On Sun, May 13, 2018 at 05:05 pm, Al Sines wrote:
I recall your advice in the manual that components rarely failInteresting that you should mention that!
"Rarely" is not the same as "never." Just yesterday I did some troubleshooting on a U3S that had died after about a year's service. All the programmed functions were OK and my nearby receiver was picking up a weak, but correct, signal coming off the synth board, but that was all. Transistor was getting warm, so I figured I was getting power and I looked at every connection on the board to see what was bad and found nothing imperfect, but I reflowed the solder through all the connections at that end and those in the LPF Still nothing. So I hooked up the dummy load and discovered that the measured voltage was so chaotic the DMM couldn't even get a fix on a single digit of the readout. Looked like it had to be a bad BS170...and it was. I replaced the original no-name BS170 transistor with a Fairchild and the U3S was instantly back in business. These Fairchilds seem to produce a measurably stronger output as well.
I'm not sure I've ever seen this happen before. I assume it was just a casualty of too many thermal flux cycles. [shrug]
I'm happy to hear you're back in business!