I have this Yamaha receiver where the relay circuitry is acting up and not allowing the amplifier to function.
Anyone have the schematics of this?
Thanks
Tom
Anyone have the schematics of this?
Thanks
Tom
Hi tmblack,
What's happening exactly? BTW, Yamaha loves to use lamps in muting and protection circuits. If there are any burnt out, replace them and your problem may go away.
Sorry, no longer have that manual.
-Chris
What's happening exactly? BTW, Yamaha loves to use lamps in muting and protection circuits. If there are any burnt out, replace them and your problem may go away.
Sorry, no longer have that manual.
-Chris
Sometimes the unit turns on after a very long wait and the relays make a click, then it might make a loud crack and the unit goes off again.
Maybe there is a leaky capacitor or dc offset?
Not a bad looking unit for the late 70's, I'd like to fix it.
Tom
Maybe there is a leaky capacitor or dc offset?
Not a bad looking unit for the late 70's, I'd like to fix it.
Tom
Hi Tom,
Sounds like an offset problem all right. It is a good rcvr.
If I'm not mistaken, that unit uses an STK voltage amp, doesn't it?
If so, I'll bet that's gone bad. You can try resoldering the pins first. Clean off the old solder and use flux.
-Chris
Sounds like an offset problem all right. It is a good rcvr.
If I'm not mistaken, that unit uses an STK voltage amp, doesn't it?
If so, I'll bet that's gone bad. You can try resoldering the pins first. Clean off the old solder and use flux.
-Chris
Yamaha cr-820
Hi
Go to www.stereo411.com/forum and ask Age for the
Yamaha CR-820 service manuals,
if he hasn't the schematics , write u'r e-mail address and i sent u the CR-1020 or CR-620D
Regards
Dudu
Hi
Go to www.stereo411.com/forum and ask Age for the
Yamaha CR-820 service manuals,
if he hasn't the schematics , write u'r e-mail address and i sent u the CR-1020 or CR-620D
Regards
Dudu
Start by replacing the cap on the base of TR804, then the caps on the base of TR704, TR705 to ground.
There may be other problems.
http://www2.yamaha.co.jp/manual/pdf/av/english/AFR/CR-820.pdf
There may be other problems.
http://www2.yamaha.co.jp/manual/pdf/av/english/AFR/CR-820.pdf
Hi djk,
Thanks for the link, I can almost make out the numbers.
Tom,
Look to see if there are bad solder joints. They will look frosty rather than smooth now, there may be a tiny black ring around the component lead. Remove the old solder, add flux and resolder. Don't use too much solder (avoid leaving solder blobs). Clean the PCB with lacquer thinner and look for solder wiskers when you are done. Replacing the electrolytic caps as djk suggested may improve the sound quality at this age.
-Chris
Thanks for the link, I can almost make out the numbers.
Tom,
Look to see if there are bad solder joints. They will look frosty rather than smooth now, there may be a tiny black ring around the component lead. Remove the old solder, add flux and resolder. Don't use too much solder (avoid leaving solder blobs). Clean the PCB with lacquer thinner and look for solder wiskers when you are done. Replacing the electrolytic caps as djk suggested may improve the sound quality at this age.
-Chris
Wow,
thanks for the links guys.
I am very impressed!
Yes, I will replace those caps and look around the board.
Do relays usually need replacing after a couple od decades?
Tom
thanks for the links guys.
I am very impressed!
Yes, I will replace those caps and look around the board.
Do relays usually need replacing after a couple od decades?
Tom
It's not likely to be the relay.
The relay drive circuit has an RC time constant before it latches, that is the first cap I want you to replace. The drive circuit also senses DC and cuts the relay off. The second set of caps I listed can affect DC off-set.
As Chris pointed out, the loud noise when it cuts out is probably DC. The DC could be from many things. IIRC, TR713, TR714 run hot and the solder joints can go bad. It could take some time to actually find the problem.
The relay drive circuit has an RC time constant before it latches, that is the first cap I want you to replace. The drive circuit also senses DC and cuts the relay off. The second set of caps I listed can affect DC off-set.
As Chris pointed out, the loud noise when it cuts out is probably DC. The DC could be from many things. IIRC, TR713, TR714 run hot and the solder joints can go bad. It could take some time to actually find the problem.
I'm in agreement with djk. Just desolder and resolder the warm running components and try it. Also change the caps, they are old and leave the big filter caps for now.
-Chris
-Chris
Old tread but here it goes:
Got a constant buzzing trought speakers and headphone jacks. Most likely 50hz. Changed the main caps and also c814, 815, 816, 817, C807 and 808 but no improvement apart from relay getting stable. It´s not a loud buzz more like a d r r r r r noise. Someone mentioned the bridge rectifier might be the cause, what do you think?
Got a constant buzzing trought speakers and headphone jacks. Most likely 50hz. Changed the main caps and also c814, 815, 816, 817, C807 and 808 but no improvement apart from relay getting stable. It´s not a loud buzz more like a d r r r r r noise. Someone mentioned the bridge rectifier might be the cause, what do you think?
Hi IsakAlexander,
No, it's not the bridge rectifier.
What do we know?
The noise exists on both channels of the amplifier output. The headphones come from the main amp.
What to look for:
The very first thing you should do when servicing equipment is to confirm all the power supplies are at the correct voltage and have acceptable appearance when viewing on an oscilloscope. You should be using the "trigger from line" feature on your oscilloscope. We know the noise will be synced from the line as a trigger. Regulated supplies shouldn't have anything more that random noise at a low level showing.
-Chris
No, it's not the bridge rectifier.
What do we know?
The noise exists on both channels of the amplifier output. The headphones come from the main amp.
What to look for:
The very first thing you should do when servicing equipment is to confirm all the power supplies are at the correct voltage and have acceptable appearance when viewing on an oscilloscope. You should be using the "trigger from line" feature on your oscilloscope. We know the noise will be synced from the line as a trigger. Regulated supplies shouldn't have anything more that random noise at a low level showing.
-Chris
Hi IsakAlexander,
You need to gain access to the oscilloscope. That can tell you volumes that you'll never, ever know without using one.
Check out local electronics shops to see if they can let you view the 'scope looking at your power supplies. Maybe a university or vocational school may be easier. Somewhere, somehow, you need to look a the power supply rails.
Go ahead with the measurements in case something is obvious.
-Chris
You need to gain access to the oscilloscope. That can tell you volumes that you'll never, ever know without using one.
Check out local electronics shops to see if they can let you view the 'scope looking at your power supplies. Maybe a university or vocational school may be easier. Somewhere, somehow, you need to look a the power supply rails.
Go ahead with the measurements in case something is obvious.
-Chris
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