I've noticed a commonality over the years from dudes fixing blown up amps, including myself:
1. The output trannies & brown resistors get replaced
2. Couple pages later, oops I missed an open emitter resistor cuz it wasn't visibly fried
3. Aw **** it still won't bias right
4. 5 pages later after a bunch of testing & shotgun replacements later we find...
5. A bad diode farm toward the front end
Just observations & not to pick on anyone
I know that "repair it first" is a good rule for a reason. I often have a difficult time doing that because my electronic theory skills and being able to understand a circuit are still quite limited.
When, as is often the case, my initial theory proves to be wrong, and the second, and the third, more and more it seems like that is the time to simply stop.
And ask for help, and use the time to try to learn more.
But it gets really tough to just sit there and wait, especially since a lot of people just don't have the time to help all of us. I get impatient.
But I also know that at some point I am going to have to re-solder every damn part in the unit.
So I have a tendency to choose a section and one at a time remove each part, test it, document the result, and either replace it (carbon film resistor, diode, zener diode) or re-install it.
Move on to the next section...repeat. I test and document every single part and measurement, including new parts. Adding dates to the notes helps, especially when I re-measure something at a later date.
I make a couple of copies of the schematic and highlight the good parts in green, bad parts in pink on one. Another copy of the schematic has every shown voltage highlighted in yellow and every measurement is recorded in a notepad and also written directly on the schematic.
Some of this is probably not a good practice, especially the getting impatient part. Some of it has proven to be useful.
I need to learn how to use the damn oscilloscope.
Also just observations, and self critique. Load, lock and fire away...
James
LOL
