"* A better description is that the class B output stage includes signal tracking supplies for each rail employing switching, buck regulators. "

The way I see it, the main thing it accomplishes is to get the filter out of the output line.

"The attraction of this example is the extreme simplicity and low parts count - in part made possible by the use of Sanken power Darlingtons rated at 70MHz. "

What kind of frequency does that thing actually switch at ? Or didn't you check. No biggie if you didn't, I probably wouldn't.

Were your bad connections on the outputs themselves or the regulators ? If on the outputs, your theory bout the thermal expansion is probably right, but if on the regulators I think the high frequency had an effect on it.

However, of late it is starting to look like the HF has less of a deleterious effect on the unleaded solder than it did on leaded solder, though that is only supposition at this time, I don't have enough data. Not sure, but it is possible that even with all its faults, unleaded solder has a lower resistance than leaded, I don't feel like looking it up right now but that might explain it. In this newer stuff I am seeing good connections in the SMPS but bad one like at the display driver. And I get some strange ones, like in a microphone input that don't even respond to resoldering and I have to install jumpers. I'll get to the bottom of that one day but for now I just get the job out.

By the way, do you use unleaded solder on repairs ? I don't. I remember there was a time when I used Tektronix 2 % silver bearing solder on certain critical spots. You didn't see them but we had the Magnavox (before Phillips bought them) T995 chassis TVs that were actually a fire hazard because of the yoke connections. I used it on them.

But someone did ask on a forum and I said no, why would I use something that doesn't work as well ? That law is for manufacturers. I got a nice big pound roll of 63/37 that'll probably last me a lifetime.

Another question - you said you had to unscrew all the transistors, was there no way to remove the heatsink with the board attached ? Or did they make it so you can't do that ? I swear sometimes I wonder how they manage to even build these things. I mean, if it is that cumbersome to take apart, how the hell did they achieve a decent production rate putting it together ? Since labor is such a "huge" cost they say, why not make it easy ?