Yamaha MSR100 speaker problem...

[panhandler]

One of my yamaha MSR100 powered speakers has no output on both of the 1/4" TS channels. (channels 2&3) The LowZ (chan 1) works fine.

 

This unit worked fine when I last used it about 6 months ago. I don't know what could have gone wrong while in storage?

 

Any ideas or suggestions would be much appreciated.

 

Thanks... GW.

[mike42]

I know absolutely zilch about your system. I would guess looking the panel shot that this is what's referred to as a tri-amp unit? It's likely that the problem would be a fairly simple fix. Maybe even as simple as an internal fuse, etc.. But, you're probably going to need to find a schematic diagram for it and post a link, or the diagram itself for anybody to help.

[WRGKMC]

Since its the 1/4" only my first guess is a bad cord. The 1/4" connection meets up with the low z in the circuit and passes through the same amplifier so there isnt a whole lot of circuitry differences between the two inputs besides the low Z impediance matching. This is done with either a trancformer or additionsl gain circuitry. The pots would also limit the inputs.

[panhandler]

Well I went into it this evening and all the fuses are good, something smells a lil burnt, but not too stinky I see nothing burnt. Connections all seem good.

I also discovered that the two, 1/4" TS inputs DO have sound. I just have to turn the MASTER and the VOLUME all the way up. And even then, the volume is LOW and VERY MUDDY/BASSY.

[mike42]

Umm,... again without knowing squat about this thing I would guess the first stages (pre-amp may be the wrong term?) are maybe Okay if you're getting something. Although that could be bleed over from the good channel or even bleed-through a bad component if you're cranking it all the way up. WRGK is saying everything is actually going into pretty much the same power section. If that's the case, then your power amp has to be good so the prob would have to be in front end of the bad sections. If it were mine I'd probably hope for and look for, a bad solder joint.

 

Actually, I think I'm pretty much just shooting in the dark here - be nice to know something about how this thing is put together. When you say it was in storage, was it somewhere where some big temperature swings could have caused the boards to flex?

[panhandler]

 

If it were mine I'd probably hope for and look for, a bad solder joint. When you say it was in storage, was it somewhere where some big temperature swings could have caused the boards to flex?

 

 

I did look for a bad solder... no luck.

It was just stored in the music room with everything else climate controlled about 8 mos since last use, and then I used one of the 1/4" inputs, worked fine.

 

Want me to post pics of the guts?

[WRGKMC]

Take it to a repair shop and let them signal trace it.

[mike42]

Yeah, I'm Pretty much out of simple fix ideas. I don't think pics would help me - a schematic maybe - but I looked at the Yamaha site last night, found the amp but no drawings.

 

Since the thing was just sitting, the fuses are good, I would still bet a bad joint is a pretty high probability. I have to have a good light, and I generally use a little photo loupe magnifier to check boards. Seems to me over the last 20 - 25 years, bad joints have become almost epidemic. Sometimes you get one that looks good at first glance, but if you look really close the component lead was never really soldered, just surrounded by solder. Get a little corrosive buildup and it's an open connection.

[WRGKMC]

Wave soldering boards has always had problems. They begin with the quality of the flux thats supposed to remove oxidation from the pads and components before passing the board through the solder.

 

The quality of the solder itself which is a 60/40 tin and lead can be an issue. Too much tin can cause flow issues. Then theres the component leads which are all kinds of thicknesses and alloys. The leads may need different temps to have toner adhere properly do the solder temp is super critical.

 

When they pass boards through the solder the solder cools causing consecutive boards to be soldered at a slightly lower temp. Then defluxing and inspestion come into play. Most boards are tested on a computer, but visual inspection cannot see all the possible cold solder joints especially with multi layerd boards.

 

With the newer boards, components on both sides, layerd boards and micro components, the problems get even tougher. If the mounting pads for the board are uneven it can flex boards and open joints over time. Vibration, even an uneven table which a unit sits on can cause a frame to sag, plastic covers warp with heat, you name it. Then you can also have static issues that can blow parts in dry cool weather.

 

From the posters comments saying the sound was muffeled, it sounds like there may be a bad cap in the front end someplace, but its still something you need to trace out to determine.

[panhandler]

Thanks for the suggestions fellas... There's a place not too far away that is a factory repair ctr for Yamaha audio products and they seem to have a good reputation.

I had hoped it was an obvious broken wire, but my life ain't like that

 

GW,