Hey guys, here's another thread necro.
I went ahead and got an SG-100/A in need of repair after coming across this thread and seeing that there are owners on the forum here. After some preliminary testing, I've discovered that:
1. Fuse F5 on the signal output is open. I don't know what caused it, but probing the other side shows that the sine wave output seems to be working properly (frequency, gain, offset).
2. Although all function/arbitrary/pulse options are available in the firmware, I'm getting no output of the expected signals. I recall AwArD_RzD's first post with the PCB picture, and sure enough U21 is missing (I'm sad, there isn't even a socket soldered
).
This (2.) leads to my first question: is it normal for an SG-100/A with no arbitrary output option installed to have the options available in firmware, but U21 un-populated? (my guess is yes, but more evidence would help)
3. Probing the pins on the MAX532 (U45), I find that VDD and VSS, which are nominally +12/-12V from Telulex's schematic, measure at +15.6V/-15.1V. From Maxim's datasheet, I see that 15V power supply is fine, but should I be concerned that voltages are not as indicated on the manufacturer's schematic? (if someone could probe the test points for their MAX532, I would really appreciate it)
If all is as expected, my plan is to replace the blown fuse and install a socket+DAC. Can anyone please advise if I should proceed or if there are further pitfalls I should look for first?
Thanks!
Addendum: My SW version is 3.3, HW version is 1.7. The unit identifies itself as "SG100" on power up, so I'm further convinced that this is the normal behavior of an SG-100 without the A option (despite the label on the front panel).