QUESTION: Yamaha MX-1000 Power Amplifier Problem

[EADGBE]

I recently acquired a used Yamaha MX-1000 Power Amplifier that was
VERY dirty.

I opened it up and found probably 3 cats' worth of fur covering the
components inside. You could barely identify the various capacitors,
resistors, etc.

I am no stranger to cleaning out dirty audio gear, and so I took my
trusty Hoover and **CAREFULLY** vacuumed out all of the fuzz and lint
I could see. I also used a small paintbrush as a miniature whisk
broom to get in the tighter areas.

I was very, VERY careful not to disturb any wiring connections.

I carefully put the top cover back on and used the amplifier for a
couple of days with no problems whatsoever.

But now I have noticed that the digital wattage readout on the front
of the amp no longer lights up. I believe that it DID light up
normally after I re-assembled the amplifier, but I still can't help
wondering if I did something to break a connection somewhere.

Does anyone have a schematic for this amplifier? It's really not a
very important feature, but it bothers me that it no longer works.

Is this a common problem on these amplifiers?

Any assistance will be GREATLY appreciated! Thanks in
advance..........

(I also posted this to rec.audio.tech, not knowing which
newsgroup was more appropriate....my apologies......)

 

[Jamie]

I recently acquired a used Yamaha MX-1000 Power Amplifier that was
VERY dirty.

I opened it up and found probably 3 cats' worth of fur covering the
components inside. You could barely identify the various capacitors,
resistors, etc.

I am no stranger to cleaning out dirty audio gear, and so I took my
trusty Hoover and **CAREFULLY** vacuumed out all of the fuzz and lint
I could see. I also used a small paintbrush as a miniature whisk
broom to get in the tighter areas.

I was very, VERY careful not to disturb any wiring connections.

I carefully put the top cover back on and used the amplifier for a
couple of days with no problems whatsoever.

But now I have noticed that the digital wattage readout on the front
of the amp no longer lights up. I believe that it DID light up
normally after I re-assembled the amplifier, but I still can't help
wondering if I did something to break a connection somewhere.

Does anyone have a schematic for this amplifier? It's really not a
very important feature, but it bothers me that it no longer works.

Is this a common problem on these amplifiers?

Any assistance will be GREATLY appreciated! Thanks in
advance..........

(I also posted this to rec.audio.tech, not knowing which
newsgroup was more appropriate....my apologies......)

It's very hard to say, if the unit has been sitting around for a long
time, it's possible you operating it may have kicked out a bad cap that
just was aged, and the minor heat you were generating did it in.

I don't know what type of display you have how ever, if it's a
fluorescent display, you may have a bad electrolytic cap in the
inverter section that supplies the HV low current for the display..


http://webpages.charter.net/jamie_5"

 

[EADGBE]

I don't know what type of display you have how ever, if it's a
fluorescent display, you may have a bad electrolytic cap in the
inverter section that supplies the HV low current for the display..

The power meters are the liquid crystal type; however, the digital
wattage readout (which is the part that doesn't work), seems to be
your standard LED digital readout.

 

[Jamie]

The power meters are the liquid crystal type; however, the digital
wattage readout (which is the part that doesn't work), seems to be
your standard LED digital readout.

You may have stand alone panel module meters.
You need to check the connections going to them and
power supply.
At min, they should be displaying "0"

http://webpages.charter.net/jamie_5"

 

[EADGBE]

You may have stand alone panel module meters.
You need to check the connections going to them and
power supply.
At min, they should be displaying "0"

You are exactly right. When they were working, they would read "0.0"
whenever the amp was idle.

 

[EADGBE]

My guess is that I will have to check the common-cathode connection
for the LED digital display, to see if everything is OK there. I will
also do the customary power supply check, to make sure that the
circuit is even getting any power to begin with.