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Yamaha P1150 mono power amp (protection mode)

PROJECT 2501

PROJECT 2501

Active Member
Looking for advice on how I could reset or fix the issue that's caused the amp to go into protection. I've been learning how to do basic repair and restoration over the years with the help from this forum and I think this amp will be the perfect step up in challenge. Ive downloaded all of the manuals available for it but I've yet to see anything that tells me where to begin. So, is there anyone familiar with this amp that could share a little knowledge to point me in the right direction?

Thanks in advance.
 
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On the PA-A board . Find TP 205.. With the multimeter red probe to TP205 and black probe to metal chassis ground. Measure for DC volts.. Should be pretty close to zero volts +/- 20mv..
 
avionic said:
On the PA-A board . Find TP 205.. With the multimeter red probe to TP205 and black probe to metal chassis ground. Measure for DC volts.. Should be pretty close to zero volts +/- 20mv..
Click to expand...



I apologize for the long absence.. life got in the way but I've got 2.16 volts DC
 
avionic said:
On the PA-A board . Find TP 205.. With the multimeter red probe to TP205 and black probe to metal chassis ground. Measure for DC volts.. Should be pretty close to zero volts +/- 20mv..
Click to expand...



After about 15 minutes of warm up time it's centered around 2.2 volts well above what you spec'd out for 20 millivolts
 
Whooooooooaaaahh!!!!

As I'm sitting here right in front of the power amp and typing this on my phone the amp just clicked out of protection by itself.... I didn't touch anything
 
I still have my negative probe alligator clip clipped to chassis but that's all that's going on here and it popped out of protection just like that
 
Look for cold solder connections in this area..

upload_2022-9-13_17-41-15.png

IC201 is your DC servo.. It is suppose to keep your DC offset around 20mv constantly/ automatically..
 
Do you have any tips on how to locate cold solder joints? The only thing that I know what to look for is the ring around the pin with dull colored solder. And after locating one, what can I use to safely mark the PCB and flag it?
Please excuse this question but there are two spots on the board where three pins have solder that's flowing into one another, I'm unsure if every pin is supposed to be separated, not touching one another or if a junction of sort is allowed like the one I'm describing...
Thanks in advance
 
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