Discussion in 'Yamaha' started by JPromo, Dec 31, 2017.
i always like a happy ending
Panasonic's version of the same relay. Just in case the Omron's are not available.
Yep.......perfect fit....and only took two days to get from Texas to Hamilton, Ontario.
Great service from Mouser.
Unfortunately, the relay didn't do it for me. Must have just been coincidence when I smacked it that it cut back in.
Checking the output transistors, all read a steady 30V at the base all the time. Across the E and C I had one in the right channel that was stone 0.0 while the others read 0.6v. Something caused the channel to cut back in and I got a chance to test the previously 0.0 E to C and it was a perfect 0.6V. Can an output transistor be intermittent? Because it's got good voltage at the base even when the channel is out.
i am pretty sure you have BCE mixed up a little .
reading between the lines the output with 0v has maybe lost its drive .
look for cold solder joints
2nd the motion..
I absolutely do. Collector voltage is 30v. I'm used to tubes, where my tester makes up for what I don't know.
So I've got one output transistor with intermittent 0v across B and E. Randomly goes in and out, but smacking in the area of will regularly bring it back.
Joints look good, none look broken or cold. Might be worth a reflow next time the iron is hot though.
Wiggle the part and watch the solder connection for any movement while your wiggl'n.
have had this with sockets . no idea if any socket connections with this unit .
narrow it down some if you just checked if base voltage is stable .
Pay close attention to TO-220 and TO-126 transistors. They run warm/hot and over a long period of time they will develope annular ring cracks in the solder connection. Large resistors as well generally get warm and can generate enough heat over time to compromise the solder connection.
Fresh solder on all TO-220 transistors didn't do it. Added star washers to all the brass screws holding the pcb and heatsink. Still cuts out in the right channel and tapping one of those right output transistors usually brings it right back.
Next time I have the bottom cover off, I'll do a real close check on the transistor traces, then check solder at some other large components, but besides that, I don't know where to look. Can a transistor be intermittent? I know failure is typically catastrophic.
Thanks for your input and patience!
yes anything can happen .substitution will confirm it .or not as the case may be . get in closer with a plastic prodder .
I will go ahead and try subbing transistors.
Searching through the forums, I saw the recommendation of TIP41C/TIP42C in place of my D525 B595 pair. Good option? How many should I buy to expect a decent pairing match?
no real need to match unless working in pairs or more ..
others may disagree . i have never had a problem if ordered together .
So should I just try and replace the two in the bad channel, or replace both pairs? I'm realize there could be conflicting views on this too.
i would get that one side working first then decide .. i bet if both sides working properly you wont notice any difference .
Just got the output transistors installed for the right channel and that seems to have been the issue all along. Ran it for about an hour last night with nothing cutting out so I'm calling it solved. Thanks for all the help!
For search reference--output transistors can be intermittent.
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