Vintageaudiorevival

No dice. Swapped the input board plugs from left to right channel. Buzz stayed in right channel. Got to be somewhere else. I’ve checked all the pre drivers. drivers. Input transistors, all the capacitors, everything is good. All voltages and rails come up and down evenly. Everything is within spec.

That’s a good idea. When I have the input board disconnected, it is silent. So that may be a clue. I’ll try it and report back. Thank you!

Got all finished up. With new Electrolytic capacitors, the thump is nearly non-existent! It is there ever so slightly on Power off, moreover, when I power it on, There is a loud "Buzz" Type "Inrush" Sound in the RIGHT speaker Only. It happens quickly and then goes quiet, Powering down there is nearly nothing. Interesting enough, when I tried to apply the "No Thump modification" (Or whatever it is that you're all calling it) It was near silent when powering on and off, however, when the circuit modification was in place, there a lot of white noise (High noise floor) on the RIGHT channel. I moved the "Mod" components from right to left channel and the problem stays in the right channel. Which tells me that there must be something else wrong in that channel. I am guessing that it is related to the "Surge" sound when powering up in the right channel. It has done that since I have gotten it. Any Ideas. I tried searching but have not found much. Added a Video so you can hear it. it's an odd one. Its only in One channel Thank you! Untitled design.mp4

Thank you everyone! Going to just do it all. Just ordered all the parts. Anything worth doing is worth overdoing. I only Paid $100 for the stack, so throwing another $300 into it is a no brainer! Thank you again!

Hello everybody. I found an M–1.0t a at Goodwill a few years ago. Long before I had the confidence to work on it myself. It did not work so I sold it not working. Always wondering what I was missing out on. Well, last week I came across another one with a C1 preamp and tuner. It of course also didn’t work, but this time I am determined to fix it. So after some troubleshooting, I found that the PreDrivers were shorted on both channels preventing it from powering on all the way. I have since replaced those, it powered up all voltages were good. I set the Bias and have been listening all day. It sounds great and I’m glad I was able to find another one. However, I have a very loud pop in the speakers about 5 seconds after I switch off the amplifier. It seems that the longer it is powered on the louder the “pop” I have read the service bulletin about the the “turn on / turn off thump” and I’ve ordered the parts to complete the repair however, my question is, is THAT noise THE thump? I have heard amplifiers thump before, but this was a very loud pop. I wouldn’t describe it as a low. I have a hard time believing this “thump fix“ is going to take care of this. Also. this is a Non-inverting model Any insight would be greatly appreciated. Thank you so much.