This was a fantastic series. Thank you for taking the time to share it. I know it is hard to set something aside, and not always convenient, but I have to do the same thing when I am working on these old amplifiers.
Before beginning any project, I take several photos in good lighting (outdoor sunlight is ideal) of the ORIGINAL (unfixed, un-modded) unit's interior, pcbs, etc . Makes reassembly easier. And discrepancies between the actual unit vs. the serv. manual unit trivial.
Thank you for your time! On grave-shift flight line maintenance, we used to call your brute force method, swap-tronics. It's effective but time consuming; in the end it is about results! Genuine troubleshooting like that is born out of experience, and you did not let this amp best you. Marantz seems to have had some very creative circuit design engineers back in the day; really looking forward to more pieces from this period. Thanks again.
It's always the last place you look ! Great effort in getting to the root of that problem, I can imagine how something like that would keep you up late trying to figure out and maybe even wake you up in the night to have another go at it ! I never enjoyed the sound of Marantz amps, they always sounded too clean and sharp (cold) for my tastes and that square wave confirms what my ears hear, I prefer a warmer sound myself.
On tough problems I'll often walk away and sleep on it. The next day I can approach it with a fresh view and believe it or not, this works for me most of the time
@@TrevorsBench That often works for me too, sometimes I can be so focused on the issue that I can't think straight and the solution eludes me. Then I come back the following day and immediately figure out a way to resolve it which seems perfectly obvious but was completely unfathomable previously !
The first problem really threw me off course because it affected both channels and I was convinced it was a PS issue. Marantz saved $0.03 for designing the resistor divider to bias BOTH channels instead of doing them independently
Having the solder iron on the collector for half a second is in the same ballpark. Both methods need to be done really quick, so no other components see the change.
I had to redraw an entire section of a power supply or audio circuit, it was years ago so I'm not exacty sure which one it was, on a Marantz 125 tuner. I wasn't impressed with the schematic at all.
