?

thanks!
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Postby burnedfingers » Thu Feb 04, 2010 6:26 am

I think you figured it out. Your soldering skills seem to require more practice. Did you do any damage? I doubt it.
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Postby EWBrown » Thu Feb 04, 2010 1:28 pm

On the bottlehead web site, it has often been stated that about 90% of amplifier problems are caused by basic soldering problems, some of which can show up immediately, and others don't fail until afer many hours' operation. If a solder connection doesn't look right, IE, shiny and smooth, with no roughness, holes or gaps, it is probably going to fail at some time. I've been soldering for over 45 years, and I still bung it up once in a while.

Then there was the Heathkit radio kit I saw back in the 1960s, which had all of its connections glued, rather than soldered. The kid's father wouldn't allow him to use a soldering iron, because he deemed it too dangerous. Needless to say, glue doesn't work very well. uggghhhhhhh.

/ed
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Postby mesherm » Thu Feb 04, 2010 6:17 pm

As an old timer who has been soldering since dirt was still rock I keep forgeting that there are people out there that have not had much soldering experience. I will list just a few tips.
1. Pick a soldering iron with the right heat for the job. For most electronic soldering a 25-40 watt iron with a iron-plated copper tip is plenty.
2. Clean the tip before soldering. A dirty tip will not conduct heat no matter how hot the tip gets. Too many people will crank up the heat on an adjustable iron trying to get the solder to melt. That only oxidizes the tip quicker and makes it harder to solder.
3. Put the soldering tip on the joint and feed a bit of solder at the iron tip to get the heat transfer then as it melts feed in more solder to fill the joint.
4. On hard to reach joints, I keep a small bottle of flux handy to flux the joint then load a gob of solder on the tip and quickly press it to the joint.
5. If you have an iron with a screw-in tip make sure its tightly screwed into the body of the soldering iron. Efficient heat trasfer from the heating element to the tip is vital to good soldering. If your tip is old and corroded, replace the tip.
Mike's N-1 Rule: When looking for N number of components to finish a job, you have a 95% chance of only finding N-1 of them.
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Postby TomMcNally » Fri Feb 05, 2010 5:35 pm

I was trying to figure out when I started soldering, and found this
picture, I was just getting into electrical stuff at age 4. The box
is a Model Rectifier HO Train power supply. My dad and I took
it apart and mounted the rheostats and switches on a big
wooden control panel. It had a hefty transformer and a big
3 inch diameter selenium rectifier that smelled really cool
when you drew too much current. I remember my dad showing
me how to wire a DPDT toggle switch to reverse the polarity
to the track to make the train go the other way.

In any case, I don't see a soldering iron in the picture, there is
a knife and a pair of forceps and a pack of Lucky Strikes, if
dad didn't smoke them he'd probably still be around.

Image
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