Yamaha M-80 in PROTECTION MODE

Here is a typical list of damaged components when and output transistor shorts C-E.
Some may diode check OK but.. They are all within the debris field and have been exposed to excessive current.

TR104,106,108,110,112,114,118,120,124,126
R136,138,152,154,158,160
D112,114,116,118---114 & 118 are zener diodes

I've seen TR102 ( 2SK389BL) take a fatal hit on several occasions.

Each case is a little different .Maybe more parts,maybe less.
Thats why I stated earlier to check all the transistors and diodes in the bad channel.
I print out this shematic on legal pad sized paper and highlight those parts that check bad as well as those that check good. Helps me plot the path(s) of destruction.

http://akdatabase.com/AKview/albums/userpics/10004/Yamaha M80 Schematic with TSB66.pdf

I won't hijack the thread, but we need to work on a plot for my dead MX-2000 some day. :D

I think I have the input board sorted out, but one channel board has .5VDC on the idle current and it's still coming up in protect. I'm baffled. :scratch2:
 
I remove both caps from the main and cleaned out the putty on the board and components. None of the components were bad as far as I know.

2 of the right channel PNPs 2SA1169 were bad along with 2 of the 0.22 ohm Micron resistors. Avionic from the thread suggested that I check out all of the transistors/diodes/resistors on the board. A big job since this is my 1st repair project-will go ahead!
 
Avionics,

I will followup with your suggestions as you noted. A lot of work but will move forward with the plan. Hope to update back to you soon.

Best
 
Avionic from the thread suggested that I check out all of the transistors/diodes/resistors on the board
Just on the bad channel...There ya go. I just cut your task in half.:D
 
Start by checking the transistors for dead shorts in circuit. Any that are suspect, pull and test again. You can then start to map out the path of destruction.

I'm lucky to have an old cricket that can test the trans in circuit, I just hope it catches everything.
 
Welcome.
Do you know how to read a schematic ? how are your soldering/desoldering skills ?

Do any of the front panel LED's illuminate ? If so, we need to check voltages on a couple testing points. To check for any DC voltage at the output of each amplifier circuit.
Helo dear.. as i seen you are doing a great job by helping peoples like me... I have yamaha m80 that was had glue issues but working perfectly. Than on i decided to remove that glue and clean up the amp but now it goes to protection mode please help me to figure me out the actu6a problem thank you
 
Helo dear.. as i seen you are doing a great job by helping peoples like me... I have yamaha m80 that was had glue issues but working perfectly. Than on i decided to remove that glue and clean up the amp but now it goes to protection mode please help me to figure me out the actu6a problem thank you
Welcome to AK. Did you replace anything ?
 
Welcome to AK. Did you replace anything ?
no i did not replace anything. But firstly when this problem start i observe a transistor on main board (Left channel) near 1000 uf 100 volt capacitor was bad solder joints. I resolded that and the amp release from protection mode. But than i observe a transistor (green color) on x power supply board getting hot when i plug in the amp. So i resold many joints to solve this problem but it didn't work. At the end that green transistor stop getting hot but the amp again goes to protection mode. I hope this details eill help you to figyfi out the actual problem.
 
Those have a bad habit of unsoldering themselves.
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Those have a bad habit of unsoldering themselves.
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I resold all components but my m80 is in protection mode.
Two times when i was resolding components i plugged in my yamaha m80 and it was not in protection mode but as i connect speaker wires and turn it on again it goes to protection mode. This happens. Second time i didn't connect speaker wires but input it with music and its meter start working but as i conecon speakers wires it goes to protection mode again... Help me whats problem with my m80?
 
. Help me whats problem with my m80?
Look over all the little greenish fusible resistors. Most of them are standing on end. Look for darkened bands around there centers.
I resold all components but my m80 is in protection mode.
Did you resolder any connections on the main board? Especially the TO-126 transistors. These are also notorious for ring cracks around the leads in the solder connection.
 
Avionics is giving you good advice here. Go meticulously over the main and power boards. Time spent in this area is worth your time.
 
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Check and make sure you don't have a short somewhere in your speaker wires or speakers. I had this problem once with a different receiver when I had stapled wires to the wall for overhead surrounds, one of the staples pierced the two conductors causing a short. Took forever for me to figure out what was happening. It may not be that simple, but it is easily overlooked and may be the problem.
I say this because you said it went into protection mode only after you connected the speakers.
 
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